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Publisher: Elsevier   (Total: 3163 journals)

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Showing 1 - 200 of 3163 Journals sorted alphabetically
A Practical Logic of Cognitive Systems     Full-text available via subscription   (Followers: 9)
AASRI Procedia     Open Access   (Followers: 14)
Academic Pediatrics     Hybrid Journal   (Followers: 30, SJR: 1.655, CiteScore: 2)
Academic Radiology     Hybrid Journal   (Followers: 22, SJR: 1.015, CiteScore: 2)
Accident Analysis & Prevention     Partially Free   (Followers: 88, SJR: 1.462, CiteScore: 3)
Accounting Forum     Hybrid Journal   (Followers: 25, SJR: 0.932, CiteScore: 2)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 35, SJR: 1.771, CiteScore: 3)
Achievements in the Life Sciences     Open Access   (Followers: 5)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 7)
Acta Astronautica     Hybrid Journal   (Followers: 395, SJR: 0.758, CiteScore: 2)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 2)
Acta Biomaterialia     Hybrid Journal   (Followers: 27, SJR: 1.967, CiteScore: 7)
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: 0.18, CiteScore: 1)
Acta Haematologica Polonica     Free   (Followers: 1, SJR: 0.128, CiteScore: 0)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.661, CiteScore: 2)
Acta Materialia     Hybrid Journal   (Followers: 243, SJR: 3.263, CiteScore: 6)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5, SJR: 0.504, CiteScore: 1)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.542, CiteScore: 1)
Acta Oecologica     Hybrid Journal   (Followers: 10, SJR: 0.834, CiteScore: 2)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription  
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 2, SJR: 0.307, CiteScore: 0)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 1, SJR: 1.793, CiteScore: 6)
Acta Poética     Open Access   (Followers: 4, SJR: 0.101, CiteScore: 0)
Acta Psychologica     Hybrid Journal   (Followers: 27, SJR: 1.331, CiteScore: 2)
Acta Sociológica     Open Access  
Acta Tropica     Hybrid Journal   (Followers: 6, SJR: 1.052, CiteScore: 2)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 3, SJR: 0.374, CiteScore: 1)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 2)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 3, SJR: 0.344, CiteScore: 1)
Actas Urológicas Españolas (English Edition)     Full-text available via subscription   (Followers: 1)
Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 6, SJR: 0.19, CiteScore: 0)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 3)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 6)
Acute Pain     Full-text available via subscription   (Followers: 15, SJR: 2.671, CiteScore: 5)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.53, CiteScore: 4)
Addictive Behaviors     Hybrid Journal   (Followers: 16, SJR: 1.29, CiteScore: 3)
Addictive Behaviors Reports     Open Access   (Followers: 8, SJR: 0.755, CiteScore: 2)
Additive Manufacturing     Hybrid Journal   (Followers: 9, SJR: 2.611, CiteScore: 8)
Additives for Polymers     Full-text available via subscription   (Followers: 22)
Advanced Cement Based Materials     Full-text available via subscription   (Followers: 3, SJR: 0.732, CiteScore: 3)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 137, SJR: 4.09, CiteScore: 13)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 11, SJR: 1.167, CiteScore: 4)
Advanced Powder Technology     Hybrid Journal   (Followers: 16, SJR: 0.694, CiteScore: 3)
Advances in Accounting     Hybrid Journal   (Followers: 8, SJR: 0.277, CiteScore: 1)
Advances in Agronomy     Full-text available via subscription   (Followers: 12, SJR: 2.384, CiteScore: 5)
Advances in Anesthesia     Full-text available via subscription   (Followers: 28, SJR: 0.126, CiteScore: 0)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 2)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 10, SJR: 0.992, CiteScore: 1)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 10, SJR: 1.551, CiteScore: 4)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 22, SJR: 2.089, CiteScore: 5)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 14, SJR: 0.572, CiteScore: 2)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.61, CiteScore: 7)
Advances in Botanical Research     Full-text available via subscription   (Followers: 2, SJR: 0.686, CiteScore: 2)
Advances in Cancer Research     Full-text available via subscription   (Followers: 29, SJR: 3.043, CiteScore: 6)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 7, SJR: 1.453, CiteScore: 2)
Advances in Catalysis     Full-text available via subscription   (Followers: 5, SJR: 1.992, CiteScore: 5)
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: 0.156, CiteScore: 1)
Advances in Child Development and Behavior     Full-text available via subscription   (Followers: 10, SJR: 0.713, CiteScore: 1)
Advances in Chronic Kidney Disease     Full-text available via subscription   (Followers: 10, SJR: 1.316, CiteScore: 2)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 28, SJR: 1.562, CiteScore: 3)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 19, SJR: 1.977, CiteScore: 8)
Advances in Computers     Full-text available via subscription   (Followers: 14, SJR: 0.205, CiteScore: 1)
Advances in Dermatology     Full-text available via subscription   (Followers: 15)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 11)
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: 23)
Advances in Ecological Research     Full-text available via subscription   (Followers: 42, SJR: 2.524, CiteScore: 4)
Advances in Engineering Software     Hybrid Journal   (Followers: 27, SJR: 1.159, CiteScore: 4)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 7)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 43, SJR: 5.39, CiteScore: 8)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 1)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 9)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 53, SJR: 0.591, CiteScore: 2)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 17)
Advances in Genetics     Full-text available via subscription   (Followers: 15, SJR: 1.354, CiteScore: 4)
Advances in Genome Biology     Full-text available via subscription   (Followers: 8, SJR: 12.74, CiteScore: 13)
Advances in Geophysics     Full-text available via subscription   (Followers: 6, SJR: 1.193, CiteScore: 3)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 21, SJR: 0.368, CiteScore: 1)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 11, SJR: 0.749, CiteScore: 3)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 22)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 2, SJR: 0.193, CiteScore: 0)
Advances in Immunology     Full-text available via subscription   (Followers: 37, SJR: 4.433, CiteScore: 6)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 1.163, CiteScore: 2)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 2, SJR: 1.938, CiteScore: 3)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 6, SJR: 0.176, CiteScore: 0)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 3)
Advances in Life Course Research     Hybrid Journal   (Followers: 8, SJR: 0.682, CiteScore: 2)
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: 0.88, CiteScore: 2)
Advances in Mathematics     Full-text available via subscription   (Followers: 11, SJR: 3.027, CiteScore: 2)
Advances in Medical Sciences     Hybrid Journal   (Followers: 6, SJR: 0.694, CiteScore: 2)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 4, SJR: 1.158, CiteScore: 3)
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: 0.182, CiteScore: 0)
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: 16, SJR: 1.875, CiteScore: 4)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 6, SJR: 0.174, CiteScore: 0)
Advances in Parasitology     Full-text available via subscription   (Followers: 5, SJR: 1.579, CiteScore: 4)
Advances in Pediatrics     Full-text available via subscription   (Followers: 24, SJR: 0.461, CiteScore: 1)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 10)
Advances in Pharmacology     Full-text available via subscription   (Followers: 16, SJR: 1.536, CiteScore: 3)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 0.574, CiteScore: 1)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.109, CiteScore: 1)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 8)
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: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 19, SJR: 0.791, CiteScore: 2)
Advances in Psychology     Full-text available via subscription   (Followers: 59)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6, SJR: 0.371, CiteScore: 1)
Advances in Radiation Oncology     Open Access   (SJR: 0.263, CiteScore: 1)
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 3, SJR: 0.101, CiteScore: 0)
Advances in Space Biology and Medicine     Full-text available via subscription   (Followers: 5)
Advances in Space Research     Full-text available via subscription   (Followers: 385, SJR: 0.569, CiteScore: 2)
Advances in Structural Biology     Full-text available via subscription   (Followers: 5)
Advances in Surgery     Full-text available via subscription   (Followers: 10, SJR: 0.555, CiteScore: 2)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 30, SJR: 2.208, CiteScore: 4)
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: 2.262, CiteScore: 5)
Advances in Water Resources     Hybrid Journal   (Followers: 46, SJR: 1.551, CiteScore: 3)
Aeolian Research     Hybrid Journal   (Followers: 6, SJR: 1.117, CiteScore: 3)
Aerospace Science and Technology     Hybrid Journal   (Followers: 338, SJR: 0.796, CiteScore: 3)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.42, CiteScore: 2)
African J. of Emergency Medicine     Open Access   (Followers: 6, SJR: 0.296, CiteScore: 0)
Ageing Research Reviews     Hybrid Journal   (Followers: 10, SJR: 3.671, CiteScore: 9)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 437, SJR: 1.238, CiteScore: 3)
Agri Gene     Hybrid Journal   (SJR: 0.13, CiteScore: 0)
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 15, SJR: 1.818, CiteScore: 5)
Agricultural Systems     Hybrid Journal   (Followers: 31, SJR: 1.156, CiteScore: 4)
Agricultural Water Management     Hybrid Journal   (Followers: 43, SJR: 1.272, CiteScore: 3)
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: 1.747, CiteScore: 4)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.589, CiteScore: 3)
Air Medical J.     Hybrid Journal   (Followers: 6, SJR: 0.26, CiteScore: 0)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.19, CiteScore: 0)
Alcohol     Hybrid Journal   (Followers: 11, SJR: 1.153, CiteScore: 3)
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: 0.604, CiteScore: 3)
Alexandria J. of Medicine     Open Access   (Followers: 1, SJR: 0.191, CiteScore: 1)
Algal Research     Partially Free   (Followers: 10, SJR: 1.142, CiteScore: 4)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 2)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.504, CiteScore: 1)
Allergology Intl.     Open Access   (Followers: 5, SJR: 1.148, CiteScore: 2)
Alpha Omegan     Full-text available via subscription   (SJR: 3.521, CiteScore: 6)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 9, SJR: 0.201, CiteScore: 1)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 50, SJR: 4.66, CiteScore: 10)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 4, SJR: 1.796, CiteScore: 4)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 4, SJR: 1.108, CiteScore: 3)
Ambulatory Pediatrics     Hybrid Journal   (Followers: 6)
American Heart J.     Hybrid Journal   (Followers: 50, SJR: 3.267, CiteScore: 4)
American J. of Cardiology     Hybrid Journal   (Followers: 51, SJR: 1.93, CiteScore: 3)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 44, SJR: 0.604, CiteScore: 1)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 10)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 14, SJR: 1.524, CiteScore: 3)
American J. of Human Genetics     Hybrid Journal   (Followers: 32, SJR: 7.45, CiteScore: 8)
American J. of Infection Control     Hybrid Journal   (Followers: 26, SJR: 1.062, CiteScore: 2)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 34, SJR: 2.973, CiteScore: 4)
American J. of Medicine     Hybrid Journal   (Followers: 43)
American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3, SJR: 1.967, CiteScore: 2)
American J. of Obstetrics and Gynecology     Hybrid Journal   (Followers: 201, SJR: 2.7, CiteScore: 4)
American J. of Ophthalmology     Hybrid Journal   (Followers: 61, SJR: 3.184, CiteScore: 4)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 5, SJR: 0.265, CiteScore: 0)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.289, CiteScore: 1)
American J. of Otolaryngology     Hybrid Journal   (Followers: 25, SJR: 0.59, CiteScore: 1)
American J. of Pathology     Hybrid Journal   (Followers: 27, SJR: 2.139, CiteScore: 4)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 27, SJR: 2.164, CiteScore: 4)
American J. of Surgery     Hybrid Journal   (Followers: 37, SJR: 1.141, CiteScore: 2)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.767, CiteScore: 1)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 6)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.144, CiteScore: 3)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 63, SJR: 0.138, CiteScore: 0)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 15, SJR: 0.411, CiteScore: 1)
Anales de Cirugia Vascular     Full-text available via subscription  
Anales de Pediatría     Full-text available via subscription   (Followers: 3, SJR: 0.277, CiteScore: 0)
Anales de Pediatría (English Edition)     Full-text available via subscription  
Anales de Pediatría Continuada     Full-text available via subscription  
Analytic Methods in Accident Research     Hybrid Journal   (Followers: 5, SJR: 4.849, CiteScore: 10)
Analytica Chimica Acta     Hybrid Journal   (Followers: 39, SJR: 1.512, CiteScore: 5)
Analytical Biochemistry     Hybrid Journal   (Followers: 175, SJR: 0.633, CiteScore: 2)
Analytical Chemistry Research     Open Access   (Followers: 10, SJR: 0.411, CiteScore: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 11)
Anesthésie & Réanimation     Full-text available via subscription   (Followers: 2)
Anesthesiology Clinics     Full-text available via subscription   (Followers: 23, SJR: 0.683, CiteScore: 2)
Angiología     Full-text available via subscription   (SJR: 0.121, CiteScore: 0)
Angiologia e Cirurgia Vascular     Open Access   (Followers: 1, SJR: 0.111, CiteScore: 0)

