Subjects -> PHYSICS (Total: 857 journals)
    - ELECTRICITY AND MAGNETISM (10 journals)
    - MECHANICS (22 journals)
    - NUCLEAR PHYSICS (53 journals)
    - OPTICS (92 journals)
    - PHYSICS (625 journals)
    - SOUND (25 journals)
    - THERMODYNAMICS (30 journals)

OPTICS (92 journals)

Showing 1 - 89 of 89 Journals sorted alphabetically
ACS Photonics     Hybrid Journal   (Followers: 16)
Advanced Optical Materials     Hybrid Journal   (Followers: 11)
Advanced Photonics     Open Access   (Followers: 3)
Advanced Photonics Research     Open Access   (Followers: 2)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 24)
Advances in Nonlinear Optics     Open Access   (Followers: 10)
Advances in Optical Technologies     Open Access   (Followers: 3)
Advances in Optics     Open Access   (Followers: 12)
Advances in Optics and Photonics     Full-text available via subscription   (Followers: 18)
Annual Review of Vision Science     Full-text available via subscription   (Followers: 4)
Applied Optics     Hybrid Journal   (Followers: 48)
Applied Physics B: Lasers and Optics     Hybrid Journal   (Followers: 35)
Atmospheric and Oceanic Optics     Hybrid Journal   (Followers: 8)
Biomedical Optics Express     Open Access   (Followers: 6)
Biomedical Photonics     Open Access  
Chinese Optics Letters     Full-text available via subscription   (Followers: 9)
EPJ Photovoltaics     Open Access   (Followers: 2)
European Journal of Hybrid Imaging     Open Access  
Fiber and Integrated Optics     Hybrid Journal   (Followers: 22)
Frontiers of Optoelectronics     Hybrid Journal   (Followers: 3)
High Power Laser Science and Engineering     Open Access   (Followers: 4)
Hindsight : The Journal of Optometry History     Open Access   (Followers: 1)
IEEE Photonics Journal     Open Access   (Followers: 17)
IEEE Photonics Technology Letters     Hybrid Journal   (Followers: 14)
International Journal of Optics     Open Access   (Followers: 14)
International Journal of Optics and Applications     Open Access   (Followers: 7)
International Journal of Optoelectronic Engineering     Open Access   (Followers: 1)
International Journal of Spectroscopy     Open Access   (Followers: 6)
International Journal of Sustainable Lighting     Open Access  
Journal of Astronomical Telescopes, Instruments, and Systems     Hybrid Journal   (Followers: 6)
Journal of Atomic, Molecular, and Optical Physics     Open Access   (Followers: 13)
Journal of Biomedical Photonics & Engineering     Open Access  
Journal of Laser Applications     Full-text available via subscription   (Followers: 14)
Journal of Mass Spectrometry and Advances in the Clinical Lab     Open Access  
Journal of Modern Optics     Hybrid Journal   (Followers: 12)
Journal of Nanoelectronics and Optoelectronics     Full-text available via subscription   (Followers: 1)
Journal of Nonlinear Optical Physics & Materials     Hybrid Journal   (Followers: 2)
Journal of Optical Microsystem     Hybrid Journal   (Followers: 1)
Journal of Optical Technology     Full-text available via subscription   (Followers: 4)
Journal of Optics     Hybrid Journal   (Followers: 14)
Journal of Optics Applications     Open Access   (Followers: 14)
Journal of Optoelectronics Engineering     Open Access   (Followers: 5)
Journal of Photonics     Open Access   (Followers: 5)
Journal of Photonics for Energy     Hybrid Journal   (Followers: 2)
Journal of Physics B: Atomic, Molecular and Optical Physics     Hybrid Journal   (Followers: 32)
Journal of the Optical Society of America A     Hybrid Journal   (Followers: 11)
Journal of the Optical Society of America B     Hybrid Journal   (Followers: 12)
Journal of the Optical Society of Korea     Open Access   (Followers: 2)
Laser & Photonics Reviews     Hybrid Journal   (Followers: 5)
Laser Physics     Hybrid Journal   (Followers: 2)
Lasers in Medical Science     Hybrid Journal   (Followers: 2)
LEUKOS : The Journal of the Illuminating Engineering Society     Hybrid Journal  
Materials Today Electronics     Open Access   (Followers: 1)
Microwave and Optical Technology Letters     Hybrid Journal   (Followers: 11)
Nature Photonics     Full-text available via subscription   (Followers: 37)
Ophthalmic and Physiological Optics     Hybrid Journal   (Followers: 3)
Optica     Open Access   (Followers: 6)
Optical and Quantum Electronics     Hybrid Journal   (Followers: 3)
Optical Engineering     Hybrid Journal   (Followers: 22)
Optical Fiber Technology     Hybrid Journal   (Followers: 10)
Optical Materials     Hybrid Journal   (Followers: 11)
Optical Materials : X     Open Access  
Optical Materials Express     Open Access   (Followers: 7)
Optical Memory and Neural Networks     Hybrid Journal   (Followers: 2)
Optical Nanoscopy     Open Access   (Followers: 1)
Optical Review     Hybrid Journal   (Followers: 2)
Optics & Laser Technology     Hybrid Journal   (Followers: 27)
Optics and Lasers in Engineering     Hybrid Journal   (Followers: 38)
Optics and Photonics Journal     Open Access   (Followers: 18)
Optics and Photonics Letters     Open Access   (Followers: 11)
Optics and Photonics News     Partially Free   (Followers: 7)
Optics and Spectroscopy     Hybrid Journal   (Followers: 8)
Optics Communications     Hybrid Journal   (Followers: 17)
Optics Express     Open Access   (Followers: 23)
Optics Letters     Hybrid Journal   (Followers: 19)
Optik     Hybrid Journal   (Followers: 9)
Optik & Photonik     Open Access  
Optoelectronics Letters     Hybrid Journal   (Followers: 1)
Photonic Sensors     Open Access   (Followers: 7)
Photonics     Open Access   (Followers: 4)
Photonics Letters of Poland     Open Access  
Photonics Research     Open Access   (Followers: 2)
PhotonicsViews     Hybrid Journal  
Progress in Optics     Full-text available via subscription   (Followers: 6)
Results in Optics     Open Access   (Followers: 3)
SIAM Journal on Imaging Sciences     Hybrid Journal   (Followers: 7)
Thin Solid Films     Hybrid Journal   (Followers: 11)
Trends in Opto-Electro & Optical Communications     Full-text available via subscription   (Followers: 1)
Virtual Journal for Biomedical Optics     Hybrid Journal   (Followers: 1)
Similar Journals
Journal Cover
Journal of Laser Applications
Journal Prestige (SJR): 0.741
Citation Impact (citeScore): 2
Number of Followers: 14  
 
  Full-text available via subscription Subscription journal
ISSN (Print) 1042-346X
Published by AIP Homepage  [27 journals]
  • Intermixing behavior of 1.4430 stainless steel and 1.4718 valve steel in
           in situ alloying using coaxial laser double-wire laser directed energy
           deposition

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      Authors: Nick Schwarz, Marius Lammers, Jörg Hermsdorf, Stefan Kaierle, Henning Ahlers, Roland Lachmayer
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Coaxial laser wire directed energy deposition promises a direction-independent buildup of near net shape geometries and surface coatings. Simultaneously introducing two different wire materials into the processing zone enables the production of in situ alloyed or even functionally graded structures. Functionally graded materials and in situ alloyed parts aim to extend the range of materials for development purposes. This work covers the intermixing behavior of two wire materials with greatly differing element contents. Therefore, a multiple diode coaxial laser (DiCoLas) processing head is used consisting of three individually controllable fiber coupled laser diodes with a combined maximum output power of 660 W and a wavelength of 970 nm. Two metal wires, 1.4430 and 1.4718, with a diameter of 0.8 mm are provided simultaneously to the processing zone under an incidence angle of 3.5° to the processing head's middle axis. The DiCoLas processing head enables a stable welding process with good dimensional accuracy of the single welding geometries. Single weld seams and multiple-layer structures are investigated to cover the intermixing behavior for different applications of additive manufacturing. Thermal images of the melting process provide an insight into the melting behavior of the two wire materials and the formation of the weld seam. energy-dispersive x-ray-mappings and line scans display the element distribution of the main alloying elements along the seam cross section. Furthermore, hardness measurements examine the hardness progression along the multiple-layer welding structures showing an even progression of the hardness values over the entire cross section.
      Citation: Journal of Laser Applications
      PubDate: 2023-01-25T12:44:52Z
      DOI: 10.2351/7.0000776@jla.2022.ICALEO2022.issue-1
       
  • Fusing optical coherence tomography and photodiodes for diagnosis of weld
           features during remote laser welding of copper-to-aluminum

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      Authors: Tine Brežan, Pasquale Franciosa, Matija Jezeršek, Dariusz Ceglarek
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      This study has been designed to investigate whether variations in the features of laser weldments can be isolated and diagnosed by fusing photodiodes and optical coherence tomography (OCT). Two manufacturing scenarios (variation in laser power and focal offset) have been considered during remote laser welding of 0.2 mm thick Cu foils on 2 mm thick Al 1050 plates with an adjustable ring mode laser integrated with a 1D oscillation head. The process was monitored by measuring weld penetration depth with OCT and by process emissions (plasma and back-reflection) via photodiodes. The acquisition frequency of all signals was 40 kHz. Strong correlations (r > 0.75) were shown between plasma, back-reflection, and OCT signals and measured depth and width of the weld. Weak correlations (r 
      Citation: Journal of Laser Applications
      PubDate: 2023-01-17T12:56:28Z
      DOI: 10.2351/7.0000803@jla.2022.ICALEO2022.issue-1
       
  • Utilizing ultrafast lasers for postprocessing to improve mechanical
           properties of 3D-printed parts

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      Authors: Darshan Yadav, Ilya Mingareev
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Recent advances in additive manufacturing technologies have already led to the wide-scale adoption of 3D-printed parts in the aerospace, medical, automotive, tooling, and electronics industries. The expansion in choice of materials that can be processed, in particular, using fused deposition modeling (FDM), selective laser sintering/melting, and stereolithography, and the steady advancements in dimensional accuracy control, have extended the range of applications beyond rapid prototyping. However, additive manufacturing still has considerable limitations compared to traditional and subtractive manufacturing processes. This work addresses limitations associated with the as-deposited surface roughness of 3D-printed parts. The effects of roughness-induced stress concentrations on the mechanical strength were studied, and ultrafast laser postprocessing was utilized to reduce the surface roughness of 3D-printed parts. The samples were manufactured using a commercial desktop FDM system and standard ASTM flat dogbone geometries. The samples were then postprocessed with a high-repetition-rate ultrafast Yb-fiber laser using a multi-layer scan approach. This novel postprocessing method enables high-efficiency material removal without inducing excessive thermal residual stresses into the material and, therefore, is suitable for postprocessing thermally sensitive materials, such as PLA and other polymers as well as parts with engineered porosity. In this work, we vary laser process parameters, such as average power and number of laser-processed layers, to achieve various levels of surface roughness. Values of tensile strength of the specimens were compared between 3D-printed samples featuring initial roughness and laser postprocessed samples with different values of surface roughness. The results indicate that the laser-processed samples exhibit an almost 10% increase in tensile strength depending on specific laser processing parameters.
      Citation: Journal of Laser Applications
      PubDate: 2023-01-04T10:59:26Z
      DOI: 10.2351/7.0000804@jla.2022.ICALEO2022.issue-1
       
  • Pliable solid medium as a plasma confinement layer for laser peening

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      Authors: Yang Zhang, Takumi Besshi, Miho Tsuyama, Manabu Heya, Hitoshi Nakano
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Laser peening is a promising surface treatment technique for enhancing the mechanical performance of metals. In laser peening, the plasma confinement layer contributes to the generation of high-pressure shockwaves by suppressing the expansion of laser-induced plasma. Therefore, the choice of a plasma confinement layer is important for improving laser peening effectiveness. For laser peening in environments where liquid materials cannot be used as a plasma confinement layer, alginate gel, which is a pliable material with shape-following capabilities, has been proposed to reduce the acoustic impedance mismatch caused by surface roughness when using solid materials. In this study, the feasibility of alginate gel as a plasma confinement layer and an appropriate process window for laser irradiation were investigated. The results of this study are then presented.
      Citation: Journal of Laser Applications
      PubDate: 2023-01-03T11:55:33Z
      DOI: 10.2351/7.0000753@jla.2022.ICALEO2022.issue-1
       
  • Influence of the process speed in laser melt injection for reinforcing
           skin-pass rolls

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      Authors: Philipp Warneke, Annika Bohlen, Thomas Seefeld
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Laser melt injection is a technology for producing metal matrix composite (MMC) layers on tools such as skin-pass rolls by injecting hard particles into a laser-induced weld pool. However, low process speeds prevent the application of laser melt injection on a large scale. To overcome this drawback, a new approach is presented: High-speed laser melt injection (HSLMI) is a promising method for generating highly wear-resistant MMC layers on tools with high productivity. For the first time, high process speeds of up to 100 m/min were reached with HSLMI of spherical fused tungsten carbide (SFTC) particles into the steel 1.2362 that is used for skin-pass rolls. In this paper, the influence of the process speed on the microstructure and on the wear resistance of the MMC layer is investigated. The microstructure of the steel matrix changes from a dendritic to a needle-shaped structure when process speeds of 60 m/min or higher are applied. Furthermore, the steel matrix often features cracks. The SFTC particles show a dissolution seam. It was found that both the crack susceptibility and the SFTC dissolution can be reduced significantly by increasing the process speed. The wear behavior of the MMC layers was studied in a pin-on-plate test. It was found that the SFTC reinforcement leads to a significant improvement in wear resistance over the nonreinforced steel substrate. The wear volume was reduced from 3.6 to 0.1 to 0.3 mm3 by an SFTC particle-reinforcement. Abrasion was the substantial wear mechanism.
      Citation: Journal of Laser Applications
      PubDate: 2022-12-27T11:47:43Z
      DOI: 10.2351/7.0000781@jla.2022.ICALEO2022.issue-1
       
  • Hand-Held Laser Welding of AISI301LN for components with aesthetic
           requirements: Toward the integration of machine and human intelligence

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      Authors: Leonardo Caprio, Giulio Borzoni, Barbara Previtali, Ali Gökhan Demir
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      The use of Hand-Held Laser Welding (HHLW) systems in the industry has been rapidly growing in recent years as an alternative solution to conventional manual arc-based welding systems. The decreasing cost of fiber laser sources and optics has been a driving factor in enabling a wider use of HHLW systems, beyond the established advantages of laser technology with respect to arc-based systems. While the industrial use of HHLW increases, the subject matter has been studied sparingly in the scientific literature. Due to the intrinsic flexibility of the technology, HHLW systems are highly appealing for joining relatively low thickness metals (≤2 mm) in autogenous configuration in sectors where production lots present low batch and high variability. However, a critical aspect of HHLW is correlated to the operator skill, where welding velocities can vary within and between the welds affecting both their aesthetic and mechanical properties. Hence, the development of combined digital and physical approaches to support manual operations may be highly beneficial. The current study presents an open laboratory HHLW system designed for process development purposes. Beyond conventional manual welding operations, the welding torch could be arranged in different configurations. The system could be combined with a linear axis (enabling welding with stable velocity and inclination) or manually with the aid of a newly developed roller device designed to provide constant speed and inclination. First, the process was benchmarked by joining in butt weld configuration 2 mm thick AISI301LN stainless steel sheets with the linear axis. Successively, four operators with different levels of training (rookie and professional) realized welds with the system in hand-held configuration and with the mechanical roller. The weld width variability was assessed as a direct indicator for aesthetic compliance while tensile tests were allowed to determine the mechanical properties of the joint obtained with different configurations.
      Citation: Journal of Laser Applications
      PubDate: 2022-12-22T11:20:09Z
      DOI: 10.2351/7.0000746@jla.2022.ICALEO2022.issue-1
       
  • Suppression of denudation zone using laser profile control in vacuum
           selective laser melting

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      Authors: Masahiro Ihama, Yuji Sato, Yuta Mizuguchi, Norio Yoshida, Sasitorn Srisawadi, Dhritti Tanprayoon, Tetsuo Suga, Masahiro Tsukamoto
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      A vacuum selective laser melting method with a beam profile control was developed to fabricate the high quality 3D object. To investigate the quality of 3D fabrication, the denudation zone (DZ) as a quality indicator was evaluated to make a single bead. The main challenge is to clarify the correlation between the DZ and beam profiles. The beam profiles, such as a Gaussian mode, a doughnut mode, and a flat-top mode, were formed in several modes, by a dioptric system with a beam shaper. A stainless steel 316L (SS316L) powder was irradiated in arbitrary pressure to form a single bead, and then the DZ was measured. As a result, it was found that the flat-top mode recorded the minimum value of the DZ under atmospheric pressure. Thus, the dynamics of the metal vapor while the laser irradiation were observed by the Schlieren imaging technique under atmospheric pressure. The average velocity of metal vapor with flat-top mode was the slowest, i.e., 0.199 m/s. It was found that the DZ becomes small depending on the dynamics of metal vapor. The ambient pressure was reduced to 300 Pa in order to reduce the gas movement, and the DZ with flat-top mode was improved to record a minimum value of 0.048 mm, 1/3 of the DZ at atmospheric pressure.
      Citation: Journal of Laser Applications
      PubDate: 2022-12-21T11:12:40Z
      DOI: 10.2351/7.0000749@jla.2022.ICALEO2022.issue-1
       
  • High-speed cleaving of glass and polymers using ultrafast fiber laser

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      Authors: Bogusz Stępak, Natalia Grudzień, Katarzyna Kowalska, Yuriy Stepanenko, Michał Nejbauer
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Glass cleaving by Bessel-like beams is one of the leading techniques providing high processing throughput and high edge quality. With the possibility to apply it to different transparent materials, this method has great potential in the high-volume production of flat panel displays, camera windows, medical devices, and others. The principle of glass cleaving is the controlled weakening of a hard transparent material by the induction of microcracks along a tight, elongated focus. These microcracks are oriented in a predefined, constant direction, limiting the flexibility of round shape fabrication. In contrast to dynamic beam manipulation techniques, the regime of direction-independent cutting was achieved through proper temporal pulse shaping. The setup does not consist of any active components in the beam path. The obtained quality and process speed are comparable with other, more complex laser cleaving techniques. Additionally, the successful cutting of polymers is presented, which are difficult to separate by the Bessel beam due to the limited possibility of microcrack generation.
      Citation: Journal of Laser Applications
      PubDate: 2022-12-21T11:12:39Z
      DOI: 10.2351/7.0000798@jla.2022.ICALEO2022.issue-1
       
  • New approach for multi-material design: Combination of laser beam and
           electromagnetic melt pool displacement by induced Lorentz forces

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      Authors: Jennifer Heßmann, Kai Hilgenberg
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Multimaterial structures are a promising solution to reduce vehicle weight and save fuel or electric energy in automotive design. However, thermal joining of steel and aluminum alloys is a challenge to overcome due to different material properties and the formation of brittle intermetallic phases. In this study, a new joining approach for producing overlap line-shaped joints is presented. The lower joining partner (EN AW 5754) is melted by a laser beam, and this melt is displaced into a line-shaped cavity of the upper joining partner (1.0330) by induced Lorentz forces. The melt solidifies in the cavity to a material and form-fitting joint. This approach needs no auxiliary joining elements or filler materials. Previous investigation to produce spot-shaped joints by using this approach showed that quality and reproducibility were limited by known melt pool dynamics of aluminum alloys (keyhole collapses). For line-shaped joints, the melt displacement can take place behind the keyhole. This allows the displacement process to be spatially uncoupled from the influence of keyhole collapses. The study shows that this improved the process stability and the quality of the joint. The created line-shaped joints were microstructurally characterized by transversal sections. Intermetallic phases were identified by electron backscatter diffraction and EDX analysis. The detected intermetallic phases consist of a 5–6 μm compact phase seam of Al5.6Fe2 and a needle-shaped phase of Al13Fe4. Tensile shear tests were carried out to quantify the load capacity. It was possible to create a joint with a load capacity of about 2 kN.
      Citation: Journal of Laser Applications
      PubDate: 2022-12-01T12:42:02Z
      DOI: 10.2351/7.0000763@jla.2022.ICALEO2022.issue-1
       
