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Showing 1 - 200 of 3175 Journals sorted alphabetically
A Practical Logic of Cognitive Systems     Full-text available via subscription   (Followers: 8)
AASRI Procedia     Open Access   (Followers: 14)
Academic Pediatrics     Hybrid Journal   (Followers: 28, SJR: 1.402, h-index: 51)
Academic Radiology     Hybrid Journal   (Followers: 22, SJR: 1.008, h-index: 75)
Accident Analysis & Prevention     Partially Free   (Followers: 90, SJR: 1.109, h-index: 94)
Accounting Forum     Hybrid Journal   (Followers: 25, SJR: 0.612, h-index: 27)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 33, SJR: 2.515, h-index: 90)
Achievements in the Life Sciences     Open Access   (Followers: 5)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 6, SJR: 0.338, h-index: 19)
Acta Astronautica     Hybrid Journal   (Followers: 377, SJR: 0.726, h-index: 43)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 2)
Acta Biomaterialia     Hybrid Journal   (Followers: 27, SJR: 2.02, h-index: 104)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription   (Followers: 2)
Acta de Investigación Psicológica     Open Access   (Followers: 3)
Acta Ecologica Sinica     Open Access   (Followers: 8, SJR: 0.172, h-index: 29)
Acta Haematologica Polonica     Free   (Followers: 1, SJR: 0.123, h-index: 8)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.604, h-index: 38)
Acta Materialia     Hybrid Journal   (Followers: 236, SJR: 3.683, h-index: 202)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5, SJR: 0.615, h-index: 21)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.442, h-index: 21)
Acta Oecologica     Hybrid Journal   (Followers: 10, SJR: 0.915, h-index: 53)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription  
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 2, SJR: 0.311, h-index: 16)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 1)
Acta Poética     Open Access   (Followers: 4)
Acta Psychologica     Hybrid Journal   (Followers: 25, SJR: 1.365, h-index: 73)
Acta Sociológica     Open Access  
Acta Tropica     Hybrid Journal   (Followers: 6, SJR: 1.059, h-index: 77)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 3)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 2)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 3, SJR: 0.383, h-index: 19)
Actas Urológicas Españolas (English Edition)     Full-text available via subscription   (Followers: 1)
Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 5, SJR: 0.141, h-index: 3)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 3, SJR: 0.112, h-index: 2)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 6)
Acute Pain     Full-text available via subscription   (Followers: 14)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.967, h-index: 57)
Addictive Behaviors     Hybrid Journal   (Followers: 15, SJR: 1.514, h-index: 92)
Addictive Behaviors Reports     Open Access   (Followers: 7)
Additive Manufacturing     Hybrid Journal   (Followers: 9, SJR: 1.039, h-index: 5)
Additives for Polymers     Full-text available via subscription   (Followers: 22)
Advanced Cement Based Materials     Full-text available via subscription   (Followers: 3)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 129, SJR: 5.2, h-index: 222)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 11, SJR: 1.265, h-index: 53)
Advanced Powder Technology     Hybrid Journal   (Followers: 16, SJR: 0.739, h-index: 33)
Advances in Accounting     Hybrid Journal   (Followers: 8, SJR: 0.299, h-index: 15)
Advances in Agronomy     Full-text available via subscription   (Followers: 12, SJR: 2.071, h-index: 82)
Advances in Anesthesia     Full-text available via subscription   (Followers: 27, SJR: 0.169, h-index: 4)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 2)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 10, SJR: 1.054, h-index: 35)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 10, SJR: 0.801, h-index: 26)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 22, SJR: 1.286, h-index: 49)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 14, SJR: 3.31, h-index: 42)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.277, h-index: 43)
Advances in Botanical Research     Full-text available via subscription   (Followers: 2, SJR: 0.619, h-index: 48)
Advances in Cancer Research     Full-text available via subscription   (Followers: 28, SJR: 2.215, h-index: 78)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 7, SJR: 0.9, h-index: 30)
Advances in Catalysis     Full-text available via subscription   (Followers: 5, SJR: 2.139, h-index: 42)
Advances in Cell Aging and Gerontology     Full-text available via subscription   (Followers: 3)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 12)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 27, SJR: 0.183, h-index: 23)
Advances in Child Development and Behavior     Full-text available via subscription   (Followers: 10, SJR: 0.665, h-index: 29)
Advances in Chronic Kidney Disease     Full-text available via subscription   (Followers: 10, SJR: 1.268, h-index: 45)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 28, SJR: 0.938, h-index: 33)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 19, SJR: 2.314, h-index: 130)
Advances in Computers     Full-text available via subscription   (Followers: 14, SJR: 0.223, h-index: 22)
Advances in Dermatology     Full-text available via subscription   (Followers: 14)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 10)
Advances in Digestive Medicine     Open Access   (Followers: 8)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 5)
Advances in Drug Research     Full-text available via subscription   (Followers: 21)
Advances in Ecological Research     Full-text available via subscription   (Followers: 42, SJR: 3.25, h-index: 43)
Advances in Engineering Software     Hybrid Journal   (Followers: 27, SJR: 0.486, h-index: 10)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 6)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 42, SJR: 5.465, h-index: 64)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 1)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 7)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 54, SJR: 0.674, h-index: 38)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 15)
Advances in Genetics     Full-text available via subscription   (Followers: 14, SJR: 2.558, h-index: 54)
Advances in Genome Biology     Full-text available via subscription   (Followers: 7)
Advances in Geophysics     Full-text available via subscription   (Followers: 6, SJR: 2.325, h-index: 20)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 21, SJR: 0.906, h-index: 24)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 0.497, h-index: 31)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 23)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 1, SJR: 0.396, h-index: 27)
Advances in Immunology     Full-text available via subscription   (Followers: 36, SJR: 4.152, h-index: 85)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 1.132, h-index: 42)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 2, SJR: 1.274, h-index: 27)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 6)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 3)
Advances in Life Course Research     Hybrid Journal   (Followers: 8, SJR: 0.764, h-index: 15)
Advances in Lipobiology     Full-text available via subscription   (Followers: 1)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 9)
Advances in Marine Biology     Full-text available via subscription   (Followers: 14, SJR: 1.645, h-index: 45)
Advances in Mathematics     Full-text available via subscription   (Followers: 10, SJR: 3.261, h-index: 65)
Advances in Medical Sciences     Hybrid Journal   (Followers: 6, SJR: 0.489, h-index: 25)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 4, SJR: 1.44, h-index: 51)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 21)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 8)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 7, SJR: 0.324, h-index: 8)
Advances in Nanoporous Materials     Full-text available via subscription   (Followers: 3)
Advances in Oncobiology     Full-text available via subscription   (Followers: 1)
Advances in Organ Biology     Full-text available via subscription   (Followers: 1)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15, SJR: 2.885, h-index: 45)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 6, SJR: 0.148, h-index: 11)
Advances in Parasitology     Full-text available via subscription   (Followers: 5, SJR: 2.37, h-index: 73)
Advances in Pediatrics     Full-text available via subscription   (Followers: 24, SJR: 0.4, h-index: 28)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 10)
Advances in Pharmacology     Full-text available via subscription   (Followers: 15, SJR: 1.718, h-index: 58)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 0.384, h-index: 26)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.248, h-index: 11)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 7)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 5)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 17)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 18, SJR: 1.5, h-index: 62)
Advances in Psychology     Full-text available via subscription   (Followers: 59)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6, SJR: 0.478, h-index: 32)
Advances in Radiation Oncology     Open Access  
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 3, SJR: 0.1, h-index: 2)
Advances in Space Biology and Medicine     Full-text available via subscription   (Followers: 5)
Advances in Space Research     Full-text available via subscription   (Followers: 378, SJR: 0.606, h-index: 65)
Advances in Structural Biology     Full-text available via subscription   (Followers: 5)
Advances in Surgery     Full-text available via subscription   (Followers: 9, SJR: 0.823, h-index: 27)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 29, SJR: 1.321, h-index: 56)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 17)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 13)
Advances in Virus Research     Full-text available via subscription   (Followers: 5, SJR: 1.878, h-index: 68)
Advances in Water Resources     Hybrid Journal   (Followers: 46, SJR: 2.408, h-index: 94)
Aeolian Research     Hybrid Journal   (Followers: 6, SJR: 0.973, h-index: 22)
Aerospace Science and Technology     Hybrid Journal   (Followers: 334, SJR: 0.816, h-index: 49)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.318, h-index: 36)
African J. of Emergency Medicine     Open Access   (Followers: 6, SJR: 0.344, h-index: 6)
Ageing Research Reviews     Hybrid Journal   (Followers: 9, SJR: 3.289, h-index: 78)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 432, SJR: 1.385, h-index: 72)
Agri Gene     Hybrid Journal  
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 15, SJR: 2.18, h-index: 116)
Agricultural Systems     Hybrid Journal   (Followers: 31, SJR: 1.275, h-index: 74)
Agricultural Water Management     Hybrid Journal   (Followers: 43, SJR: 1.546, h-index: 79)
Agriculture and Agricultural Science Procedia     Open Access   (Followers: 1)
Agriculture and Natural Resources     Open Access   (Followers: 2)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 56, SJR: 1.879, h-index: 120)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.434, h-index: 14)
Air Medical J.     Hybrid Journal   (Followers: 5, SJR: 0.234, h-index: 18)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.285, h-index: 3)
Alcohol     Hybrid Journal   (Followers: 11, SJR: 0.922, h-index: 66)
Alcoholism and Drug Addiction     Open Access   (Followers: 9)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 1, SJR: 0.436, h-index: 12)
Alexandria J. of Medicine     Open Access   (Followers: 1)
Algal Research     Partially Free   (Followers: 9, SJR: 2.05, h-index: 20)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 2)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.46, h-index: 29)
Allergology Intl.     Open Access   (Followers: 5, SJR: 0.776, h-index: 35)
Alpha Omegan     Full-text available via subscription   (SJR: 0.121, h-index: 9)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 9, SJR: 0.158, h-index: 9)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 48, SJR: 4.289, h-index: 64)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 4)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 4)
Ambulatory Pediatrics     Hybrid Journal   (Followers: 6)
American Heart J.     Hybrid Journal   (Followers: 50, SJR: 3.157, h-index: 153)
American J. of Cardiology     Hybrid Journal   (Followers: 50, SJR: 2.063, h-index: 186)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 42, SJR: 0.574, h-index: 65)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 10, SJR: 1.091, h-index: 45)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 14, SJR: 1.653, h-index: 93)
American J. of Human Genetics     Hybrid Journal   (Followers: 31, SJR: 8.769, h-index: 256)
American J. of Infection Control     Hybrid Journal   (Followers: 26, SJR: 1.259, h-index: 81)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 32, SJR: 2.313, h-index: 172)
American J. of Medicine     Hybrid Journal   (Followers: 42, SJR: 2.023, h-index: 189)
American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3)
American J. of Obstetrics and Gynecology     Hybrid Journal   (Followers: 190, SJR: 2.255, h-index: 171)
American J. of Ophthalmology     Hybrid Journal   (Followers: 62, SJR: 2.803, h-index: 148)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 6)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.249, h-index: 88)
American J. of Otolaryngology     Hybrid Journal   (Followers: 25, SJR: 0.59, h-index: 45)
American J. of Pathology     Hybrid Journal   (Followers: 27, SJR: 2.653, h-index: 228)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 27, SJR: 2.764, h-index: 154)
American J. of Surgery     Hybrid Journal   (Followers: 36, SJR: 1.286, h-index: 125)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.653, h-index: 70)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 6)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.066, h-index: 51)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 61, SJR: 0.124, h-index: 9)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 14)
Anales de Cirugia Vascular     Full-text available via subscription  
Anales de Pediatría     Full-text available via subscription   (Followers: 2, SJR: 0.209, h-index: 27)
Anales de Pediatría (English Edition)     Full-text available via subscription  
Anales de Pediatría Continuada     Full-text available via subscription   (SJR: 0.104, h-index: 3)
Analytic Methods in Accident Research     Hybrid Journal   (Followers: 4, SJR: 2.577, h-index: 7)
Analytica Chimica Acta     Hybrid Journal   (Followers: 39, SJR: 1.548, h-index: 152)
Analytical Biochemistry     Hybrid Journal   (Followers: 165, SJR: 0.725, h-index: 154)
Analytical Chemistry Research     Open Access   (Followers: 10, SJR: 0.18, h-index: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 11)
Anesthésie & Réanimation     Full-text available via subscription   (Followers: 1)
Anesthesiology Clinics     Full-text available via subscription   (Followers: 22, SJR: 0.421, h-index: 40)
Angiología     Full-text available via subscription   (SJR: 0.124, h-index: 9)
Angiologia e Cirurgia Vascular     Open Access   (Followers: 1)