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Journal Cover
Additive Manufacturing
Journal Prestige (SJR): 2.611
Citation Impact (citeScore): 8
Number of Followers: 9  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 2214-8604
Published by Elsevier Homepage  [3163 journals]
  • A challenge for enhancing the dimensional accuracy of a low-cost 3D
           printer by means of self-replicated parts
    • Authors: Paolo Minetola; Manuela Galati; Luca Iuliano; Eleonora Atzeni; Alessandro Salmi
      Pages: 203 - 208
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): P. Minetola, M. Galati
      Owing to the lack of optimization, the dimensional accuracy of low-cost 3D printers is quite limited. In order to enhance the performances of a Prusa i3 3D printer, an optimization challenge was assigned to the students of the Specializing Master in Industrial Automation of the Politecnico di Torino. The enhancements were applied to four printers by manufacturing new self-replicated parts by means of the same 3D printers. Finally, a benchmarking activity was used to check and validate the results of the optimization activities. The benchmarking involved the fabrication of replicas of an innovative reference artifact by means of the modified printers. A coordinate measuring machine (CMM) was then used to inspect the dimensions of the replicas. Measures were used to compare the performances of the four optimized printers in terms of dimensional accuracy using ISO IT grades. The form errors of the geometrical features of the replicas were also evaluated according to the GD&T system. The benchmarking results show that the most effective modifications to the original printer were those related to the improvement of the structure stiffness and chatter reduction.
      Graphical abstract image

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.procir.2017.12.200
      Issue No: Vol. 67 (2018)
  • Microstructure and performance evolution and underlying thermal mechanisms
           of Ni-based parts fabricated by selective laser melting
    • Authors: Dongdong Gu; Qimin Shi; Kaijie Lin; Lixia Xi
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Dongdong Gu, Qimin Shi, Kaijie Lin, Lixia Xi
      This work presented a comprehensive study of microstructural evolution, microhardness and quantitative thermodynamic analysis within the molten pool during Selective Laser Melting (SLM) of Inconel 718 parts. Microstructures and corresponding microhardness of different zones within the molten pool experienced the following evolution: fine cellular dendrites or equiaxed grains on the top surface (387HV); columnar dendrites with single direction of grain growth at the bottom (337HV); columnar dendrites with multiple directions of grain growth at the edge of the molten pool (340HV-350HV); microstructures between cellular and columnar grains around the center of the molten pool (363HV). The impact of Gaussian-distributed laser energy and relatively weak thermal conductivity and convection of Inconel 718 contributed to the variation of temperature gradient at different zones within the molten pool. The formation of different kinds of microstructures in the molten pool was controlled by the temperature gradient (which determined the direction of grain growth) and the cooling rate (which determined the size of grain growth). The variation of microhardness within the molten pool was ascribed to the number of grain boundaries and the stress characteristics of different kinds of microstructures under mechanical load. The zones with fine cellular grains had elevated mechanical performance due to the superior capability to endure the load. This work hopefully provides scientific and theoretical support for SLM-processed Inconel 718 parts with favorable properties.
      Graphical abstract image

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.05.019
      Issue No: Vol. 22 (2018)
  • Absorption cross-sections of Disperse Orange 13 and Irgacure 784
           determined with mask projection vat photopolymerization
    • Authors: Pekka Lehtinen; Matti Kaivola; Jouni Partanen
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Pekka Lehtinen, Matti Kaivola, Jouni Partanen
      It is necessary to understand the photoinitiated curing process, which occurs in vat photopolymerization resins during exposure, to develop high quality end products. Usually a curable resin contains photosensitizers, crosslinkable monomers and neutral absorbers, which have different roles in the curing process. The photosensitizer initiates the process by absorbing a photon and creating a chain initiator species, which causes the monomers to polymerize, crosslink and form a solid shape. While a photoinitiator is essential to achieve curing, a neutral absorber is required to control the cure depth. Short cure depth results in thin layers and high resolution end products, whereas large cure depth increases manufacturing speed. Thus, information about the absorptive properties of both the initiator and the absorber is crucial for the development of additive manufacturing techniques that are based on photoinitiated curing. To investigate these absorptive properties, a working curve method is applied with a mask projection vat photopolymerization apparatus to determine the absorption cross-sections of Irgacure 784 and Disperse Orange 13 and compare the results to ones obtained with spectrophotometry. With both methods, the results for each substance are within the same order of magnitude, but photobleaching seems to affect the vat photopolymerization results.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.05.006
      Issue No: Vol. 22 (2018)
  • A physical modeling and predictive simulation of the laser cladding
    • Authors: Florian Wirth; Konrad Wegener
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Florian Wirth, Konrad Wegener
      A 3D finite element simulation model of the laser cladding process has been developed taking into account heat transfer, fluid flow, surface tension and free surface movement. All input parameters and data, which are independent of the process parameters but depend only on the material and machine properties, have been obtained from measurements. Thereby the melt pool and the resulting surface contour can be simulated without compromising assumptions or calibration, because the machine parameters are the only variable input parameters of the model. Thus, the model can easily be transferred to other material combinations or other machines. For the surface contour calculation a modified height function method is applied. The model surface follows this contour as an arbitrary Lagrangian Eulerian (ALE) method is used allowing for mesh deformations. The model was implemented using the commercial finite element software COMSOL Multiphysics and validated by comparing the simulation results with caloric measurements of the effective heat input and metallographic cross sections from experiments, where the nickel-base alloy MetcoClad® 625 in powder form was deposited on structural steel S235JRC + C and the process parameters of laser power, feed speed, laser beam spot size and powder mass flow were varied within a range of at least 50% of their mean value each. The maximum deviation of the simulation results compared to the experimental data regarding track geometry is 14% for the parameter sets without weld defects so that these parameter sets could be industrially applied, whereas the average deviation of track width and height is below 5.1%. Moreover, the maximum difference of the simulated absorptivity compared to the measurement results is 6.9%, while the average difference is only 1.7%, meaning the model shows a high predictive capability especially regarding the heat input.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.05.017
      Issue No: Vol. 22 (2018)
  • Direct write fabrication of high-density parallel silver interconnects
    • Authors: Alan Shen; Dustin Caldwell; Anson W.K. Ma; Sameh Dardona
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Alan Shen, Dustin Caldwell, Anson W.K. Ma, Sameh Dardona
      This study investigates the suitability of direct write (DW) technology for the fabrication of high-resolution wear sensors. We demonstrate the production of high-density parallel interconnect traces and provide recommendations for processing conditions to minimize line width and line spacing based on DW ink rheology. To create parallel silver lines with 50 μm center-to-center spacing and 15 μm line width on alumina substrates, we used an nScrypt DW system and sintered the lines at 625 °C in air. The sintered lines exhibited an electrical resistivity of 5.29 × 10−8 Ω m (about three times bulk silver resistivity reported in the literature) with a standard deviation of 3.68 × 10-9 Ω m (ca. 7% variation). To determine the conditions needed to consistently create fine conductive lines, we simulated the volumetric flow rate and analyzed the effects on line geometry of several printing parameters including valve opening, dispensing gap, and substrate translation speed. Our results indicate decreasing the valve opening, decreasing the dispensing gap, and/or increasing the translation speed of the substrate reduces the resultant printing flow rate and cross-sectional area of DW lines. For a fixed valve opening and dispensing gap, we also observed broken lines due to overstretching of the inks at exceedingly high substrate translation speeds.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.05.010
      Issue No: Vol. 22 (2018)
  • Simulation and validation of three dimension functionally graded materials
           by material jetting
    • Authors: Eduardo Salcedo; Dongcheon Baek; Aaron Berndt; Jong Eun Ryu
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Eduardo Salcedo, Dongcheon Baek, Aaron Berndt, Jong Eun Ryu
      The goal of this work is to validate the material models for parts created with a Material Jetting 3-dimensional printer through the comparison of Finite Element Analysis (FEA) simulations and physical tests. The strain maps generated by a video extensometer for multi-material samples are compared to the FEA results based on our material models. Two base materials (ABS-like and rubber-like) and their composites are co-printed in the graded tensile test samples. The graded islands are embedded in the rubber-like test specimens. The simulations were conducted utilizing previously fitted material models, a two-parameter Mooney-Rivlin model for the elastic materials (Tango Black+, DM95, and DM60) and a bilinear model for the rigid material (Vero White+). The results show that the simulation results based on our material models can predict the deformation behaviors of the multi-material samples during a uniaxial tensile test. Our simulation results are able to predict the maximum strain in the matrix material (TB+) within 5% error. Both global deformation pattern and local strain level confirm the validity of the simulated material models.
      Graphical abstract image