  • Interpreting acoustic emissions to determine the weld depth during laser
           beam welding

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      Authors: Lazar Tomcic, Armin Ederer, Sophie Grabmann, Michael Kick, Johannes Kriegler, Michael F. Zaeh
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      The interpretation of sensor system data is critical for monitoring industrial welding processes and providing reliable information about the condition of the weld seam. Previous investigations have shown that acoustic emissions of frequencies up to several kilohertz during laser beam welding are parameter-dependent and contain valuable information about the process. A microphone was employed to record the acoustic emissions produced when performing deep penetration laser beam welding of copper. Experiments were conducted in which the laser power and the feed rate were varied so as to obtain acoustic data comprising frequencies of up to 1 MHz. The signals were preprocessed and features were extracted using Fourier and wavelet analysis as well as speech analysis techniques. The relationship between the features extracted from the acoustic signal and the weld depth was modeled using Gaussian process regression. The results showed that acoustic emissions during laser beam welding can be used to predict the weld depth without having to rely on process parameters, i.e., the laser power and the feed rate. Overall, 17 features were extracted from acoustic signals, with the zero-crossing rate displaying the highest significance for determining the weld depth. These investigations open up new possibilities of robust quality assurance for laser beam welding applications based on acoustic emissions.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-28T03:53:03Z
      DOI: 10.2351/7.0000796@jla.2022.ICALEO2022.issue-1
       
  • Interpreting acoustic emissions to determine the weld depth during laser
           beam welding

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      Authors: Lazar Tomcic, Armin Ederer, Sophie Grabmann, Michael Kick, Johannes Kriegler, Michael F. Zaeh
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      The interpretation of sensor system data is critical for monitoring industrial welding processes and providing reliable information about the condition of the weld seam. Previous investigations have shown that acoustic emissions of frequencies up to several kilohertz during laser beam welding are parameter-dependent and contain valuable information about the process. A microphone was employed to record the acoustic emissions produced when performing deep penetration laser beam welding of copper. Experiments were conducted in which the laser power and the feed rate were varied so as to obtain acoustic data comprising frequencies of up to 1 MHz. The signals were preprocessed and features were extracted using Fourier and wavelet analysis as well as speech analysis techniques. The relationship between the features extracted from the acoustic signal and the weld depth was modeled using Gaussian process regression. The results showed that acoustic emissions during laser beam welding can be used to predict the weld depth without having to rely on process parameters, i.e., the laser power and the feed rate. Overall, 17 features were extracted from acoustic signals, with the zero-crossing rate displaying the highest significance for determining the weld depth. These investigations open up new possibilities of robust quality assurance for laser beam welding applications based on acoustic emissions.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-28T03:53:03Z
      DOI: 10.2351/7.0000796
       
  • Laser etching of 2D materials with single-layer precision up to ten layers

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      Authors: Yikun Yao, Xinjia Zhao, Xiangqian Tang, Jianmei Li, Xinyan Shan, Xinghua Lu
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Patterned 2D materials with layer-controlled thickness and precise lateral resolution are of great potential for many applications. Laser etching is a promising technique for large-scale patterning of 2D materials, but better control in film thickness is strongly desired. Here, we explore the dynamic characteristics in the laser etching process in which a local temperature lock phenomenon is observed as laser power reaches the etching threshold. A layer-by-layer etching strategy is then developed based on the temporal evolution of the local temperature as measured by in-situ Raman spectroscopy. Employing such a method in a typical layered material MoS2, we demonstrate thickness control up to ten layers in layer-by-layer laser etching. The local temperature lock during laser etching is explained by thermodynamic simulation of temperature distribution within the 2D material under laser illumination. The influence of substrate thermal conductivity on the thickness of the controlled laser etching has been revealed. The results are valuable for potential applications of 2D material devices built with complex layered structures.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-18T11:12:10Z
      DOI: 10.2351/7.0000848
       
  • Analysis of weld seam characteristic parameters identification for laser
           welding of dissimilar materials based on image segmentation

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      Authors: Yuewei Ai, Chang Lei, Pengcheng Yuan, Jian Cheng
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Welded joints of dissimilar materials increase the flexibility in design and manufacturing process greatly and, hence, have been widely used in aerospace, rail transportation, and other related industries. Due to the difference in physical and chemical properties of dissimilar materials, the formed weld during laser welding is different from that of the same material welding. The geometric morphology of the formed weld is an important factor affecting the welded joints performance. Therefore, an identification method of weld seam characteristic parameters is proposed in this paper for evaluating the welding quality by image segmentation in the laser welding of low carbon steel (Q235) and stainless steel (316L). The region of interest of the weld metallograph from experimental observation is defined, converted into grayscale image and then denoised by filter. The weld is segmented by the seeded region growing method with initial seed automatic selection. The weld seam characteristic parameters including the weld area, left weld width, right weld width, and weld penetration in the laser welding of dissimilar materials are identified based on the segmented image. The obtained results are validated by the experimental measurements of weld and good agreement between them has been found. The identified weld seam characteristic parameters are adopted for assessing weld fusion status, depth-to-width ratio, and symmetry quantitatively. The results indicate that the proposed method is reasonable and feasible for the weld quality evaluation to improve the laser welding quality of dissimilar materials in practical production.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-15T02:38:41Z
      DOI: 10.2351/7.0000734@jla.2022.ICALEO2022.issue-1
       
  • Analysis of weld seam characteristic parameters identification for laser
           welding of dissimilar materials based on image segmentation

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      Authors: Yuewei Ai, Chang Lei, Pengcheng Yuan, Jian Cheng
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Welded joints of dissimilar materials increase the flexibility in design and manufacturing process greatly and, hence, have been widely used in aerospace, rail transportation, and other related industries. Due to the difference in physical and chemical properties of dissimilar materials, the formed weld during laser welding is different from that of the same material welding. The geometric morphology of the formed weld is an important factor affecting the welded joints performance. Therefore, an identification method of weld seam characteristic parameters is proposed in this paper for evaluating the welding quality by image segmentation in the laser welding of low carbon steel (Q235) and stainless steel (316L). The region of interest of the weld metallograph from experimental observation is defined, converted into grayscale image and then denoised by filter. The weld is segmented by the seeded region growing method with initial seed automatic selection. The weld seam characteristic parameters including the weld area, left weld width, right weld width, and weld penetration in the laser welding of dissimilar materials are identified based on the segmented image. The obtained results are validated by the experimental measurements of weld and good agreement between them has been found. The identified weld seam characteristic parameters are adopted for assessing weld fusion status, depth-to-width ratio, and symmetry quantitatively. The results indicate that the proposed method is reasonable and feasible for the weld quality evaluation to improve the laser welding quality of dissimilar materials in practical production.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-15T02:38:41Z
      DOI: 10.2351/7.0000734
       
  • Online detection and source tracing of crop straw burning

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      Authors: Yanpeng Ye, Enlai Wan, Zhongmou Sun, Xinyang Zhang, Zhirong Zhang, Yuzhu Liu
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      The carbon dioxide, sulfur dioxide, and metal ions produced by straw burning can severely pollute the atmosphere; thus, online detection and traceability for straw burning is very important. However, to our best knowledge, there is no comprehensive system that can satisfy online detection, classification, and traceability due to the challenging online detection and traceability of straw burning. In this paper, a new system based on laser-induced breakdown spectroscopy (LIBS) and machine learning is developed, and this developed system is employed for the first time in online detection and traceability of straw combustion. Four different types of straw are selected and the straw burning smoke is monitored online using this developed system. The analysis of straw smoke spectra shows that there are Fe, Mn, and Ba heavy metal spectra in the smoke spectra. By comparing the smoke spectra of different types of straw, the characteristic spectral lines with large differences are selected and dimensionality reduction is performed by linear discriminant analysis algorithm. Then, combined with random forest to achieve classification, the final smoke recognition accuracy reaches 87.0%. Straw ash is then used as a reference analysis and the same operation is performed on it. Mn, Ba, and Li heavy metal spectral lines are found in the spectra of ash, and the final recognition accuracy is 92.6%. The innovative and developed system based on LIBS and machine learning is fast, online, and in situ and has far-reaching application prospects in the environment.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-11T12:16:59Z
      DOI: 10.2351/7.0000866
       
  • Characterization of the powder stream propagation behavior of a discrete
           coaxial nozzle for laser metal deposition

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      Authors: Annika Bohlen, Thomas Seefeld, Armin Haghshenas, Rodion Groll
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Laser metal deposition (LMD) is a blown powder process which can be used for the additive manufacturing of large components or the generation of functional geometries on semifinished parts. In LMD, it is crucial that both the laser intensity and powder mass flow distribution within the process zone are precisely matched for a welding bead of predefined shape and a consistent layer quality. While there are many common tools for the characterization of laser intensity distributions, a deep understanding of powder propagation behavior is still missing. Therefore, the present work thoroughly characterizes the powder stream propagation behavior of a discrete coaxial nozzle with three angle-adjustable powder jets. A line laser is used to selectively illuminate individual layers horizontally to the nozzle, and the intensity of the illuminated powder is recorded with the aid of a CCD camera. An envelope of the powder distribution is then plotted from the individual layers, analogous to a caustic of a laser beam, and, thus, the powder stream is evaluated. A novel method is presented to compensate for the radial asymmetry of a discrete powder nozzle in the evaluation, thus making it comparable with continuous nozzles. The method is validated by characterizing the powder stream propagation behavior of a three-jet discrete nozzle. Influencing factors on the powder stream are the protective gas flow, the powder mass flow, the angle of the powder nozzles, and the interaction of the three powder jets. The investigations are supplemented by a point-particle large-eddy simulation of the particle-laden flow.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-10T11:02:58Z
      DOI: 10.2351/7.0000775@jla.2022.ICALEO2022.issue-1
       
  • Characterization of the powder stream propagation behavior of a discrete
           coaxial nozzle for laser metal deposition

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      Authors: Annika Bohlen, Thomas Seefeld, Armin Haghshenas, Rodion Groll
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Laser metal deposition (LMD) is a blown powder process which can be used for the additive manufacturing of large components or the generation of functional geometries on semifinished parts. In LMD, it is crucial that both the laser intensity and powder mass flow distribution within the process zone are precisely matched for a welding bead of predefined shape and a consistent layer quality. While there are many common tools for the characterization of laser intensity distributions, a deep understanding of powder propagation behavior is still missing. Therefore, the present work thoroughly characterizes the powder stream propagation behavior of a discrete coaxial nozzle with three angle-adjustable powder jets. A line laser is used to selectively illuminate individual layers horizontally to the nozzle, and the intensity of the illuminated powder is recorded with the aid of a CCD camera. An envelope of the powder distribution is then plotted from the individual layers, analogous to a caustic of a laser beam, and, thus, the powder stream is evaluated. A novel method is presented to compensate for the radial asymmetry of a discrete powder nozzle in the evaluation, thus making it comparable with continuous nozzles. The method is validated by characterizing the powder stream propagation behavior of a three-jet discrete nozzle. Influencing factors on the powder stream are the protective gas flow, the powder mass flow, the angle of the powder nozzles, and the interaction of the three powder jets. The investigations are supplemented by a point-particle large-eddy simulation of the particle-laden flow.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-10T11:02:58Z
      DOI: 10.2351/7.0000775
       
  • Nanosecond laser high-precision fabrication of microgrooves on TC4
           surface: Morphology simulation and drag reduction performance of
           microgrooves

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      Authors: Xulin Wang, Jianwei Ma, Zhenyuan Jia, Chuanheng Gui, Xiaoqian Qi, Wei Liu
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      With the increasing global awareness of environmental protection, higher requirements are also placed on the fuel consumption rate of aircraft. Microgrooves can reduce the near-wall frictional resistance of aircraft to save fuel, which has become the focus of research in the aviation industry. To realize the low-cost and high-precision fabrication of microgrooves with drag reduction effect, an efficient and high-precision numerical simulation method for nanosecond pulsed laser etching TC4 titanium alloy is studied. A laser processing strategy is formulated. Furthermore, an efficient and high-precision computational fluid dynamics simulation method is studied to verify the drag reduction effect of microgrooves. The research results show that the size error of prepared microgrooves is less than 2%, and their drag reduction rate is as high as 9.6%, which verifies the validity and reliability of the research method in this paper. This work can guide the design of high-density functional microstructures and their high-efficiency and high-precision fabrication. The research results can provide technical parameters for aircraft drag reduction, which has essential engineering practical value.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-09T11:22:48Z
      DOI: 10.2351/7.0000745
       
  • Investigations of process by-products by means of Schlieren imaging during
           the powder bed fusion of metals using a laser beam

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      Authors: Siegfried Baehr, Lukas Melzig, Dominik Bauer, Thomas Ammann, Michael F. Zaeh
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      To produce geometrically complex parts with good mechanical properties, various industries increasingly apply the powder bed fusion of metals using a laser beam. Sufficient control of this laser-based additive manufacturing process is necessary to achieve a reliable development as well as reproducible part properties. Besides adjusting the standard process parameters, such as the laser power or the scanning speed, the process gas is an important parameter that influences the part characteristics. In addition to the inertization of the atmosphere, process by-products can be removed during the manufacturing with a constant gas flow across the build plate. Typically, argon or nitrogen is applied. This study investigated the effects of various argon-helium mixtures in comparison to pure argon gas on the heat balance of process by-products during the processing of a high-strength aluminum alloy by means of Schlieren imaging. The method enables visualizations of the process by-products and is further capable of studying evaporation phenomena. For this purpose, a Schlieren imaging setup was designed and installed in an AconityMINI machine. The experimental results were exploited to validate a simplified heat transfer model introduced in this work. The results indicate that the addition of helium to the process gas lowers the amount of fumes and incandescent spatters and thus could decrease evaporation. Also, it was found that the higher thermal conductivity of helium compared to argon leads to significantly higher cooling of process by-products.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-08T11:05:14Z
      DOI: 10.2351/7.0000808@jla.2022.ICALEO2022.issue-1
       
  • Toward defect-free components in laser metal deposition with coaxial wire
           feeding through closed-loop control of the melt pool temperature

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      Authors: Christian Bernauer, Avelino Zapata, Michael F. Zaeh
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Laser metal deposition (LMD) is an additive manufacturing process in which a metal powder or wire is added to a laser-induced molten pool. This localized deposition of material is used for the manufacturing, modification, and repair of a wide range of metal components. The use of wire as feedstock offers various advantages over the use of powder in terms of the contamination of the process environment, the material utilization rate, the ease of handling, and the material price. However, to achieve a stable process as well as defined geometrical and microstructural properties over many layers, precise knowledge on the effects of the input variables of the process on the resulting deposition characteristics is required. In this work, the melt pool temperature was used as an input parameter in LMD with coaxial wire feeding of stainless steel, which was made possible through the use of a dedicated closed-loop control system based on pyrometry. Initially, a temperature range was determined for different process conditions in which a stable deposition was obtained. Within this range, the cause-effect relationships between the melt pool temperature and the resulting geometry as well as the material properties were investigated for individual weld beads. It was found that the melt pool temperature is positively correlated with the width of the weld bead as well as the dilution. In addition, a dependence of the microhardness distribution over the cross section of a weld bead on the melt pool temperature was demonstrated, with an increased temperature negatively affecting the hardness.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-08T11:05:14Z
      DOI: 10.2351/7.0000773
       
  • Investigations of process by-products by means of Schlieren imaging during
           the powder bed fusion of metals using a laser beam

    • Free pre-print version: Loading...

      Authors: Siegfried Baehr, Lukas Melzig, Dominik Bauer, Thomas Ammann, Michael F. Zaeh
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      To produce geometrically complex parts with good mechanical properties, various industries increasingly apply the powder bed fusion of metals using a laser beam. Sufficient control of this laser-based additive manufacturing process is necessary to achieve a reliable development as well as reproducible part properties. Besides adjusting the standard process parameters, such as the laser power or the scanning speed, the process gas is an important parameter that influences the part characteristics. In addition to the inertization of the atmosphere, process by-products can be removed during the manufacturing with a constant gas flow across the build plate. Typically, argon or nitrogen is applied. This study investigated the effects of various argon-helium mixtures in comparison to pure argon gas on the heat balance of process by-products during the processing of a high-strength aluminum alloy by means of Schlieren imaging. The method enables visualizations of the process by-products and is further capable of studying evaporation phenomena. For this purpose, a Schlieren imaging setup was designed and installed in an AconityMINI machine. The experimental results were exploited to validate a simplified heat transfer model introduced in this work. The results indicate that the addition of helium to the process gas lowers the amount of fumes and incandescent spatters and thus could decrease evaporation. Also, it was found that the higher thermal conductivity of helium compared to argon leads to significantly higher cooling of process by-products.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-08T11:05:14Z
      DOI: 10.2351/7.0000808
       
  • Some observations on additive manufacturing

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      Authors: William Maxwell Steen
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Some comments on how Jyoti Mazumder started his laser career, how additive manufacturing (AM) started, and where it is going.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-08T11:05:12Z
      DOI: 10.2351/7.0000857
       
  • Visible laser attenuation characteristics using various polymeric
           nanocomposites

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      Authors: A. A. Qader
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      The attenuation characteristic of a semiconductor laser and green laser beam power with various polymer nanocomposites including PbS, TiO2, V2O5, and CuO are investigated experimentally. Various polymeric nanocomposites with the same concentration of different nanoparticles were prepared using a solution casting technique. The distance between the sample and detector as well as the sample and laser source, and the laser beam incident angle on the surface of the sample are found to be important factors to obtain robust measurements of the attenuation of the semiconductor and green laser beam power. The nanocomposite thin film doped with CuO has more laser beam power attenuation compared to the other prepared nanocomposite thin films. Polymer nanocomposites have various applications, e.g., cut-off laser filters, optical limiting laser, and laser beam power attenuation.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-07T11:35:04Z
      DOI: 10.2351/7.0000849
       
  • Additive manufactured of pure copper by blue diode laser induced selective
           laser melting

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      Authors: Keisuke Takenaka, Yuji Sato, Norio Yoshida, Mitunari Yoshitani, Manabu Heya, Masahiro Tsukamoto
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      The authors developed a galvano selective laser melting (SLM) system equipped with a blue diode laser and clarified that the volume of the fabricated pure copper part has an influence on the relative density. SLM is a 3D printing technology. Blue diode laser is anticipated to effectively form pure copper parts because the absorptance of 450 nm light on pure copper is higher than that of conventional 1 μm light. In our previous study, the authors reported a newly developed blue diode laser whose wavelength was 450 nm. Laser power and fiber core diameter were 200 W and 100 μm, respectively. In this study, the height and width of the copper part were changed, and their influence on the density of the parts was investigated. As a result, it was found that the larger the volume of the fabricated copper part, the lower the density. In addition, the diluted layer of pure copper and the stainless steel baseplate in the copper part were measured. By controlling the amount of laser heat input between the diluted layer and the undiluted layer, it was possible to form a pure copper part with a high density of 99.6%.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-04T10:29:02Z
      DOI: 10.2351/7.0000748@jla.2022.ICALEO2022.issue-1
       
  • Additive manufactured of pure copper by blue diode laser induced selective
           laser melting

