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Abstract: Abstract This study uses a composite material with copper powder added in Polylactide (PLA) to manufacture the metallic parts by 3D printing. The content of composite filament is with 90% copper and 10% PLA in terms of mass percentage. In practices, the printed parts are first printed using a 3D printer and then they are sintered in a high-temperature furnace to remove the PLA and strengthen their mechanical and thermal properties of the printed part. In this study, the sintering process is divided into two processes: (1) the heating process in which printed part is heated such that the PLA in the printed part is decomposed and then combusted away, and (2) the sintering process in which the contacting particles are bonded to form a solid object. A 3D numerical simulation has been performed to study the heat transfer characteristics of the system during heating process. In this study, a completion fraction is defined to indicate the local completion level between the thermal decomposition and the combustion reactions of the PLA in the printed parts. PubDate: 2022-06-01
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Abstract: Abstract 3D printing of spare parts onboard ships is becoming increasingly interesting due to advances in filament materials and printing technology. Several companies and navies have installed 3D printers onboard a limited number of vessels to test the feasibility. Further tests should be conducted to determine if the printed spare part meets the stringent regulations and standards for equipment onboard ships. Thus, it also becomes a topic for future training of seafarers. In this paper, we present examples of the introduction of 3D printing into seafarer training. An ideal example of a printed spare part is the universal key for an electric locker. It is often lost. Therefore, a spare part should be available. Fused deposition modeling (FDM) 3D printing technology is used by the students to make such a key. The printed key was tested on a real locker and served its purpose. In addition, students responded enthusiastically to problem-based learning, which is ideal for 3D manufacturing teaching. The paper also presents other printed parts. The parts described can be used in education. The limitations of the considered project are in real life implementation. Namely, most of the parts to be replaced are made of metals, and this type of printing is not suitable for metals. Dielectric materials (insulators) could be printed in this way. Additionally, we provided the cost analysis. PubDate: 2022-06-01
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Abstract: Abstract Due to their high specific strength and temperature resistance, γ-titanium aluminides (γ-TiAl) have a growing importance for automotive and aerospace applications. However, conventional processing is very challenging due to the inherent brittleness of the material. Therefore, new manufacturing techniques and methods have to be established. Additive manufacturing techniques such as electron powder bed fusion (PBF-EB/M) are favored, since they enable near net shape manufacturing of highly complex geometries. The high preheating temperatures, which typically occur during PBF-EB/M, can significantly improve the processability of TiAl and facilitate the fabrication of complex parts. In this study, a previously optimized material condition of the β-solidifying TNM alloy TNM-B1 (Ti-43.5Al-4Nb-1Mo-0.1B) was manufactured by PBF-EB/M. The resulting microstructure, defect distribution and morphology, and mechanical properties were characterized by means of characterization methods, e.g., CT, SEM, light microscopy, hardness measurements, and tensile tests. A special focus was on the mechanical high-temperature behavior. The pronounced sensitivity of the material to defects and internal notches, e.g., due to lack of fusion defects (misconnections) which were found in the as-built condition, was identified as a main cause for premature failure below the yield point due to the low ductility. This failure was analyzed and potential improvements were identified. PubDate: 2022-06-01
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Abstract: Abstract Direct-powder bed selective laser processing (D-PBSLP) is a promising technique for the manufacturing of complex-shaped parts of Silicon Carbide (SiC) ceramic. In this work, a complex optimization of the process parameters was performed by numerical and experimental analysis. The numerical model was used to determine and optimize the effect of laser power, scanning speed and hatching distance at different layer thicknesses of 20, 30 and 40 µm. Regarding the experimental process parameters study, powder compaction was also studied and optimized. The optimization parameter criteria were to achieve reproducible and high relative density parts. Concerning the experimental manufacturing process, D-PBSLP of alpha-silicon carbide parts with a maximum relative density of 81% were manufactured. Moreover, the process viability can be confirmed with the manufacturing of SiC complex shapes in absence of any additives in the initial powder and without or post-treatment. The results from this study could be used as a guide for process parameters selection. PubDate: 2022-05-19