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.05.027
      Issue No: Vol. 22 (2018)
  • Observations of particle-melt pool impact events in directed energy
    • Authors: James C. Haley; Julie M. Schoenung; Enrique J. Lavernia
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): James C. Haley, Julie M. Schoenung, Enrique J. Lavernia
      In the rapidly growing field of Additive Manufacturing (AM), the Laser Directed Energy Deposition (L-DED) process is the focus of intense technical attention due to its potential to generate high quality components with location specific composition and microstructural control. Despite the variety of experimental and modelling efforts devoted to the subject, no studies directly observe the interactions between individual powder particles and the liquid pool of metal at a high enough temporal frequency to characterize these discrete contact events. The frequency and nature of these powder-pool impingements govern overall process behavior, and are a poorly quantified fundamental building block of L-DED. In this work, we report novel results in which the melt pool is imaged at up to 200,000 frames per second, with pixel resolution of up to 3.6 μm. Video images reveal that particles often impact and float on the surface of the melt pool for several hundreds of microseconds before melting into it. Further incoming particles were observed to rebound from the melt pool by these floating particles. Through modelling this process analytically, particle self-shielding is shown to impose unavoidable upper limits on overall powder capture efficiency for the L-DED process.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.04.028
      Issue No: Vol. 22 (2018)
  • Revealing mechanisms of residual stress development in additive
           manufacturing via digital image correlation
    • Authors: Jamison L. Bartlett; Brendan P. Croom; Jeffrey Burdick; Daniel Henkel; Xiaodong Li
      Pages: 1 - 12
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Jamison L. Bartlett, Brendan P. Croom, Jeffrey Burdick, Daniel Henkel, Xiaodong Li
      The severe thermal gradients associated with selective laser melting (SLM) additive manufacturing (AM) generate large residual stresses (RS) that geometrically distort and otherwise alter the performance of printed parts. Despite broad research interest in this field, it has remained challenging to measure warpage in general as well as RS distributions in situ, which has obfuscated the mechanisms of stress formation during the printing process. In pursuit of this goal, we have developed a non-destructive framework for RS measurement in SLM parts using three-dimensional digital image correlation (3D-DIC) to capture in situ surface distortion. A two-dimensional analytical model was developed to convert DIC surface curvature measurements to estimates of in-plane residual stresses. Experimental validation using stainless steel 316 L “inverted-cone” parts demonstrated that residual stress varied across the surface of the printed part, and strongly interacted with the component geometry. The 3D-DIC based RS measurements were validated by X-ray diffraction (XRD), with an average error of 6% between measured and analytically derived stresses. Systematic variation in RS was attributed to the sector-based laser raster strategy, which was supported by complementary finite element calculations. Calculations showed that the heterogeneous RS distribution in the parts emerged from the sequential re-heating and cooling of the new surface, and changed dynamically between layers. The unique DIC based RS methodology brings substantial benefits over alternatively proposed in situ AM RS measurements, and should facilitate enhanced process optimization and understanding leading towards AM part qualification.
      Graphical abstract image

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.04.025
      Issue No: Vol. 22 (2018)
  • Dielectric strength heterogeneity associated with printing orientation in
           additively manufactured polymer materials
    • Authors: Brad W. Hoff; Sabrina S. Maestas; Steven C. Hayden; Daniel J. Harrigan; Rachael O. Grudt; Michele L. Ostraat; John C. Horwath; Serhiy Leontsev
      Pages: 21 - 30
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Brad W. Hoff, Sabrina S. Maestas, Steven C. Hayden, Daniel J. Harrigan, Rachael O. Grudt, Michele L. Ostraat, John C. Horwath, Serhiy Leontsev
      Anisotropy in dielectric properties can have deleterious effects in structures intended for use in high-field environments. We show that dielectric anisotropy is introduced into parts fabricated using additive manufacturing techniques based on the orientation in which the part is printed. Dielectric strength testing data, based on the ASTM D149 standard, are presented for samples fabricated using the polymer jetting (PolyJet), stereolithography (SLA), fused deposition modeling (FDM), and selective laser sintering (SLS) additive manufacturing techniques. Each unique printing direction available, based on the printing method, was examined in turn. Each printing technique was found to introduce anisotropic dielectric properties within the sample coupons that were a function of the original orientation in which the part was printed, and the direction of structural susceptibility was found to be print-method dependent. Differences in dielectric strength for coupons printed in different orientations were found to exceed 70% for some combinations of printing technique and polymer. Overall, test coupons printed with stereolithography (SLA) were found to exhibit the lowest degree of dielectric strength anisotropy between print orientations. Dielectric failure mechanisms are discussed.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.04.010
      Issue No: Vol. 22 (2018)
  • Towards space-grade 3D-printed, ALD-coated small satellite propulsion
           components for fluidics
    • Authors: Antti Kestilä; Kalle Nordling; Ville Miikkulainen; Mikko Kaipio; Tuomas Tikka; Mika Salmi; Aleksi Auer; Markku Leskelä; Mikko Ritala
      Pages: 31 - 37
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Antti Kestilä, Kalle Nordling, Ville Miikkulainen, Mikko Kaipio, Tuomas Tikka, Mika Salmi, Aleksi Auer, Markku Leskelä, Mikko Ritala
      Space technology has been an early adopter of additive manufacturing (AM) as a way of quickly producing relatively complex systems and components that would otherwise require expensive and custom design and production. Space as an environment and long-term survivability pose challenges to materials used in AM and these challenges need to be addressed. Atomic layer deposition (ALD) is an effective coating method enabling conformal and precise coating of the complete AM print. This work analyses how an ALD coating of aluminium oxide on acrylonitrile butadiene styrene (ABS) and polyamide PA 2200 plastic AM prints benefits and protects them. This was studied in the context of in-space propulsion fluidics, where propellant flow properties also matter. AM was performed with material extrusion and selective laser sintering methods that are commonly used. Tests were performed with a simple bang-bang controller test setup and a mass spectrometer, and the existence of the coating was confirmed with scanning electron microscope imaging.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.04.023
      Issue No: Vol. 22 (2018)
  • Model-guided design and characterization of a high-precision 3D printing
           process for carbohydrate glass
    • Authors: M.K. Gelber; G. Hurst; T.J. Comi; R. Bhargava
      Pages: 38 - 50
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): M.K. Gelber, G. Hurst, T.J. Comi, R. Bhargava
      Water-soluble glass patterned by 3D printing is a versatile tool for tissue engineering and microfluidics. Glasses can be patterned layer-by-layer as in conventional fused deposition modeling but also along 3D, “freeform” paths. In the latter approach, extruding heated material through a nozzle translating in 3D space allows for fabrication of sparse, freestanding networks of cylindrical filaments. These freeform structures are suitable for sacrificial molding with a variety of media, leaving complex microchannel networks. However, 3D printing carbohydrate glass in this way presents several unique challenges: 1) the material must resist degradation and crystallization during printing, 2) the glass must be hot enough to flow freely during extrusion and fuse to the printed construct, while cooling rapidly to retain its shape upon exiting the nozzle, 3) the extruder needs to apply high pressure, with rapid stop and start times and 4) the net force that acts on the filament during extrusion must be minimized so that the filament shape is predictable, i.e., coincides with the path taken by the nozzle. First, we review the properties of commercially available carbohydrate glasses and provide a guide for processing isomalt, our material of choice, to achieve the best printing performance. A pressure-controlled, piston-driven extruder is then described which allows for rapid responses and precise control over the material flow rate. We then analyze the heat transfer within the filament and the forces that contribute to the filament’s final shape. We find that the dominant force is due to the radial flow of the molten glass as it exits the nozzle. This analysis is validated on a purpose-built isomalt 3D printer, which we utilize to characterize relationships between extrusion pressure, translation speed, filament diameter, and viscous force. The insights of the physics of the printing process enable fabrication of intricate freeform prints as well as layer-by-layer designs. The practical and theoretical considerations should facilitate adoption of additive manufacturing of carbohydrate glasses with applications to a wide variety of fields, including tissue engineering and microfluidics.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.04.026
      Issue No: Vol. 22 (2018)
  • Fused filament fabrication melting model
    • Authors: Tim A. Osswald; John Puentes; Julian Kattinger
      Pages: 51 - 59
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Tim A. Osswald, John Puentes, Julian Kattinger
      This paper presents an analytical melting model inside the nozzle of a fused filament fabrication process. The model presents the limiting case scenario where the maximum melting rate is controlled by the applied force. Here, instead of having a nozzle filled with polymer melt, the melt is reduced to a melt film at the tip of the filament as it is pushed against the exit of the nozzle. The model uses a mode of melting that is governed by melting with pressure flow melt removal. The model includes effects of initial filament temperatures, heater temperature, applied force, nozzle tip angle, capillary diameter and length as well as rheological and thermal properties. The analytical solution is compared to controlled experiments done on a specially designed set-up. Furthermore, the model is used to assess the effect of nozzle tip angle, heater temperature and initial filament temperature on the melting rate within the nozzle. The comparison between the experiments and the model show that assumptions used for the model development are plausible, and that the model can be used to optimize the melting within a material extrusion additive manufacturing process, as well as predicting the performance of new materials.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.04.030
      Issue No: Vol. 22 (2018)
  • The effects of electrically-assisted ultrasonic nanocrystal surface
           modification on 3D-printed Ti-6Al-4V alloy
    • Authors: Hao Zhang; Jingyi Zhao; Jun Liu; Haifeng Qin; Zhencheng Ren; G.L. Doll; Yalin Dong; Chang Ye
      Pages: 60 - 68
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Hao Zhang, Jingyi Zhao, Jun Liu, Haifeng Qin, Zhencheng Ren, G.L. Doll, Yalin Dong, Chang Ye
      3D-printed Ti-6Al-4V components have great potential in the aerospace and biomedical industries. However, their wide application is limited by some inherent disadvantages, such as poor surface finish and high porosity. In this study, an innovative method, electrically-assisted ultrasonic nanocrystal surface modification (EA-UNSM) was introduced to process 3D-printed Ti-6Al-4V samples. The effect of EA-UNSM on surface finish, microstructure, porosity and in-depth hardness was investigated. Compared with the conventional UNSM process, smoother surfaces and lower subsurface porosities were obtained after EA-UNSM. EA-UNSM also led to a thicker plastically-affected depth compared with conventional UNSM. Numerical modelling showed that localized heating occurs near the pores in 3D-printed Ti-6Al-4V subjected to electric current. This localized heating could potentially facilitate pore closure under ultrasonic striking.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.04.035
      Issue No: Vol. 22 (2018)
  • Selectively-deposited energetic materials: A feasibility study of the
           piezoelectric inkjet printing of nanothermites
    • Authors: Allison K. Murray; Whitney A. Novotny; Trevor J. Fleck; I. Emre Gunduz; Steven F. Son; George T.-C Chiu; Jeffrey F. Rhoads
      Pages: 69 - 74
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Allison K. Murray, Whitney A. Novotny, Trevor J. Fleck, I. Emre Gunduz, Steven F. Son, George T.-C Chiu, Jeffrey F. Rhoads
      This work investigated the utility of three piezoelectric inkjet printers as energetic material deposition systems, focusing on the ability of each system to achieve the seamless integration of energetic material into small-scale electronic devices. Aluminum copper (II) oxide nanothermite was deposited using the three deposition systems. The printers were evaluated based on their robustness to energetic ink solids loading, drop formation reliability, drop quality degradation over time, and the energetic performance of the deposited material. These metrics correlate to the feasibility of a deposition system to successfully achieve high sample throughput while maintaining the energetic performance of the printed material. After initial system testing, the PipeJet P9 500 μm pipe was used to demonstrate the successful deposition of nanothermite in varying geometric patterns with micrometer precision. From these samples, preliminary propagation speed measurements were obtained, which showed a correlation between the printed line widths and burning rates.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.05.003
      Issue No: Vol. 22 (2018)
  • Microstructure and mechanical characteristics of surface oxide
           dispersion-strengthened Zircaloy-4 cladding tube
    • Authors: Hyun-Gil Kim; Il-Hyun Kim; Yang-Il Jung; Dong-Jun Park; Jung-Hwan Park; Jae-Ho Yang; Yang-Hyun Koo
      Pages: 75 - 85
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Hyun-Gil Kim, Il-Hyun Kim, Yang-Il Jung, Dong-Jun Park, Jung-Hwan Park, Jae-Ho Yang, Yang-Hyun Koo
      To increase the mechanical strength of Zircaloy-4 cladding at high temperatures, partial oxide dispersion-strengthened (ODS) treatment of the cladding tube surface was achieved by using laser processing technology. The microstructural characteristics and stability of the ODS layer formed on the Zircaloy-4 cladding surface were analyzed at temperatures up to 1000 °C. Ring tensile and loss-of-coolant accident (LOCA) simulation tests were performed to evaluate the mechanical properties of the surface ODS treated Zircaloy-4 cladding tube. The formation and uniform distribution of Y2O3 particles formed in the Zr matrix were identified, and the stability of the particles was confirmed up to 1000 °C. When compared to the reference Zircaloy-4 cladding tube, the surface ODS treated Zircaloy-4 cladding tube showed improved mechanical properties at both room temperature and 500 °C, as well as under LOCA simulation conditions.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.05.002
      Issue No: Vol. 22 (2018)
  • Study of the spatter distribution on the powder bed during selective laser
    • Authors: Ahmad Bin Anwar; Quang-Cuong Pham
      Pages: 86 - 97
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Ahmad Bin Anwar, Quang-Cuong Pham
      In Selective Laser Melting (SLM), inert gas is pumped into the chamber to eliminate the deleterious by-products, which includes spatter. Despite this, traces of spatter on the powder bed have always been observed. Earlier research mainly focussed on the formation and characterization of spatter particles that were freshly ejected from the melt pool. However, in this study, the quantification of the spatter distribution on the powder bed was performed, following their transport by the inert gas flow which was varied at two gas pump settings (60 and 67%). Image processing for spatter detection based on contrast was first conducted. The sieved out spatter particles were quantified by precision weighing of mass. Optical microscopy was then utilised for size determination. The majority of spatter particles were originally distributed along the −x direction, as observed from the top down images taken. It was found that spatter was generally transported in the −x direction with the mass and size gradually decreasing with distance from the scanned regions. However, increasing the gas flow velocity did not correspond to a lesser mass distribution. Computations on the Stk number revealed that at the gas pump setting of 67%, spatter particles of greater size were deposited earlier on the powder bed, suggesting that increasing the gas flow velocity to a large extent would increase the likelihood of powder bed contamination. The forward extrapolation of the exponential Stk number trendlines also elucidated the reason for the limitations on the width of the powder bed in machines designed by SLM Solutions.
      Graphical abstract image