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      Authors: Keisuke Takenaka, Yuji Sato, Norio Yoshida, Mitunari Yoshitani, Manabu Heya, Masahiro Tsukamoto
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      The authors developed a galvano selective laser melting (SLM) system equipped with a blue diode laser and clarified that the volume of the fabricated pure copper part has an influence on the relative density. SLM is a 3D printing technology. Blue diode laser is anticipated to effectively form pure copper parts because the absorptance of 450 nm light on pure copper is higher than that of conventional 1 μm light. In our previous study, the authors reported a newly developed blue diode laser whose wavelength was 450 nm. Laser power and fiber core diameter were 200 W and 100 μm, respectively. In this study, the height and width of the copper part were changed, and their influence on the density of the parts was investigated. As a result, it was found that the larger the volume of the fabricated copper part, the lower the density. In addition, the diluted layer of pure copper and the stainless steel baseplate in the copper part were measured. By controlling the amount of laser heat input between the diluted layer and the undiluted layer, it was possible to form a pure copper part with a high density of 99.6%.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-04T10:29:02Z
      DOI: 10.2351/7.0000748
       
  • Damage characteristics of continuous-wave laser ablation triple-junction
           solar cells

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      Authors: Wei Guo, Hao Chang, Cheng Hao Yu, Ming Yu Li
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      The effect of laser irradiation on triple-junction GaAs cells studied via cell irradiation experiments was carried out using a continuous-wave laser with a wavelength of 808 nm. In the experiments, a thermal imaging system was used to measure the surface temperature of the cell, and the surface morphology of the irradiated cell was analyzed. The output performance of the irradiated cell was measured by a source meter, and the results show that the change rate of cell surface temperature increased with increasing laser power density. When the cell damage intensifies, the output characteristics of the cell gradually decay, and the cell loses its photoelectric effect.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-04T10:29:01Z
      DOI: 10.2351/7.0000671
       
  • Influence of process parameters in blue laser welding of copper and
           aluminum thin sheets

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      Authors: Eriel Perez Zapico, Alessandro Ascari, Alessandro Fortunato, Erica Liverani, Vincenzo Dimatteo
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      The present study deals with using a blue laser to weld dissimilar thin sheets for applications in the e-mobility field. A 1.5 kW laser source, emitting at 450 nm, was exploited in the lap welding of 0.3 mm thick copper sheets over 0.4 mm thick aluminum 1050 ones. The relatively small spot (485 μm) exploited allowed smooth and narrow beads at a welding speed up to 120 mm/s, guaranteeing a good contact area suitable for achieving electrical and mechanical performance. Design of experiment approach was exploited to properly plan the number of trials constituting the experimental campaign. The welding results were characterized using metallographic analysis that pointed out the geometric features of the fused zone and the eventual presence of cracks and pores. The role of process parameters was also investigated in terms of influence on mechanical and electrical performances. The specimens were tested, in fact, through shear tensile and electrical resistance tests. Hence, assessing the general applicability of that kind of welding on a real potential application was possible.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-04T10:28:59Z
      DOI: 10.2351/7.0000836@jla.2022.ICALEO2022.issue-1
       
  • Influence of process parameters in blue laser welding of copper and
           aluminum thin sheets

    • Free pre-print version: Loading...

      Authors: Eriel Perez Zapico, Alessandro Ascari, Alessandro Fortunato, Erica Liverani, Vincenzo Dimatteo
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      The present study deals with using a blue laser to weld dissimilar thin sheets for applications in the e-mobility field. A 1.5 kW laser source, emitting at 450 nm, was exploited in the lap welding of 0.3 mm thick copper sheets over 0.4 mm thick aluminum 1050 ones. The relatively small spot (485 μm) exploited allowed smooth and narrow beads at a welding speed up to 120 mm/s, guaranteeing a good contact area suitable for achieving electrical and mechanical performance. Design of experiment approach was exploited to properly plan the number of trials constituting the experimental campaign. The welding results were characterized using metallographic analysis that pointed out the geometric features of the fused zone and the eventual presence of cracks and pores. The role of process parameters was also investigated in terms of influence on mechanical and electrical performances. The specimens were tested, in fact, through shear tensile and electrical resistance tests. Hence, assessing the general applicability of that kind of welding on a real potential application was possible.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-04T10:28:59Z
      DOI: 10.2351/7.0000836
       
  • Combination of Eulerian and ray-tracing approaches for copper laser
           welding simulation

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      Authors: Julien Daligault, Morgan Dal, Cyril Gorny, Frédéric Coste, Rémy Fabbro
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Laser welding of pure copper and its alloys is a challenging process with a growing industrial interest due to the latest development in the field of electric mobility. The difficulties are mainly related to the material's high thermal conductivity and a poor absorptivity of few percent at the classical IR laser (YAG). It is also well known that such a configuration can lead to the formation of undesirable defects, such as pores or spatters as a consequence of melt pool instabilities. It has been observed experimentally that the usage of a laser at both high speed and high power tends to limit those instabilities. Although this positive influence has already been observed for equivalent materials, a physical explanation is not yet available. In this perspective, a multiphysical simulation of the process at the melt pool scale is currently being developed by using comsol Multiphysics® software. The latter includes an Eulerian interface tracking method for the liquid-gas interface (phase field) and a ray-tracing description of the laser beam to take into account the well-known beam trapping effect under a keyhole regime. For the sake of time computation, the numerical model is first developed in an axisymmetric coordinate system (r,z) to be representative of a laser spot welding process and to validate the numerical coupling methodology. The model will then be extended to a 3D welding case and used as a predictive tool to make appropriate choices on welding parameters to obtain good quality welds (stable melt pool, low porosity rate, etc.).
      Citation: Journal of Laser Applications
      PubDate: 2022-11-04T10:28:58Z
      DOI: 10.2351/7.0000786@jla.2022.ICALEO2022.issue-1
       
  • Combination of Eulerian and ray-tracing approaches for copper laser
           welding simulation

    • Free pre-print version: Loading...

      Authors: Julien Daligault, Morgan Dal, Cyril Gorny, Frédéric Coste, Rémy Fabbro
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Laser welding of pure copper and its alloys is a challenging process with a growing industrial interest due to the latest development in the field of electric mobility. The difficulties are mainly related to the material's high thermal conductivity and a poor absorptivity of few percent at the classical IR laser (YAG). It is also well known that such a configuration can lead to the formation of undesirable defects, such as pores or spatters as a consequence of melt pool instabilities. It has been observed experimentally that the usage of a laser at both high speed and high power tends to limit those instabilities. Although this positive influence has already been observed for equivalent materials, a physical explanation is not yet available. In this perspective, a multiphysical simulation of the process at the melt pool scale is currently being developed by using comsol Multiphysics® software. The latter includes an Eulerian interface tracking method for the liquid-gas interface (phase field) and a ray-tracing description of the laser beam to take into account the well-known beam trapping effect under a keyhole regime. For the sake of time computation, the numerical model is first developed in an axisymmetric coordinate system (r,z) to be representative of a laser spot welding process and to validate the numerical coupling methodology. The model will then be extended to a 3D welding case and used as a predictive tool to make appropriate choices on welding parameters to obtain good quality welds (stable melt pool, low porosity rate, etc.).
      Citation: Journal of Laser Applications
      PubDate: 2022-11-04T10:28:58Z
      DOI: 10.2351/7.0000786
       
  • Using photodiodes and supervised machine learning for automatic
           classification of weld defects in laser welding of thin foils
           copper-to-steel battery tabs

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      Authors: Giovanni Chianese, Pasquale Franciosa, Tianzhu Sun, Dariusz Ceglarek, Stanislao Patalano
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      This paper has been designed to study whether photodiodes and supervised machine learning (ML) algorithms are sufficient to automatically classify weld defects caused by simultaneous variation of the part-to-part gap and laser power during remote laser welding (RLW) of thin foils, with applications in battery tabs. Photodiodes are used as the primary source of data and are collected in real-time during RLW of copper-to-steel thin foils in the lap joint. Experiments are carried out by the nLight Compact 3 kW fiber laser integrated with the Scout-200 2D scanner. The paper reviews and compares seven supervised ML algorithms (namely, k-nearest neighbors, decision tree, random forest, Naïve–Bayes, support vector machine, discriminant analysis, and discrete wavelet transform combined with the neural network) for automatic classification of weld defects. Up to 97% classification rate is obtained for scenarios with simultaneous variations of weld penetration depth and part-to-part gap. The main causes of misclassification are imputed to the interaction between welding parameters (part-to-part gap and laser power) and process instability at high part-to-part gap (high variation in the process not captured by the photodiodes). Arising opportunities for further development based on sensor fusion, integration with real-time multiphysical simulation, and semi-supervised ML are discussed throughout the paper.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-04T10:28:57Z
      DOI: 10.2351/7.0000800@jla.2022.ICALEO2022.issue-1
       
  • Using photodiodes and supervised machine learning for automatic
           classification of weld defects in laser welding of thin foils
           copper-to-steel battery tabs

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      Authors: Giovanni Chianese, Pasquale Franciosa, Tianzhu Sun, Dariusz Ceglarek, Stanislao Patalano
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      This paper has been designed to study whether photodiodes and supervised machine learning (ML) algorithms are sufficient to automatically classify weld defects caused by simultaneous variation of the part-to-part gap and laser power during remote laser welding (RLW) of thin foils, with applications in battery tabs. Photodiodes are used as the primary source of data and are collected in real-time during RLW of copper-to-steel thin foils in the lap joint. Experiments are carried out by the nLight Compact 3 kW fiber laser integrated with the Scout-200 2D scanner. The paper reviews and compares seven supervised ML algorithms (namely, k-nearest neighbors, decision tree, random forest, Naïve–Bayes, support vector machine, discriminant analysis, and discrete wavelet transform combined with the neural network) for automatic classification of weld defects. Up to 97% classification rate is obtained for scenarios with simultaneous variations of weld penetration depth and part-to-part gap. The main causes of misclassification are imputed to the interaction between welding parameters (part-to-part gap and laser power) and process instability at high part-to-part gap (high variation in the process not captured by the photodiodes). Arising opportunities for further development based on sensor fusion, integration with real-time multiphysical simulation, and semi-supervised ML are discussed throughout the paper.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-04T10:28:57Z
      DOI: 10.2351/7.0000800
       
  • Study on microstructures and mechanical performance of laser transmission
           welding of poly-ether-ether-ketone (PEEK) and carbon fiber reinforced PEEK
           (CFR-PEEK)

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      Authors: Yuxuan Liu, Wuxiang Zhang, Junyan Liu, Yingchun Guan, Xilun Ding
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      The reliable assembly of poly-ether-ether-ketone (PEEK) and carbon fiber-reinforced PEEK (CFR-PEEK) is crucial to effective load transfer within lightweight and high-stiffness structures, which are commonly demanded in aeronautical, automobile, and medical industries. In this work, laser transmission welding of PEEK and CFR-PEEK has been performed by using a 1070 nm Nd:YAG fiber laser. The effects of process parameters including laser power, laser scanning speed, and clamping pressure on joining quality have been investigated via mechanical, morphological, and thermal characterization. Results show that strong bonds have been formed by entanglements of polymer chains at the joining interface and the mechanical embedment between carbon fibers and PEEK. The formation mechanisms of bubble defects have been classified into three types. One of them was eliminated by scanning the joints twice, which significantly improved joints' mechanical performance and hermeticity with the maximum joining strength reaching 11.6 MPa. Also, a comparative study between PEEK/PEEK and PEEK/CFR-PEEK joints shows that the existence of carbon fibers within the CFR-PEEK significantly increased joints' decomposition threshold, joining region, and strength due to their great thermal conductivity. Besides, the influence of the welding process on the crystallinity of PEEK was analyzed, which was then improved from 11.7% to 34.1% through annealing.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-04T10:28:56Z
      DOI: 10.2351/7.0000823
       
  • Electrochemical behavior of laser powder bed fusion fabricated 316L
           stainless steel in a nitric acid solution

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      Authors: Sahar Soleimani, Mahdi Yeganeh, Seyed Mohammad Lari Baghal
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      The purpose of this work is to study the microstructure and electrochemical performance of 316L stainless steel fabricated by the laser powder bed fusion (LPBF) and commercial rolling (Roll) in 0.5M nitric acid solution. The LPBF-manufactured 316L stainless steel had a higher corrosion resistance in nitric acid solution than the Roll steel. According to the electrochemical studies, the impedance modulus ( Z 10mHz) of the LPBF alloy was twice as great as its roll counterpart after 1 day of immersion in nitric acid solution and about 1 kΩ cm2. Moreover, the potentiodynamic polarization test showed that the LPBF alloy had one-fourth the ipass value as the Roll sample, suggesting that the passive layer on the surface of additive manufactured samples is more stable and enriched with Cr2O3. Additionally, the LPBF microstructure did not contain harmful phases like TiN, which can adversely affect the protection performance of the passive layer.
      Citation: Journal of Laser Applications
      PubDate: 2022-11-01T11:16:25Z
      DOI: 10.2351/7.0000824
       
  • Deposition strategies for generating cuboid volumes using extreme
           high-speed directed energy deposition

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      Authors: Jonathan Schaible, David Hausch, Thomas Schopphoven, Constantin Häfner
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Extreme high-speed directed energy deposition (EHLA) is a variant of directed energy deposition (DED-LB) developed at Fraunhofer ILT in cooperation with RWTH Aachen University. Because of a powder gas jet setup that is aimed at melting particles in the laser beam before they enter the melting pool, high process speeds of up to several hundred meters per minute and a layer thickness as thin as 25 μm can be achieved. EHLA is generally applied for rotationally symmetric coating applications. In previous experiments on a prototype machine of ponticon GmbH, EHLA was used for building up dense volumes, thus qualifying its use for additive manufacturing, now termed EHLA 3D. In this work, using iron-base alloy 1.4404 and a process speed of 40 m/min, cubic volumes are produced with EHLA 3D. Different deposition strategies commonly used in DED-LB are tested for their transferability to EHLA 3D. The results of different deposition strategies achieving the best near net shape geometry are shown in comparison to DED-LB. Furthermore, the influence of the deposition strategy and used technology on thermal management and microstructure are investigated. The best near net shape is achieved in this comparison using a contour-hatch strategy with 1.5 contours per layer and a 90° rotation of the hatch, both for EHLA and DED-LB. The microstructure of EHLA 3D built cubes is more similar to a typical laser powder bed fusion microstructure than to a typical DED-LB microstructure with respect to grain size and structure.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-31T09:35:04Z
      DOI: 10.2351/7.0000770
       
  • Deep learning-based penetration depth prediction in Al/Cu laser welding
           using spectrometer signal and CCD image

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      Authors: Sanghoon Kang, Minjung Kang, Yong Hoon Jang, Cheolhee Kim
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      In the laser welding of thin Al/Cu sheets, proper penetration depth and wide interface bead width ensure stable joint strength and low electrical conductance. In this study, we proposed deep learning models to predict the penetration depth. The inputs for the prediction models were 500 Hz-sampled low-cost charge-coupled device (CCD) camera images and 100 Hz-sampled spectral signals. The output was the penetration depth estimated from the keyhole depth measured coaxially using optical coherence tomography. A unisensor model using a CCD image and a multisensor model using a CCD image and the spectrometer signal were proposed in this study. The input and output of the data points were resampled at 100 and 500 Hz, respectively. The 500 Hz models showed better performance than the 100 Hz models, and the multisensor models more accurately predicted the penetration depth than the unisensor models. The most accurate model had a coefficient of determination (R2) of 0.999985 and mean absolute error of 0.02035 mm in the model test. It was demonstrated that low-cost sensors can successfully predict the penetration depth during Al/Cu laser welding.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-31T09:35:02Z
      DOI: 10.2351/7.0000767@jla.2022.ICALEO2022.issue-1
       
  • Deep learning-based penetration depth prediction in Al/Cu laser welding
           using spectrometer signal and CCD image

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      Authors: Sanghoon Kang, Minjung Kang, Yong Hoon Jang, Cheolhee Kim
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      In the laser welding of thin Al/Cu sheets, proper penetration depth and wide interface bead width ensure stable joint strength and low electrical conductance. In this study, we proposed deep learning models to predict the penetration depth. The inputs for the prediction models were 500 Hz-sampled low-cost charge-coupled device (CCD) camera images and 100 Hz-sampled spectral signals. The output was the penetration depth estimated from the keyhole depth measured coaxially using optical coherence tomography. A unisensor model using a CCD image and a multisensor model using a CCD image and the spectrometer signal were proposed in this study. The input and output of the data points were resampled at 100 and 500 Hz, respectively. The 500 Hz models showed better performance than the 100 Hz models, and the multisensor models more accurately predicted the penetration depth than the unisensor models. The most accurate model had a coefficient of determination (R2) of 0.999985 and mean absolute error of 0.02035 mm in the model test. It was demonstrated that low-cost sensors can successfully predict the penetration depth during Al/Cu laser welding.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-31T09:35:02Z
      DOI: 10.2351/7.0000767
       
  • Expanding the capabilities of laser-based powder bed fusion of polymers
           through the use of electrophotographic powder application

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      Authors: Sebastian-Paul Kopp, Vadim Medvedev, Thomas Frick, Stephan Roth
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Generating multimaterial parts, reaching higher efficiency in powder consumption, and decoupling of powder application behavior from powder properties such as powder flowability are key aspects for using electrophotographic powder application (EPA) in laser-based powder bed fusion of polymers (PBF-LB/P). Moreover, EPA allows the layer thickness to be reduced from around 100–150 μm, depending on respective particle size distribution, in the case of conventional doctor blade or roller-based powder application methods to the diameter of the applied polymer particles (typically between 50 and 130 μm). This can have positive effects on the interlayer connection and, therefore, the mechanical properties of the additively manufactured part because less powder volume has to be fused with the already generated underlying part. Moreover, due to the above-mentioned independence of EPA from powder flowability, the addition of flow aids, such as nano silica, can be reduced to a minimum or even avoided completely. This is the first comprehensive study on resulting properties of parts generated by PBF-LB/P using EPA taking into account both the reduction in layer thickness and reduced addition of flow aids. In addition to improving mechanical properties of generated parts, the independence of powder flowability, in particular, offers the possibility of qualifying currently unsuitable materials for PBF-LB/P. For this purpose, besides widely employed polyamide 12 (PA12), a polypropylene (PP) powder is used that is very difficult to process in conventional PBF-LB/P and can only be applied there with the help of flow aids.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-27T09:54:42Z
      DOI: 10.2351/7.0000774@jla.2022.ICALEO2022.issue-1
       
  • Behavior of melt flow and porosity formation in laser welding of steel to
           aluminum with cold-sprayed steel interlayer

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      Authors: Kyohei Maeda, Yuji Sato, Keisuke Takenaka, Shumpei Fujio, Reiichi Suzuki, Tetsuo Suga, Masahiro Tsukamoto
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      A multimaterial car body design, using light materials in combination with steel, has become widespread in recent years in order to reduce a vehicle's weight. The joining of dissimilar materials is one of the most critical issues in this area. In our previous research, we reported on a new dissimilar laser lap joining method, using a cold-spray process. In that procedure, a steel coating was first sprayed onto an aluminum surface, after which a steel sheet, together with the coating, was laser welded. However, it was found that porosity occurred in the weld metal due to melting of the coating. In this study, we investigated the effects of welding parameters on porosity formation in this joining process as well as the behavior patterns of the flow and bubbles in a molten pool. The porosity increased as the laser input energy decreased. It was also discovered that the porosity could be reduced drastically by the melting of the aluminum substrate, together with the steel sheet and coating, even at lower input energy. Electron probe microanalyzer results showed that both the solidification rate, related to the input energy, and aluminum's melting were strongly associated with the generation of flow from the bottom to the surface of the molten pool. This was captured by means of an x-ray in situ observation, using tungsten tracers, behind the keyhole. The bubbles, moving upward and reaching the surface of the pool, were also observed there in the welding conditions, where only a little porosity occurred. These results demonstrated that this flow helped the bubbles move up and go outside the molten pool and, hence, prevented porosity formation.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-27T09:54:42Z
      DOI: 10.2351/7.0000754@jla.2022.ICALEO2022.issue-1
       
  • Expanding the capabilities of laser-based powder bed fusion of polymers
           through the use of electrophotographic powder application

    • Free pre-print version: Loading...