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Journal Cover Additive Manufacturing
  [SJR: 1.039]   [H-I: 5]   [9 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 2214-8604
   Published by Elsevier Homepage  [3175 journals]
  • Material interactions in laser polishing powder bed additive manufactured
           Ti6Al4V components
    • Authors: Yingtao Tian; Wojciech S. Gora; Aldara Pan Cabo; Lakshmi L. Parimi; Duncan P. Hand; Samuel Tammas-Williams; Philip B. Prangnell
      Pages: 11 - 22
      Abstract: Publication date: March 2018
      Source:Additive Manufacturing, Volume 20
      Author(s): Yingtao Tian, Wojciech S. Gora, Aldara Pan Cabo, Lakshmi L. Parimi, Duncan P. Hand, Samuel Tammas-Williams, Philip B. Prangnell
      Laser polishing (LP) is an emerging technique with the potential to be used for post-build, or in-situ, precision smoothing of rough, fatigue-initiation prone, surfaces of additive manufactured (AM) components. LP uses a laser to re-melt a thin surface layer and smooths the surface by exploiting surface tension effects in the melt pool. However, rapid re-solidification of the melted surface layer and the associated substrate thermal exposure can significantly modify the subsurface material. This study has used an electron beam melted (EBM) Ti6Al4V component, representing the worst case scenario in terms of roughness for a powder bed process, as an example to investigate these issues and evaluate the capability of the LP technique for improving the surface quality of AM parts. Experiments have shown that the surface roughness can be reduced to below Sa = 0.51 μm, which is comparable to a CNC machined surface, and high stress concentrating defects inherited from the AM process were removed by LP. However, the re-melted layer underwent a change in texture, grain structure, and a martensitic transformation, which was subsequently tempered in-situ by repeated beam rastering and resulted in a small increase in sub-surface hardness. In addition, a high level of near-surface tensile residual stresses was generated by the process, although they could be relaxed to near zero by a standard stress relief heat treatment.
      Graphical abstract image

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2017.12.010
      Issue No: Vol. 20 (2018)
  • Achieving low surface roughness AlSi10Mg_200C parts using direct metal
           laser sintering
    • Authors: Mohsen Mohammadi; Hamed Asgari
      Pages: 23 - 32
      Abstract: Publication date: March 2018
      Source:Additive Manufacturing, Volume 20
      Author(s): Mohsen Mohammadi, Hamed Asgari
      Laser sintered aluminum alloys produced by metal 3D printers can replace cast aluminum alloys in aerospace, defense, and marine industries by offering better mechanical properties, less porosity, and competitive fatigue characteristics. One of the major issues currently is the considerable surface roughness of additively manufactured aluminum alloys demanding post-processing procedures such as bead blasting or machining. In the current study, the process parameters such as laser power, scan speed, and hatch spacing were altered such that better surface roughness could be achieved for AlSi10Mg_200C using a Direct Metal Laser Sintering (DMLS) system. The process parameters were chosen such that three samples with the same core properties but different upskin characteristics were produced. The achieved surface roughness of the additively manufactured aluminum samples were almost as low as one fifth of the regular samples manufactured using standard process parameters. The microstructure and the porosity level of the samples printed by different process parameters were studied to reveal the causality of the low surface roughness for the proposed process.

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2017.12.012
      Issue No: Vol. 20 (2018)
  • A study on the effect of energy input on spatter particles creation during
           selective laser melting process
    • Authors: Mohsen Taheri Andani; Reza Dehghani; Mohammad Reza Karamooz-Ravari; Reza Mirzaeifar; Jun Ni
      Pages: 33 - 43
      Abstract: Publication date: March 2018
      Source:Additive Manufacturing, Volume 20
      Author(s): Mohsen Taheri Andani, Reza Dehghani, Mohammad Reza Karamooz-Ravari, Reza Mirzaeifar, Jun Ni
      Selective laser melting (SLM) is a promising manufacturing technique for the production of complex metallic components. One of the crucial factors influencing the mechanical properties of the final product is spatter particles formation during the process. In this study, high- speed photography is utilized to record the formation mechanisms and the dynamic behavior of spatter particles. An image processing analysis framework is utilized to assess the distribution of spatter particles under various energy inputs. It is found that changing the laser scan velocity has more influences on spatter formation in comparison with the energy input. The relationship between the numbers of created spatter particles, induced unmelted regions and density variability are interpreted and discussed based on other observations, such as microscopic examination and density analysis of SLM parts. The obtained results could be used to enhance the current manufacturing process parameters optimization methods in SLM process.

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2017.12.009
      Issue No: Vol. 20 (2018)
  • Numerical modeling of the strand deposition flow in extrusion-based
           additive manufacturing
    • Authors: Raphaël Comminal; Marcin P. Serdeczny; David B. Pedersen; Jon Spangenberg
      Pages: 68 - 76
      Abstract: Publication date: March 2018
      Source:Additive Manufacturing, Volume 20
      Author(s): Raphaël Comminal, Marcin P. Serdeczny, David B. Pedersen, Jon Spangenberg
      We propose a numerical model to simulate the extrusion of a strand of semi-molten material on a moving substrate, within the computation fluid dynamics paradigm. According to the literature, the deposition flow of the strands has an impact on the inter-layer bond formation in extrusion-based additive manufacturing, as well as the surface roughness of the fabricated part. Under the assumptions of an isothermal Newtonian fluid and a creeping laminar flow, the deposition flow is controlled by two parameters: the gap distance between the extrusion nozzle and the substrate, and the velocity ratio of the substrate to the average velocity of the flow inside the nozzle. The numerical simulation fully resolves the deposition flow and provides the cross-section of the printed strand. For the first time, we have quantified the effect of the gap distance and the velocity ratio on the size and the shape of the strand. The cross-section of the strand ranges from being almost cylindrical (for a fast printing and with a large gap) to a flat cuboid with rounded edges (for a slow printing and with a small gap), which substantially differs from the idealized cross-section typically assumed in the literature. Finally, we found that the printing force applied by the extruded material on the substrate has a negative linear relationship with the velocity ratio, for a constant gap.

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2017.12.013
      Issue No: Vol. 20 (2018)
  • Process dependent porosity and the influence of shot peening on porosity
           morphology regarding selective laser melted AlSi10Mg parts
    • Authors: James Damon; Stefan Dietrich; Florian Vollert; Jens Gibmeier; Volker Schulze
      Pages: 77 - 89
      Abstract: Publication date: March 2018
      Source:Additive Manufacturing, Volume 20
      Author(s): James Damon, Stefan Dietrich, Florian Vollert, Jens Gibmeier, Volker Schulze
      This paper investigates the porosity distribution and morphology of selective laser melted rotation bending test samples before and after shot peening by means of micro-tomography analysis. The as-built samples show porosity clusters close to the surface, which are attributed to the contour-core scan strategy. In the following steps the effect of shot peening on pore size and morphology in dependency of depth was examined. A strong porosity shrinkage could be achieved in near-surface areas (0–500 μm), but also in depths that did not seem accessible via shot peening, leading to an overall relative porosity reduction between 15–30%. Furthermore, shot peening led to a pore sphericity increase, especially for large pores. The individual orientation of the pores were compared before and after shot peening, where the former mostly had their longest axis in surface normal direction, while the latter showed a more randomly orientation distribution. X-ray diffractography detected residual compressive stresses for the as-built as well as the shot peened samples. Finally fatigue tests were performed, indicating an increase in low- and high-cycle-fatigue resistance after shot peening by 20 MPa.