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.04.036
      Issue No: Vol. 22 (2018)
  • 3D printing of extremely viscous materials using ultrasonic vibrations
    • Authors: I.E. Gunduz; M.S. McClain; P. Cattani; G.T.-C. Chiu; J.F. Rhoads; S.F. Son
      Pages: 98 - 103
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): I.E. Gunduz, M.S. McClain, P. Cattani, G.T.-C. Chiu, J.F. Rhoads, S.F. Son
      Heterogeneous materials used in biomedical, structural and electronics applications contain a high fraction of solids (>60 vol.%) and exhibit extremely high viscosities (μ > 1000 Pa s), which hinders their 3D printing using existing technologies. This study shows that inducing high-amplitude ultrasonic vibrations within a nozzle imparts sufficient inertial forces to these materials to drastically reduce effective wall friction and flow stresses, enabling their 3D printing with moderate back pressures (<1 MPa) at high rates and with precise flow control. This effect is utilized to demonstrate the printing of a commercial polymer clay, an aluminum-polymer composite and a stiffened fondant with viscosities up to 14,000 Pa·s with minimal residual porosity at rates comparable to thermoplastic extrusion. This new method can significantly extend the type of materials that can be printed to produce functional parts without relying on special shear/thermal thinning formulations or solvents to lower viscosity of the plasticizing component. The high yield strength of the printed material also allows freeform 3D fabrication with minimal need for supports.
      Graphical abstract image

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.04.029
      Issue No: Vol. 22 (2018)
  • Selective laser melting of tungsten carbide reinforced maraging steel
    • Authors: Nan Kang; Wenyou Ma; Lorène Heraud; Mohamed El Mansori; Fuhai Li; Min Liu; Hanlin Liao
      Pages: 104 - 110
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Nan Kang, Wenyou Ma, Lorène Heraud, Mohamed El Mansori, Fuhai Li, Min Liu, Hanlin Liao
      In this work, tungsten carbide (WC) reinforced maraging steel matrix composites were in-situ manufactured by selective laser melting (SLM) from powder mixture. The SLM processed samples presented high relative density (over 99%) with a homogenous distribution of WC. The as-fabricated surface quality of SLM processed samples was improved significantly by the addition of WC. Focused ion beam and transmission electron microscopy were employed to characterize the interfacial properties between tungsten carbide and steel matrix. The elemental analysis indicates that metallurgical bonding appears at interfacial region due to the diffusion. Tensile behavior of SLM processed maraging steel was different from their composite with several WC contents.
      Graphical abstract image

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.04.031
      Issue No: Vol. 22 (2018)
  • Effects of pore distribution and chemistry on physical, mechanical, and
           biological properties of tricalcium phosphate scaffolds by binder-jet 3D
    • Authors: Dongxu Ke; Susmita Bose
      Pages: 111 - 117
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Dongxu Ke, Susmita Bose
      Porous tricalcium phosphate (TCP) scaffolds are becoming more and more important for treating musculoskeletal diseases. With the maturation of 3D printing (3DP) technology in the past two decades, porous TCP scaffolds can also be easily prepared with complex design and high dimensional accuracy. However, the mechanical and biological properties of porous TCP scaffolds prepared by 3D printing still need improvements. In this study, novel 3D printed TCP and MgO/ZnO-TCP scaffolds were prepared by an binder-jet 3D printer. Scaffolds had a dense core and porous surface feature with a designed pore size of 500 μm and a designed porosity of 18%. After printing, scaffolds were sintered in a muffle furnace at 1250 °C. The presence of MgO and ZnO increased the surface area of TCP from 1.18 ± 0.01 m2/g to 2.65 ± 0.02 m2/g, the bulk density from 37.89 ± 0.83% to 50.82 ± 1.10%, and the compressive strength from 17.94 ± 1.65 MPa to 27.46 ± 2.63 MPa. Enhanced osteoblast proliferation was shown in doped 3D printed TCP scaffolds compared to the pure 3DP TCP. In addition, the use of 3D printing as well as dense core and porous surface design enhanced the surface roughness and osteoblast proliferation of TCP scaffolds. This novel 3D printed MgO/ZnO-TCP scaffold shows enhanced mechanical and biological properties, which is promising for orthopedic and dental applications.
      Graphical abstract image