      Authors: Sebastian-Paul Kopp, Vadim Medvedev, Thomas Frick, Stephan Roth
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Generating multimaterial parts, reaching higher efficiency in powder consumption, and decoupling of powder application behavior from powder properties such as powder flowability are key aspects for using electrophotographic powder application (EPA) in laser-based powder bed fusion of polymers (PBF-LB/P). Moreover, EPA allows the layer thickness to be reduced from around 100–150 μm, depending on respective particle size distribution, in the case of conventional doctor blade or roller-based powder application methods to the diameter of the applied polymer particles (typically between 50 and 130 μm). This can have positive effects on the interlayer connection and, therefore, the mechanical properties of the additively manufactured part because less powder volume has to be fused with the already generated underlying part. Moreover, due to the above-mentioned independence of EPA from powder flowability, the addition of flow aids, such as nano silica, can be reduced to a minimum or even avoided completely. This is the first comprehensive study on resulting properties of parts generated by PBF-LB/P using EPA taking into account both the reduction in layer thickness and reduced addition of flow aids. In addition to improving mechanical properties of generated parts, the independence of powder flowability, in particular, offers the possibility of qualifying currently unsuitable materials for PBF-LB/P. For this purpose, besides widely employed polyamide 12 (PA12), a polypropylene (PP) powder is used that is very difficult to process in conventional PBF-LB/P and can only be applied there with the help of flow aids.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-27T09:54:42Z
      DOI: 10.2351/7.0000774
       
  • Behavior of melt flow and porosity formation in laser welding of steel to
           aluminum with cold-sprayed steel interlayer

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      Authors: Kyohei Maeda, Yuji Sato, Keisuke Takenaka, Shumpei Fujio, Reiichi Suzuki, Tetsuo Suga, Masahiro Tsukamoto
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      A multimaterial car body design, using light materials in combination with steel, has become widespread in recent years in order to reduce a vehicle's weight. The joining of dissimilar materials is one of the most critical issues in this area. In our previous research, we reported on a new dissimilar laser lap joining method, using a cold-spray process. In that procedure, a steel coating was first sprayed onto an aluminum surface, after which a steel sheet, together with the coating, was laser welded. However, it was found that porosity occurred in the weld metal due to melting of the coating. In this study, we investigated the effects of welding parameters on porosity formation in this joining process as well as the behavior patterns of the flow and bubbles in a molten pool. The porosity increased as the laser input energy decreased. It was also discovered that the porosity could be reduced drastically by the melting of the aluminum substrate, together with the steel sheet and coating, even at lower input energy. Electron probe microanalyzer results showed that both the solidification rate, related to the input energy, and aluminum's melting were strongly associated with the generation of flow from the bottom to the surface of the molten pool. This was captured by means of an x-ray in situ observation, using tungsten tracers, behind the keyhole. The bubbles, moving upward and reaching the surface of the pool, were also observed there in the welding conditions, where only a little porosity occurred. These results demonstrated that this flow helped the bubbles move up and go outside the molten pool and, hence, prevented porosity formation.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-27T09:54:42Z
      DOI: 10.2351/7.0000754
       
  • Investigations on laser beam welding of thick steel plates using a
           high-power diode laser beam source

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      Authors: Oliver Seffer, Sarah Nothdurft, Alexander Hilck, Michael Hustedt, Jörg Hermsdorf, Stefan Kaierle
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      For joining of thick steel plates, commonly arc welding and partially laser-arc hybrid welding are used. Both techniques offer individual disadvantages besides their advantages. Arc welding processes are typically characterized by low welding speeds, high heat inputs, high distortions, and high filler material consumptions. Laser-arc hybrid welding processes are limited to weldable material thicknesses regarding weld imperfections as well as the ability to bridge gaps. Therefore, the investigations presented are about high-power diode laser beam welding of steel with plate thicknesses t between 15 and 30 mm using output powers PL of up to 60 kW and welding speeds v between 0.5 and 1.0 m/min. The welding experiments contain butt welds by using weld backing materials. Among other things, influence of energy per unit length (laser beam power PL, welding speed v), focal position z, and plate thickness t are analyzed for different reproducible processes. The evaluation of weld seams includes visual inspection, metallographic analyses regarding geometric characteristics, and weld imperfections as well as radiographic inspections. The investigations show achievable qualities and characteristics of the weld seams depending on the plate thickness t by using high-power diode laser beam sources. Weld seams on plates with thicknesses t of 15 and 22 mm were welded without cracks or other weld imperfections according to metallographic analyses and radiographic testing by using a laser beam power PL of 40 kW and the suitable process parameters developed. As a result, relatively high plate thicknesses t can be welded in a single layer with high quality as well as comparatively high welding speed v.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-27T09:54:41Z
      DOI: 10.2351/7.0000783@jla.2022.ICALEO2022.issue-1
       
  • Investigations on laser beam welding of thick steel plates using a
           high-power diode laser beam source

    • Free pre-print version: Loading...

      Authors: Oliver Seffer, Sarah Nothdurft, Alexander Hilck, Michael Hustedt, Jörg Hermsdorf, Stefan Kaierle
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      For joining of thick steel plates, commonly arc welding and partially laser-arc hybrid welding are used. Both techniques offer individual disadvantages besides their advantages. Arc welding processes are typically characterized by low welding speeds, high heat inputs, high distortions, and high filler material consumptions. Laser-arc hybrid welding processes are limited to weldable material thicknesses regarding weld imperfections as well as the ability to bridge gaps. Therefore, the investigations presented are about high-power diode laser beam welding of steel with plate thicknesses t between 15 and 30 mm using output powers PL of up to 60 kW and welding speeds v between 0.5 and 1.0 m/min. The welding experiments contain butt welds by using weld backing materials. Among other things, influence of energy per unit length (laser beam power PL, welding speed v), focal position z, and plate thickness t are analyzed for different reproducible processes. The evaluation of weld seams includes visual inspection, metallographic analyses regarding geometric characteristics, and weld imperfections as well as radiographic inspections. The investigations show achievable qualities and characteristics of the weld seams depending on the plate thickness t by using high-power diode laser beam sources. Weld seams on plates with thicknesses t of 15 and 22 mm were welded without cracks or other weld imperfections according to metallographic analyses and radiographic testing by using a laser beam power PL of 40 kW and the suitable process parameters developed. As a result, relatively high plate thicknesses t can be welded in a single layer with high quality as well as comparatively high welding speed v.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-27T09:54:41Z
      DOI: 10.2351/7.0000783
       
  • Laser microdrilling of CFRP with a nanosecond-pulsed high-power laser

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      Authors: R. Staehr, V. Wippo, P. Jaeschke, S. Kaierle
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      The global demand for air travel and air transport is expected to further increase in the next couple of years, and so the environmental protection will also increasingly come into focus again. In the aviation sector, this means not only saving fuel and reducing emissions but also reducing the noise pollution caused by aircrafts. For this purpose, sound-absorbing acoustic liners are used, which consist of a sandwich structure with one perforated skin layer. To reduce weight, these outer layers are often made of carbon fiber-reinforced plastic (CFRP). For manufacturing these CFRP skin layers, laser drilling offers specific benefits, but when it comes to industrial applications, further process improvements are necessary. Although laser microdrilling is a well-known process in laser materials’ processing, it has not yet been sufficiently investigated for the processing of carbon fiber-reinforced plastics. This study investigates the quality and efficiency of laser microdrilling with a 1.5 kW nanosecond-pulsed high-power laser for percussion drilling and helical drilling of thin CFRP laminates. The efficiency was evaluated in terms of drilling depth, the amount of energy required to remove a specific volume of material, and the time required to remove a specific volume of the material. The quality evaluation focused on the heat-affected zone and the hole taper. The efficiency and quality results were set in relation to higher-level parameters such as energy fluence in the laser spot, pulse overlap, or total energy applied. This facilitates future transferability to similar laser processes that may use laser machines and system technology with deviating specifications.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-25T11:47:22Z
      DOI: 10.2351/7.0000809@jla.2022.ICALEO2022.issue-1
       
  • Laser microdrilling of CFRP with a nanosecond-pulsed high-power laser

    • Free pre-print version: Loading...

      Authors: R. Staehr, V. Wippo, P. Jaeschke, S. Kaierle
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      The global demand for air travel and air transport is expected to further increase in the next couple of years, and so the environmental protection will also increasingly come into focus again. In the aviation sector, this means not only saving fuel and reducing emissions but also reducing the noise pollution caused by aircrafts. For this purpose, sound-absorbing acoustic liners are used, which consist of a sandwich structure with one perforated skin layer. To reduce weight, these outer layers are often made of carbon fiber-reinforced plastic (CFRP). For manufacturing these CFRP skin layers, laser drilling offers specific benefits, but when it comes to industrial applications, further process improvements are necessary. Although laser microdrilling is a well-known process in laser materials’ processing, it has not yet been sufficiently investigated for the processing of carbon fiber-reinforced plastics. This study investigates the quality and efficiency of laser microdrilling with a 1.5 kW nanosecond-pulsed high-power laser for percussion drilling and helical drilling of thin CFRP laminates. The efficiency was evaluated in terms of drilling depth, the amount of energy required to remove a specific volume of material, and the time required to remove a specific volume of the material. The quality evaluation focused on the heat-affected zone and the hole taper. The efficiency and quality results were set in relation to higher-level parameters such as energy fluence in the laser spot, pulse overlap, or total energy applied. This facilitates future transferability to similar laser processes that may use laser machines and system technology with deviating specifications.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-25T11:47:22Z
      DOI: 10.2351/7.0000809
       
  • Laser specific energy consumption: How do laser systems compare to other
           manufacturing processes'

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      Authors: Lewis C. R. Jones, Nicholas Goffin, Jinglei Ouyang, Nazanin Mirhossein, Jiaji Xiong, Yufeng Li, Lin Li, John Tyrer, Zhu Liu, Elliot Woolley, Yan He, Gaoyang Mi, Paul Mativenga
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Laser material interactions are routinely praised for their selective processing and high processing rates. However, this does not guarantee that the total manufacturing system has a low energy intensity compared to conventional manufacturing processes. This paper presents the results of a collaborative UK and China research project to improve the comprehension of the total energy consumption and carbon emissions for laser-based manufacturing. A range of individual laser cutting, welding, and cleaning processes were studied to assess their energy efficiency, including the laser and its ancillary subsystems (e.g., cooling and extraction). The project developed a systematic analysis method, adapted from BS ISO 14955-1:2017, which incorporated time and subsystem level studies to quantify all energy consumption components of a laser system. Previous research has identified that the laser system's most significant contributor to the total energy consumption are the auxiliary or supporting subsystems, not the laser emission. This identified that using only the absorbed radiation to evaluate manufacturing efficiency is misleading. All the processes evaluated followed a negative correlation between processing rate (kg/h) and specific energy consumption (J/kg). The new data conclude that laser processes have a relatively high energy intensity compared to conventional manufacturing alternatives. The results can be used to identify where the most significant improvements to individual laser systems can be made. The comprehensive comparison of processes allows manufacturers to select processes to improve environmental impact.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-25T11:47:21Z
      DOI: 10.2351/7.0000790@jla.2022.ICALEO2022.issue-1
       
  • Selective laser crystallization and amorphization in polymer fibers

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      Authors: Francesca Wheeler, John R. Tyrer, Lewis C. R. Jones
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Textile finishing is a huge industry for modification of textile surface properties to align with the desired end use spanning medical, engineering, and apparel applications. Laser-induced polymer morphology modification has been studied by researchers, with evidence suggesting a correlation between laser fluence and crystallinity. However, a lack of data has resulted in the mechanism for change remaining unknown. This paper aims to identify the mechanism of initial Young’s modulus control in polyethylene terephthalate (PET) monofilament yarn and explain the relationship between Young’s modulus and the degree of crystallinity using Takayanagi’s model. PET monofilament yarns were treated using a CO2 infrared laser at a 10.6 μm wavelength at fluences up to 0.086 J/mm2. Young’s modulus data obtained from stress-strain curves at 0.2% strain and fraction crystallinities obtained from differential scanning calorimetry were compared with Takayanagi’s series model. Laser surface treatment within a fluence range up to 0.087 J/mm2 on PET resulted in stable Young’s modulus values. A 3.5% reduction in Young’s modulus of PET was seen with a 6.1% reduction in crystallinity, which was in good agreement with Takayanagi’s series model. Lasers offer rapid material processing capable of increasing or decreasing fractional crystallinity selectively along the fiber where desired. Selective amorphization increases chemical absorption, allowing increased surface finishing uptake at milder processing conditions, whereas increasing fractional crystallinity imparts fiber strength. The relationship between fiber crystallinity and Young’s modulus for PET can be described by Takayanagi’s model, allowing a prediction of material properties, which can be extended from fibers to all thin-film polymers.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-25T11:47:21Z
      DOI: 10.2351/7.0000736@jla.2022.ICALEO2022.issue-1
       
  • Laser specific energy consumption: How do laser systems compare to other
           manufacturing processes'

    • Free pre-print version: Loading...

      Authors: Lewis C. R. Jones, Nicholas Goffin, Jinglei Ouyang, Nazanin Mirhossein, Jiaji Xiong, Yufeng Li, Lin Li, John Tyrer, Zhu Liu, Elliot Woolley, Yan He, Gaoyang Mi, Paul Mativenga
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Laser material interactions are routinely praised for their selective processing and high processing rates. However, this does not guarantee that the total manufacturing system has a low energy intensity compared to conventional manufacturing processes. This paper presents the results of a collaborative UK and China research project to improve the comprehension of the total energy consumption and carbon emissions for laser-based manufacturing. A range of individual laser cutting, welding, and cleaning processes were studied to assess their energy efficiency, including the laser and its ancillary subsystems (e.g., cooling and extraction). The project developed a systematic analysis method, adapted from BS ISO 14955-1:2017, which incorporated time and subsystem level studies to quantify all energy consumption components of a laser system. Previous research has identified that the laser system's most significant contributor to the total energy consumption are the auxiliary or supporting subsystems, not the laser emission. This identified that using only the absorbed radiation to evaluate manufacturing efficiency is misleading. All the processes evaluated followed a negative correlation between processing rate (kg/h) and specific energy consumption (J/kg). The new data conclude that laser processes have a relatively high energy intensity compared to conventional manufacturing alternatives. The results can be used to identify where the most significant improvements to individual laser systems can be made. The comprehensive comparison of processes allows manufacturers to select processes to improve environmental impact.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-25T11:47:21Z
      DOI: 10.2351/7.0000790
       
  • Selective laser crystallization and amorphization in polymer fibers

    • Free pre-print version: Loading...

      Authors: Francesca Wheeler, John R. Tyrer, Lewis C. R. Jones
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Textile finishing is a huge industry for modification of textile surface properties to align with the desired end use spanning medical, engineering, and apparel applications. Laser-induced polymer morphology modification has been studied by researchers, with evidence suggesting a correlation between laser fluence and crystallinity. However, a lack of data has resulted in the mechanism for change remaining unknown. This paper aims to identify the mechanism of initial Young’s modulus control in polyethylene terephthalate (PET) monofilament yarn and explain the relationship between Young’s modulus and the degree of crystallinity using Takayanagi’s model. PET monofilament yarns were treated using a CO2 infrared laser at a 10.6 μm wavelength at fluences up to 0.086 J/mm2. Young’s modulus data obtained from stress-strain curves at 0.2% strain and fraction crystallinities obtained from differential scanning calorimetry were compared with Takayanagi’s series model. Laser surface treatment within a fluence range up to 0.087 J/mm2 on PET resulted in stable Young’s modulus values. A 3.5% reduction in Young’s modulus of PET was seen with a 6.1% reduction in crystallinity, which was in good agreement with Takayanagi’s series model. Lasers offer rapid material processing capable of increasing or decreasing fractional crystallinity selectively along the fiber where desired. Selective amorphization increases chemical absorption, allowing increased surface finishing uptake at milder processing conditions, whereas increasing fractional crystallinity imparts fiber strength. The relationship between fiber crystallinity and Young’s modulus for PET can be described by Takayanagi’s model, allowing a prediction of material properties, which can be extended from fibers to all thin-film polymers.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-25T11:47:21Z
      DOI: 10.2351/7.0000736
       
  • High speed melt flow monitoring and development of an image processing
           algorithm for laser fusion cutting

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      Authors: Max Schleier, Cemal Esen, Ralf Hellmann
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      This contribution presents high-speed camera monitoring of melt pool dynamics for steel during laser fusion cutting and compares the images with recordings in aluminum. The experiments are performed by a 4 kW multimode fiber laser with an emission wavelength of 1070 nm. To visualize the thermal radiation from the process zone during the cutting process, the kerf is captured at sample rates of up to 170 000 frames per second without external illumination with a spectral response between 400 and 700 nm, allowing measurements of the melt flow dynamics from geometric image features. The dependencies of the melt flow dynamics on laser processing parameters, such as feed rate, gas pressure, and laser power, can be evaluated. The monitoring system is placed both off-axis and mounted to a conventional cutting head, with the monitoring path aligned to the processing laser for a coaxial and lateral view of the cut kerf. The measured signal characteristics of the images captured from the melt pool are examined in the visible spectral range of the emitted thermal radiation from the process zone. Moreover, a specifically developed image processing algorithm is developed that process and analyze the captured images and extract geometric information for a measurement of the melt flow.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-25T11:47:20Z
      DOI: 10.2351/7.0000785@jla.2022.ICALEO2022.issue-1
       
  • High speed melt flow monitoring and development of an image processing
           algorithm for laser fusion cutting

    • Free pre-print version: Loading...