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Abstract: Abstract Material selection is an important task in the mechanical design of industrial components such as piping and valves. Industrial valves play a vital role in fluid control in the piping systems used in various industries, including the oil and gas industry. Low-alloy steel materials are widely used for subsea valves in size ranges of 3″ and above. In a recent subsea project that included 13 manifolds and 1056 valves, 34% of the subsea valves were made of low-alloy steel material, whereas 66% of them in size range less than 3″ were in super duplex. If the valve body is made from duplex stainless steel rather than low-alloy steel plus Inconel 625, the price of each valve could be 1.10–1.15 times higher than the unit prices in the following table. Since low-alloy steel is not a corrosion-resistant alloy (CRA), its extensive uses raises concerns about its application in the harsh and corrosive subsea environment, which is at the same time a precious and increasingly embattled ecosystem. The external corrosion of low-alloy steel body valves can be prevented by a combination of coating and cathodic protection. The internal corrosion of this material is prevented by applying 3 mm of Inconel 625 cladding in two layers. This article offers recommendations for future research, such as the application of low-alloy steel materials for other parts of subsea valves and the use of laser weld technology for applying an Inconel 625 weld overlay. PubDate: 2022-05-19
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Abstract: Abstract The present study investigates the different post-heat treatments (PHTs) (850 °C, 950 °C, and 1050 °C) to tailor the microstructure and mechanical properties of laser powder bed fusion (LPBF)-processed Ti6Al4V alloy. The microstructural features, chemical composition and micro-hardness of as-printed and heat-treated Ti6Al4V samples in longitudinal and transverse directions were characterised using optical microscopy, SEM, EDS, X-ray diffraction (XRD) and Vickers’ micro-hardness tester. Detailed XRD analysis was performed to quantify the phase volume fractions in the heat-treated samples. The microstructure of the heat-treated Ti6Al4V samples differed from the as-printed samples in grain structure and morphology. The width of α lath increased nearly twice with PHT temperature (from 850 to 1050 °C) in LPBF-processed samples. During PHT under furnace cooling, the growth of α lath width marginally increases due to a slower cooling rate than air cooling. XRD investigation revealed that the presence of β phase content in the PHTs at 950 °C and 1050 °C was consistent. Further, PHT at a higher temperature (i.e. 1050 °C) favours a higher amount of β phase content than the other PHT temperatures. The presence of (002)-closed pack planes was significantly lower for LPBF-processed Ti6Al4V samples, heat-treated under 1050 °C. The heat-treated LPBF-processed Ti6Al4V sample at 1050 °C exhibited a higher hardness (~ 27%) than the as-printed Ti6Al4V sample due to the higher β content among all the samples. The studied PHTs schemes were beneficial in generating the homogeneous and desirable microstructures for distinctive LPBF parts made of Ti6Al4V alloy befitting practical industrial applications. PubDate: 2022-05-14
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Abstract: Abstract This study aims to compare the fatigue behavior of similar and dissimilar polymer weld joints created after an additive manufacturing process. The fatigue samples were 3D printed in ABS and PLA using a fused filament fabrication printer. Various weld joints, including ABS/ABS, PLA/PLA, and PLA/ABS, were produced utilizing the rotary friction welding process. The fatigue behavior of these joints was evaluated using rotating-beam fatigue testing at various load levels. In addition, fatigue tests were performed on non-welded PLA and ABS samples. The findings revealed that PLA/PLA joints had superior fatigue resistance than non-welded PLA. Furthermore, in this sequence, PLA/PLA, ABS/ABS, and PLA/ABS had the highest fatigue resistance. PubDate: 2022-05-11
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Abstract: Abstract To increase industrial adoption, part qualification and certification of the additive manufacturing (AM) process are crucial through geometric benchmarking as well as optimising the properties and process parameters. However, an extensive research gap remains concerning the geometric dimensioning and tolerancing (GD&T) of AM parts. This paper presents a review on the state-of-art GD&T benchmarking of powder bed fusion techniques enabling complex geometrical features like lattices. The study found a lack of design guidelines and standardised measurement techniques for lattice features and profiles. PubDate: 2022-05-06
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Abstract: Abstract The applicability of Additive Manufacturing for operational parts expands with the availability of new materials with specific properties. For elastomeric components produced with Fused Filament Fabrication, challenges associated with the printing process due to the nature of the material are faced. This paper investigates the effect of under-extrusion in this process regarding the feeding system and, predominantly, the moisture for thermoplastic polyurethanes with 3D printing experiments and thermomechanical testing. In particular, the filament flow control with a Bowden extruder provides a challenge. A microscopic analysis reveals the signs of under-extrusion, along with the influence of material drying to reduce the moisture content. The drying may depend not only on time and temperature, but also on mass and surface effects. Water uptake measurements exhibit absorptions up to 1.89% in weight, most of which take place during the first 24 h of the experiments. Tensile tests performed on samples with different moisture contents show their influence in the ultimate stresses. The moisture in the material causes under-extrusion induced failures. Those failures are less likely to happen at lower moisture levels, resulting in occasional higher tensile strengths. Overall, the importance of proper storage of the material throughout printing is verified, even under moderate humidity conditions due to its hygroscopic nature. PubDate: 2022-04-29