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.04.020
      Issue No: Vol. 22 (2018)
  • Additive manufacturing of Ti-45Al-4Nb-C by selective electron beam melting
           for automotive applications
    • Authors: V. Juechter; M.M. Franke; T. Merenda; A. Stich; C. Körner; R.F. Singer
      Pages: 118 - 126
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): V. Juechter, M.M. Franke, T. Merenda, A. Stich, C. Körner, R.F. Singer
      Selective electron beam melting (SEBM) is shown to be a viable production route for titanium aluminides components. Fully dense and crack free parts can be produced. In the present paper a titanium aluminide alloy Ti-45Al-4Nb-C was investigated and the complete processing chain was developed, i.e. starting from the determination of the processing window, the evaluation of corresponding material properties for cube like specimens and finally the production of turbocharger wheels. The material properties were optimized by adjusting scanning strategy as well as heat treatment with particular consideration of the application to turbocharger wheels. The issue of dimensional accuracy and the feasibility of joining will be discussed and a proof test is performed.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.05.008
      Issue No: Vol. 22 (2018)
  • Effects of atomizing media and post processing on mechanical properties of
           17-4 PH stainless steel manufactured via selective laser melting
    • Authors: Somayeh Pasebani; Milad Ghayoor; Sunil Badwe; Harish Irrinki; Sundar V. Atre
      Pages: 127 - 137
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Somayeh Pasebani, Milad Ghayoor, Sunil Badwe, Harish Irrinki, Sundar V. Atre
      Water-atomized and gas-atomized 17-4 PH stainless steel powder were used as feedstock in selective laser melting process. Gas atomized powder revealed single martensitic phase after printing and heat treatment independent of energy density. As-printed water atomized powder contained dual martensitic and austenitic phase regardless of energy density. The H900 heat treatment cycle was not effective in enhancing mechanical properties of the water-atomized powder after laser melting. However, after solutionizing at 1315ºC and aging at 482 °C fully martensitic structure was observed with hardness (40.2 HRC), yield strength (1000 MPa) and ultimate tensile strength (1261 MPa) comparable to those of gas atomized (42.7 HRC, 1254 MPa and 1300 MPa) and wrought alloy (39 HRC, 1170 MPa and 1310 MPa), respectively. Improved mechanical properties in water-atomized powder was found to be related to presence of finer martensite and higher volume fraction of fine Cu-enriched precipitates. Our results imply that water-atomized powder is a promising cheaper feedstock alternative to gas-atomized powder.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.05.011
      Issue No: Vol. 22 (2018)
  • Fire resistance of additively manufactured water filled polymer parts
    • Authors: Hadley Brooks; Chris Wright; Stephen Harris; Andrew Fsadni
      Pages: 138 - 145
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Hadley Brooks, Chris Wright, Stephen Harris, Andrew Fsadni
      This paper introduces the concept of additively manufactured (AM) water filled parts (WFPs). By combining the energy absorbing properties of water with polymers, it is possible to significantly improve the time to ignition of AM parts with open internal structures. Theory relating the flame temperature to the maximum wall temperature of WFPs is developed. A range of water-polymer configurations are presented as a basis for WFP designs. Three separate thermal experiments were conducted to test different aspects of the WFPs. The time to ignition for cone calorimetry samples was extended 794% over plain photopolymers. Case studies were used to demonstrate the effectiveness of WFPs with complex shapes. The results of thermo-fluid finite element simulations showed good agreement with experimental observations and provide a useful tool for the evaluation and optimisation of WFP designs. The fire resistance of thin walled structures with internal water volumes was found to be significantly improved. The water filling strategy was found to be more effective than adding intumescent coatings. Finally further work and recommendations are discussed.
      Graphical abstract image