      Authors: Max Schleier, Cemal Esen, Ralf Hellmann
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      This contribution presents high-speed camera monitoring of melt pool dynamics for steel during laser fusion cutting and compares the images with recordings in aluminum. The experiments are performed by a 4 kW multimode fiber laser with an emission wavelength of 1070 nm. To visualize the thermal radiation from the process zone during the cutting process, the kerf is captured at sample rates of up to 170 000 frames per second without external illumination with a spectral response between 400 and 700 nm, allowing measurements of the melt flow dynamics from geometric image features. The dependencies of the melt flow dynamics on laser processing parameters, such as feed rate, gas pressure, and laser power, can be evaluated. The monitoring system is placed both off-axis and mounted to a conventional cutting head, with the monitoring path aligned to the processing laser for a coaxial and lateral view of the cut kerf. The measured signal characteristics of the images captured from the melt pool are examined in the visible spectral range of the emitted thermal radiation from the process zone. Moreover, a specifically developed image processing algorithm is developed that process and analyze the captured images and extract geometric information for a measurement of the melt flow.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-25T11:47:20Z
      DOI: 10.2351/7.0000785
       
  • Optimization and design for additive manufacturing of a fuel cell end
           plate

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      Authors: Dirk Herzog, Tim Röver, Sagynysh Abdolov, Florian Becker, Christoph Gentner
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Proton exchange membrane fuel cells (PEMFCs) represent today one of the most common types of fuel cells for mobility applications due to their comparatively high-power density, low operating temperature, and low costs. A PEMFC regularly consists of a stack of individual cells in which each consists of polar plates and a membrane electrode assembly. To achieve the best possible electric conductivity over the series connection of cells, the contact pressure in between the cells must be uniformly distributed over the cell area. This pressure is usually applied to the stack by end plates, which frame the stack and are clamped together by bolts, which are tightened by a defined torque. Typically, these end plates are made from bulk material with no or limited optimization. Looking at mobility applications, e.g., in aerospace, a fuel cell should ideally provide high efficiency at the lowest weight. Based on this assumption, this paper uses topology optimization varying the material as well as the design space to derive new design concepts for the end plates of a PEMFC. The designs are compared with respect to an even stress distribution to the fuel cell stack, the weight of the plates, and the manufacturability in the laser powder bed fusion process. The most promising design is manufactured and results in a weight decrease of 48% compared to previously used aluminum bulk plates. Finally, the optimized base plates are applied to a test cell and the performance is compared to their conventional counterparts, showing a 1% increase in electric stack power despite the lower mass.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-25T11:47:19Z
      DOI: 10.2351/7.0000789@jla.2022.ICALEO2022.issue-1
       
  • Research progress on heteromorphic structure parts fabricated by additive
           manufacturing based on inside-laser coaxial powder feeding

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      Authors: Yuwei Zhao, Jiaqiang Li, Gangxian Zhu, Shihong Shi, Geyan Fu
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Inside-laser material feeding laser cladding deposition (IMF-LCD) is a directed energy deposition technology featuring “hollow beam, annular spot, centered powder, and coaxial powder feeding.” IMF-LCD offers distinct advantages over traditional outside laser material feeding laser cladding deposition (OMF-LCD), such as a good laser-powder coupling effect, high powder utilization, high forming flexibility, uniform thermal field distribution in molten pools, and excellent forming surface quality. IMF-LCD would significantly improve forming efficiency and surface quality while it was applied to rapid direct manufacturing and repair of complex metallic parts compared to OMF-LCD. In this manuscript, the working principle of IMF-LCD technology is briefly introduced. Mostly, the research progress on heteromorphic structure parts fabricated by IMF-LCD was summarized, focusing on layered design, posture change, forming strategy optimization, and process parameter adjustment. The heteromorphic structure included a twisted thin-walled structure, variant height/width structure, overhanging structure, and closed structure. Based on the excellent characteristics of this technology, the exploration of high forming quality heteromorphic structural parts is carried out by changing the process parameters and forming processes such as the variable attitude stacking method, the conformal discrete layering method and the normal layering method, and the surface roughness is as low as 1.323 μm, the dimensional accuracy is as high as 1.6%. Simultaneously, the powder utilization rate of IMF-LCD reached 60%–80% on average, in accordance with the advantages of the laser-powder coupling effect. Finally, the remarkable research and application of IMF-LCD technology in high flexibility, high precision, high surface quality, and high material utilization would further promote the development of additive manufacturing with higher performance, higher quality, and lower cost in the future.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-25T11:47:19Z
      DOI: 10.2351/7.0000689
       
  • Optimization and design for additive manufacturing of a fuel cell end
           plate

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      Authors: Dirk Herzog, Tim Röver, Sagynysh Abdolov, Florian Becker, Christoph Gentner
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Proton exchange membrane fuel cells (PEMFCs) represent today one of the most common types of fuel cells for mobility applications due to their comparatively high-power density, low operating temperature, and low costs. A PEMFC regularly consists of a stack of individual cells in which each consists of polar plates and a membrane electrode assembly. To achieve the best possible electric conductivity over the series connection of cells, the contact pressure in between the cells must be uniformly distributed over the cell area. This pressure is usually applied to the stack by end plates, which frame the stack and are clamped together by bolts, which are tightened by a defined torque. Typically, these end plates are made from bulk material with no or limited optimization. Looking at mobility applications, e.g., in aerospace, a fuel cell should ideally provide high efficiency at the lowest weight. Based on this assumption, this paper uses topology optimization varying the material as well as the design space to derive new design concepts for the end plates of a PEMFC. The designs are compared with respect to an even stress distribution to the fuel cell stack, the weight of the plates, and the manufacturability in the laser powder bed fusion process. The most promising design is manufactured and results in a weight decrease of 48% compared to previously used aluminum bulk plates. Finally, the optimized base plates are applied to a test cell and the performance is compared to their conventional counterparts, showing a 1% increase in electric stack power despite the lower mass.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-25T11:47:19Z
      DOI: 10.2351/7.0000789
       
  • Visualization of cathode spot control using laser irradiation and oxide
           addition in wire arc additive manufacturing of titanium alloys

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      Authors: Tae Hyun Lee, Cheolhee Kim, Je Hoon Oh, Dong Hyuck Kam
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Arc instability is one of the most critical problems in gas-metal-arc (GMA) based wire arc additive manufacturing of titanium (Ti) alloys. It can result in a poor bead surface, surface oxidation, and spattering. In particular, the relocation of the cathode spot area is the main cause of big spatters because of the high thermal energy of the molten droplet at the molten pool surface. In this study, two cathode spot control techniques were applied using auxiliary laser heating and prelaid oxides, and the behaviors of the cathode spots and arc were visualized using high-speed photography. When the laser beam was irradiated in front of the GMA, a cathode spot was formed at the laser irradiation position, and the cathode jet did not interfere with the arc plasma and droplet transfer from the GMA. However, when the distance between the GMA and the laser irradiation position increased by more than 8 mm, multiple cathode spots were established, and spattering increased. The prelaid Ti oxide particles increased the metal deposition efficiency by establishing multiple and dispersed cathode spots rather than a concentrated cathode spot by droplet impingement. It was found that the volumetric transfer efficiencies (excluding spattering) for the laser-assisted control and Ti oxide powder were up to 99.87% and 91.2%, respectively.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-21T11:12:58Z
      DOI: 10.2351/7.0000738
       
  • Influence of the free surface reconstruction on the spatial laser energy
           distribution in high power laser beam welding modeling

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      Authors: Xiangmeng Meng, Stephen Nugraha Putra, Marcel Bachmann, Antoni Artinov, Michael Rethmeier
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      An accurate and efficient description of the spatial distribution of laser energy is a crucial factor for the modeling of laser material processing, e.g., laser welding, laser cutting, or laser-based additive manufacturing. In this study, a 3D heat transfer and fluid flow model coupled with the volume-of-fluid algorithm for free surface tracking is developed for the simulation of molten pool dynamics in high-power laser beam welding. The underlying laser-material interactions, i.e., the multiple reflections and Fresnel absorption, are considered by a ray-tracing method. Two strategies of free surface reconstruction used in the ray-tracing method are investigated: a typical piecewise linear interface calculation (PLIC)-based method and a novel localized level-set method. The PLIC-based method is discrete, resulting in non-continuous free surface reconstruction. In the localized level-set method, a continuous free surface is reconstructed, and, thus, the exact reflection points can be determined. The calculated spatial laser energy distribution and the corresponding molten pool dynamics from the two methods are analyzed and compared. The obtained numerical results are evaluated with experimental measurements to assure the validity of the proposed model. It is found that distinct patterns of the beam multiple reflections are obtained with the different free surface reconstructions, which shows significant influence not only on the molten pool behaviors but also on the localized keyhole dynamics.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-21T11:12:57Z
      DOI: 10.2351/7.0000739@jla.2022.ICALEO2022.issue-1
       
  • Influence of the free surface reconstruction on the spatial laser energy
           distribution in high power laser beam welding modeling

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      Authors: Xiangmeng Meng, Stephen Nugraha Putra, Marcel Bachmann, Antoni Artinov, Michael Rethmeier
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      An accurate and efficient description of the spatial distribution of laser energy is a crucial factor for the modeling of laser material processing, e.g., laser welding, laser cutting, or laser-based additive manufacturing. In this study, a 3D heat transfer and fluid flow model coupled with the volume-of-fluid algorithm for free surface tracking is developed for the simulation of molten pool dynamics in high-power laser beam welding. The underlying laser-material interactions, i.e., the multiple reflections and Fresnel absorption, are considered by a ray-tracing method. Two strategies of free surface reconstruction used in the ray-tracing method are investigated: a typical piecewise linear interface calculation (PLIC)-based method and a novel localized level-set method. The PLIC-based method is discrete, resulting in non-continuous free surface reconstruction. In the localized level-set method, a continuous free surface is reconstructed, and, thus, the exact reflection points can be determined. The calculated spatial laser energy distribution and the corresponding molten pool dynamics from the two methods are analyzed and compared. The obtained numerical results are evaluated with experimental measurements to assure the validity of the proposed model. It is found that distinct patterns of the beam multiple reflections are obtained with the different free surface reconstructions, which shows significant influence not only on the molten pool behaviors but also on the localized keyhole dynamics.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-21T11:12:57Z
      DOI: 10.2351/7.0000739
       
  • Designing of aluminium case lid of prismatic battery cell for laser powder
           bed fusion

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      Authors: Heikki Saariluoma, Aki Piiroinen, Eero Immonen, Heidi Piili, Antti Salminen
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      The present work provides an overview on an additive manufacturing (AM) design case of a novel battery cell lid structure (patent pending) for electrical vehicle applications. The benefits of AM have not yet been explored on metal case structures of prismatic battery cells. The method allows the manufacturing of complex hollow structures and integration of multiple functions in one part. The main challenge is to address thermal management in an optimal location in the battery cell. More efficient charging and discharging by maintaining the batteries at optimum operating conditions allows a longer battery lifetime. Recent research shows that elevating the charging temperature enables significantly shorter charging times. The aim of this study is to develop a lid structure to support higher peak current, faster charging, and reduced production steps and enable mass customization. The optimum performance simulated with computational fluid dynamics calculations is realized to determine the optimum design. The design case study is verified via laser powder bed fusion prototypes. This study shows that it is possible to produce integrated thermal management liquid channels to the battery lid. Significant improvement is achieved with localized battery cell temperature management. The novel design integrates six critical functionalities of the lid in one part. The design of the features is optimized to avoid support structures in AM and to maximize the number of parts in the printing chamber volume. The better thermal management extends the driving range of the vehicle and improves vehicle safety. Reducing the parts significantly simplifies cell production.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-21T11:12:56Z
      DOI: 10.2351/7.0000743@jla.2022.ICALEO2022.issue-1
       
  • Designing of aluminium case lid of prismatic battery cell for laser powder
           bed fusion

    • Free pre-print version: Loading...

      Authors: Heikki Saariluoma, Aki Piiroinen, Eero Immonen, Heidi Piili, Antti Salminen
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      The present work provides an overview on an additive manufacturing (AM) design case of a novel battery cell lid structure (patent pending) for electrical vehicle applications. The benefits of AM have not yet been explored on metal case structures of prismatic battery cells. The method allows the manufacturing of complex hollow structures and integration of multiple functions in one part. The main challenge is to address thermal management in an optimal location in the battery cell. More efficient charging and discharging by maintaining the batteries at optimum operating conditions allows a longer battery lifetime. Recent research shows that elevating the charging temperature enables significantly shorter charging times. The aim of this study is to develop a lid structure to support higher peak current, faster charging, and reduced production steps and enable mass customization. The optimum performance simulated with computational fluid dynamics calculations is realized to determine the optimum design. The design case study is verified via laser powder bed fusion prototypes. This study shows that it is possible to produce integrated thermal management liquid channels to the battery lid. Significant improvement is achieved with localized battery cell temperature management. The novel design integrates six critical functionalities of the lid in one part. The design of the features is optimized to avoid support structures in AM and to maximize the number of parts in the printing chamber volume. The better thermal management extends the driving range of the vehicle and improves vehicle safety. Reducing the parts significantly simplifies cell production.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-21T11:12:56Z
      DOI: 10.2351/7.0000743
       
  • Effect of blue diode laser intensity on welding of pure copper wire using
           blue-IR hybrid laser

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      Authors: Shumpei Fujio, Keisuke Takenaka, Yuji Sato, Rika Ito, Eiji Hori, Masahiro Tsukamoto
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      A welding of a pure copper wire was conducted with a hybrid laser system, which combines a blue laser and an infrared (IR) laser to achieve a highly efficient and spatterless laser welding of pure copper. In the experiment, a blue-IR hybrid laser was irradiated onto a 3 × 3 × 20 mm3 pure copper wire, and the intensity of the blue laser was varied to clarify the effect of the combining of the blue diode laser. While irradiating the laser, the sample was observed by using a high-speed video camera, and the temperature of the processing point was measured by using a thermal camera. After laser irradiation, a molten volume and welding efficiency was evaluated. It was clarified that the welding efficiency of the pure copper wire increased as the intensity of the blue laser increased. At the maximum, the welding efficiency with a 6.31 × 107 W/cm2 IR laser became 1.88 times higher by combining a 9.98 × 105 W/cm2 blue laser. This finding can contribute to a further increase in the welding efficiency of pure copper wires, leading to high production efficiency in the pure copper welding process.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-20T10:25:17Z
      DOI: 10.2351/7.0000795@jla.2022.ICALEO2022.issue-1
       
  • Effect of blue diode laser intensity on welding of pure copper wire using
           blue-IR hybrid laser

    • Free pre-print version: Loading...

      Authors: Shumpei Fujio, Keisuke Takenaka, Yuji Sato, Rika Ito, Eiji Hori, Masahiro Tsukamoto
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      A welding of a pure copper wire was conducted with a hybrid laser system, which combines a blue laser and an infrared (IR) laser to achieve a highly efficient and spatterless laser welding of pure copper. In the experiment, a blue-IR hybrid laser was irradiated onto a 3 × 3 × 20 mm3 pure copper wire, and the intensity of the blue laser was varied to clarify the effect of the combining of the blue diode laser. While irradiating the laser, the sample was observed by using a high-speed video camera, and the temperature of the processing point was measured by using a thermal camera. After laser irradiation, a molten volume and welding efficiency was evaluated. It was clarified that the welding efficiency of the pure copper wire increased as the intensity of the blue laser increased. At the maximum, the welding efficiency with a 6.31 × 107 W/cm2 IR laser became 1.88 times higher by combining a 9.98 × 105 W/cm2 blue laser. This finding can contribute to a further increase in the welding efficiency of pure copper wires, leading to high production efficiency in the pure copper welding process.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-20T10:25:17Z
      DOI: 10.2351/7.0000795
       
  • Enabling laser transmission welding of additively manufactured
           thermoplastic parts using an expert system based on neural networks

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      Authors: Julian Kuklik, Torben Mente, Verena Wippo, Peter Jaeschke, Stefan Kaierle, Ludger Overmeyer
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      In order to use laser transmission welding (LTW) for additively manufactured parts such as prototypes, small series, or one-off products, an enhanced process knowledge is needed to overcome the difficulties in the part composition resulting from the additive manufacturing process itself. In comparison to an injection molding process for thermoplastic parts, the additive manufacturing process fused deposition modeling leads to an inhomogeneous structure with trapped air inside the volume. In this paper, a neural network-based expert system is presented that provides the user with process knowledge in order to improve the weld seam quality of laser welded additively manufactured parts. Both additive manufacturing and LTW process are assisted by the expert system. First, the designed expert system supports the user in setting up the additive manufacturing process to increase the transmissivity. During welding, the additive manufacturing and LTW process parameters are used to predict the weld seam strength. To create the database for the expert system, specimens of transparent and black polylactide are additively manufactured. In order to change the transmissivity at an emission wavelength of 940 nm of the diode laser used, the manufacturing parameters for the transparent parts are varied. The transmissivity of the parts is measured with a spectroscope. The transparent samples are welded to the black samples with laser powers between 8 and 14 W in the overlap configuration and shear tensile tests are performed. In this work, the predictions of the transmissivity and the shear tensile force are demonstrated with an accuracy of more than 88.1% of the neural networks used for the expert system.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-20T10:25:16Z
      DOI: 10.2351/7.0000787@jla.2022.ICALEO2022.issue-1
       
  • Remote laser spot welding of AISI 430 sheets by fiber lasers—A
           phenomenal effect in refining weld microstructure with nanosecond pulses

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      Authors: Aniruddha Kumar, Nilabja Kanti Sarkar, Suman Neogy
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      In the present work, we have compared the results of microstructural and mechanical property characterization of AISI 430 ferritic stainless steel spot welds made remotely using a repetitive nanosecond pulsed fiber laser and a CW fiber laser. Optical/electron microscopy, microhardness test, and tensile shear tests were performed for evaluation of the welds. Welds made by the pulsed nanosecond laser were found to be superior due to the presence of the very narrow heat-affected zone along with finer grains in the fusion zone. The welds were also found to withstand more load before fracture and were more ductile. Use of short duration laser pulses with lower heat input were found to be responsible for the refinement of grains in the fusion zone and improvement of mechanical properties of nanosecond laser weld specimens.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-20T10:25:16Z
      DOI: 10.2351/7.0000712
       
  • Enabling laser transmission welding of additively manufactured
           thermoplastic parts using an expert system based on neural networks

    • Free pre-print version: Loading...

      Authors: Julian Kuklik, Torben Mente, Verena Wippo, Peter Jaeschke, Stefan Kaierle, Ludger Overmeyer
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      In order to use laser transmission welding (LTW) for additively manufactured parts such as prototypes, small series, or one-off products, an enhanced process knowledge is needed to overcome the difficulties in the part composition resulting from the additive manufacturing process itself. In comparison to an injection molding process for thermoplastic parts, the additive manufacturing process fused deposition modeling leads to an inhomogeneous structure with trapped air inside the volume. In this paper, a neural network-based expert system is presented that provides the user with process knowledge in order to improve the weld seam quality of laser welded additively manufactured parts. Both additive manufacturing and LTW process are assisted by the expert system. First, the designed expert system supports the user in setting up the additive manufacturing process to increase the transmissivity. During welding, the additive manufacturing and LTW process parameters are used to predict the weld seam strength. To create the database for the expert system, specimens of transparent and black polylactide are additively manufactured. In order to change the transmissivity at an emission wavelength of 940 nm of the diode laser used, the manufacturing parameters for the transparent parts are varied. The transmissivity of the parts is measured with a spectroscope. The transparent samples are welded to the black samples with laser powers between 8 and 14 W in the overlap configuration and shear tensile tests are performed. In this work, the predictions of the transmissivity and the shear tensile force are demonstrated with an accuracy of more than 88.1% of the neural networks used for the expert system.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-20T10:25:16Z
      DOI: 10.2351/7.0000787
       
  • In-situ x-ray phase contrast observation of the full penetration spot
           welding on limited aluminum material thickness

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      Authors: Woo-Sik Chung, André Häusler, Marc Hummel, Alexander Olowinsky, Arnold Gillner, Felix Beckmann, Julian Moosmann
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      The laser-spot welding process of aluminum alloy 1050A with a limited thickness is observed with the x-ray phase contrast method to investigate the melt dynamic especially when the melt penetrates the material. The laser-spot welding is investigated with two different wavelengths of the laser beam source: 515 and 1030 nm to investigate the influence of the absorptivity. The melt progressively penetrates the material during the spot-welding process until reaching the bottom side of the material and when the melt penetrates the lower side of the material, the so-called “lens-like” melt appears at the lower side due to the surface tension. At a comparable beam intensity value, the oscillation of the “lens-like” melt at the lower side of the material is driven by the expansion of vapor capillary. This expansion occurs inside of the material and directly above the “lens-like” melt. The shape of the expanded vapor determines the volume as well as the geometry of the resulting melt volume. Furthermore, the transition from the heat conduction welding mode to the keyhole welding mode is investigated by defocusing the laser beam for the beam source with a 515 nm wavelength. At a given variation, a clear difference between either mode is observed with the x-ray phase contrast method.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-17T11:35:38Z
      DOI: 10.2351/7.0000772@jla.2022.ICALEO2022.issue-1
       
  • In-situ x-ray phase contrast observation of the full penetration spot
           welding on limited aluminum material thickness

    • Free pre-print version: Loading...