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2018.01.001
      Issue No: Vol. 20 (2018)
  • Open-source parametric 3-D printed slot die system for thin film
           semiconductor processing
    • Authors: L.Y. Beeker; Adam M. Pringle; Joshua M. Pearce
      Pages: 90 - 100
      Abstract: Publication date: March 2018
      Source:Additive Manufacturing, Volume 20
      Author(s): L.Y. Beeker, Adam M. Pringle, Joshua M. Pearce
      Slot die coating is growing in popularity because it is a low operational cost and easily scaled processing technique for depositing thin and uniform films rapidly, while minimizing material waste. The complex inner geometry of conventional slot dies require expensive machining that limits accessibility and experimentation. In order to overcome these issues this study follows an open hardware approach, which uses an open source 3-D printer to both fabricate the slot die and then to functionalize a 3-D slot die printing system. Polymer materials are tested and selected for compatibility with common solvents and used to fabricate a custom slot die head. This slot die is then integrated into a 3-D printer augmented with a syringe pump to form an additive manufacturing platform for thin film semiconductor devices. The full design of the slot die system is disclosed here using an open source license including software and operational protocols. This study demonstrates that functional lab-grade slot dies may be 3-D printed using low-cost open source hardware methods A case study using NiO2 found an RMS value 0.486 nm, thickness of 17–49 nm, and a maximum optical transmission of 99.1%, which shows this additive manufacturing approach to slot die depositions as well of fabrication is capable of producing viable layers of advanced electronic materials. Using this method, a cost savings of over 17,000% was obtained when compared to commercial slot die systems for laboratories.
      Graphical abstract image

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2017.12.004
      Issue No: Vol. 20 (2018)
  • In-situ distortions in LMD additive manufacturing walls can be measured
           with digital image correlation and predicted using numerical simulations
    • Authors: M. Biegler; B. Graf; M. Rethmeier
      Pages: 101 - 110
      Abstract: Publication date: March 2018
      Source:Additive Manufacturing, Volume 20
      Author(s): M. Biegler, B. Graf, M. Rethmeier
      Distortions in Additive Manufacturing (AM) Laser Metal Deposition (LMD) occur in the newly-built component due to rapid heating and solidification and can lead to shape deviations and cracking. This paper presents a novel approach to quantify the distortions experimentally and to use the results in numerical simulation validation. Digital Image Correlation (DIC) is applied together with optical filters to measure in-situ distortions directly on a wall geometry produced with LMD. The wall shows cyclic expansion and shrinking with the edges bending inward and the top of the sample exhibiting a slight u‐shape as residual distortions. Subsequently, a structural Finite Element Analysis (FEA) of the experiment is established, calibrated against experimental temperature profiles and used to predict the in-situ distortions of the sample. A comparison of the experimental and numerical results reveals a good agreement in length direction of the sample and quantitative deviations in height direction, which are attributed to the material model used. The suitability of the novel experimental approach for measurements on an AM sample is shown and the potential for the validated numerical model as a predictive tool to reduce trial-and-error and improve part quality is evaluated.

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2017.12.007
      Issue No: Vol. 20 (2018)
  • Design approach for additive manufacturing employing Constructal Theory
           for point-to-circle flows
    • Authors: Tobias Kamps; Manuel Biedermann; Christian Seidel; Gunther Reinhart
      Pages: 111 - 118
      Abstract: Publication date: March 2018
      Source:Additive Manufacturing, Volume 20
      Author(s): Tobias Kamps, Manuel Biedermann, Christian Seidel, Gunther Reinhart
      Design is crucial for additive manufacturing (AM). Not only does it affect manufacturability and cost but more importantly does it determine the functional performance of a part. Design for additive manufacturing (DFAM) methods consider these aspects and aim to leverage the available design freedom in order to generate functionally optimized parts. The following research work presents a method that is based on design principles from the so-called Constructal Theory. Two design principles are selected form this discipline, which considers design a field of science. The first principle outlines how a fluid flow can be distributed efficiently using a tree-shaped structure. The second principle emphasizes to first create the flow structure and then fit the surrounding solid body around it following the flow of mechanical stress. To demonstrate the approach, a case study of a gear wheel design is presented, which integrates cooling lubricant channels and focuses on minimal part mass. Based on analytical relations, a design concept is generated that provides a mass reduction of 25% and a fluid channel structure with minimal required pumping power. The resulting design serves as starting point for a more detailed simulation-based design optimization.

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2017.12.005
      Issue No: Vol. 20 (2018)
  • Printed Wheatstone bridge with embedded polymer based piezoresistive
           sensors for strain sensing applications
    • Authors: H.F. Castro; V. Correia; N. Pereira; P. Costab; J. Oliveiraa; S. Lanceros-Méndez
      Pages: 119 - 125
      Abstract: Publication date: March 2018
      Source:Additive Manufacturing, Volume 20
      Author(s): H.F. Castro, V. Correia, N. Pereira, P. Costab, J. Oliveiraa, S. Lanceros-Méndez
      Printed sensors find an increasing interest essentially due to their characteristics of flexibility and low cost per unit area. In this work a screen printed Wheatstone bridge is presented, suitable for strain sensing applications. A piezoresistive ink composite based on biocompatible thermoplastic elastomer styrene-ethylene/butylene-styrene (SEBS) as matrix and multi-walled carbon nanotubes (MWCNT) as nanofillers was used as a piezoresistive sensing material. Different deposition techniques, such as, screen printing, spray painting and drop casting were evaluated in order to optimize the resistance variation related to the piezoresistive effect. Several Wheatstone bridges with one and two sensors were designed to obtain an output sensitivity as a function of the strain submitted to the sensors. Further, different sensor geometries were evaluated to maximize the strain output sensitivity. Electro-mechanical bending tests showed a good linearity and a sensitivity up to 18 mV/V in the all screen printed half Wheatstone bridge output with two MWCNT/SEBS sensors.
      Graphical abstract image

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2018.01.004
      Issue No: Vol. 20 (2018)
  • Internal surface measurement of metal powder bed fusion parts
    • Authors: Adam Thompson; Nicola Senin; Ian Maskery; Lars Körner; Simon Lawes; Richard Leach
      Pages: 126 - 133
      Abstract: Publication date: March 2018
      Source:Additive Manufacturing, Volume 20
      Author(s): Adam Thompson, Nicola Senin, Ian Maskery, Lars Körner, Simon Lawes, Richard Leach
      Recent advances in X-ray computed tomography (XCT) have allowed for measurement resolutions approaching the point where XCT can be used for measuring surface topography. These advances make XCT appealing for measuring hard-to-reach or internal surfaces, such as those often present in additively manufactured parts. To demonstrate the feasibility and potential of XCT for topography measurement, topography datasets obtained using two XCT systems are compared to those acquired using coherence scanning interferometry and focus variation microscopy. A hollow Ti6Al4V part produced by laser powder bed fusion is used as a measurement artefact. The artefact comprises two component halves that can be separated to expose the internal surfaces. Measured surface datasets are accurately aligned and similarly cropped, and compared by various qualitative and quantitative means, including the computation of ISO 25178-2 areal surface texture parameters, commonly used in part quality assessment. Results show that XCT can non-destructively provide surface information comparable with more conventional surface measurement technologies, thus representing a viable alternative to more conventional measurement, particularly appealing for hard-to-reach and internal surfaces.

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2018.01.003
      Issue No: Vol. 20 (2018)
  • Laser processing of Ti composite coatings reinforced with hydroxyapatite
           and bioglass
    • Authors: Vaibhav Chalisgaonkar; Mitun Das; Vamsi Krishna Balla
      Pages: 134 - 143
      Abstract: Publication date: March 2018
      Source:Additive Manufacturing, Volume 20
      Author(s): Vaibhav Chalisgaonkar, Mitun Das, Vamsi Krishna Balla
      Composite coatings of titanium reinforced separately with hydroxyapatite (HAp) and bioglass (BG) were deposited on titanium substrate using Laser Engineered Net Shaping (LENS™). The microstructure, phase constituents, in vitro electrochemical, tribological and biological properties of these composite coatings deposited using different laser powers was studied. The composite coatings showed several reaction products such as Ca2P2O7, CaTiO3, Na2Ca2Si3O9 due to high temperature interaction of HAp and BG with Ti. The average top surface hardness of the Ti substrate was 148 ± 5 HV and that of the composite coatings was between 720 and 740 HV. As a result, the composite coatings exhibited significant increase in the in vitro wear resistance. The incorporation of HAp and BG in Ti increased the corrosion current, possibly due to the presence of residual stresses, but shifted the corrosion potential towards noble direction due bioactive reinforcements. In vitro proliferation of mouse embryonic fibroblast cells (NIH3T3) was found to be more on composite coatings than on titanium substrate demonstrating their superior cell-materials interactions.

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2018.01.008
      Issue No: Vol. 20 (2018)
  • Tailoring selective laser melting process for titanium drug-delivering
           implants with releasing micro-channels
    • Authors: Hany Hassanin; Laurane Finet; Sophie C. Cox; Parastoo Jamshidi; Liam M. Grover; Duncan E.T. Shepherd; Owen Addison; Moataz M. Attallah
      Pages: 144 - 155
      Abstract: Publication date: March 2018
      Source:Additive Manufacturing, Volume 20
      Author(s): Hany Hassanin, Laurane Finet, Sophie C. Cox, Parastoo Jamshidi, Liam M. Grover, Duncan E.T. Shepherd, Owen Addison, Moataz M. Attallah
      The use of drug-delivering implants can minimise implant failure due to infection through a controlled medication release into the surrounding tissues. In this study, selective laser melting (SLM) was employed to manufacture Ti-6Al-4 V samples, with internal reservoirs and releasing Micro-channels (MCs) to simulate what could be a drug-delivering orthopaedic or dental implant. Investigations were performed to optimise the design and SLM process parameters required to create the releasing MCs with minimum dimensional deviation to allow a controlled dosing of the drugs, while considering the process impact on the surface roughness and porosity of the builds. The build orientation, internal contour spacing, and laser process parameters were varied to assess their effect on the resolution of the MCs with diameters of ∼200–500 μm. It was found that, vertically oriented channels were found to have the least dimensional deviation from the target dimensions compared with horizontally-oriented or inclined channels. The dimensional deviation of the MCs was found in range of 220–427 μm, while the horizontal surface roughness (Ra) was in range of 1.46–11.46 μm and the vertical surface roughness (Ra) was in range of 8.5–13.23 μm when applying energy density varying from of 27–200 J/mm3. It was found that, there was a clear correlation between the energy density with both dimensional deviation and horizontal surface roughness, while no correlation was found for the vertical’ surface roughness. The study identified the optimum conditions to manufacture drug-delivering metallic implants, creating hollow samples with releasing MCs equivalent diameter of ∼271 μm, horizontal surface roughness (Ra) of 4.4 μm, vertical surface roughness of (Ra) 9.2 μm, and build porosity of 1.4% using an internal contour of 150 μm and energy density of 35.7 J/mm3.
      Graphical abstract image

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2018.01.005
      Issue No: Vol. 20 (2018)
  • A fundamental study of printed ink resiliency for harsh mechanical and
           thermal environmental applications
    • Authors: Clayton Neff; Edwin Elston; Matthew Burfeindt; Nathan Crane; Amanda Schrand
      Pages: 156 - 163
      Abstract: Publication date: March 2018
      Source:Additive Manufacturing, Volume 20
      Author(s): Clayton Neff, Edwin Elston, Matthew Burfeindt, Nathan Crane, Amanda Schrand
      The integration of novel additively manufactured (AM) materials and processes with traditional materials and manufacturing techniques, including the insertion of commercial off-the-shelf (COTS) components such as resistors, switches, batteries and light emitting diodes (LEDs), has led to the development of increasingly complex ‘hybrid’ electronics including: antennas, waveguides, radio frequency identification (RFID) tags, various sensors, circuits and devices. However, in order to utilize these novel electronics in mechanically and thermally harsh environments (e.g. defense applications), more rigorous characterization and testing methods are required. Here we examine the resiliency and radio frequency (RF) performance of two commercially available conductive inks (DuPont CB028 and KA801) printed onto a radar transparent substrate (poly ether, ether ketone; PEEK). The quality of ink adhesion, a factor found to directly correlate with antenna performance, is examined via adhesion testing after exposure to high accelerations up to 20,000 g and temperature cycling from −54 °C to +71 °C. Overall, the designs, procedures and results provide a framework for multi-materials resiliency assessment as well as aspects unique to materials resiliency under harsh environmental conditions.