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.04.015
      Issue No: Vol. 22 (2018)
  • Computed tomography metrological examination of additive manufactured
           acetabular hip prosthesis cups
    • Authors: Nadia Kourra; Jason M. Warnett; Alex Attridge; Greg Dibling; James McLoughlin; Sarah Muirhead-Allwood; Richard King; Mark A. Williams
      Pages: 146 - 152
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Nadia Kourra, Jason M. Warnett, Alex Attridge, Greg Dibling, James McLoughlin, Sarah Muirhead-Allwood, Richard King, Mark A. Williams
      Additive manufacturing (AM) is uniquely suitable for healthcare applications due to its design flexibility and cost effectiveness for creating complex geometries. Successful arthroplasty requires integration of the prosthetic implant with the bone to replace the damaged joint. Bone-mimetic biomaterials are utilised due to their mechanical properties and porous structure that allows bone ingrowth and implant fixation. The predictability of predetermined interconnected porous structures produced by AM ensures the required shape, size and properties that are suitable for tissue ingrowth and prevention of the implant loosening. The quality of the manufacturing process needs to be established before the utilisation of the parts in healthcare. This paper demonstrates a novel examination method of acetabular hip prosthesis cups based on X-ray computed tomography (CT) and image processing. The method was developed based on an innovative hip prosthesis acetabular cup prototype with a prescribed non-uniform lattice structure forming struts over the surface, with the interconnected porosity encouraging bone adhesion. This non-destructive, non-contact examination method can provide information of the interconnectivity of the porous structure, the standard deviation of the size of the pores and struts, the local thickness of the lattice structure in its size and spatial distribution. In particular, this leads to easier identification of weak regions that could inhibit a successful bond with the bone.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.04.033
      Issue No: Vol. 22 (2018)
  • Electrochemical behavior of AISI316L stainless steel parts produced by
           laser-based powder bed fusion process and the effect of post annealing
    • Authors: Ali Hemmasian Ettefagh; Shengmin Guo
      Pages: 153 - 156
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Ali Hemmasian Ettefagh, Shengmin Guo
      This paper presents the investigation of the corrosion behavior of AISI316L samples prepared by laser-based powder bed fusion additive manufacturing (AM) method. Both AM and conventional stainless steel 316L samples were examined in NaCl 3.5% solution before and after the annealing process using Tafel curves, Electrochemical Impedance Spectroscopy, and X-ray diffraction. The results indicate that the AM parts have an improved corrosion behavior than the conventional wrought samples. Besides, the heat treatment process is found to further decrease the corrosion rate of the AM parts through the relieving of the residual stress. In contrast, the post annealing induced improvement to corrosion resistance for the wrought samples is due to the elimination of martensite phase which almost always exists after the plastic deformation during their production process.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.05.014
      Issue No: Vol. 22 (2018)
  • Evaluation of compressive and flexural properties of continuous fiber
           fabrication additive manufacturing technology
    • Authors: Miguel Araya-Calvo; Ignacio López-Gómez; Nicolette Chamberlain-Simon; José Luis León-Salazar; Teodolito Guillén-Girón; Juan Sebastián Corrales-Cordero; Olga Sánchez-Brenes
      Pages: 157 - 164
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Miguel Araya-Calvo, Ignacio López-Gómez, Nicolette Chamberlain-Simon, José Luis León-Salazar, Teodolito Guillén-Girón, Juan Sebastián Corrales-Cordero, Olga Sánchez-Brenes
      This study focuses on the characterization of additive manufacturing technology based on composite filament fabrication (CFF). CFF utilizes a similar method of layer by layer printing as fused filament fabrication but is also capable of reinforcing parts with layers of various continuous fibers into a polymer matrix. Due to the orthotropic characteristics of additive manufacturing based on fused filament fabrication, 3D printed parts may present different mechanical behavior under different orientations of stress. Furthermore, technologies such as CFF allow a range of configurations to fabricate and reinforce the parts. In this study, mechanical characterization of polyamide 6 (PA6) reinforced with carbon fiber was conducted by design of experiment as a statistical method, to investigate the effect of reinforcement pattern, reinforcement distribution, print orientation and percentage of fiber on compressive and flexural mechanical properties. CFF technology 3D print stronger parts than conventional additive manufacturing technologies. Maximized compressive response was achieved with a 0.2444 Carbon Fiber volume ratio, concentric and equidistant reinforcement configuration, resulting in a compressive modulus of 2.102 GPa and a stress at proportional limit of 53.3 MPa. Maximized flexural response was achieved with 0.4893 Carbon Fiber volume ratio, concentric reinforcement and perpendicular to the applied force, resulting in a flexural modulus of 14.17 GPa and a proportional limit of 231.1 MPa.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.05.007
      Issue No: Vol. 22 (2018)
  • An investigation into 3D printing of fibre reinforced thermoplastic
    • Authors: L.G. Blok; M.L. Longana; H. Yu; B.K.S. Woods
      Pages: 176 - 186
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): L.G. Blok, M.L. Longana, H. Yu, B.K.S. Woods
      Fused filament fabrication (FFF) is a 3D printing technique which allows layer-by-layer build-up of a part by the deposition of thermoplastic material through a nozzle. The technique allows for complex shapes to be made with a degree of design freedom unachievable with traditional manufacturing methods. However, the mechanical properties of the thermoplastic materials used are low compared to common engineering materials. In this work, composite 3D printing feedstocks for FFF are investigated, wherein carbon fibres are embedded into a thermoplastic matrix to increase strength and stiffness. First, the key processing parameters for FFF are reviewed, showing how fibres alter the printing dynamics by changing the viscosity and the thermal profile of the printed material. The state-of-the-art in composite 3D printing is presented, showing a distinction between short fibre feedstocks versus continuous fibre feedstocks. An experimental study was performed to benchmark these two methods. It is found that printing of continuous carbon fibres using the MarkOne printer gives significant increases in performance over unreinforced thermoplastics, with mechanical properties in the same order of magnitude of typical unidirectional epoxy matrix composites. The method, however, is limited in design freedom as the brittle continuous carbon fibres cannot be deposited freely through small steering radii and sharp angles. Filaments with embedded short carbon microfibres (∼100 μm) show better print capabilities and are suitable for use with standard printing methods, but only offer a slight increase in mechanical properties over the pure thermoplastic properties. It is hypothesized that increasing the fibre length in short fibre filament is expected to lead to increased mechanical properties, potentially approaching those of continuous fibre composites, whilst keeping the high degree of design freedom of the FFF process.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.04.039
      Issue No: Vol. 22 (2018)
  • Finite element analysis of thermoplastic polymer extrusion 3D printed
           material for mechanical property prediction
    • Authors: Sunil Bhandari; Roberto Lopez-Anido
      Pages: 187 - 196
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Sunil Bhandari, Roberto Lopez-Anido
      A space frame lattice and shell finite element model was created to predict the linearly elastic response of test coupons made with a modified polyetherimide (PEI) material. This approach was employed because it provides an efficient procedure to design and optimize 3D printed parts. The modeled coupons were 3D printed by extrusion of molten thermoplastic polymer. The finite element model was verified by comparing the predicted values of elastic modulus, shear modulus, and Poisson’s ratio in two material directions with the corresponding values obtained from quasi-static mechanical experiments. The values obtained for the moduli and the Poisson’s ratios from the finite element model matched closely with those obtained from the experiments.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.05.009
      Issue No: Vol. 22 (2018)
  • Complex flow and temperature history during melt extrusion in material
           extrusion additive manufacturing
    • Authors: Fang Peng; Bryan D. Vogt; Miko Cakmak
      Pages: 197 - 206
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Fang Peng, Bryan D. Vogt, Miko Cakmak
      3D printing using the materials extrusion additive manufacturing (ME-AM) process is highly nonisothermal. In this process, a solid polymer filament is mechanically drawn into a heated hot end (liquefier) where the polymer is ideally melted to a viscous liquid. This melt is extruded through an orifice using applied pressure of the solid filament that is continuously being drawn into the extruder. The extruded filament melt is deposited to build up the desired part. The poor thermal conductivity of most polymers inevitably leads to temperature gradients, in both the radial and axial directions. Here we quantify the temperature evolution of the polymer filament in axial direction using embedded fine thermocouples as a function of process parameters. Information about the radial gradients is obtained by introducing dye markers within the filament through understanding the flow behavior through the extruder by the deformation of the dye from a linear to pseudo parabolic profile. The polymer is heated above the glass transition temperature for less than 30 s for reasonable print conditions with the center of the filament remaining cooler than the liquefier temperature throughout the process. These process measurements provide critical data to enable improved simulation and modeling of the ME-AM process and the properties of the printed parts.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.05.015
      Issue No: Vol. 22 (2018)
  • Effect of laser focus shift on surface quality and density of Inconel 718
           parts produced via selective laser melting
    • Authors: Glenn E. Bean; David B. Witkin; Tait D. McLouth; Dhruv N. Patel; Rafael J. Zaldivar
      Pages: 207 - 215
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Glenn E. Bean, David B. Witkin, Tait D. McLouth, Dhruv N. Patel, Rafael J. Zaldivar
      Selective laser melting (SLM) is a method of laser powder bed fusion additive manufacturing (AM) currently being pursued in numerous industries, including space launch and space flight. In this study we performed an extensive parameter development investigation to better understand the effect of laser parameters on surface roughness, density, and porosity of SLM Inconel 718 parts. Laser energy density was varied via laser focus shift, and the effects on porosity in both as-printed and post-HIP treated states were analyzed. Tensile testing was also conducted to investigate the effect of processing conditions on the mechanical properties of SLM 718. It was found that for these laser parameters, while the material met ultimate tensile strength and yield strength requirements per AMS 5662, the strain-to-failure was reduced with negative focus shift due to increases in porosity levels. It was also found that while correlations were observed between surface roughness, density, and porosity within the laser focus shift range investigated, porosity measurement appears to be the clearest indicator of build quality for AM processed 718.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.04.024
      Issue No: Vol. 22 (2018)
  • Experimental analysis of metal/plastic composites made by a new hybrid
    • Authors: Javaid Butt; Hassan Shirvani
      Pages: 216 - 222
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Javaid Butt, Hassan Shirvani
      The purpose of this paper is to identify the key elements of a new hybrid process to produce high quality metal/plastic composites. The process is a combination of Fused Deposition Modelling (FDM), vacuum forming and CNC machining. The research aims to provide details of the proposed hybrid process, equipment used, and the experimental results of the composites produced. The research has been separated into three study areas. In the first, the hybrid process has been defined as a whole whereas the second area deals with the breakdown of steps to produce the metal/plastic composites. The third area explains the varied materials used for the production and testing of the composites. Composites have been made by joining copper (99.99% pure) mesh with ABS (acrylonitrile butadiene styrene). Strain measurement has been carried out on Cu/ABS sample to analyse the effect of metal mesh and to verify the effectiveness of the hybrid process. The resulting composites (Cu/ABS) have also been subjected to tensile loading with different layers of metal mesh, followed by microstructural analysis and comparative studies to serve as a proof of the methodology. The results show that the proposed hybrid process is very effective in producing metal/plastic composites with lower strain values compared to the parent plastic indicating a lower level of deformation due to interlocking of the metal and plastic layers. This effect has been reinforced by the tensile testing where the composites showed higher fracture load values compared to the parent plastic. Microstructural analysis shows the layer of metal mesh sandwiched between ABS layers indicating the existence of a bond holding the layers of metal and plastic together. These results demonstrate the capabilities and effectiveness of the proposed process that has shown promising results under tensile and static loading.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.05.029
      Issue No: Vol. 22 (2018)
  • Mesostructure and porosity effects on the thermal conductivity of
           additively manufactured interpenetrating phase composites
    • Authors: Abdel R. Moustafa; Ralph B. Dinwiddie; Alexander E. Pawlowski; Derek A. Splitter; Amit Shyam; Zachary C. Cordero
      Pages: 223 - 229
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Abdel R. Moustafa, Ralph B. Dinwiddie, Alexander E. Pawlowski, Derek A. Splitter, Amit Shyam, Zachary C. Cordero
      We have investigated the relationship between structure and thermal conductivity in additively manufactured interpenetrating A356/316L composites. We used X-ray microcomputed tomography to characterize the pore structure in as-fabricated composites, finding microporosity in both constituents as well as a 50 μm thick layer of interfacial porosity separating the constituents. We measured the thermal conductivity of a 43 vol% 316L composite to be 53 Wm−1K−1, which is significantly less than that predicted by a simple rule-of-mixtures approximation, presumably because of the residual porosity. Motivated by these experimental results we used periodic homogenization theory to determine the combined effects of porosity and unit cell structure on the effective thermal conductivity. This analysis showed that in fully dense composites, the topology of the constituents has a weak effect on the thermal conductivity, whereas in composites with interfacial porosity, the size and structure of the unit cell strongly influence the thermal conductivity. We also found that an approximation formula of the strong contrast expansion method gives excellent estimates of the effective thermal conductivity of these composites, providing a powerful tool for designing functionally graded composites and for identifying mesostructures with optimal thermal conductivity values.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.05.018
      Issue No: Vol. 22 (2018)
  • The influence of laser parameters, scanning strategies and material on the
           fatigue strength of a stochastic porous structure
    • Authors: Shaaz Ghouse; Sarat Babu; Kenneth Nai; Paul A. Hooper; Jonathan R.T. Jeffers
      Pages: 290 - 301
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Shaaz Ghouse, Sarat Babu, Kenneth Nai, Paul A. Hooper, Jonathan R.T. Jeffers
      Additive manufactured (AM) porous materials behave quantitatively and qualitatively differently in fatigue than bulk materials, and the relationships normally used for the fatigue design of continuous bulk materials are not applicable to AM porous materials particularly for low stiffness applications. This study investigated how the manufacturing methods and the material used during powder bed fusion affects the compressive strength and high cycle fatigue strength of a stochastic porous material for a given stiffness. Specimens were manufactured using varying laser parameters, 3 scan strategies (Contour, Points, Pulsing) and 4 materials. The materials investigated were two titanium alloys: commercially pure grade 2 (CP-Ti) and Ti6Al4V ELI, commercially pure tantalum (Ta) and a titanium-tantalum alloy (Ti-30Ta). The trends observed during fatigue testing for monolithic metals and statically for solid and porous AM materials were not always indicative of the high cycle fatigue behaviour of porous AM materials. Unlike their solid counterparts, porous tantalum and the titanium-tantalum alloy had the greatest fatigue strength for a given stiffness, 8% greater than CP-Ti and 19% greater than Ti6Al4V ELI. Optimisation of the laser parameters and scan strategies was found to also increase the fatigue strength for a given stiffness of porous AM materials by 7–8%.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.05.024
      Issue No: Vol. 22 (2018)
  • Correlation of selective laser melting-melt pool events with the tensile
           properties of Ti-6Al-4V ELI processed by laser powder bed fusion
    • Authors: Manisha Bisht; Nachiketa Ray; Frederik Verbist; Sam Coeck
      Pages: 302 - 306
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Manisha Bisht, Nachiketa Ray, Frederik Verbist, Sam Coeck
      In this study, we present the first results of a newly developed melt pool monitoring tool for selective laser melting, called DMP-meltpool. A manual data analysis method is given, and the events indicated by the analysis (DMP-meltpool events) are shown to correlate to the static tensile properties of the samples built. These events indicate the probability of material discontinuities (defects) in the metal additive manufacturing (AM) parts. In order to do so, cylindrical bars of Ti-6Al-4V ELI were built and monitored using DMP-meltpool. The tensile properties of the printed cylinders were correlated with the events detected by DMP-meltpool. An inverse relation between plastic elongation and the DMP-meltpool event density was observed. These results show that DMP-meltpool can be used to predict the quality of AM parts by detecting variations in the signals and tagging these events throughout the build as defects. Thus the technique can be employed for first stage in-line quality control of AM parts and for sorting out parts with potential defects non-destructively. The DMP-meltpool events could have significant correlations with other mechanical properties (like fatigue, hardness, fracture toughness, and crack propagation) since such properties are influenced by defects originating from the process instabilities.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.05.004
      Issue No: Vol. 22 (2018)
  • Metastable carbides and their impact on recrystallisation in IN738LC
           processed by selective laser melting
    • Authors: O.M.D.M. Messé; R. Muñoz-Moreno; T. Illston; S. Baker; H.J. Stone
      Pages: 394 - 404
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): O.M.D.M. Messé, R. Muñoz-Moreno, T. Illston, S. Baker, H.J. Stone
      Selective laser melting of nickel based superalloys opens up new possibilities for gas turbine engine manufacturers; namely, efficient production of low component volumes, decreased component cost through reduced post-machining procedures and access to new component geometries that cannot be fabricated by conventional processing methods. However, processing high performance nickel-based superalloys components via additive manufacturing, without the occurrence of defects, is challenging and requires a better understanding of the resulting microstructure, especially as different compositions can lead to significant changes in the microstructure obtained. In addition, carefully selected post-processing heat-treatments are required to alter the microstructure and attain the required mechanical properties. In this study, the microstructure of the nickel base superalloy IN738LC has been characterised in the as-deposited and stress relieved heat-treated states, as well as following high temperature heat treatments. The data acquired highlights the influence of the stress relief step on the recrystallisation temperature and its relation with the distribution of carbide particles present in the alloy's microstructure.

      PubDate: 2018-06-05T12:44:49Z
      DOI: 10.1016/j.addma.2018.05.030
      Issue No: Vol. 22 (2018)
  • A pragmatic part scale model for residual stress and distortion prediction
           in powder bed fusion
    • Authors: Richard J. Williams; Catrin M. Davies; Paul A. Hooper
      Pages: 416 - 425
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Richard J. Williams, Catrin M. Davies, Paul A. Hooper
      Parts manufactured by laser powder bed fusion contain significant residual stress. This stress causes failures during the build process, distorts parts and limits in-service performance. A pragmatic finite element model of the build process is introduced here to predict residual stress in a computationally efficient manner. The part is divided into coarse sections which activate at the melting temperature in an order that imitates the build process. Temperature and stress in the part are calculated using a sequentially coupled thermomechanical analysis with temperature dependent material properties. The model is validated against two sets of experimental measurements: the first from a bridge component made from 316L stainless steel and the second from a cuboidal component made from Inconel 718. For the bridge component the simulated distortion is within 5% of the experimental measurement when modelled with a section height of 0.8 mm. This is 16 times larger than the 50 μm layer height in the experimental part. For the cuboid component the simulated distortion is within 10% of experimental measurement with a section height 10 times larger than the experiment layer height. These results show that simulation of every layer in the build process is not required to obtain accurate results, reducing computational effort and enabling the prediction of residual stress in larger components.