      Authors: Woo-Sik Chung, André Häusler, Marc Hummel, Alexander Olowinsky, Arnold Gillner, Felix Beckmann, Julian Moosmann
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      The laser-spot welding process of aluminum alloy 1050A with a limited thickness is observed with the x-ray phase contrast method to investigate the melt dynamic especially when the melt penetrates the material. The laser-spot welding is investigated with two different wavelengths of the laser beam source: 515 and 1030 nm to investigate the influence of the absorptivity. The melt progressively penetrates the material during the spot-welding process until reaching the bottom side of the material and when the melt penetrates the lower side of the material, the so-called “lens-like” melt appears at the lower side due to the surface tension. At a comparable beam intensity value, the oscillation of the “lens-like” melt at the lower side of the material is driven by the expansion of vapor capillary. This expansion occurs inside of the material and directly above the “lens-like” melt. The shape of the expanded vapor determines the volume as well as the geometry of the resulting melt volume. Furthermore, the transition from the heat conduction welding mode to the keyhole welding mode is investigated by defocusing the laser beam for the beam source with a 515 nm wavelength. At a given variation, a clear difference between either mode is observed with the x-ray phase contrast method.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-17T11:35:38Z
      DOI: 10.2351/7.0000772
       
  • Module platform for hybrid PBF-LB manufacturing

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      Authors: Timo Rautio, Jarmo Mäkikangas, Aappo Mustakangas, Antti Järvenpää
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      This study presents a module platform for additive manufacturing (AM) of parts with the laser powder bed fusion (PBF-LB) technique. The proposed configurable platform enables hybrid manufacturing, because the bulk of the part can be manufactured with traditional methods and the complex part with AM combining the best qualities of both. The main objective was to find a new way of combining manufacturing techniques to reduce costs both in printing and in the postprocessing phase of production. Mechanical testing and microstructural analysis were used to verify the joint quality and strength between the printed part and the sheet metal. PBF-LB manufacturing was experimented directly on 316L and P355GH sheet metal steels, and in both cases, the results showed that the joints did not degrade the material properties. In addition to specimens for tensile testing, parts for a flexural bending machine were manufactured as a proof of concept. The module platform was successfully used to manufacture parts with reduced material cost and printing time, and the print job could be performed without any support structures, obviating the need for post processing. The proposed platform design can be used not only as a new tool for improving the production efficiency of the PBF-LB technique, but also to overcome some of the limitations in part design.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-14T10:01:52Z
      DOI: 10.2351/7.0000722@jla.2022.ICALEO2022.issue-1
       
  • Module platform for hybrid PBF-LB manufacturing

    • Free pre-print version: Loading...

      Authors: Timo Rautio, Jarmo Mäkikangas, Aappo Mustakangas, Antti Järvenpää
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      This study presents a module platform for additive manufacturing (AM) of parts with the laser powder bed fusion (PBF-LB) technique. The proposed configurable platform enables hybrid manufacturing, because the bulk of the part can be manufactured with traditional methods and the complex part with AM combining the best qualities of both. The main objective was to find a new way of combining manufacturing techniques to reduce costs both in printing and in the postprocessing phase of production. Mechanical testing and microstructural analysis were used to verify the joint quality and strength between the printed part and the sheet metal. PBF-LB manufacturing was experimented directly on 316L and P355GH sheet metal steels, and in both cases, the results showed that the joints did not degrade the material properties. In addition to specimens for tensile testing, parts for a flexural bending machine were manufactured as a proof of concept. The module platform was successfully used to manufacture parts with reduced material cost and printing time, and the print job could be performed without any support structures, obviating the need for post processing. The proposed platform design can be used not only as a new tool for improving the production efficiency of the PBF-LB technique, but also to overcome some of the limitations in part design.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-14T10:01:52Z
      DOI: 10.2351/7.0000722
       
  • Toward the flexible production of large-format lithium-ion batteries using
           laser-based cell-internal contacting

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      Authors: Sophie Grabmann, Michael K. Kick, Christian Geiger, Felix Harst, Andreas Bachmann, Michael F. Zaeh
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Lithium-ion battery cells are used for energy storage in many industrial sectors, such as consumer electronics or electromobility. Due to the diversity of these applications, the demand for tailored battery cells is increasing. Consequently, the technical development of the cells leads to numerous coexisting cell variants. Examples of such variants are altering cell materials, formats, and capacities. Different target capacities can be realized by changing the geometrical dimensions of the individual electrodes or the number of electrodes in the cell cores. The increasing quantity of variants poses challenges within battery cell manufacturing, such as the need to adapt the process parameters for the cell-internal contacting of a higher number of electrode sheets in the cell stack. Each new cell variant currently requires elaborate experimental parameter studies for its manufacture. An approach for selecting suitable process parameters for laser-based cell-internal contacting in terms of a modification of the cell properties is presented in this paper. A model was built to determine the weld depth in copper sheets using a millisecond pulsed laser welding strategy. The process parameters for welding stacks of electrode sheets to an arrester tab were calculated on the basis of this model. The necessary weld depth in the arrester tab for achieving suitable mechanical properties of the cell-internal joint was considered. The presented approach was validated by welding different numbers of foils to an arrester tab and varying the thickness of the foils. It was shown that the experimental effort for the selection of the process parameters for laser-based contacting can be reduced significantly.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-13T10:17:04Z
      DOI: 10.2351/7.0000778@jla.2022.ICALEO2022.issue-1
       
  • Toward the flexible production of large-format lithium-ion batteries using
           laser-based cell-internal contacting

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      Authors: Sophie Grabmann, Michael K. Kick, Christian Geiger, Felix Harst, Andreas Bachmann, Michael F. Zaeh
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Lithium-ion battery cells are used for energy storage in many industrial sectors, such as consumer electronics or electromobility. Due to the diversity of these applications, the demand for tailored battery cells is increasing. Consequently, the technical development of the cells leads to numerous coexisting cell variants. Examples of such variants are altering cell materials, formats, and capacities. Different target capacities can be realized by changing the geometrical dimensions of the individual electrodes or the number of electrodes in the cell cores. The increasing quantity of variants poses challenges within battery cell manufacturing, such as the need to adapt the process parameters for the cell-internal contacting of a higher number of electrode sheets in the cell stack. Each new cell variant currently requires elaborate experimental parameter studies for its manufacture. An approach for selecting suitable process parameters for laser-based cell-internal contacting in terms of a modification of the cell properties is presented in this paper. A model was built to determine the weld depth in copper sheets using a millisecond pulsed laser welding strategy. The process parameters for welding stacks of electrode sheets to an arrester tab were calculated on the basis of this model. The necessary weld depth in the arrester tab for achieving suitable mechanical properties of the cell-internal joint was considered. The presented approach was validated by welding different numbers of foils to an arrester tab and varying the thickness of the foils. It was shown that the experimental effort for the selection of the process parameters for laser-based contacting can be reduced significantly.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-13T10:17:04Z
      DOI: 10.2351/7.0000778
       
  • Controlling nozzle and kerf gas dynamics to manage hazardous laser cutting
           fume

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      Authors: Jacob J. Lavin, Mathew T. Jones, Edward J. Long, John R. Tyrer, Julian T. Spencer, Jonathan M. Dodds, Lewis C. R. Jones
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Conventional laser cutting is optimized for cut speed and quality but does not consider process fume. When processing hazardous materials in environments where global extraction is not practical, such as during in situ nuclear decommissioning, consideration of process fume is critically important. Fume generation in laser cutting is governed by forces applied to the molten cut front; dynamic interactions between the assist-gas and the cut front control these forces. This paper investigates the causal links between key gas-dynamic features and fume generation mechanisms in laser cutting. Its aim is to provide the preliminary understanding required to design process setups targeted at reducing the fine particle fraction. During laser cutting, the assist-gas boundary layer separates (BLS) from the molten cut front and, therefore, downstream forces applied on the melt are significantly changed. In this work, the BLS point is analyzed, captured via schlieren imaging, in an idealized environment. This separation point is related to features on the cut wall of laser-cut samples, validating the gas-dynamic interactions. The samples were cut from 3 mm thick 304 stainless steel, using a 1 kW Nd:Yb fiber laser. Control of the surface stagnation pressure and gas flow boundary conditions were used to relocate the point of BLS within the cut front, and the relationship of these parameters was analyzed. The results demonstrate that shifting the point of BLS along the cut front can be used to control fume generation mechanisms. This study successfully provided the preliminary understanding necessary to manage fume generation during the laser cutting process.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-11T11:40:26Z
      DOI: 10.2351/7.0000747@jla.2022.ICALEO2022.issue-1
       
  • Controlling nozzle and kerf gas dynamics to manage hazardous laser cutting
           fume

    • Free pre-print version: Loading...

      Authors: Jacob J. Lavin, Mathew T. Jones, Edward J. Long, John R. Tyrer, Julian T. Spencer, Jonathan M. Dodds, Lewis C. R. Jones
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Conventional laser cutting is optimized for cut speed and quality but does not consider process fume. When processing hazardous materials in environments where global extraction is not practical, such as during in situ nuclear decommissioning, consideration of process fume is critically important. Fume generation in laser cutting is governed by forces applied to the molten cut front; dynamic interactions between the assist-gas and the cut front control these forces. This paper investigates the causal links between key gas-dynamic features and fume generation mechanisms in laser cutting. Its aim is to provide the preliminary understanding required to design process setups targeted at reducing the fine particle fraction. During laser cutting, the assist-gas boundary layer separates (BLS) from the molten cut front and, therefore, downstream forces applied on the melt are significantly changed. In this work, the BLS point is analyzed, captured via schlieren imaging, in an idealized environment. This separation point is related to features on the cut wall of laser-cut samples, validating the gas-dynamic interactions. The samples were cut from 3 mm thick 304 stainless steel, using a 1 kW Nd:Yb fiber laser. Control of the surface stagnation pressure and gas flow boundary conditions were used to relocate the point of BLS within the cut front, and the relationship of these parameters was analyzed. The results demonstrate that shifting the point of BLS along the cut front can be used to control fume generation mechanisms. This study successfully provided the preliminary understanding necessary to manage fume generation during the laser cutting process.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-11T11:40:26Z
      DOI: 10.2351/7.0000747
       
  • Spatially tailored laser energy distribution using innovative optics for
           gas-tight welding of casted and wrought aluminum alloys in e-mobility

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      Authors: Mauritz Möller, Patrick Haug, Philipp Scheible, Christian Buse, Conrad Frischkorn, Nicolai Speker
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Electric mobility is undergoing a very rapid maturation process [A. Kampker, K. Kreisköther, P. Treichel, T. Möller, Y. Boelsen, and D. Neb, “Electromobility trends and challenges of future mass production,” in Handbook Industry 4.0, edited by W. Frenz (Springer, Berlin, 2022), D. Ziegler and N. Abdelkafi, “Business models for electric vehicles: Literature review and key insights,” J. Cleaner Prod. 330, 129803 (2022)]. While conventional vehicle design disciplines such as car body design are established, electromobility-specific disciplines are in the technological orientation and ramp-up phase. In particular, the demand for components like batteries, e-motors, and power electronics is growing continuously [A. Kampker, K. Kreisköther, P. Treichel, T. Möller, Y. Boelsen, and D. Neb, “Electromobility trends and challenges of future mass production,” in Handbook Industry 4.0, edited by W. Frenz (Springer, Berlin, 2022), D. Ziegler and N. Abdelkafi, “Business models for electric vehicles: Literature review and key insights,” J. Cleaner Prod. 330, 129803 (2022)]. One of the major materials chosen for these parts is aluminum alloys [C. Prieto, E. Vaamonde, D. Diego-Vallejo, J. Jimenez, B. Urbach, Y. Vidne, and E. Shekel, “Dynamic laser beam shaping for laser aluminium welding in e-mobility applications,” Procedia CIRP. 94, 596–600 (2020)]. Next to the material-specific challenges and mentioned requirements, the focus is on the gas-tight welding of aluminum alloys for parts like casted power electronics housings and heat exchangers made of sheet metal or extrusion profiles. Gas-tightness is a requirement, on the one hand, to shield electronic components from the influence of the surrounding environment and, on the other hand, to prevent leakage of the water-cooling circuit [C. Prieto, E. Vaamonde, D. Diego-Vallejo, J. Jimenez, B. Urbach, Y. Vidne, and E. Shekel, “Dynamic laser beam shaping for laser aluminium welding in e-mobility applications,” Procedia CIRP. 94, 596–600 (2020), A. Artinov, M. Bachmann, X. Meng, V. Karkhin, and M. Rethmeier, “On the relationship between the bulge effect and the hot cracking formation during deep penetration laser beam welding,” Procedia CIRP 94, 5–10 (2020)]. This paper offers insight into the requirements of these parts and an innovative optics approach with a novel MultiFocus solution. Material-specific challenges (e. g. porosity), especially, for helium-tight welding of aluminum casted housings with forging alloys are characterized. This analysis is conducted using gas-tightness measurements, CT-scans, micrographs, and high-speed recordings in order to elaborate on the fundamental laser-material-process interdependencies and the correlation between the process and resulting quality, in terms of tightness. Furthermore, high-speed synchrotron recordings are conducted at the DESY and based on that, a detailed evaluation of laser and material interaction is conducted. This allows an explanation of the interactions for the prevention of pore formation in aluminum alloys and, thus, the characterization of the boundary conditions for a reliable process of gas-tight welding on aluminum alloys [C. Prieto, E. Vaamonde, D. Diego-Vallejo, J. Jimenez, B. Urbach, Y. Vidne, and E. Shekel, “Dynamic laser beam shaping for laser aluminium welding in e-mobility applications,” Procedia CIRP. 94, 596–600 (2020)].
      Citation: Journal of Laser Applications
      PubDate: 2022-10-07T10:04:52Z
      DOI: 10.2351/7.0000735@jla.2022.ICALEO2022.issue-1
       
  • Spatially tailored laser energy distribution using innovative optics for
           gas-tight welding of casted and wrought aluminum alloys in e-mobility

    • Free pre-print version: Loading...

      Authors: Mauritz Möller, Patrick Haug, Philipp Scheible, Christian Buse, Conrad Frischkorn, Nicolai Speker
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Electric mobility is undergoing a very rapid maturation process [A. Kampker, K. Kreisköther, P. Treichel, T. Möller, Y. Boelsen, and D. Neb, “Electromobility trends and challenges of future mass production,” in Handbook Industry 4.0, edited by W. Frenz (Springer, Berlin, 2022), D. Ziegler and N. Abdelkafi, “Business models for electric vehicles: Literature review and key insights,” J. Cleaner Prod. 330, 129803 (2022)]. While conventional vehicle design disciplines such as car body design are established, electromobility-specific disciplines are in the technological orientation and ramp-up phase. In particular, the demand for components like batteries, e-motors, and power electronics is growing continuously [A. Kampker, K. Kreisköther, P. Treichel, T. Möller, Y. Boelsen, and D. Neb, “Electromobility trends and challenges of future mass production,” in Handbook Industry 4.0, edited by W. Frenz (Springer, Berlin, 2022), D. Ziegler and N. Abdelkafi, “Business models for electric vehicles: Literature review and key insights,” J. Cleaner Prod. 330, 129803 (2022)]. One of the major materials chosen for these parts is aluminum alloys [C. Prieto, E. Vaamonde, D. Diego-Vallejo, J. Jimenez, B. Urbach, Y. Vidne, and E. Shekel, “Dynamic laser beam shaping for laser aluminium welding in e-mobility applications,” Procedia CIRP. 94, 596–600 (2020)]. Next to the material-specific challenges and mentioned requirements, the focus is on the gas-tight welding of aluminum alloys for parts like casted power electronics housings and heat exchangers made of sheet metal or extrusion profiles. Gas-tightness is a requirement, on the one hand, to shield electronic components from the influence of the surrounding environment and, on the other hand, to prevent leakage of the water-cooling circuit [C. Prieto, E. Vaamonde, D. Diego-Vallejo, J. Jimenez, B. Urbach, Y. Vidne, and E. Shekel, “Dynamic laser beam shaping for laser aluminium welding in e-mobility applications,” Procedia CIRP. 94, 596–600 (2020), A. Artinov, M. Bachmann, X. Meng, V. Karkhin, and M. Rethmeier, “On the relationship between the bulge effect and the hot cracking formation during deep penetration laser beam welding,” Procedia CIRP 94, 5–10 (2020)]. This paper offers insight into the requirements of these parts and an innovative optics approach with a novel MultiFocus solution. Material-specific challenges (e. g. porosity), especially, for helium-tight welding of aluminum casted housings with forging alloys are characterized. This analysis is conducted using gas-tightness measurements, CT-scans, micrographs, and high-speed recordings in order to elaborate on the fundamental laser-material-process interdependencies and the correlation between the process and resulting quality, in terms of tightness. Furthermore, high-speed synchrotron recordings are conducted at the DESY and based on that, a detailed evaluation of laser and material interaction is conducted. This allows an explanation of the interactions for the prevention of pore formation in aluminum alloys and, thus, the characterization of the boundary conditions for a reliable process of gas-tight welding on aluminum alloys [C. Prieto, E. Vaamonde, D. Diego-Vallejo, J. Jimenez, B. Urbach, Y. Vidne, and E. Shekel, “Dynamic laser beam shaping for laser aluminium welding in e-mobility applications,” Procedia CIRP. 94, 596–600 (2020)].
      Citation: Journal of Laser Applications
      PubDate: 2022-10-07T10:04:52Z
      DOI: 10.2351/7.0000735
       
  • Investigations on the effect of standing ultrasonic waves on the
           microstructure and hardness of laser beam welded butt joints of stainless
           steel and nickel base alloy

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      Authors: Jan Grajczak, Christian Nowroth, Jens Twiefel, Jörg Wallaschek, Sarah Nothdurft, Jörg Hermsdorf, Stefan Kaierle
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Joining dissimilar metals with superior quality is important to provide tailored, lightweight, and cost-efficient components. Expensive and durable materials are exceptionally used where the cheaper material would not withstand the requirements. With laser beam welding, dissimilar metals can already be joined with high precision, low heat input, and a customizable mixing degree. Introducing ultrasonic excitation into the weld pool is a promising approach for further improvements like customizing the solidification morphology and avoiding weld defects. The experiments are carried out with round bars of 30 mm diameter made of 1.4301 steel alloy and 2.4856 nickel base alloy. Ultrasonic-assisted laser beam butt welding is conducted on rotating specimens with a laser beam power of 7.75 kW and a welding speed of 0.95 m/min. The specimens are evaluated by metallographic cross sections, hardness measurements, and energy-dispersive x-ray spectroscopy (EDX). The ultrasound is used to excite an eigenmode of the sample and the weld position is varied at stress- and displacement-nodes. Two different mechanisms of acoustic grain refinement are revealed. Heterogeneous nucleation is fostered in weld seams that are positioned in stress-nodes, and the fragmentation of dendrites is fostered in displacement-nodes. The welds' chemical compositions correspond to the change of solidification morphology.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-07T10:04:50Z
      DOI: 10.2351/7.0000765@jla.2022.ICALEO2022.issue-1
       
  • Investigations on the effect of standing ultrasonic waves on the
           microstructure and hardness of laser beam welded butt joints of stainless
           steel and nickel base alloy

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      Authors: Jan Grajczak, Christian Nowroth, Jens Twiefel, Jörg Wallaschek, Sarah Nothdurft, Jörg Hermsdorf, Stefan Kaierle
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Joining dissimilar metals with superior quality is important to provide tailored, lightweight, and cost-efficient components. Expensive and durable materials are exceptionally used where the cheaper material would not withstand the requirements. With laser beam welding, dissimilar metals can already be joined with high precision, low heat input, and a customizable mixing degree. Introducing ultrasonic excitation into the weld pool is a promising approach for further improvements like customizing the solidification morphology and avoiding weld defects. The experiments are carried out with round bars of 30 mm diameter made of 1.4301 steel alloy and 2.4856 nickel base alloy. Ultrasonic-assisted laser beam butt welding is conducted on rotating specimens with a laser beam power of 7.75 kW and a welding speed of 0.95 m/min. The specimens are evaluated by metallographic cross sections, hardness measurements, and energy-dispersive x-ray spectroscopy (EDX). The ultrasound is used to excite an eigenmode of the sample and the weld position is varied at stress- and displacement-nodes. Two different mechanisms of acoustic grain refinement are revealed. Heterogeneous nucleation is fostered in weld seams that are positioned in stress-nodes, and the fragmentation of dendrites is fostered in displacement-nodes. The welds' chemical compositions correspond to the change of solidification morphology.
      Citation: Journal of Laser Applications
      PubDate: 2022-10-07T10:04:50Z
      DOI: 10.2351/7.0000765
       
  • Overlap welded joint strength of 2.0 GPa-strength steel sheets using
           single-mode laser wobbling

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      Authors: Minjung Kang, Yeonho Kwak, Hyeonjeong You, Sanghoon Kang, Cheolhee Kim
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      During laser overlap welding of high strength steels, a wide interface-bead width is a prerequisite for ensuring joint strength. However, a wide weld bead is accompanied by thermal effects such as thermal deformation and softening of the heat-affected zone owing to the high heat input during welding. Hot-press-forming steel with a strength of 2.0 GPa is the highest strength steel sheet in the automotive industry. When laser-welded, the minimum hardness in the heat-affected zone is less than 2/3 of the base metal hardness. In this study, single-mode laser and beam wobbling was employed to obtain a proper bead width while minimizing the heat input in the lap welding of steel sheets with a strength of 2.0 GPa. Two strategies—high frequency wobbling/high travel speed and low frequency wobbling/low travel speed—were evaluated with a laser power fixed at 1 kW. In the high frequency wobbling/high travel speed condition, the load-carrying at the overlap joint increased as the travel speed and wobbling frequency decreased. However, even in the case with the maximum fracture load, the fracture location in the tensile–shear test was the weld metal. The low frequency wobbling/low travel speed strategy was more effective in ensuring joint strength, and the fracture location in the tensile–shear test moved to the heat-affected zone. An equivalent tensile strength of 1 GPa or more was achieved by selecting appropriate parameters. Under optimal conditions, multiple weld penetrations and sufficient interface beads were confirmed on the cross section.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-30T09:53:39Z
      DOI: 10.2351/7.0000730@jla.2022.ICALEO2022.issue-1
       
  • Overlap welded joint strength of 2.0 GPa-strength steel sheets using
           single-mode laser wobbling

    • Free pre-print version: Loading...