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2018.01.009
      Issue No: Vol. 20 (2018)
  • Selective electroplating of 3D printed parts
    • Authors: Kristin Angel; Harvey H. Tsang; Sarah S. Bedair; Gabriel L. Smith; Nathan Lazarus
      Pages: 164 - 172
      Abstract: Publication date: March 2018
      Source:Additive Manufacturing, Volume 20
      Author(s): Kristin Angel, Harvey H. Tsang, Sarah S. Bedair, Gabriel L. Smith, Nathan Lazarus
      Fused filament fabrication (FFF) 3D printers have been largely limited to thermoplastics in the past but with new composite materials available on the market there are new possibilities for what these machines can produce. Using a conductive composite filament, electronic components can be manufactured but due to the filament’s relatively poor electrical properties, the resulting traces are typically highly resistive. Selective electroplating on these parts is one approach to incorporate materials with high conductivity onto 3D-printed structures. In this paper, non-conductive and conductive filaments printed in the same part are used to enable selective electroplating directly on regions defined by the conductive filament to create metallic parts through 3D printing. This technique is demonstrated for the creation of multiple distinct conductive segments and to electroplate the same part with multiple metals to, for instance, allow a magnetic metal such as nickel and a highly conductive one such as copper to be incorporated in the same part. Following the characterization of the process, a representative 3D printed electrical device, a selectively electroplated solenoid inductor with low frequency inductance and resistance of 191 nH and 18.7 mΩ respectively was manufactured using this technique. This is a five order of magnitude reduction in resistance over the original value of 3 kΩ for the inductor before electroplating.

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2018.01.006
      Issue No: Vol. 20 (2018)
  • Microstructure characterization of SLM-processed Al-Mg-Sc-Zr alloy in the
           heat treated and HIPed condition
    • Authors: A.B. Spierings; K. Dawson; P. Dumitraschkewitz; S. Pogatscher; K. Wegener
      Pages: 173 - 181
      Abstract: Publication date: March 2018
      Source:Additive Manufacturing, Volume 20
      Author(s): A.B. Spierings, K. Dawson, P. Dumitraschkewitz, S. Pogatscher, K. Wegener
      Sc- Zr-modified Al-Mg alloy, processed by selective laser melting, offers excellent properties in the as processed condition, due to the formation of a desirable microstructure. As in conventional processing, such alloys are age hardenable, thereby precipitating a high fraction of finely dispersed coherent Al3(Scx Zr1-x) intermetallics, which serve for the improvement of the mechanical strength. Electron backscatter diffraction measurements and transmission electron microscopy were used to determine the effects of heat treatment and HIP on the microstructures of SLM processed specimens. In addition, the chemistry and number density of Al3Sc particles was analysed by atom probe tomography. The results show that the bi-modal grain size distribution observed in the as-processed condition can be maintained even after a heat treatment, due to a high density of intragranular Al3(ScxZr1-x) precipitates, and various other particles pinning the grain boundaries. A HIP post-processing can lead to grain growth in certain coarser grained areas, probably due to a local imbalance between driving and dragging forces, hence higher defect density and fewer pinning precipitates. Applying a heat treatment results in an increase of the density of ≤5 nm sized intragranular Al3(Scx Zr1-x) particles by a factor of 4–6, reaching 3·1023 m−3 to 5·1023 m−3.
      Graphical abstract image

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2017.12.011
      Issue No: Vol. 20 (2018)
  • Towards additive manufacturing of compressor impellers: 3D modeling of
           multilayer laser solid freeform fabrication of nickel alloy 625 powder
           mixed with nano-CeO2 on AISI 4140
    • Authors: G. Fayaz; Saman Kazemzadeh
      Pages: 182 - 188
      Abstract: Publication date: Available online 20 February 2018
      Source:Additive Manufacturing
      Author(s): Gholamreza Fayaz, Saman Kazemzadeh
      Gas turbine blades, turbine shafts and centrifugal compressor impellers are often damaged by erosion and/or corrosion. By laser cladding technique, a coating layer can be deposited on the base material in order to rebuild, repair and improve anti-erosion or anti-corrosion properties of the sensitive machine parts. In this paper, a three-dimensional finite element modeling of the laser solid freeform fabrication (LSFF) process for nickel alloy 625 powder mixed with nano-CeO2 on AISI 4140 steel is extensively studied. Using Comsol Multiphysics software and the finite element method (FEM), the heat transfer equation, moving mesh equation and stress tensor are numerically solved. The dynamic geometry of the molten zone is studied by a 3D moving mesh based on Arbitrary Lagrangian-Eulerian (ALE) module. Clad shape, temperature distribution and stress fields are obtained. The effects of preheating as well as addition of nano-CeO2 are investigated. Dependence of the clad height on the scanning velocity of the laser is also studied.

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2018.02.001
      Issue No: Vol. 20 (2018)
  • Synchronized material deposition rate control with path velocity on fused
           filament fabrication machines
    • Authors: Deniz Sera Ertay; Alexander Yuen; Yusuf Altintas
      Pages: 205 - 213
      Abstract: Publication date: January 2018
      Source:Additive Manufacturing, Volume 19
      Author(s): Deniz Sera Ertay, Alexander Yuen, Yusuf Altintas
      Additive manufacturing (AM) technologies are used in three dimensional (3D) printing of parts using thermo-plastic extruders, or laser and electron beam based metal deposition methods. This paper presents an integrated methodology for planning of tangential path velocity, material deposition rate and temperature control of the extruded material which is deposited along curved paths. The tangential velocity along the path is smoothed and optimized while respecting the heater’s and extruder’s capacities, as well as the feed drives’ jerk, acceleration and velocity limits. The extrusion rate is controlled proportional to the tangential path velocity while keeping the temperature of the deposited thermo-plastic material at the desired temperature by adaptively controlling current supply to the heater. The experimentally proven algorithm leads to more uniform material deposition at sharp curvatures and resulting improved dimensional accuracy of printed parts. The proposed methodology can be extended to laser and electron beam based metal printing applications.

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2017.05.011
      Issue No: Vol. 19 (2018)
  • Thermal conductivity of metal powders for powder bed additive
    • Authors: Lien Chin Wei; Lili E. Ehrlich; Matthew J. Powell-Palm; Colt Montgomery; Jack Beuth; Jonathan A. Malen
      Abstract: Publication date: Available online 25 February 2018
      Source:Additive Manufacturing
      Author(s): Lien Chin Wei, Lili E. Ehrlich, Matthew J. Powell-Palm, Colt Montgomery, Jack Beuth, Jonathan A. Malen
      The thermal conductivities of five metal powders for powder bed additive manufacturing (Inconel 718, 17-4 stainless steel, Inconel 625, Ti-6Al-4V, and 316L stainless steel) were measured using the transient hot wire method. These measurements were conducted with three infiltrating gases (argon, nitrogen, and helium) within a temperature range of 295-470 K and a gas pressure range of 1.4-101 kPa. The measurements of thermal conductivity indicate that the pressure and the composition of the gas have a significant influence on the effective thermal conductivity of the powder, but that the metal powder properties and temperature do not. Our measurements improve the accuracy upon which laser parameters can be optimized in order to improve thermal control of powder beds in selective laser melting processes, especially in overhanging and cellular geometries where heat dissipation by the powder is critical.

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2018.02.002
  • Surface roughness in Selective Laser Melted Ti-6Al-4V alloy components
    • Authors: Zhuoer Chen; Xinhua Wu; Dacian Tomus; Chris H.J. Davies
      Abstract: Publication date: Available online 25 February 2018
      Source:Additive Manufacturing
      Author(s): Zhuoer Chen, Xinhua Wu, Dacian Tomus, Chris H.J. Davies
      A rational design of experiments was employed to evaluate the correlation between scan parameters and the resulting surface roughness of Selective Laser Melted Ti-6Al-4V components. There is a statistically significant difference in surface roughness values from specimens built with identical laser exposure parameters but located at different positions on the build platform. We hypothesise that this is a consequence of changing powder particle size distributions across the powder bed resulting from the combined actions of the recoater arm and gas flow. We further hypothesise that orientation of a part and the projected shape of the incident laser beam play a part in surface roughness variation at any given location. We found that during the powder re-coating process, fine particles tend to settle within a short distance from the re-coater starting position, accompanied by higher variability of local powder size distribution. Spatter material was found to be distributed across the powder bed by the gas flow. However, once at any given location the surface roughness of inclined surfaces is affected by the orientation of the surface to the centre of the build platform at which the laser beam originates. Each of these factors affects the surface roughness and has implications for the order in which parts are built in Selective Laser Melting.
      Graphical abstract image

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2018.02.009
  • Comparison of virgin Ti-6Al-4V powders for additive manufacturing
    • Authors: Yu Sun; Mark Aindow; Rainer J. Hebert
      Abstract: Publication date: Available online 24 February 2018
      Source:Additive Manufacturing
      Author(s): Yu Sun, Mark Aindow, Rainer J. Hebert
      Ti-6Al-4V powders from six different vendors were compared with respect to their microstructures, size-distributions, chemistries, surface appearances, flow behavior, and packing densities. The analysis approaches followed closely ASTM F3049, the standard guide for characterization of additive manufacturing metal powders. Chemistries, including impurity content, agreed well with the standard requirements. Powder particle microstructures revealed acicular alpha prime for all vendors. Measurable differences were observed primarily in the size-distributions and the flow behavior.