      PubDate: 2018-06-08T12:54:13Z
      DOI: 10.1016/j.addma.2018.05.038
      Issue No: Vol. 22 (2018)
  • Direct laser fabrication of meso-scale 2D and 3D architectures with
           micrometric feature resolution
    • Authors: Angelo Accardo; Rémi Courson; Roberto Riesco; Vincent Raimbault; Laurent Malaquin
      Pages: 440 - 446
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Angelo Accardo, Rémi Courson, Roberto Riesco, Vincent Raimbault, Laurent Malaquin
      The realization of 2D and 3D meso-scale architectures is an area of research involving a wide range of disciplines ranging from materials science, microelectronics, phononics, microfluidics to biomedicine requiring millimeter to centimeter-sized objects embedding micrometric features. In the recent years, several technologies have been employed to provide optimal features in terms of object size flexibility, printing resolution, large materials library and fabrication speed. In this work, we report a fully customizable single-photon absorption 3D fabrication methodology based on direct laser fabrication. To validate this approach and highlight the versatility of the setup, we have fabricated a comprehensive ensemble of 2D and 3D designs with potential applications in biomimetics, 3D scaffolding and microfluidics. The high degree of tunability of the reported fabrication system allows tailoring the laser power, slicing and fabrication speed for each single area of the design. These unique features enable a rapid prototyping of millimeter to centimeter-sized objects involving 3D architectures with true freestanding subunits and micrometric feature reproducibility. The presented strategy fills indeed the current technological gap related to the development of meso-scale architectures required in multidisciplinary fields of research.
      Graphical abstract image

      PubDate: 2018-06-08T12:54:13Z
      DOI: 10.1016/j.addma.2018.04.027
      Issue No: Vol. 22 (2018)
  • Design, testing, and mechanical behavior of additively manufactured casing
           with optimized lattice structure
    • Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Matthew E. Lynch, Matthew Mordasky, Lin Cheng, Albert To
      Additively manufactured internal lattice structures offer a unique approach to lightweight components and adding multi-functionality. Design methods for parts based on lattices are emerging and include a family of topology optimization schemes for tailoring local cell density to service loadings. In order to gain confidence, these methods must be validated in a controlled manner. In this paper, we report optimization, analysis, manufacturing, and mechanical test validation of a casing-like test article. The test article was optimized using a stress-based homogenized topology optimization approach and achieved a 53% weight reduction versus a solid, fully-dense casing with the same form factor. The optimized geometry was studied with high-fidelity finite element analysis and then additively manufactured. Mechanical testing was performed and demonstrated good correlation between the homogenized finite element model used for optimization, the high-fidelity finite element model, and experimental results. The findings validate the optimization approach for the particular use and load case and start to build confidence in the approach as an accepted method.

      PubDate: 2018-06-19T11:52:03Z
  • Processing and Characterization of Crack-Free Aluminum 6061 Using
           High-Temperature Heating in Laser Powder Bed Fusion Additive Manufacturing
    • Authors: Syed Z. Uddin; Lawrence E. Murr; Cesar A. Terrazas; Philip Morton; David A. Roberson; Ryan B. Wicker
      Abstract: Publication date: Available online 1 June 2018
      Source:Additive Manufacturing
      Author(s): Syed Z. Uddin, Lawrence E. Murr, Cesar A. Terrazas, Philip Morton, David A. Roberson, Ryan B. Wicker
      During solidification of many so-called high-performance engineering alloys, such as 6000 and 7000 series aluminum alloys, which are also unweldable autogenously, volumetric solidification shrinkage and thermal contraction produces voids and cracks. During additive manufacturing processing, these defects can span the length of columnar grains, as well as intergranular regions. In this research, laser powder bed fusion (LPBF) of aluminum alloy (AA) 6061 used powder bed heating at 500 °C in combination with other experimentally determined processing parameters to produce crack-free components. In addition, melt-pool banding, which is a normal solidification feature in LPBF, was eliminated, illustrating solidification process modification as a consequence of powder bed heating. Corresponding microindentation hardness and tensile testing of the as-fabricated AA6061 components indicated an average Vickers hardness of HV 54, and tensile yield, ultimate strength, and elongation values of 60 MPa, 130 MPa, and 15%, respectively. These mechanical properties and those of heat treated parts showed values comparable to annealed and T6 heat treated wrought products, respectively. X-ray diffraction and optical microscopy revealed columnar grain growth in the build direction with the as-fabricated, powder-bed heated product microstructure characterized by [100] textured, elongated grains (~ 25 µm wide by 400 μm in length), and both intragranular and intergranular, noncoherent Al-Si-O precipitates which did not contribute significantly to the mechanical properties. The results of this study are indicative that powder bed heating may be used to assist with successful fabrication of AA6061 and other alloy systems susceptible to additive manufacturing solidification cracking.

      PubDate: 2018-06-02T17:03:07Z
      DOI: 10.1016/j.addma.2018.05.047
  • Effect of energy per layer on the anisotropy of selective laser melted
           AlSi12 aluminium alloy
    • Authors: R. Rashid; S.H. Masood; D. Ruan; S. Palanisamy; R.A. Rahman Rashid; J. Elambasseril; M. Brandt
      Abstract: Publication date: Available online 31 May 2018
      Source:Additive Manufacturing
      Author(s): R. Rashid, S.H. Masood, D. Ruan, S. Palanisamy, R.A. Rahman Rashid, J. Elambasseril, M. Brandt
      The anisotropy in the tensile properties of AlSi12 alloy fabricated using selective laser melting (SLM) additive manufacturing process was investigated. The tensile samples were printed in three different orientations, horizontal (H - 0°), inclined (I - 45°), and vertical (V - 90°), and found to exhibit yield strength between 225 MPa and 263 MPa, tensile strength between 260 MPa and 365 MPa, and ductility between 1 and 4%, showing distinct fracture patterns. It was established that the build orientation had insignificant effect on the microstructural characteristics of the SLM-printed samples, while XRD phase analysis showed variations in the Al (111) and Al (200) peak intensities. Consequently, the anisotropy in the mechanical properties of the SLM-printed AlSi12 samples was attributed to the differences in their relative density. Although the energy density was kept constant when printing the samples along different orientations, the “energy per layer” was found to be different owing to the variation in the printing area along the build direction. Further investigation on the effect of printing area, and correspondingly energy per layer, on the relative density was carried out. It was found that energy per layer in the range of 504 – 895 J yielded ≥ 99.8% relatively dense AlSi12 SLM-printed samples. This study puts forth a new idea that the density of the SLM-printed samples could be controlled using energy per layer as an input process parameter.

      PubDate: 2018-06-02T17:03:07Z
      DOI: 10.1016/j.addma.2018.05.040
  • Mechanical properties of Sn63Pb37 components by fused coating technology
    • Authors: Guangxi Zhao; Zhengying Wei Jun Ruwei Geng Siyuan
      Abstract: Publication date: Available online 29 May 2018
      Source:Additive Manufacturing
      Author(s): Guangxi Zhao, Zhengying Wei, Jun Du, Ruwei Geng, Siyuan Xu
      The fused coating process is a new material jetting additive manufacturing technology that proposes to solve the problem of high cost, low efficiency and high material requirements of laser-based process and electron beam process. The structure and operating principles of the fused coating machine are explained in this paper. Sn63Pb37 is taken as the experimental material because of its low melting temperature, small surface tension coefficient and high viscosity. Tensile test specimens were made both parallel and perpendicular to the forming trajectory. Tensile strengths were measured and the corresponding fractographies were observed. It is found that large plastic deformation has occurred before the fracture, and the plasticity of fused components that the tensile direction parallel to the forming trajectory, is higher. The densification degree of fused coating component is measured by the drainage method. The average value is up to 99.78% which indicates that the internal structure is indistinguishable from extruded Sn63Pb37. The Vickers hardness of the fused coated component and raw casted material were tested by 5 points respectively, the results showed that the average Vickers hardness of the fused coating component is 14.6% higher than the casted one.

      PubDate: 2018-05-30T16:59:46Z
  • Characterization, functionality and application of siliceous sponge
           spicules additive-based manufacturing biopolymer composites
    • Authors: Chin-San
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Chin-San Wu
      Polyhydroxyalkanoate (PHA) composites containing siliceous sponge spicules (SSS) were prepared from three-dimensional (3D) printing filaments. Acrylic acid (AA)-grafted polyhydroxyalkanoate (PHA-g-AA) and SSS were used to improve the compatibility of the SSS within the PHA matrix. Mechanical and morphological characterizations indicated that the improved adhesion between the SSS and PHA-g-AA enhanced the tensile strength at failure and Young’s modulus of the composite compared with that of PHA/SSS. The PHA-g-AA/SSS composites were also more water-resistant than the PHA/SSS composites. Human foreskin fibroblasts (FBs) were seeded on two series of these composites to assess cytocompatibility. FB proliferation was greater for the PHA/SSS composites than the PHA-g-AA/SSS composites. Moreover, SSS enhanced the antioxidant, anti-inflammatory and antibacterial properties of PHA-g-AA/SSS and PHA/SSS composites, demonstrating the potential of PHA-g-AA/SSS and PHA/SSS composites for biomedical material applications.
      Graphical abstract image

      PubDate: 2018-05-28T13:48:58Z
  • Accuracy in dental surgical guide fabrication using different 3-D printing
    • Authors: Mamta Juneja; Niharika Thakur Dinesh Kumar Ankur Gupta Babandeep Bajwa
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Mamta Juneja, Niharika Thakur, Dinesh Kumar, Ankur Gupta, Babandeep Bajwa, Prashant Jindal
      Accuracy in dental prosthesis plays a significant role. Surgical guides are widely used for accurate positioning of dental implants. Designing of guides using modern software is useful in achieving precision; however, translation of these images into actual fabricated parts can be achieved using Three-dimensional (3-D) printing. Conventionally, guides were fabricated using vacuum forming technique which leads to several dimensional inaccuracies. Computed Tomography (CT) images of patients with missing teeth are modeled to design surgical guide using Computer Aided Design (CAD) / Computer Aided Manufacturing (CAM) software which is then combined with surface scan files in Standard Tessellation Language (STL) formats to design the guide. In this work, surgical guides have been 3-D printed using different technologies like Material Jetting technology (MJT), Vat photopolymerization (VP) and Material extrusion (ME). Depth, diameter, Area and Volume of the printed guides have been calculated using vernier caliper and scan measurements. These dimensions have then been compared with the dimensions obtained from software modeled images. Least error has been found for the guides fabricated using MJT. The experimental work in this paper, hence, suggests MJT be the most preferred printing technique due to its superior accuracy for printing dental prosthesis like aligners, implants, and crowns, etc.