      Authors: Minjung Kang, Yeonho Kwak, Hyeonjeong You, Sanghoon Kang, Cheolhee Kim
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      During laser overlap welding of high strength steels, a wide interface-bead width is a prerequisite for ensuring joint strength. However, a wide weld bead is accompanied by thermal effects such as thermal deformation and softening of the heat-affected zone owing to the high heat input during welding. Hot-press-forming steel with a strength of 2.0 GPa is the highest strength steel sheet in the automotive industry. When laser-welded, the minimum hardness in the heat-affected zone is less than 2/3 of the base metal hardness. In this study, single-mode laser and beam wobbling was employed to obtain a proper bead width while minimizing the heat input in the lap welding of steel sheets with a strength of 2.0 GPa. Two strategies—high frequency wobbling/high travel speed and low frequency wobbling/low travel speed—were evaluated with a laser power fixed at 1 kW. In the high frequency wobbling/high travel speed condition, the load-carrying at the overlap joint increased as the travel speed and wobbling frequency decreased. However, even in the case with the maximum fracture load, the fracture location in the tensile–shear test was the weld metal. The low frequency wobbling/low travel speed strategy was more effective in ensuring joint strength, and the fracture location in the tensile–shear test moved to the heat-affected zone. An equivalent tensile strength of 1 GPa or more was achieved by selecting appropriate parameters. Under optimal conditions, multiple weld penetrations and sufficient interface beads were confirmed on the cross section.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-30T09:53:39Z
      DOI: 10.2351/7.0000730
       
  • Study on the mechanism of ultrasonic-assisted laser processing carbon
           fiber reinforced plastics in ethanol solution

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      Authors: Liao Zhou, Hui Jiao, Ting Qin, Ping Huang, Guanghui Zhang, Yuxing Huang, Jia Zhou, Yuhong Long
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      The water-assisted laser processing of carbon fiber-reinforced plastics (CFRPs) can reduce thermal damage. However, the machining quality and efficiency will be reduced by laser-induced cavitation bubbles when laser processing in the water. A method of in situ ultrasonic vibration-assisted laser processing of CFRPs in the ethanol solution was proposed to reduce the adverse effect of cavitation bubbles on machining. The influence of process parameters on machining was studied by the design of experiments. The dynamic ablation behavior of the laser-ablated area was captured in situ by a high-speed camera. The machining mechanism was analyzed. The results show that the volume of the cavitation bubble is reduced in the ethanol solution, and the laser scattering is reduced. The machining quality is improved. When the volume fraction of ethanol exceeds 40%, the laser extinction rate is increased by the accumulation of cavitation bubbles. The heat-affected zone (HAZ) and the etching depth were reduced by 57% and 25%, respectively. The ultrasonic vibration can explode the cavitation bubble, and the interference of the cavitation bubble to the laser is reduced. The effect of mechanical erosion is enhanced. The etching depth was increased by 119%. The cooling effect of the ablated area is enhanced by ultrasonic vibration. The HAZ is reduced by 57%. According to the findings of this study, the material deposition can be effectively reduced when the method of the paper is used, a clean groove is generated, the fiber pull-out is improved, and better machining quality can be obtained.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-30T09:53:38Z
      DOI: 10.2351/7.0000811
       
  • Investigations on laser beam welding of thin foils of copper and aluminum
           regarding weld seam quality using different laser beam sources

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      Authors: Sarah Nothdurft, Oliver Seffer, Jörg Hermsdorf, Ludger Overmeyer, Stefan Kaierle
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Nowadays, there is a strong and growing ambition to switch from combustion technology to battery-electric drives, and energy storage is spotlighted. Laser beam welding is an appropriate and favorable welding technology in battery production. Due to the high welding speed, the local heat input, the contact freeness efficient, and automatable processes can be established. Materials used in batteries for electrodes that have to be connected are commonly copper and aluminum. Specifically, copper is highly reflective for widely used infrared laser beam wavelengths. Furthermore, the thickness in the area of 10 μm is quite challenging to deal with, in terms of gap free clamping and avoidance of damage to the material as well as distortion during welding. There is a fine line regarding energy input between burning the material and generating a lack of fusion. In the presented research, welding approaches with different laser beam sources emitting laser beams with infrared wavelengths, various beam shapes, and welding modes (continuous and pulsed) are studied. A total of 40 copper foils with a thickness of 10 μm and 40 aluminum foils with a thickness of 15 μm are welded to similar sheet metals. Aim of the process development are welds with high quality and high connection widths to provide the best electric conductivity.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-26T10:38:34Z
      DOI: 10.2351/7.0000777@jla.2022.ICALEO2022.issue-1
       
  • Investigations on laser beam welding of thin foils of copper and aluminum
           regarding weld seam quality using different laser beam sources

    • Free pre-print version: Loading...

      Authors: Sarah Nothdurft, Oliver Seffer, Jörg Hermsdorf, Ludger Overmeyer, Stefan Kaierle
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Nowadays, there is a strong and growing ambition to switch from combustion technology to battery-electric drives, and energy storage is spotlighted. Laser beam welding is an appropriate and favorable welding technology in battery production. Due to the high welding speed, the local heat input, the contact freeness efficient, and automatable processes can be established. Materials used in batteries for electrodes that have to be connected are commonly copper and aluminum. Specifically, copper is highly reflective for widely used infrared laser beam wavelengths. Furthermore, the thickness in the area of 10 μm is quite challenging to deal with, in terms of gap free clamping and avoidance of damage to the material as well as distortion during welding. There is a fine line regarding energy input between burning the material and generating a lack of fusion. In the presented research, welding approaches with different laser beam sources emitting laser beams with infrared wavelengths, various beam shapes, and welding modes (continuous and pulsed) are studied. A total of 40 copper foils with a thickness of 10 μm and 40 aluminum foils with a thickness of 15 μm are welded to similar sheet metals. Aim of the process development are welds with high quality and high connection widths to provide the best electric conductivity.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-26T10:38:34Z
      DOI: 10.2351/7.0000777
       
  • High deposition rate welding with a laser line optics with the
           laser-assisted double-wire deposition welding process with nontransferred
           arc

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      Authors: Kai Biester, Alexander Barroi, Tjorben Bokelmann, Marius Lammers, Jörg Hermsdorf, Stefan Kaierle
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Laser-assisted double-wire welding with a nontransferred arc is used for cladding workpieces. The wire material is melted by an arc and dropped onto the substrate, where a laser beam is oscillated by a galvanometer scanner to achieve bonding of the melt with good contact angles that do not result in undercuts. In this study, the galvanometer scanner was replaced by a beam shaping optics generating a line with a width of 1.2 mm and a length of 9.1 mm. Based on Design of Experiments, the laser power was varied in a range from 1500 to 2000 W and the welding speed in a range from 600 to 800 mm/min. Single weld beads of AISI 316L were welded onto a mild steel of AISI 1024 according to a full factorial design at three repetitions per parameter set. The paper examines whether the contact angles of the weld beads produced with the line optics are comparable to those obtained by oscillating the laser beam. In addition, the dilution of the material with the substrate was determined in micrographs. The results show that the bonding to the substrate can be achieved. The parameter window for the laser power with beam shaping line optics is different from that with the oscillated laser beam. The required laser power is 1.5–2 times greater.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-22T10:08:00Z
      DOI: 10.2351/7.0000758@jla.2022.ICALEO2022.issue-1
       
  • High deposition rate welding with a laser line optics with the
           laser-assisted double-wire deposition welding process with nontransferred
           arc

    • Free pre-print version: Loading...

      Authors: Kai Biester, Alexander Barroi, Tjorben Bokelmann, Marius Lammers, Jörg Hermsdorf, Stefan Kaierle
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Laser-assisted double-wire welding with a nontransferred arc is used for cladding workpieces. The wire material is melted by an arc and dropped onto the substrate, where a laser beam is oscillated by a galvanometer scanner to achieve bonding of the melt with good contact angles that do not result in undercuts. In this study, the galvanometer scanner was replaced by a beam shaping optics generating a line with a width of 1.2 mm and a length of 9.1 mm. Based on Design of Experiments, the laser power was varied in a range from 1500 to 2000 W and the welding speed in a range from 600 to 800 mm/min. Single weld beads of AISI 316L were welded onto a mild steel of AISI 1024 according to a full factorial design at three repetitions per parameter set. The paper examines whether the contact angles of the weld beads produced with the line optics are comparable to those obtained by oscillating the laser beam. In addition, the dilution of the material with the substrate was determined in micrographs. The results show that the bonding to the substrate can be achieved. The parameter window for the laser power with beam shaping line optics is different from that with the oscillated laser beam. The required laser power is 1.5–2 times greater.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-22T10:08:00Z
      DOI: 10.2351/7.0000758
       
  • Application of adjustable ring mode laser in remote laser welding of
           additive manufactured AlSi10Mg alloy

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      Authors: Tianzhu Sun, Nesta Ferguson, Conghui Liu, Greg Gibbons, Pasquale Franciosa
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Additive manufacturing (AM) is an innovative manufacturing technology that offers the ability to build parts with both geometric and material complexities. However, limitations, including low build volume capability and production rate, yield its rapid application in high volume production. This paper presents the potential of remote laser welding (RLW) as a post-AM joining approach to scale up the AM components. The AM AlSi10Mg alloy was fabricated by direct metal laser sintering and subsequently joined by RLW without filler wire or shielding gas. A novel adjustable ring mode (ARM) laser beam was employed during the RLW process where the ring beam is designed to stabilize the keyhole by providing the preheating and postheating while the core beam guarantees a sufficient weld penetration. The impact of the ARM laser on weld porosity was evaluated in both fillet lap and bead-on-plate welding configurations, accompanied by the variation of core/ring beam power ratios. Crack-free welds with promising weld appearance were obtained among all welding trials, indicating that the ARM-RLW process can be employed for the robust connection of AM AlSi10Mg alloys. Optimizing the power ratio can substantially reduce the weld porosity area ratio from 24.3% to 13.5% in the fillet lap configuration and from 24.2% to 14.4% in the bead-on-plate configuration. Analysis of variance tests statistically confirmed the significant impact of the power ratio on the porosity area ratio. Future work has been suggested for the process maturation of RLW as a post-AM joining approach in industrial application.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-20T09:49:01Z
      DOI: 10.2351/7.0000794@jla.2022.ICALEO2022.issue-1
       
  • Application of adjustable ring mode laser in remote laser welding of
           additive manufactured AlSi10Mg alloy

    • Free pre-print version: Loading...

      Authors: Tianzhu Sun, Nesta Ferguson, Conghui Liu, Greg Gibbons, Pasquale Franciosa
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Additive manufacturing (AM) is an innovative manufacturing technology that offers the ability to build parts with both geometric and material complexities. However, limitations, including low build volume capability and production rate, yield its rapid application in high volume production. This paper presents the potential of remote laser welding (RLW) as a post-AM joining approach to scale up the AM components. The AM AlSi10Mg alloy was fabricated by direct metal laser sintering and subsequently joined by RLW without filler wire or shielding gas. A novel adjustable ring mode (ARM) laser beam was employed during the RLW process where the ring beam is designed to stabilize the keyhole by providing the preheating and postheating while the core beam guarantees a sufficient weld penetration. The impact of the ARM laser on weld porosity was evaluated in both fillet lap and bead-on-plate welding configurations, accompanied by the variation of core/ring beam power ratios. Crack-free welds with promising weld appearance were obtained among all welding trials, indicating that the ARM-RLW process can be employed for the robust connection of AM AlSi10Mg alloys. Optimizing the power ratio can substantially reduce the weld porosity area ratio from 24.3% to 13.5% in the fillet lap configuration and from 24.2% to 14.4% in the bead-on-plate configuration. Analysis of variance tests statistically confirmed the significant impact of the power ratio on the porosity area ratio. Future work has been suggested for the process maturation of RLW as a post-AM joining approach in industrial application.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-20T09:49:01Z
      DOI: 10.2351/7.0000794
       
  • Influence of superimposed intensity distributions on weld seam quality and
           spatter behavior during laser beam welding of copper with green laser
           radiation

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      Authors: Florian Kaufmann, Andreas Maier, Julian Schrauder, Stephan Roth, Michael Schmidt
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      With the increasing demand for copper connections in the field of renewable energies, e.g., for electric vehicle applications, various approaches were pursued to reduce the challenging spatter and melt ejection susceptibility in laser beam welding of copper materials. One is the use of adjustable intensity profiles of multi-mode beam sources with a combination of a core and ring beam in order to affect a modification of the flow field in the melt pool surrounding the highly dynamic keyhole in the deep penetration welding process. This should favor a reduction of spattering and melt pool ejections, especially at low weld speeds and high penetration depths in pure copper, therefore enabling a more stable deep penetration welding process. In this work, the influence of different superimposed intensity distribution ratios for green laser radiation with summarized power up to 3 kW on the generation of process imperfections was investigated conducting welding experiments on Cu-ETP using high-speed imaging for enhanced process understanding. In addition, the effects of different power distribution conditions and welding speeds on the seam dimensions were analyzed. It was found that a significant amount of laser power in the ring beam leads to a widening of the melt pool in the area near the sample top-surface, which effectively reduces spatter behavior. The associated change in process zone morphology in laser beam direction was furthermore observed via sandwich analysis, allowing a detailed view into the laser–matter interaction area through a borosilicate glass sheet clamped in front of a processed sample. This setup was found to be a cost-effective method for obtaining further information about the keyhole formation mechanism and melt dynamics under comparative boundary conditions.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-20T09:49:00Z
      DOI: 10.2351/7.0000771@jla.2022.ICALEO2022.issue-1
       
  • Influence of superimposed intensity distributions on weld seam quality and
           spatter behavior during laser beam welding of copper with green laser
           radiation

    • Free pre-print version: Loading...

      Authors: Florian Kaufmann, Andreas Maier, Julian Schrauder, Stephan Roth, Michael Schmidt
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      With the increasing demand for copper connections in the field of renewable energies, e.g., for electric vehicle applications, various approaches were pursued to reduce the challenging spatter and melt ejection susceptibility in laser beam welding of copper materials. One is the use of adjustable intensity profiles of multi-mode beam sources with a combination of a core and ring beam in order to affect a modification of the flow field in the melt pool surrounding the highly dynamic keyhole in the deep penetration welding process. This should favor a reduction of spattering and melt pool ejections, especially at low weld speeds and high penetration depths in pure copper, therefore enabling a more stable deep penetration welding process. In this work, the influence of different superimposed intensity distribution ratios for green laser radiation with summarized power up to 3 kW on the generation of process imperfections was investigated conducting welding experiments on Cu-ETP using high-speed imaging for enhanced process understanding. In addition, the effects of different power distribution conditions and welding speeds on the seam dimensions were analyzed. It was found that a significant amount of laser power in the ring beam leads to a widening of the melt pool in the area near the sample top-surface, which effectively reduces spatter behavior. The associated change in process zone morphology in laser beam direction was furthermore observed via sandwich analysis, allowing a detailed view into the laser–matter interaction area through a borosilicate glass sheet clamped in front of a processed sample. This setup was found to be a cost-effective method for obtaining further information about the keyhole formation mechanism and melt dynamics under comparative boundary conditions.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-20T09:49:00Z
      DOI: 10.2351/7.0000771
       
  • Fiber laser cutting of steel materials with twin spot beam-twin spot
           setting in kerf width direction

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      Authors: Kota Morimoto, Atsushi Yagi, Naoto Kai, Yasuhiro Okamoto, Akira Okada, Hiroaki Ishiguro, Ryohei Ito, Akihiko Sugiyama, Hiroshi Okawa
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      In laser cutting, the temperature distribution would have significant influence on cutting characteristics, and the intensity distribution of a laser beam has a possibility to improve the cutting quality. In this study, a fiber laser beam of Gaussian distribution was divided into two beams by a roof axicon lens, and the cutting characteristics were investigated by using the twin spot Gaussian beam setting in the kerf directions. The cutting experiment of a cold-rolled steel plate with a thickness of 3.2 mm was carried out by a 3 kW fiber laser with a nitrogen assist gas, and the Gaussian mode of 114 μm spot and the twin Gaussian mode of two 110 μm spots were used with the variation of power ratio in twin spot processing. At the exit side of kerf by the twin spot process, the width of the cutting front in the low intensity side became wider than that in the high intensity side, and the dross could be reduced in the low intensity side due to sufficient ejection of the molten metal from the front wall rather than the side wall of kerf. The twin spot process could reduce the dross height below 18 μm in the low intensity side, which is smaller than that by the single Gaussian beam process.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-20T09:48:59Z
      DOI: 10.2351/7.0000740@jla.2022.ICALEO2022.issue-1
       
  • Research on in situ laser cladding of 304 stainless steel coating on Q235
           substrate in underwater environment

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      Authors: Ning Guo, Shuai Zhang, Yunlong Fu, Qi Cheng, Xin Zhang, Jinlong He
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      In this research, 304 stainless steel coating was prepared on the surface of Q235 steel by in situ laser cladding technology in both underwater and in-air environments. The optimal process parameters of laser cladding in the underwater environment were first investigated by using a homemade local dry laser torch. The effects of the laser power, scanning speed, and wire feed speed on macroscopic forming, geometric characteristics, and the microstructure of the cladding layers were investigated. Under the optimal process parameters, the effects of the water environment on macroscopic forming, geometric characteristics, and the microstructure and microhardness of the cladding layers were studied. The results showed that as the environment transferred from underwater to air, the height (H) and cladding angle (α) of the deposited region (DR) decreased, but the fusion width (W) and the depth (h) of the fusion region (FR) increased due to the slow cooling rate and long residence time at high temperatures. For both underwater and in-air cladding layers, the microstructure of DR and FR was equiaxed dendrites and columnar dendrites. Besides, a cellular structure appeared in the FR of the underwater cladding layer. The width of the lathy δ ferrite in the FR in the underwater environment was smaller than that of the in-air environment. Finally, the grain size of the underwater specimen was finer, so the average microhardness value of the in-air specimen was lower than that of the underwater specimen.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-20T09:48:59Z
      DOI: 10.2351/7.0000723
       
  • Fiber laser cutting of steel materials with twin spot beam-twin spot
           setting in kerf width direction

    • Free pre-print version: Loading...