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Abstract: Abstract Open-cell titanium lattice structures produced by selective laser melting (SLM) are attractive for creation of patient-specific implants with high level of bone ingrowth. In this work, irregular SLM lattice structures made of titanium (cp-Ti) with an average beam thickness of 300 μm and an average porous size of 600 μm were investigated. Optimal processing conditions of SLM for obtaining irregular open-cell cp-Ti lattice structures with mechanical and porous geometry close to human cancellous bone were developed. It was observed that the main parameter of SLM affected on beam thickness is volumetric energy density. Influence of orientation of cubic samples on the construction platform (on the plane, on the edge or on the corner) on properties of lattice structures was investigated. The corner orientation was found to be optimal. It was shown that chemical etching is effective post-treatment method for obtaining required beam thickness and removing the attached powder particles. Optimal chemical etching conditions are the following: etching solution contains 30 mL HNO3 + 45 mL HF + 120 mL water, etching time is 10 s. The elastic modulus and the elastic limit of etched lattice samples are 1.4–1.9 GPa and 44–51 MPa, respectively, which correlates with characteristics of human cancellous bone. Compression of samples during mechanical tests occurred without beams destruction. Corrosion characteristics of obtained etched and non-etched lattice structures in Hank's Balanced Salt Solution (HBSS) have been improved compared with cp-Ti bulk samples. The biological and medical tests of the obtained samples will be carrying out to determine biocompatibility, influence on the growth of bone tissue, permeability, etc. PubDate: 2022-04-29
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Abstract: Abstract Understanding the physical mechanism of laser–powder bed fusion (LPBF) additive manufacturing can benefit significantly through computational modeling. LPBF uses a laser heat source to melt a number of layer of powder particles and manufactures a part based on the CAD design. This work aims to assess the impact of Marangoni flow, buoyancy and recoil pressure to simulate the fluid flow around melt pool with a non-Gaussian laser beam to simulate the interaction between laser and powder bed. It was observed that velocity profile shows two peaks on either side of the highest temperature point owing to Marangoni convection on both sides due to gradient in surface tension. Dimensional analysis was also conducted based on Peclet number, Nusselt number and Marangoni number to determine the mode of heat transport at various laser power/scan speed combinations. Convective heat flow is the dominant form of heat transfer at higher energy input due to violent flow of the fluid and recoil pressure around the molten region, which can also create keyhole effect associated with defects such as porosities. The computational model was also validated by comparing solidified bead geometry with experimental data. PubDate: 2022-04-29
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Abstract: Abstract Invar alloys possess the peculiarity of dimensional invariance, which is of importance for high precision applications, such as measurement instruments. As ductile face-centered cubic (fcc) material, it is adequately weldable and is nowadays readily available as powder feed stock for additive manufacturing processes. Single-phase fcc alloys are known to often be highly textured, when fabricated via laser powder-bed fusion. Within this study, the thermal expansion behavior was analyzed via true differential dilatometry and the directional Young’s moduli were determined via impulse excitation technique in the temperature range up to 850 °C. The coefficient of thermal expansion was found to be nearly independent of the analyzed orientations. However, Young’s moduli differed by 20 GPa, with the highest stiffness obtained for specimens orientated parallel to the x-axis of the machines’ coordinate system. PubDate: 2022-04-28
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Abstract: Abstract Single face centered cubic (fcc) AISI (American Iron and Steel Institute)-316L stainless steel and CoCrFeMnNi-high entropy alloy (HEA) were successfully fabricated using selective laser melting (SLM). Both the SLM processed alloys reveal the presence of hierarchical microstructure (presence of columnar grains, and cellular substructures). Also, the microhardness and tensile properties of AISI 316L stainless steel and CoCrFeMnNi-HEA are similar, where the microhardness varies between 240 and 270 HV0.5 and the yield strength and ultimate tensile strength are observed to be around ~ 500 MPa and ~ 600 MPa respectively. The aim of this research is to study the influence of rapid work hardening vs steady state working hardening in two materials of same crystal structure. Accordingly, CoCrFeMnNi-HEA exhibits higher work hardening rate at lower strains (< 5% true strain); however, it lacks its work hardening stability at higher strain. While in case of AISI 316L stainless steel, even though, it shows lower work hardening at initial strain, it withstands at higher strain (high ductility) due to stable work hardening ability by twin mediated plasticity during plastic deformation. PubDate: 2022-04-21
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Abstract: Abstract Traditionally manufactured nickel-based alloys (NiBA) are widely used for their high oxidation and corrosion resistance at extreme temperatures. Recently, additive manufacturing (AM) is being rapidly used to manufacture NiBA due to the ease of obtaining complex forms, low cost, and less waste generation. However, AM route makes NiBA vulnerable to corrosion and eventual failure. Yet, there is a lack of understanding of the effects of AM route on localized corrosion resistance in NiBA. This manuscript reviews the effects of various AM process parameters on the localized corrosion resistance of NiBA. Based on the data gathering and analysis, manufacturing steps for NiBA can be optimized for corrosion resistance. This review helps the community to understand the current and future needs in research and development in additive manufacturing of alloys. PubDate: 2022-04-21