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2018.02.011
  • Additive manufacturing of Inconel 718—Copper alloy bimetallic structure
           using laser engineered net shaping (LENS™)
    • Authors: Bonny Onuike; Bryan Heer; Amit Bandyopadhyay
      Abstract: Publication date: Available online 23 February 2018
      Source:Additive Manufacturing
      Author(s): Bonny Onuike, Bryan Heer, Amit Bandyopadhyay
      To understand processing ability and measure resultant interfacial and thermal properties of Inconel 718 and copper alloy GRCop-84, bimetallic structures were fabricated using laser engineering net shaping (LENS™), a commercially available additive manufacturing technique. It was hypothesized that additively combining the two aerospace alloys would form a unique bimetallic structure with improved thermophysical properties compared to the Inconel 718 alloy. Two approaches were used: the direct deposition of GRCop-84 on Inconel 718 and the compositional gradation of the two alloys. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray Diffraction (XRD), Vickers microhardness and flash thermal diffusivity were used to characterize these bimetallic structures to validate our hypothesis. The compositional gradation approach showed a gradual transition of Inconel 718 and GRCop-84 elements at the interface, which was also reflected in the cross-sectional hardness profile across the bimetallic interface. SEM images showed columnar grain structures at the interfaces with Cr2Nb precipitate accumulation along grain boundaries and the substrate-deposit interface. The average thermal diffusivity of the bimetallic structure was measured at 11.33 mm2/s for the temperature range of 50 °C–300 °C; a 250% increase in diffusivity when compared to the pure Inconel 718 alloy at 3.20 mm2/s. Conductivity of the bimetallic structures increased by almost 300% compared to Inconel 718 as well. Such structures with designed compositional gradation and tailored thermal properties opens up the possibilities of multi-material metal additive manufacturing for next generation of aerospace structures.
      Graphical abstract image

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2018.02.007
  • Additive manufacturing of non-assembly mechanisms
    • Authors: Juan Sebastian Cuellar; Gerwin Smit; Dick Plettenburg; Amir Zadpoor
      Abstract: Publication date: Available online 21 February 2018
      Source:Additive Manufacturing
      Author(s): Juan Sebastian Cuellar, Gerwin Smit, Dick Plettenburg, Amir Zadpoor
      Fabrication of complex and multi-articulated mechanisms is often seen as a time consuming and demanding process. The development of functional multi-articulated mechanisms that could be fabricated in a single step without the need for post-manufacturing assembly is therefore very attractive. Additive manufacturing (AM) has been pointed out as a feasible solution due to its numerous advantages and high versatility in comparison to other manufacturing techniques. Nevertheless, AM techniques also present different shortcomings that limit the complexity of the mechanism for single step fabrication. Here, we review the applications of AM techniques in fabrication of non-assembly multi-articulated mechanisms and highlight the involved challenges, thereby providing a perspective regarding the advantages and limitations of current AM techniques for production of complex mechanical devices. The paper starts off with basic joint elements in rigid-body and compliant configurations and proceeds with presenting an overview of multiple arrangements of joints and assemblies with embedded mechanical components. For every case of non-assembly fabrication, the limitations of the applicable AM processes are presented and further discussed. This work concludes with a discussion of the major shortcomings found in current non-assembly mechanisms fabricated by AM and recommending alternative techniques and future developments on AM.

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2018.02.004
  • Characterization of the Fe-Co-1.5 V soft ferromagnetic alloy processed
           by Laser Engineered Net Shaping (LENS)
    • Authors: Andrew B. Kustas; Donald F. Susan; Kyle L. Johnson; Shaun R. Whetten; Mark A. Rodriguez; Daryl J. Dagel; Joseph R. Michael; David M. Keicher; Nicolas Argibay
      Abstract: Publication date: Available online 21 February 2018
      Source:Additive Manufacturing
      Author(s): Andrew B. Kustas, Donald F. Susan, Kyle L. Johnson, Shaun R. Whetten, Mark A. Rodriguez, Daryl J. Dagel, Joseph R. Michael, David M. Keicher, Nicolas Argibay
      Processing of the low workability Fe-Co-1.5 V (Hiperco® equivalent) alloy is demonstrated using the Laser Engineered Net Shaping (LENS) metals additive manufacturing technique. As an innovative and highly localized solidification process, LENS is shown to overcome workability issues that arise during conventional thermomechanical processing, enabling the production of bulk, near net-shape forms of the Fe-Co alloy. Bulk LENS structures appeared to be ductile with no significant macroscopic defects. Atomic ordering was evaluated and significantly reduced in as-built LENS specimens relative to an annealed condition, tailorable through selection of processing parameters. Fine grain, equiaxed structures were observed in as-built specimens following solidification, which then evolved toward a highly heterogeneous bimodal grain structure after annealing. The microstructure evolution in Fe-Co is discussed in the context of classical solidification theory and selective grain boundary pinning processes. Magnetic properties were also assessed and shown to fall within the extremes of conventionally processed Hiperco® alloys. Hiperco® is a registered trademark of Carpenter Technologies, Readings, PA.

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2018.02.006
  • Finite Element Analysis and Experimental Validation of the
           Thermomechanical Behavior in Laser Solid Forming of Ti-6Al-4V
    • Authors: Xufei Lu; Xin Lin; Michele Chiumenti; Miguel Cervera; JunJie Li; Liang Ma; Lei Wei; Yunlong Hu; Weidong Huang
      Abstract: Publication date: Available online 19 February 2018
      Source:Additive Manufacturing
      Author(s): Xufei Lu, Xin Lin, Michele Chiumenti, Miguel Cervera, JunJie Li, Liang Ma, Lei Wei, Yunlong Hu, Weidong Huang
      A three-dimensional (3D) thermomechanical coupled model for Laser Solid Forming (LSF) of Ti-6Al-4V alloy has been calibrated through experiments of 40-layers metal deposition using different scanning strategies. The sensitivity analysis of the mechanical parameters shows that the thermal expansion coefficient as well as the elastic limit of Ti-6Al-4V have a great impact on the mechanical behavior. Using the validated model and optimal mechanical parameters, the evolution of thermo-mechanical fields in LSF has been analyzed. It has been found that the stresses and distortions develop in two stages, after the deposition of the first layer and during the cooling phase after the manufacturing of the component. The cooling phase is the responsible of 70% of the residual stresses and 60% of the total distortions. The analyses indicate that by controlling the initial substrate temperature (pre-heating phase) and the final cooling phase it is possible to mitigate both distortion and residual stresses. Hence, the influence of different pre-heating procedures on the mechanical fields has been analyzed. The results show that increasing the pre-heating temperature of the substrate is the most effective way to reduce the distortions and residual stresses in Additive Manufacturing.

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2018.02.003
  • Fused Filament Fabrication of Fiber-Reinforced Polymers: A Review
    • Authors: Bastian Brenken; Eduardo Barocio; Anthony Favaloro; Vlastimil Kunc; R. Byron Pipes
      Abstract: Publication date: Available online 2 February 2018
      Source:Additive Manufacturing
      Author(s): Bastian Brenken, Eduardo Barocio, Anthony Favaloro, Vlastimil Kunc, R. Byron Pipes
      Recent advancements in the Additive Manufacturing (AM) Fused Filament Fabrication (FFF) approach are described with focus on the application to tooling and molds for composite materials and structures. A detailed summary of mechanical properties of printed parts for different composite material systems is presented and discussed. These material systems are comprised of discontinuous fiber-reinforced polymers characterized by fiber orientation dominantly parallel to the direction of the extrudate. An overview of the FFF process and its physical phenomena is given including the flow and resulting fiber orientation, the bond formation between adjacent beads and the thermomechanical solidification behavior of the deposited material. Based on reviewed research in these different phenomena, future research needs are discussed and desirable objectives are formulated.

      PubDate: 2018-02-26T08:24:04Z
      DOI: 10.1016/j.addma.2018.01.002
  • A literature review of powder-based electron beam melting focusing on
           numerical simulations
    • Authors: Manuela Galati; Luca Iuliano
      Pages: 1 - 20
      Abstract: Publication date: January 2018
      Source:Additive Manufacturing, Volume 19
      Author(s): Manuela Galati, Luca Iuliano
      The Electron Beam Melting (EBM) process is an additive manufacturing process in which an electron beam melts metallic powders to obtain the geometry of a specific part. The use of an electron beam in the AM field is relatively recent. Numerous applications have already been made in the aerospace and medical fields, in which the EBM process is used to produce complex parts, made of an excellent quality material, for which other technologies would be expensive or difficult to apply. Because of the growing interest of industry in this technology, the research community has been dedicating a great deal of effort to making the EBM process more reliable. The modelling of the EBM process is considered of utmost importance as it could help to reduce the process optimisation time, compared with the trial and error approach, which is currently the most widely used method. From this point of view, the aim of this paper has been to provide a literature review of numerical simulation models of the EBM process. The various studies on numerical modelling are presented in detail. These studies are mainly classified according to the level of approximation introduced into the modelling methodology. The simulations have first been categorised according to the powder modelling approach that has been adopted (i.e. mesoscopic or FE approach). The studies have then been categorised, as far as FE-based simulations are concerned, as either uncoupled or coupled modelling approaches. All the current approaches have been compared, and how the researchers have modelled the EBM process has been highlighted, considering the assumptions that have been made, the modelling of the material properties, the material state change, and the heat source. Moreover, the adopted validation approaches and the results have been described in order to point out any important achievements. Deviations between numerical and experimental results have been discussed as well as the current level of development of the simulation of the EBM process.

      PubDate: 2017-11-10T05:25:07Z
      DOI: 10.1016/j.addma.2017.11.001
      Issue No: Vol. 19 (2017)
  • On the machinability of directed energy deposited Ti6Al4V
    • Authors: Olusola Oyelola; Pete Crawforth; Rachid M’Saoubi; Adam T. Clare
      Pages: 39 - 50
      Abstract: Publication date: January 2018
      Source:Additive Manufacturing, Volume 19
      Author(s): Olusola Oyelola, Pete Crawforth, Rachid M’Saoubi, Adam T. Clare
      Current class Directed Energy Deposition (DED) techniques used for component manufacture and repair have inherently poor geometrical tolerance. Hence, there remains a requirement to apply conventional machining strategies post build in order to achieve finished components. In contrast to wrought materials, parts produced this way have markedly different localised material properties. This in turn results in non-uniform machinability within these. The present work investigates the effect of traditional machining approaches on the processability and resultant surface integrity of Ti6Al4V produced by DED. Here, heat treatments are applied post DED in order to homogenise the microstructure and in turn improve the overall machinability of the material. Fundamental metallurgical analysis reveals grain coarsening which is consistent with standard heat treatments used for wrought Ti6Al4V. Investigation of the stress condition of specimens machined from the ‘as-built’ condition and the heat treated condition show a 22% increase in compressive residual surface stress, a reduction in cutting forces of 40% in the beta condition and 24% in the alpha condition at a low machining speed of 50m/min. Furthermore, heat treatment and machining strategies are proposed which demonstrate performance improvements over standard machining techniques in the ‘as-built’ condition.