      Authors: Kota Morimoto, Atsushi Yagi, Naoto Kai, Yasuhiro Okamoto, Akira Okada, Hiroaki Ishiguro, Ryohei Ito, Akihiko Sugiyama, Hiroshi Okawa
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      In laser cutting, the temperature distribution would have significant influence on cutting characteristics, and the intensity distribution of a laser beam has a possibility to improve the cutting quality. In this study, a fiber laser beam of Gaussian distribution was divided into two beams by a roof axicon lens, and the cutting characteristics were investigated by using the twin spot Gaussian beam setting in the kerf directions. The cutting experiment of a cold-rolled steel plate with a thickness of 3.2 mm was carried out by a 3 kW fiber laser with a nitrogen assist gas, and the Gaussian mode of 114 μm spot and the twin Gaussian mode of two 110 μm spots were used with the variation of power ratio in twin spot processing. At the exit side of kerf by the twin spot process, the width of the cutting front in the low intensity side became wider than that in the high intensity side, and the dross could be reduced in the low intensity side due to sufficient ejection of the molten metal from the front wall rather than the side wall of kerf. The twin spot process could reduce the dross height below 18 μm in the low intensity side, which is smaller than that by the single Gaussian beam process.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-20T09:48:59Z
      DOI: 10.2351/7.0000740
       
  • Evaluation of narrowed weld pool shapes and their effect on resulting
           potential defects during deep penetration laser beam welding

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      Authors: Marcel Bachmann, Xiangmeng Meng, Antoni Artinov, Michael Rethmeier
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      This study presents mechanisms of the evolution of a narrowed region in the weld pool center during deep penetration laser beam welding. In numerous numerical studies presented in this study, it was also found that the local reduction of the weld pool size can cause detrimental effects on the melt flow behavior and the resulting properties of the welds. A particularly large influence of this effect was identified in three aspects. First, the local variation of the solidification sequence of the weld pool causes an increase in the hot-cracking susceptibility due to a locally delayed solidification. Second, it was proven that a change in the local length and width of the weld pool is associated with an adverse impact on the potential flow routes of the molten material that induces stronger local variations of its solidification. Thus, the element mixing, e.g., during the welding with filler materials, is blocked. This leads to a nonhomogeneous chemical composition of the final weld and can cause undesired effects on the final material properties. Finally, another observed effect is related to the reduced ability of process pores to reach the top surface. As this type of porosity is usually produced around the keyhole tip, the change of the fluid flow regime above this area plays a significant role in determining the final path of the pores until the premature solidification in the middle of the weld pool captures them. This study summarizes mainly numerical results that were supported by selected experimental validation results.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-19T11:21:17Z
      DOI: 10.2351/7.0000733@jla.2022.ICALEO2022.issue-1
       
  • Evaluation of narrowed weld pool shapes and their effect on resulting
           potential defects during deep penetration laser beam welding

    • Free pre-print version: Loading...

      Authors: Marcel Bachmann, Xiangmeng Meng, Antoni Artinov, Michael Rethmeier
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      This study presents mechanisms of the evolution of a narrowed region in the weld pool center during deep penetration laser beam welding. In numerous numerical studies presented in this study, it was also found that the local reduction of the weld pool size can cause detrimental effects on the melt flow behavior and the resulting properties of the welds. A particularly large influence of this effect was identified in three aspects. First, the local variation of the solidification sequence of the weld pool causes an increase in the hot-cracking susceptibility due to a locally delayed solidification. Second, it was proven that a change in the local length and width of the weld pool is associated with an adverse impact on the potential flow routes of the molten material that induces stronger local variations of its solidification. Thus, the element mixing, e.g., during the welding with filler materials, is blocked. This leads to a nonhomogeneous chemical composition of the final weld and can cause undesired effects on the final material properties. Finally, another observed effect is related to the reduced ability of process pores to reach the top surface. As this type of porosity is usually produced around the keyhole tip, the change of the fluid flow regime above this area plays a significant role in determining the final path of the pores until the premature solidification in the middle of the weld pool captures them. This study summarizes mainly numerical results that were supported by selected experimental validation results.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-19T11:21:17Z
      DOI: 10.2351/7.0000733
       
  • Sustainable laser metal deposition of aluminum alloys for the automotive
           industry

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      Authors: Francesco Bruzzo, Mehar Prakash Reddy Medapati, Daniele Pullini, Fabio Ronco, Andrea Bertinetti, Alessio Tommasi, Mirko Riede, Elena Lòpez, Frank Brückner
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      In the last few years, there has been increasing interest in the processing of aluminum alloys using additive manufacturing (AM) processes. Thanks to their properties, aluminium alloys are extensively used in aerospace, rail, and automotive industries. Laser metal deposition (LMD), among the AM processes, can manufacture complex features as well as reinforcement structures on pre-existing complex parts. The work performed within the SAMOA project aims to expand the knowledge of the material properties of aluminum alloys when the LMD process is performed under atmospheric conditions. Both common alloys (AlSi10Mg, AlSi1Mg) and AM-specific alloys (AM205 and AlSi1Mg + 1 wt. %Zr) were analyzed and compared. Results show significantly lower amounts of internal defects and higher mechanical properties in AM-specific alloys. This database of mechanical properties will be used to design, simulate, and fabricate reinforcement structures on car frames to enhance their crash resistance and increase vehicle security. Moreover, to reduce material waste, the SAMOA project focuses also on the effects of powder recycling by analyzing both chemical and physical changes in the powder. The higher concentration of oxygen and hydrogen was separately analyzed by artificially increasing their concentration by heat treating AlSi10Mg powder. Results showed similar processability with a reduction in UTS of −31.4% and an increased elongation at fracture of +112.5%. Recycled powder, on the other hand, could not be easily collected, sieved, and reused since the identified physical and chemical changes of the powder lower its processability.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-13T10:22:12Z
      DOI: 10.2351/7.0000741@jla.2022.ICALEO2022.issue-1
       
  • Sustainable laser metal deposition of aluminum alloys for the automotive
           industry

    • Free pre-print version: Loading...

      Authors: Francesco Bruzzo, Mehar Prakash Reddy Medapati, Daniele Pullini, Fabio Ronco, Andrea Bertinetti, Alessio Tommasi, Mirko Riede, Elena Lòpez, Frank Brückner
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      In the last few years, there has been increasing interest in the processing of aluminum alloys using additive manufacturing (AM) processes. Thanks to their properties, aluminium alloys are extensively used in aerospace, rail, and automotive industries. Laser metal deposition (LMD), among the AM processes, can manufacture complex features as well as reinforcement structures on pre-existing complex parts. The work performed within the SAMOA project aims to expand the knowledge of the material properties of aluminum alloys when the LMD process is performed under atmospheric conditions. Both common alloys (AlSi10Mg, AlSi1Mg) and AM-specific alloys (AM205 and AlSi1Mg + 1 wt. %Zr) were analyzed and compared. Results show significantly lower amounts of internal defects and higher mechanical properties in AM-specific alloys. This database of mechanical properties will be used to design, simulate, and fabricate reinforcement structures on car frames to enhance their crash resistance and increase vehicle security. Moreover, to reduce material waste, the SAMOA project focuses also on the effects of powder recycling by analyzing both chemical and physical changes in the powder. The higher concentration of oxygen and hydrogen was separately analyzed by artificially increasing their concentration by heat treating AlSi10Mg powder. Results showed similar processability with a reduction in UTS of −31.4% and an increased elongation at fracture of +112.5%. Recycled powder, on the other hand, could not be easily collected, sieved, and reused since the identified physical and chemical changes of the powder lower its processability.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-13T10:22:12Z
      DOI: 10.2351/7.0000741
       
  • Doppler diagnostics of laser evaporation of biological tissues

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      Authors: Alexander K. Dmitriev, Alexey N. Konovalov, Vladimir N. Kortunov, Valery A. Ulyanov
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      The method for Doppler diagnostics of laser evaporation of biological tissues based on autodyne detection (reception on the laser resonator) of backscattered radiation has been developed. In this method, a laser is simultaneously used both as a source of the destructive action of radiation on biotissues and as a sensor of the backscattered diagnostic signal. This review study discusses the possibilities of Doppler diagnostics in relation to the problems of investigating the processes of laser evaporation of biological tissues in real time and laser surgery. This approach can be used to create an optical-information feedback channel in automated and robotic surgical systems based on pulse-periodic pumped single-mode CO2 lasers. Laser surgical systems with such operational feedback can be used in the development of new approaches to precision low-traumatic and organ-save laser operations.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-12T10:21:45Z
      DOI: 10.2351/7.0000702
       
  • Investigation on the parameter dependency of the perforation process of
           graphite based lithium-ion battery electrodes using ultrashort laser
           pulses

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      Authors: Max-Jonathan Kleefoot, Jens Sandherr, Marc Sailer, Sara Nester, Jiří Martan, Volker Knoblauch, Malte Kumkar, Harald Riegel
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Perforation of lithium-ion battery electrodes has recently become an increasing interest in science and industry. Perforated electrodes have shown improved electrochemical properties compared to conventional, nonperforated electrodes. It has been demonstrated that through perforation, the fast-charging capability and the lifetime of these batteries can be significantly improved. The electrodes for lithium-ion batteries consist of a copper foil onto which the electrode material is applied as a porous layer. This layer is mainly composed of active material particles, which are bound together by a binder phase. Here, synthetic graphite was used as an active material. Up to now, it has been shown that an advantageous and precise perforation geometry can be produced by ultrashort laser pulse ablation. Since the ablation volumes during perforation of the porous electrode material with ultrashort laser pulses are unusually high compared to solids, this work investigates the parameter dependency on the ablation mechanisms in detail. For this purpose, in particular, single-pulse ablation was investigated with respect to the ablation thresholds at different pulse durations. The pulse durations were varied over a large range from 400 fs to 20 ps. By varying the number of pulses per perforation up to 50 and the single-pulse energy up to 45 μJ, it could be shown that a homogeneous ablation down to the conductor foil through the 63 μm thick active material layer can be achieved.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-09T09:50:25Z
      DOI: 10.2351/7.0000757@jla.2022.ICALEO2022.issue-1
       
  • Investigation on the parameter dependency of the perforation process of
           graphite based lithium-ion battery electrodes using ultrashort laser
           pulses

    • Free pre-print version: Loading...

      Authors: Max-Jonathan Kleefoot, Jens Sandherr, Marc Sailer, Sara Nester, Jiří Martan, Volker Knoblauch, Malte Kumkar, Harald Riegel
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Perforation of lithium-ion battery electrodes has recently become an increasing interest in science and industry. Perforated electrodes have shown improved electrochemical properties compared to conventional, nonperforated electrodes. It has been demonstrated that through perforation, the fast-charging capability and the lifetime of these batteries can be significantly improved. The electrodes for lithium-ion batteries consist of a copper foil onto which the electrode material is applied as a porous layer. This layer is mainly composed of active material particles, which are bound together by a binder phase. Here, synthetic graphite was used as an active material. Up to now, it has been shown that an advantageous and precise perforation geometry can be produced by ultrashort laser pulse ablation. Since the ablation volumes during perforation of the porous electrode material with ultrashort laser pulses are unusually high compared to solids, this work investigates the parameter dependency on the ablation mechanisms in detail. For this purpose, in particular, single-pulse ablation was investigated with respect to the ablation thresholds at different pulse durations. The pulse durations were varied over a large range from 400 fs to 20 ps. By varying the number of pulses per perforation up to 50 and the single-pulse energy up to 45 μJ, it could be shown that a homogeneous ablation down to the conductor foil through the 63 μm thick active material layer can be achieved.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-09T09:50:25Z
      DOI: 10.2351/7.0000757
       
  • Multispot laser welding for increased gap bridgability

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      Authors: Joerg Volpp
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      Laser beam welding is a promising technology to enable automated high-quality welding procedures at significantly higher processing speeds compared to conventional processes. However, its usability is often limited by gap bridgability. This disadvantage is related to the small laser beam spot sizes that require low gap sizes for joining, which are often practically not available, and the desired welding without additional filler materials to enable high processing speeds without direction restrictions. New possibilities of beam shaping for process control are also available now for high-power laser processing and they show promising results. The resulting complex effects require additional investigation to understand the mechanisms and the use of the technologies for process improvements. Therefore, in this work, advanced beam shaping optics with up to four separate laser beam spots was used to understand the impact of multiple-spot welding on the process dynamics and gap bridgability. Gap bridgability was measured by an opening gap setup, while spatter amounts as indicators of process dynamics were measured by high-speed imaging. It was shown that multiple-spot laser welding can increase the gap bridgability, probably due to the initiated melt flow toward the joining partners. Symmetric separation of the keyholes toward the sheets increased the gap bridgability, while additional low-intensity spots in the center were able to stabilize the melt pool and reduce spattering.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-06T01:06:33Z
      DOI: 10.2351/7.0000724@jla.2022.ICALEO2022.issue-1
       
  • Simulation and prediction of the temperature field of copper alloys
           fabricated by selective laser melting

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      Authors: Dongju Chen, Peng Wang, Kun Sun, Yuhang Tang, Shuai Kong, Jinwei Fan
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      In the selective laser melting (SLM) process, the experimental approach to determine the optimal process parameters is labor-intensive, material-intensive, and time-consuming. The use of simulation methods also requires more time support and higher hardware requirements. In this paper, a three-dimensional transient heat transfer model and a neural network optimization process parameter model in the process of preparing copper alloys by SLM are developed by combining finite element simulation methods with neural network prediction. The thermal behavior of the multitrack molten pools was investigated by ANSYS APDL, and the effects of different laser powers and scanning speeds on the temperature field and structure dimensions of the molten pools were discussed. The results show that the current single-track has a significant preheating effect on the unmachined single-track and a reheating effect on the machined single-track during the multitrack forming process. The laser power and scanning speed can be controlled to regulate the temperature, 3D size, and heat spread area of the molten pool to avoid over-melting and under-melting. The accuracy of the temperature field model was verified by single-track experiments. A neural network prediction model was constructed to predict the maximum temperature and size of the molten pool by optimizing the backpropagation neural network with a genetic algorithm, providing a methodological guide for the study of SLM process parameters.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-06T01:06:33Z
      DOI: 10.2351/7.0000718
       
  • Multispot laser welding for increased gap bridgability

    • Free pre-print version: Loading...

      Authors: Joerg Volpp
      Abstract: Journal of Laser Applications, Volume 34, Issue 4, November 2022.
      Laser beam welding is a promising technology to enable automated high-quality welding procedures at significantly higher processing speeds compared to conventional processes. However, its usability is often limited by gap bridgability. This disadvantage is related to the small laser beam spot sizes that require low gap sizes for joining, which are often practically not available, and the desired welding without additional filler materials to enable high processing speeds without direction restrictions. New possibilities of beam shaping for process control are also available now for high-power laser processing and they show promising results. The resulting complex effects require additional investigation to understand the mechanisms and the use of the technologies for process improvements. Therefore, in this work, advanced beam shaping optics with up to four separate laser beam spots was used to understand the impact of multiple-spot welding on the process dynamics and gap bridgability. Gap bridgability was measured by an opening gap setup, while spatter amounts as indicators of process dynamics were measured by high-speed imaging. It was shown that multiple-spot laser welding can increase the gap bridgability, probably due to the initiated melt flow toward the joining partners. Symmetric separation of the keyholes toward the sheets increased the gap bridgability, while additional low-intensity spots in the center were able to stabilize the melt pool and reduce spattering.
      Citation: Journal of Laser Applications
      PubDate: 2022-09-06T01:06:33Z
      DOI: 10.2351/7.0000724
       
  • In situ observation of dynamics of keyhole and molten pool in laser
           welding for development of spatter suppression

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      Authors: Tomoki Arita, Yuji Sato, Yoshiaki Kurita, Masami Mizutani, Hitoshi Nakano, Masahiro Tsukamoto
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      A real-time observation system for a longitudinal section of molten pool and temperature distribution was developed directly in real time by a combined system with the glass transmission method and two-color temperature analysis to clarify the mechanism of spatter generation during laser welding. A stainless-steel-type 304 (SS304) was employed in this study because of its application in many industries. The SS304 was set in a vacuum chamber and then a disk laser with an output power of 10 kW was irradiated and scanned on it to form a weld bead. At the same time, the behavior of the molten pool and keyhole was captured with the real-time temperature observation system and an x-ray transmission system, respectively. As a result, the temperature of the longitudinal section of the molten pool formed by laser irradiation under atmospheric pressure was about 1500 °C; however, at 10 Pa, it reached about 1700 °C, indicating that the temperature increases with a decrease in the ambient pressure. Furthermore, the fluctuation in the longitudinal sectional area of the keyhole and molten pool was evaluated. It was found that the average fluctuation in the longitudinal sectional area of the molten pool was 1.7% at 10 Pa and that of the molten pool was 18.8% under atmospheric pressure.
      Citation: Journal of Laser Applications
      PubDate: 2022-08-29T11:06:58Z
      DOI: 10.2351/7.0000744@jla.2022.ICALEO2022.issue-1
       
  • Comparative study of GaAs nanostructures synthesized in air and distilled
           water by picosecond pulsed laser ablation and application in hazardous
           molecules detection

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      Authors: A. Mangababu, Dipanjan Banerjee, Kanaka Ravi Kumar, R. Sai Prasad Goud, Venugopal Rao Soma, S. V. S. Nageswara Rao
      Abstract: Journal of Laser Applications, Volume ICALEO2022, Issue 1, November 2022.
      This work explored the fundamental differences/mechanisms between the GaAs substrates ablated in two different media of air and distilled water (DW). A scan area of 5 × 5 mm2 was ablated by a picosecond laser with a pulse duration of 30 ps, a repetition rate of 10 Hz, a wavelength of 1064 nm, and a pulse energy of 2 mJ. The spacing between raster scan lines was varied (0.05–0.35 mm), keeping the scan speed (0.15 mm/s) constant. The obtained GaAs nanostructures (NSs) were thoroughly analyzed using microscopy techniques. A clear increase in separation between the raster scan lines was observed with an increase in the scan spacing for the GaAs NSs fabricated in air, whereas the same result was not observed in DW. Moreover, structures with debris were formed in air irrespective of the spacing, unlike the formation of uniform quasiperiodic GaAs NSs throughout the sample in the case of DW ablation. To the best of our knowledge, there are no reports on the detailed studies involving DW in the fabrication of quasiperiodic NSs of GaAs. Further, these quasiperiodic GaAs NSs formed in DW were coated with a thin layer of gold using the thermal evaporation method, annealed at 400 °C for 1 h in an ambient atmosphere. As a consequence of annealing, Au NPs were uniformly decorated on the quasiperiodic NSs of GaAs imparting plasmonic nature to the whole structures. Subsequently, the Au NPs decorated GaAs NSs were utilized as surface enhanced Raman scattering substrates for the detection of methylene blue (dye molecule) and Thiram (pesticide molecule) at low concentrations.
      Citation: Journal of Laser Applications
      PubDate: 2022-08-10T10:48:50Z
      DOI: 10.2351/7.0000750@jla.2022.ICALEO2022.issue-1
       
 
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