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Abstract: Abstract Additive manufacturing (AM) technologies, generally called 3D printing, are widely used because their use provides a high added value in manufacturing complex-shaped components and objects. Defects may occur within the components at different time of manufacturing, and in this regard, non-destructive techniques (NDT) represent a key tool for the quality control of AM components in many industrial fields, such as aerospace, oil and gas, and power industries. In this work, the capability of active thermography and eddy current techniques to detect real imposed defects that are representative of the laser powder bed fusion process has been investigated. A 3D complex shape of defects was revealed by a µCT investigation used as reference results for the other NDT methods. The study was focused on two different types of defects: porosities generated in keyhole mode as well as in lack of fusion mode. Different thermographic and eddy current measurements were carried out on AM samples, providing the capability to detect volumetric irregularly shaped defects using non-destructive methods. PubDate: 2022-04-19
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Abstract: Abstract This work studies and compares the corrosion behavior of different planes of additively manufactured (AM) Ti-6Al-4V in 0.9 M NaCl solution. The samples were prepared by two different methods: electron beam melting (EBM) and selective laser melting (SLM). The obtained results indicate that the processing has a strong influence on the susceptibility to corrosion of AM Ti-6Al-4V alloy. Two interesting phenomena were observed: (a) the corrosion resistance of XY-planes of EBM and SLM Ti-6Al-4V is quite similar and is better than that of the XZ-planes; (b) the corrosion resistance of SLM Ti-6Al-4V alloy is slightly better than that of EBM Ti-6Al-4V in both XY- and XZ-planes. The effect of processing on the microstructure and corrosion resistance is discussed in detail. PubDate: 2022-04-18
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Abstract: Abstract Additive manufacturing allows designers to create geometries that would not be possible or economical to manufacture using traditional manufacturing processes. Production with these technologies does, however, introduce a large amount of variation and additional unknowns. These random variations from idealized geometry or material properties can harm the performance of the design. The current work presents an approach to improve the fatigue life of such structures, and simultaneously reduce its influence from random variations in local thickness. Following an initial numerical study, the results are experimentally validated. Experimental results show a significant improvement in fatigue life in the redesigned sample with a tailored thickness distribution. PubDate: 2022-04-18
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Abstract: Abstract The focus of this research work is to investigate the dimensional deviations obtained in the Fused Deposition Modelling process using ABS material and to perform optimization studies of 3D printing parameters. Preliminary investigations were carried out to identify the influence of size using different geometrical shapes and observed that small sized features have higher dimensional deviation. Inorder to further proceed with the optimization study, artifact with small sized geometrical features was used. Optimization studies were performed using Grey Taguchi Analysis and Taguchi Methodology considering infill percentage, layer thickness, number of shells, and speed of printing as process parameters. This study reveals that the percentage of infill material and the number of shells have a significant impact on the dimensional deviation of 33.89% and 32.43%, respectively, on 3D printed ABS samples. PubDate: 2022-04-18
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Abstract: Abstract Additive manufacturing and especially the laser-based powder bed fusion (LPBF) with full melting of the powder offers tremendous potential and versatility for manufacturing high quality, complex, precision metal parts. However, for novel powder compositions the LPBF process development is very time consuming and cost intensive due to the layer wise melting and the powder prices. This research work investigates the manufacturing of single and layered multi-material structures in a novel modular lab-scaled LPBF machining system through individual process and material development. The developed system allows the use of different laser sources, optical arrangements, individual sensor and actuator integration. In addition, the modular LPBF system enables the manufacturing of specimens with a minimum amount of powder, individual mixed powder compositions or layered multi-material parts. In an application example, a multi-material specimen made out of stainless steel 316L and Bronze 90/10 was manufactured in alternating layers. For this approach, a parameter study was performed for each material to investigate the influence of the volumetric energy density (VED) on the specimen density, surface flatness and reduced mixing zone formation. Afterwards, optimized parameters were used to demonstrate the feasibility of the system to produce a multi-material layered 316L-Bronze part. PubDate: 2022-04-07
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