      PubDate: 2017-11-23T13:32:26Z
      DOI: 10.1016/j.addma.2017.11.005
      Issue No: Vol. 19 (2017)
  • Acoustoplastic metal direct-write: Towards solid aluminum 3D printing in
           ambient conditions
    • Authors: Anagh Deshpande; Keng Hsu
      Pages: 73 - 80
      Abstract: Publication date: January 2018
      Source:Additive Manufacturing, Volume 19
      Author(s): Anagh Deshpande, Keng Hsu
      In this work the process of Acoustoplastic Metal Direct-write (AMD) is introduced for the first time. Millimeter-scale 3D aluminum articles were printed to demonstrate the process feasibility. Evidence of process-induced inter-layer and intra-layer mass transport resulting in metallurgical bonding across voxels was obtained. During voxel formation, a process temperature rise of 5° Celsius from a process ambient temperature of 25° Celsius was recorded. In addition, acoustic energy-induced microstructural changes during process were observed in the material. The work presented here not only demonstrates the feasibility of a new non-melt fusion room temperature metal 3D printing approach—capable of producing metals with more than 99 percent density—but also presents both observational study and an initial theoretical basis upon which a new athermal microstructural transformation process may be understood

      PubDate: 2017-11-23T13:32:26Z
      DOI: 10.1016/j.addma.2017.11.006
      Issue No: Vol. 19 (2017)
  • Strategies for functionally graded lattice structures derived using
           topology optimisation for Additive Manufacturing
    • Authors: Ajit Panesar; Meisam Abdi; Duncan Hickman; Ian Ashcroft
      Pages: 81 - 94
      Abstract: Publication date: January 2018
      Source:Additive Manufacturing, Volume 19
      Author(s): Ajit Panesar, Meisam Abdi, Duncan Hickman, Ian Ashcroft
      A number of strategies that enable lattice structures to be derived from Topology Optimisation (TO) results suitable for Additive Manufacturing (AM) are presented. The proposed strategies are evaluated for mechanical performance and assessed for AM specific design related manufacturing considerations. From a manufacturing stand-point, support structure requirement decreases with increased extent of latticing, whereas the design-to-manufacture discrepancies and the processing efforts, both in terms of memory requirements and time, increase. Results from Finite Element (FE) analysis for the two loading scenarios considered: intended loading, and variability in loading, provide insight into the solution optimality and robustness of the design strategies. Lattice strategies that capitalised on TO results were found to be considerably (∼40–50%) superior in terms of specific stiffness when compared to the structures where this was not the case. The Graded strategy was found to be the most desirable from both the design and manufacturing perspective. The presented pros-and-cons for the various proposed design strategies aim to provide insight into their suitability in meeting the challenges faced by the AM design community.

      PubDate: 2017-11-23T13:32:26Z
      DOI: 10.1016/j.addma.2017.11.008
      Issue No: Vol. 19 (2017)
  • Targeted rework strategies for powder bed additive manufacture
    • Authors: M. Hirsch; P. Dryburgh; S. Catchpole-Smith; R. Patel; L. Parry; S.D. Sharples; I.A. Ashcroft; A.T. Clare
      Pages: 127 - 133
      Abstract: Publication date: January 2018
      Source:Additive Manufacturing, Volume 19
      Author(s): M. Hirsch, P. Dryburgh, S. Catchpole-Smith, R. Patel, L. Parry, S.D. Sharples, I.A. Ashcroft, A.T. Clare
      A major factor limiting the adoption of powder-bed-fusion additive manufacturing for production of parts is the control of build process defects and the effect these have upon the certification of parts for structural applications. In response to this, new methods for detecting defects and to monitor process performance are being developed. However, effective utilisation of such methods to rework parts in process has yet to be demonstrated. This study investigates the use of spatially resolved acoustic spectroscopy (SRAS) scan data to inform repair strategies within a commercial selective laser melting machine. New methodologies which allow for rework of the most common defects observed in selective laser melting (SLM) manufacturing are proposed and demonstrated. Three rework methodologies are applied to targeted surface breaking pores: a hatch pattern, a spiral pattern and a single shot exposure. The work presented shows that it is possible to correct surface breaking pores using targeted re-melting, reducing the depth of defects whilst minimising changes in local texture. For the hatch rework and spiral rework, a reduction in defect depth of 50% and 31% were observed, respectively, however, no improvement was seen after the single shot exposures. This work is part of a programme to develop a method by which defects can be detected and the part reworked in-process during SLM to enable defect specification targets to be met. Although further work in developing build-characterise-rework strategies for integrated and targeted defect correction is needed, the feasibility of the underlying method of identifying and selectively reworking to reduce a defect has now been demonstrated for the first time.
      Graphical abstract image

      PubDate: 2017-12-27T05:12:16Z
      DOI: 10.1016/j.addma.2017.11.011
      Issue No: Vol. 19 (2017)
  • Topology-mechanical property relationship of 3D printed strut, skeletal,
           and sheet based periodic metallic cellular materials
    • Authors: Oraib Al-Ketan; Reza Rowshan; Rashid K. Abu Al-Rub
      Pages: 167 - 183
      Abstract: Publication date: January 2018
      Source:Additive Manufacturing, Volume 19
      Author(s): Oraib Al-Ketan, Reza Rowshan, Rashid K. Abu Al-Rub
      Recent advances in additive manufacturing facilitated the fabrication of parts with great geometrical complexity and relatively small size, and allowed for the fabrication of topologies that could not have been achieved using traditional fabrication techniques. In this work, we explore the topology-property relationship of several classes of periodic cellular materials; the first class is strut-based structures, while the second and third classes are derived from the mathematically created triply periodic minimal surfaces, namely; the skeletal-TPMS and sheet-TPMS cellular structures. Powder bed fusion technology was employed to fabricate the cellular structures of various relative densities out of Maraging steel. Scanning electron microscope (SEM) was also employed to assess the quality of the printed parts. Compressive testing was performed to deduce the mechanical properties of the considered cellular structures. Results showed that the sheet-TPMS based cellular structures exhibited a near stretching-dominated deformation behavior, while skeletal-TPMS showed a bending-dominated behavior. On the other hand, the Kelvin and Gibson-Ashby strut-based topologies exhibited a mixed mode of deformation while the Octet-truss showed a stretching-dominated behavior. Overall the sheet-TPMS based cellular structures showed superior mechanical properties among all the tested structures. The most interesting observation is that sheet-based Diamond TPMS structure showed the best mechanical performance with nearly independence of relative density. It was also observed that at decreased volume fractions the effect of geometry on the mechanical properties is more pronounced.

      PubDate: 2017-12-27T05:12:16Z
      DOI: 10.1016/j.addma.2017.12.006
      Issue No: Vol. 19 (2017)
  • Characterization of topology optimized Ti-6Al-4V components using electron
           beam powder bed fusion
    • Authors: S. Yoder; S. Morgan; C. Kinzy; E. Barnes; M. Kirka; V. Paquit; P. Nandwana; A Plotkowski; R.R. Dehoff; S.S. Babu
      Pages: 184 - 196
      Abstract: Publication date: January 2018
      Source:Additive Manufacturing, Volume 19
      Author(s): S. Yoder, S. Morgan, C. Kinzy, E. Barnes, M. Kirka, V. Paquit, P. Nandwana, A Plotkowski, R.R. Dehoff, S.S. Babu
      The use of manufacturing to generate topology optimized components shows promise for designers. However, designers who assume that additive manufacturing follows traditional manufacturing techniques may be misled due to the nuances in specific techniques. Since commercial topology optimization software tools are neither designed to consider orientation of the parts nor large variations in properties, the goal of this research is to evaluate the limitations of an existing commercial topology optimization software (i.e. Inspire®) using electron beam powder bed fusion (i.e. Arcam®) to produce optimized Ti-6Al-4V alloy components. Emerging qualification tools from Oak Ridge National Laboratory including in-situ near-infrared imaging and log file data analysis were used to rationalize the final performance of components. While the weight savings of each optimized part exceeded the initial criteria, the failure loads and locations proved instrumental in providing insight to additive manufacturing with topology optimization. This research has shown the need for a comprehensive understanding of correlations between geometry, additive manufacturing processing conditions, defect generation, and microstructure for characterization of complex components such as those designed by topology optimization.

      PubDate: 2017-12-27T05:12:16Z
      DOI: 10.1016/j.addma.2017.12.001
      Issue No: Vol. 19 (2017)
  • Critical evaluation of the pulsed selective laser melting process when
           fabricating Ti64 parts using a range of particle size distributions
    • Authors: Abdullah Yahia Alfaify; James Hughes; Keith Ridgway
      Pages: 197 - 204
      Abstract: Publication date: January 2018
      Source:Additive Manufacturing, Volume 19
      Author(s): Abdullah Yahia Alfaify, James Hughes, Keith Ridgway
      Selective Laser Melting (SLM) is a metal additive manufacturing process where parts are fabricated from metal powder based on CAD data. Selection of the best process parameters for the pulsed SLM processes is a fundamental problem due to the increased number of parameters that have a direct impact on the melt pool compared to the continuous SLM processes. In previous studies, volumetric energy density or scan speed have been used as control variables for applied energy. In this paper, the process parameters (laser power, exposure time, point distance and hatching distance) were considered individually, in addition to particle size distribution and layer thickness. The Taguchi experimental design method was used to determine and optimise the effect of the selected input parameters. The effect of exposure time and its correlation with layer thickness and particle size distribution was then investigated. The results show the best combination of process parameters which can provide fully or near fully dense parts. The results also show the minimum exposure time that can be used with different powder types and layer thicknesses. The paper concludes with a study which shows the part location has a significant impact on sample quality.