      PubDate: 2018-05-28T13:48:58Z
  • Environmentally benign metallization of material extrusion technology 3D
           printed acrylonitrile butadiene styrene parts using physical vapor
    • Authors: Justin White; Christopher Tenore Austin Pavich Ryan Scherzer Stephen Stagon
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Justin White, Christopher Tenore, Austin Pavich, Ryan Scherzer, Stephen Stagon
      Metallization has been widely used to enhance the aesthetics and performance of injection molded plastic parts, but the techniques have not been widely extended to 3D printed parts due to intrinsic differences in surface chemistry and morphology. Here, we investigate direct metallization of acrylonitrile butadiene styrene (ABS) 3D printed thermoplastic parts using low cost environmentally benign surface preparations and physical vapor deposition (PVD) to avoid the use of preparation with toxic chromic acid. Fourier transform infrared (FTIR) spectra are gathered for each surface preparation method prior to metallization. The metallized parts are then characterized for thin film adhesion, electrical resistivity, and optical reflectivity. Additionally, each part is imaged using a scanning electron microscope (SEM) post-metallization. The results show that surface preparation with solvent results in a smooth and aesthetically pleasing surface, but metallic film adhesion is poor. Conversely, when 2000 grit sandpaper is used to mechanically prepare the surfaces, the resulting films have poor electrical conductivity and optical reflectance, but excellent adhesion. Atmospheric plasma treatment of the parts results in the highest overall performance, with superior adhesion strength and optical reflectivity and low electrical resistivity. Electron microscopy and FTIR reveal that the high adhesion resulting from atmospheric plasma is caused by modification surface morphology, but not surface chemical termination. The results indicate that direct metallization of 3D printed ABS is a viable method for creating metallized parts with high performance and an aesthetically pleasing appearance and that the use of chromic acid in surface preparation is not necessary.

      PubDate: 2018-05-28T13:48:58Z
  • Improvement of the bridge curvature method to assess residual stresses in
           selective laser melting
    • Authors: Sabine Roux; Mehdi Salem Anis Hor
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Sabine Le Roux, Mehdi Salem, Anis Hor
      In the Selective Laser Melting (SLM) process, residual stresses are a major problem because they impact the dimensional accuracy and mechanical properties of the manufactured parts. A new methodology, based on distortion measurements using the bridge curvature method (BCM), is developed for the quantitative assessment of residual stresses. The bending of the surface of the released specimen is approximated by a quadratic polynomial and quantitative criteria are determined on both profiles and surface topographies measured by non-contact 3D optical microscopy. The accuracy of the method is evaluated by a statistical analysis using repeatability tests. Focus variation microscopy (FVM) measurements show better repeatability than extended field confocal microscopy. Compared to the 2D measurements generally reported in the literature, 3D characterization provides relevant information as the orientation of the main distortion, which may help to highlight the effect of SLM process parameters. In fact, the flatness parameters and curvature attributes measured on surface topographies are much more robust and repeatable than the distortion magnitude measured on isolated profiles. In particular, 3D analysis helps to show that the distortions are maximum perpendicular to the path of the laser.

      PubDate: 2018-05-28T13:48:58Z
  • Projection based light-directed electrophoretic deposition for additive
    • Authors: Jeronimo Mora; Jessica Dudoff Bryan Moran Joshua DeOtte Wyatt Frane
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Jeronimo Mora, Jessica K. Dudoff, Bryan D. Moran, Joshua R. DeOtte, Wyatt L. Du Frane, Joshua D. Kuntz, Andrew J. Pascall
      Electrophoretic deposition (EPD) is a widely used industrial coating technique for depositing polymer, ceramic, and metal thin films. Recently, there has been interested in using EPD for additive manufacturing using reconfigurable electrodes. Here, we report the first projector-based light-directed electrophoretic deposition (EPD) system that uses projected digital masks to dynamically control the electric field, eliminating the need for physical photomasks. We demonstrate a resolution limit of 10 μm for the deposited feature, which corresponds to the limits of the optical system. Furthermore, the first 3D overhanging structure made with EPD is presented, which points to the ability to create architected cellular materials. These improvements open the possibility for EPD to be a true 3D additive manufacturing technique.

      PubDate: 2018-05-28T13:48:58Z
  • The effect of multi-beam strategies on selective laser melting of
           stainless steel 316L
    • Authors: Thorsten Heeling; Konrad Wegener
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Thorsten Heeling, Konrad Wegener
      With increasing industrial application of additive manufacturing technologies, such as selective laser melting, the requirements concerning the processes’ capabilities like productivity, robustness, part quality and the range of processable materials are increasing as well. But due to high cooling rates, high thermal gradients and a layer-wise processing, parts produced by selective laser melting are subject to different kinds of defects. These defects commonly lead to high porosity, distortion, cracking and rough surfaces. But when a second beam is used to heat the vicinity of the melt pool a homogenization of the temperature field, a reduction of the cooling speeds within the melt pool and in its vicinity as well as an improved wetting behavior is possible. A proof of concept is shown, discussing general trends and possibilities, like increased surface qualities or dense microstructures with low amounts of remelting, when these strategies are elaborated.

      PubDate: 2018-05-28T13:48:58Z
  • Multi-functional flexible carbon fiber composites with controlled fiber
           alignment using additive manufacturing
    • Authors: Ali Anwer; Hani Naguib
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Ali Anwer, Hani E. Naguib
      This paper details a novel study and manufacturing approach of fiber alignment in flexible hybrid carbon fiber composites using Material extrusion. Varying carbon fiber volume fractions from 0 to 4 vol % was melt blended with a masterbatch of TPU + 10 wt% MWCNT followed by extrusion. The final extrudate was then filament wound onto a spool and two different filament layout orientations, 0° and 45°, were printed to compare their mechanical properties to validate the effect of fiber alignment during the printing process for these flexible fiber composites. The 0° printed composites exhibited up to 34% improvement in stiffness as compared to the 45° composite. To validate this fiber orientation, the flexible composite was textured using fiber-debonding and pullout phenomenon and the surfaces were visually and quantifiably characterized using SEM images and surface roughness respectively. To further elucidate the fiber alignment as indicated by the surface roughness, a water contact angle hydrophobicity test was conducted to prove that the 0° printed composite showed higher contact angle as compared with the 45° orientation, confirming greater entrapment due to fiber alignment at the surface. These composites are expected to find future potential in high strength and surface texturing applications.

      PubDate: 2018-05-28T13:48:58Z
  • Realizing a full volume component by in-situ welding during electron beam
           melting process
    • Authors: Pan Wang; Mui Ling Sharon Nai Wai Jack Sin Shenglu
      Abstract: Publication date: August 2018
      Source:Additive Manufacturing, Volume 22
      Author(s): Pan Wang, Mui Ling Sharon Nai, Wai Jack Sin, Shenglu Lu, Baicheng Zhang, Jiaming Bai, Jie Song, Jun Wei
      As one of the powder-bed-fusion additive manufacturing processes, electron beam melting (EBM) is able to produce metal parts directly. Many small volume components with high quality have been fabricated using the EBM technology. However, there are only few reports on the EBM fabrication of medium-sized components. One of the reasons is the lack of energy issue when the scan length is too long, which results in the generation of lack of fusion pores. This, in turn, drastically degrades the mechanical properties of the EBM printed parts. Here, we firstly report an in-situ welding process to overcome the lack of energy issue caused by the long scan length during EBM process. After the investigation of the corresponding microstructure, microhardness and tensile properties, it is revealed that the in-situ welding zone is fully joined and the mechanical properties of the in-situ welded part are comparable to that of the wrought counterpart. This implies that medium-sized components can be successfully fabricated using the EBM, with no compromise on the mechanical properties.

      PubDate: 2018-05-28T13:48:58Z
  • Evaluation of the mechanical performance of polymer parts fabricated using
           a production scale multi jet fusion printing process
    • Authors: Heather J.O’ Connor; Andrew N. Dickson; Denis P. Dowling
      Abstract: Publication date: Available online 21 May 2018
      Source:Additive Manufacturing
      Author(s): Heather J.O’ Connor, Andrew N. Dickson, Denis P. Dowling
      Additive manufacturing (AM) is rapidly becoming one of the most popular manufacturing techniques for short run part production and rapid prototyping. AM encompasses a range of technologies, including powder bed fusion (PBF) process. The purpose of this paper is to evaluate and benchmark the mechanical performance of polyamide 12 (PA12) parts, fabricated using a production scale powder bed fusion printing process (HP Multi Jet Fusion printing process). This system has a build volume is 380 × 254 x 350 mm. The printed polymer parts were examined to determine their hydrophobicity, morphology, porosity and roughness. Chemical and thermal properties of the PA12 parts were also evaluated using attenuated total reflection infrared spectroscopy (ATR FT-IR), x-ray photoelectron spectroscopy (XPS) and differential scanning calorimetry (DSC). The study highlights the influence of build orientation on the tensile (ISO 527-1:2012) and flexural (ISO 178:2010) properties. In terms of tensile strength, the parts exhibited isotropic behaviour with a maximum tensile strength of 49 MPa. In terms of flexural testing, the build orientations had a significant effect on the strength of the printed part. The Z orientation exhibited a 40% higher flexural strength, when compared to that of the X orientation. The maximum flexural strength observed was 70 MPa. The results of this rapid, production scale AM study are compared with previous studies that detail the mechanical performance of PA12, fabricated using PBF processes, such as selective laser sintering.

      PubDate: 2018-05-28T13:48:58Z
      DOI: 10.1016/j.addma.2018.05.035
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