      PubDate: 2017-12-27T05:12:16Z
      DOI: 10.1016/j.addma.2017.12.003
      Issue No: Vol. 19 (2017)
  • Effects of thermal cycles on the microstructure evolution of Inconel 718
           during selective laser melting process
    • Authors: Xiaoqing Wang; Kevin Chou
      Pages: 1 - 14
      Abstract: Publication date: December 2017
      Source:Additive Manufacturing, Volume 18
      Author(s): Xiaoqing Wang, Kevin Chou
      A staircase Inconel 718 block was fabricated to investigate the effects of the thermal cycles on the microstructure evolution in the selective laser melting (SLM) part using optical scope (OM), scanning electron microscope (SEM), and electron backscatter diffraction (EBSD). The laser beam scanning strategy was clearly shown in the part under OM, including laser scanning pattern and hatch spacing. The Y-plane (side surface) was characterized by elongated colonies of cellular dendrites with an average cell spacing of 0.511∼0.845μm. In addition, Laves phase was observed in the inter-layers and inter-cellular regions. Under the continuing effects of the thermal cycles, the fraction of the Laves-phase showed a significant drop with their morphology changing from coarse and interconnected particles to discrete Laves phase. This is attributed to the reheating process as Laves phase can be dissolved at a proper heat treatment. In terms of the width of the cellular dendrites, the longer the thermal cycle period is, the coarser the elongated grains are. Due to the preferred orientation of the crystal, the Y-plane and Z-plane had a strong texture of < 1 0 1> and < 0 0 1>, respectively. With the repeating thermal cycle period elongating, the maximum intensity of the texture, together with the fraction of larger grains and the high misorientation angles, increased. At the same height, there was no significant changes with the grains size, but the fraction of the high misorientation angles (>15°) increased with the subsequent building of the part. Moreover, the area fraction of the porosity was below 0.2%, with no remarkable effects found from the thermal cycles and the build height.

      PubDate: 2017-09-10T11:51:53Z
      DOI: 10.1016/j.addma.2017.08.016
      Issue No: Vol. 18 (2017)
  • Effect of printing speed on quality of printed parts in Binder Jetting
    • Authors: Hadi Miyanaj; Niknam Momenzadeh; Li Yang
      Abstract: Publication date: Available online 26 December 2017
      Source:Additive Manufacturing
      Author(s): Hadi Miyanaj, Niknam Momenzadeh, Li Yang
      Binder Jetting Process is an Additive Manufacturing technique (AM) in which a liquid binder is employed for establishing the initial strength and fabricating the geometry of components. In this process, the delivery of the binding agent is accomplished through a drop-on-demand (DOD) printhead by deposition of picoliter-sized droplets of the liquid binder. The velocity of the droplets impinging the powder bed surface might have significant effect on droplet spreading and absorption dynamics, which can be manifested in quality and integrity of the fabricated parts. In the present study, the effect of the printing speed on dimensional accuracy and equilibrium saturation level of printed samples is experimentally investigated and the observed trends are discussed in detail.

      PubDate: 2017-12-27T05:12:16Z
      DOI: 10.1016/j.addma.2017.12.008
  • Mechanical Characterization of 3D-Printed Polymers
    • Authors: John Ryan C. Dizon; Alejandro H. Espera; Qiyi Chen; Rigoberto C. Advincula
      Abstract: Publication date: Available online 9 December 2017
      Source:Additive Manufacturing
      Author(s): John Ryan C. Dizon, Alejandro H. Espera, Qiyi Chen, Rigoberto C. Advincula
      3D printing, more formally known as Additive Manufacturing (AM), is already being adopted for rapid prototyping and soon rapid manufacturing. This review provides a brief discussion about AM and also the most employed AM technologies for polymers. The commonly-used ASTM and ISO mechanical test standards which have been used by various research groups to test the strength of the 3D-printed parts have also been reported. Also a summary of an exhaustive amount of literature regarding the mechanical properties of 3D-printed parts is included. Specifically, properties under different loading types such as tensile, bending, compressive, fatigue, impact and others. Properties at low temperatures have also been discussed. Effects of fillers as well as post-processing on the mechanical properties have been discussed. Lastly, several important questions to consider in the standardization of mechanical test methods have been discussed.

      PubDate: 2017-12-27T05:12:16Z
      DOI: 10.1016/j.addma.2017.12.002
  • Acoustic emission for in situ quality monitoring in additive manufacturing
           using spectral convolutional neural networks
    • Authors: S.A. Shevchik; C. Kenel; C. Leinenbach; K. Wasmer
      Abstract: Publication date: Available online 6 December 2017
      Source:Additive Manufacturing
      Author(s): S.A. Shevchik, C. Kenel, C. Leinenbach, K. Wasmer
      Additive manufacturing, also known as 3D printing, is a new technology that obliterates the geometrical limits of the produced workpieces and promises low running costs as compared to traditional manufacturing methods Although it has high expectations in industry, the absence of a proper in situ quality monitoring and control prohibits the penetration of this technology into an extensive practice. This work investigates the feasibility of using acoustic emission for in situ quality monitoring and combines a sensitive acoustic emission sensor with machine learning. The acoustic signals were recorded using a fiber Bragg grating sensor during the powder-bed additive manufacturing process using a commercially available selective laser melting machine. The process parameters were intentionally tuned to invoke different concentration of pores inside the workpiece medium. According to this, poor, medium and high qualities were defined and were characterized by pore concentrations of 1.42±0.85, 0.3±0.18 and 0.07±0.02%, respectively. The collected acoustic signals were grouped accordingly and divided into two separate datasets; one for the training and one for the testing. The acoustic features were extracted from all the signals as the relative energies of the narrow frequency bands of the wavelet packet transform. The classifier, based on spectral convolutional neural network, was trained to differentiate the acoustic features of dissimilar quality. The confidence in classifications varies between 83 and 89%. Considering these are the first experiments with no optimization, the results can be considered as promising and they showed the feasibility of the in situ quality monitoring using acoustic emission with the sub-layer spatial resolution.
      Graphical abstract image

      PubDate: 2017-12-27T05:12:16Z
      DOI: 10.1016/j.addma.2017.11.012
  • Strength-Based Topology Optimization for Anisotropic Parts
    • Authors: Amir M. Mirzendehdel; Behzad Rankouhi; Krishnan Suresh
      Abstract: Publication date: Available online 22 November 2017
      Source:Additive Manufacturing
      Author(s): Amir M. Mirzendehdel, Behzad Rankouhi, Krishnan Suresh
      Additive manufacturing (AM) is emerging as a promising technology to fabricate cost-effective, customized functional parts. Designing such functional, i.e., load bearing, parts can be challenging and time consuming where the goal is to balance performance and material usage. Topology optimization (TO) is a powerful design method which can complement AM by automating the design process. However, for TO to be a useful methodology, the underlying mathematical model must be carefully constructed. Specifically, it is well established that parts fabricated through some AM technologies, such as fused deposition modeling (FDM), exhibit behavioral anisotropicity. This induced anisotropy can have a negative impact on functionality of the part, and must be considered. To the best of our knowledge, a robust TO method to handle anisotropy has not been proposed. In the present work, a strength-based topology optimization method for structures with anisotropic materials is presented. More specifically, we propose a new topological sensitivity formulation based on strength ratio of non-homogeneous failure criteria, such as Tsai-Wu. Implementation details are discussed throughout the paper, and the effectiveness of the proposed method is demonstrated through numerical and experimental tests.

      PubDate: 2017-11-23T13:32:26Z
      DOI: 10.1016/j.addma.2017.11.007
  • Enhanced mechanical properties of additively manufactured bulk metallic
           glasses produced through laser foil printing from continuous sheetmetal
    • Authors: Punnathat Bordeenithikasem; Yiyu Shen; Hai-Lung Tsai; Douglas C.Hofmann
      Abstract: Publication date: Available online 21 November 2017
      Source:Additive Manufacturing
      Author(s): Punnathat Bordeenithikasem, Yiyu Shen, Hai-Lung Tsai, Douglas C.Hofmann
      Metal additive manufacturing (AM) is a rapidly growing field aimed to produce high-performance net-shaped parts. Therefore, bulk metallic glasses (BMGs), known for their superlative mechanical properties, are of remarkable interest for integration with AM technology. In this study, we pioneer the utilization of commercially available BMG sheetmetal as feedstock for AM, using laser foil printing (LFP) technology. LFP and traditional casting were used to produce samples for four-point bending and Vickers hardness measurements to rigorously compare the mechanical performance of samples resulting from these two fabrication techniques. Through LFP, fully amorphous BMG samples with dimensions larger than the critical casting thickness of the same master alloy were successfully made, while exhibiting high yield strength and toughness in bending. This work exemplifies a potential method to fabricate high-value BMG commercial parts, like gears or mechanisms, where the parts are conventionally machined after printing, and greatly benefit from utilizing novel materials.

      PubDate: 2017-11-23T13:32:26Z
      DOI: 10.1016/j.addma.2017.11.010
  • Anomaly Detection and Classification in a Laser Powder Bed Additive
           Manufacturing Process using a Trained Computer Vision Algorithm
    • Authors: Luke Scime; Jack Beuth
      Abstract: Publication date: Available online 16 November 2017
      Source:Additive Manufacturing
      Author(s): Luke Scime, Jack Beuth
      Despite the rapid adoption of laser powder bed fusion (LPBF) Additive Manufacturing by industry, current processes remain largely open-loop, with limited real-time monitoring capabilities. While some machines offer powder bed visualization during builds, they lack automated analysis capability. This work presents an approach for in-situ monitoring and analysis of powder bed images with the potential to become a component of a real-time control system in an LPBF machine. Specifically, a computer vision algorithm is used to automatically detect and classify anomalies that occur during the powder spreading stage of the process. Anomaly detection and classification are implemented using an unsupervised machine learning algorithm, operating on a moderately-sized training database of image patches. The performance of the final algorithm is evaluated, and its usefulness as a standalone software package is demonstrated with several case studies.

      PubDate: 2017-11-23T13:32:26Z
      DOI: 10.1016/j.addma.2017.11.009
  • Cold Gas Dynamic Spray technology: a comprehensive review of processing
           conditions for various technological developments till to date
    • Authors: R.N. Raoelison; Y. Xie; T. Sapanathan; MP. Planche; R. Kromer; S. Costil; C. Langlade
      Abstract: Publication date: Available online 10 November 2017
      Source:Additive Manufacturing
      Author(s): R.N. Raoelison, Y. Xie, T. Sapanathan, MP. Planche, R. Kromer, S. Costil, C. Langlade
      Today, cold gas dynamic spray (CGDS) technology has thrived with considerable capabilities for manufacturing various technological depositions. The deposition conditions have been developed through many years and that have led to produce ample experimental data which is available in the literature. But, recent research and development activities also reveal innovative findings regarding various deposition conditions. This paper contains a review of experimental deposition procedures for the cold spray additive manufacturing. Details of processing conditions are reported and classified into various categories of baseline working conditions, specific processing including deposition of nanotechnological components, composites-based structures and hybrid coating with substrate deposition. Available substrate treatments and their contributions on the deposition capability were also included. A large collection of experimental data from the literature is addressed in the Appendices A1–A6 in Supplementary material.

      PubDate: 2017-11-23T13:32:26Z
      DOI: 10.1016/j.addma.2017.07.001
  • The effect of manufacturing defects on compressive strength of Ultralight
           hollow microlattices: A data-driven study
    • Authors: L. Salari-Sharif; S.W. Godfrey; M. Tootkaboni; L. Valdevit
      Abstract: Publication date: Available online 8 November 2017
      Source:Additive Manufacturing
      Author(s): L. Salari-Sharif, S.W. Godfrey, M. Tootkaboni, L. Valdevit
      Hollow microlattices constitute a model topology for architected materials, as they combine excellent specific stiffness and strength with relative ease of manufacturing. The most scalable manufacturing technique to date encompasses fabrication of a sacrificial polymeric template by the Self Propagating Photopolymer Waveguide (SPPW) process, followed by thin film coating and removal of the substrate. Accurate modeling of mechanical properties (e.g., stiffness, strength) of hollow microlattices is challenging, primarily due to the complex stress state around the hollow nodes and the existence of manufacturing-induced geometric imperfections (e.g. cracks, non-circularity, etc.). In this work, we use a variety of measuring techniques (SEM imaging, CT scanning, etc.) to characterize the geometric imperfections in a nickel-based ultralight hollow microlattice and investigate their effect on the compressive strength of the lattice. At the strut level, where a more quantitative description of geometric defects is available, the gathered data is used to build a stochastic field model of geometric imperfections using Proper Orthogonal Decomposition. Using Monte Carlo simulations, the critical buckling loads of a large set of imperfect bars created using the stochastic model are then extracted by Finite Elements Analysis. The statistics of the buckling strength in artificially generated bars is then used to explain the scatter in the strength of CT-derived bars and its correlation with the lattice strength measured experimentally. Although the quantitative results are specific to microlattices fabricated by SPPW templating, the methodology presented herein is equally applicable to architected materials produced by other manufacturing processes.

      PubDate: 2017-11-10T05:25:07Z
      DOI: 10.1016/j.addma.2017.11.003
  • Optimizing Process Parameters of Fused Deposition Modeling by Taguchi
           Method for the Fabrication of Lattice Structures
    • Authors: Guoying Dong; Grace Wijaya; Yunlong Tang; Yaoyao Fiona Zhao
      Abstract: Publication date: Available online 8 November 2017
      Source:Additive Manufacturing
      Author(s): Guoying Dong, Grace Wijaya, Yunlong Tang, Yaoyao Fiona Zhao
      The lattice structure is a type of cellular material that can achieve a variety of promising physical properties. Additive Manufacturing (AM) has relieved the difficulty of fabricating lattice structures with complex geometries. However, the quality of the AM fabricated lattice structure still needs improvement. In this paper, the influence of parameters of the Fused Deposition Modeling (FDM) process on lattice structures was investigated by the Taguchi method. S/N ratio analysis was used to find the optimal process parameters that improve the printing quality, and ANOVA provided a significance ranking of the various factors analyzed in this paper. It was found that the optimum level and significance of each process parameter vary for horizontal and inclined struts. In addition, compression tests investigate the influence of process parameters on the mechanical properties of lattice structures. The results show that process parameters optimized by print quality can also improve the elastic modulus and the ultimate strength of these lattice structures.

      PubDate: 2017-11-10T05:25:07Z
      DOI: 10.1016/j.addma.2017.11.004
  • Process-Structure-Property Effects on ABS Bond Strength in Fused Filament
    • Authors: A.C. Abbott; G.P. Tandon; R.L. Bradford; H. Koerner; J.W. Baur
      Abstract: Publication date: Available online 4 November 2017
      Source:Additive Manufacturing
      Author(s): A.C. Abbott, G.P. Tandon, R.L. Bradford, H. Koerner, J.W. Baur
      Interlayer bonds pose regions of weakness in structures produced via melt extrusion based polymer additive manufacturing. Bond strength was assessed both between layers and within layers as a function of print parameters by performing tensile tests on ABS coupons printed in two orientations. Print parameters considered were extruder temperature, print speed, and layer height. An IR camera was used to track thermal history of interlayer bond lines during the printing process. Contact length between roads was measured from mesostructure optical micrographs. Print speed was found to have a large impact on tensile strength with high speeds generally yielding lower strength. A plateau in tensile strength of 22MPa was observed for a normalized contact length greater than 0.6 independent of print orientation.

      PubDate: 2017-11-10T05:25:07Z
      DOI: 10.1016/j.addma.2017.11.002
  • Location Specific Solidification Microstructure Control in Electron Beam
           Melting of Ti-6Al-4V
    • Authors: Sneha P. Narra; Ross Cunningham; Jack Beuth; Anthony D. Rollett
      Abstract: Publication date: Available online 2 October 2017
      Source:Additive Manufacturing
      Author(s): Sneha P. Narra, Ross Cunningham, Jack Beuth, Anthony D. Rollett
      Relationships between prior beta grain size in solidified Ti-6Al-4V and melting process parameters in the Electron beam melting (EBM) process are investigated. Samples were built by varying a machine-dependent proprietary speed function to cover the process space. Optical microscopy was used to measure the prior beta grain widths and assess the number of prior beta grains present in a melt pool in the raster region of the build. Despite the complicated evolution of beta grain sizes in solid parts, beta grain width scales with melt pool width. The resulting understanding of the relationship between primary machine variables and prior beta grain widths is a key step toward enabling the location specific control of as-built microstructure in the EBM process. Control of grain width in separate specimens and within a single specimen is demonstrated.

      PubDate: 2017-10-06T11:27:37Z
      DOI: 10.1016/j.addma.2017.10.003
  • Ultrafast 3D High Precision Print of Micro Structures for Optical
           Instrument Calibration Procedures
    • Authors: Felix Ströer; Julian Hering; Matthias Eifler; Indek Raid; Georg von Freymann; Jörg Seewig
      Abstract: Publication date: Available online 9 September 2017
      Source:Additive Manufacturing
      Author(s): Felix Ströer, Julian Hering, Matthias Eifler, Indek Raid, Georg von Freymann, Jörg Seewig
      Multi-photon polymerization, like the so-called direct laser writing (DLW) technique allows for flexible additive manufacturing of three-dimensional ultra-precise structures on the micro- and nanoscale. A possible application for DLW is the manufacturing of measurement standards for calibration procedures of optical measurement instruments. This requires flexible and high precision manufacturing of individualized geometries with high quality surfaces. However, many of the process parameters in DLW have to be selected based on experience and previous knowledge. In this article, the influence of DLW process parameters on the micro-geometry and surface roughness produced are systematically studied, and optimized in terms of printing speed and manufacturing accuracy. Resulting microstructures are being evaluated with different measurement techniques, i. e., a stylus instrument, SEM and AFM. Based on optimized process parameters, a new measurement standard for the novel interferometric measurement instrument Ellipso-Height-Topometer is manufactured and examined as a case study. As a result, it can be shown, that DLW is able to manufacture ultra-precise micro geometries in a very flexible and very fast way and satisfies the tolerances for manufacturing of the designed measurement standard.

      PubDate: 2017-09-10T11:51:53Z
      DOI: 10.1016/j.addma.2017.09.001
  • A systematic study on numerical simulation of electrified jet printing
    • Authors: A. Rahmat; B. Koc; M. Yildiz
      Abstract: Publication date: Available online 31 August 2017
      Source:Additive Manufacturing
      Author(s): A. Rahmat, B. Koc, M. Yildiz
      In this paper, a numerical model based on a systematic study of electrified jet printing is presented. The Volume of Fluid (VOF) method which suits for modeling multiphase flows with a continuous interface is used. The surface tension force is calculated with the Continuum Surface Force (CSF) method and the electric forces are added to the momentum equation by taking the divergence of the Maxwell stress tensor. A systematic study is carried out by introducing three dimensionless numbers, namely Reynolds, Electro-Weber and Weber numbers. Employing these dimensionless numbers, the number of effective parameters is reduced, and a relative comparison of the importance of competing forces on the process becomes possible. It is observed that the electric forces contribute to the formation of the jet by acting on its tip, and by pulling the jet towards the deposition surface. The results show that an increase in Reynolds and Electro-Weber numbers both lead to form a thinner jet. It is also observed that further increase in Electro-Weber and Reynolds numbers leads to the formation of an unstable jet.

      PubDate: 2017-09-04T03:24:05Z
      DOI: 10.1016/j.addma.2017.08.004
  • Partitioning of Laser Energy during Directed Energy Deposition
    • Authors: Frederick Lia; Joshua Park; Jay Tressler; Richard Martukanitz
      Abstract: Publication date: Available online 30 August 2017
      Source:Additive Manufacturing
      Author(s): Frederick Lia, Joshua Park, Jay Tressler, Richard Martukanitz
      An energy balance that describes the transfer of energy is proposed for the laser-based directed energy deposition process. The partitioning of laser energy was experimentally measured and accurately validated using a special process calorimeter for Ti-6Al-4V and Inconel 625™ alloys. The total energy provided by the laser was partitioned as: the energy directly absorbed by the substrate, the energy absorbed by the powder stream and deposited onto the substrate, the energy reflected from the substrate surface, and the energy reflected or absorbed and lost from the powder stream. Titanium alloy Ti-6Al-4V showed higher overall or bulk absorption than the Inconel 625™ alloy. Processing with powder resulted in lower laser energy absorption within the substrate than without powder, due to the “shadowing” effect of the powder stream within the beam and loss of energy representing unfused powder. During processing at a laser power of approximately 1kW the total energy absorbed during the deposition process was found to be 42% for the Ti-6Al-4V alloy and 37% for the Inconel 625™ alloy. Under these conditions 14% of the total energy was lost by the Ti-6Al-4V unfused powder; whereas only 11% was lost by the Inconel 625™ powder.

      PubDate: 2017-09-04T03:24:05Z
      DOI: 10.1016/j.addma.2017.08.012
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