PSI - Issue 19

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2019) 000–000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2019) 000–000

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ScienceDirect

Procedia Structural Integrity 19 (2019) 556–565

Fatigue Design 2019 Influencing factors on the fatigue strength of selectively laser melted structures Wolfgang Schneller a,* , Martin Leitner a , Sebastian Springer a , Florian Beter a , Florian Grün a a Montanuniversität Leoben, Department of Product Engineering, Chair of Mechanical Engineering, 8700 Leoben, Austria Abstract This research focusses on influencing factors on the fatigue strength of selectively laser melted (SLM) aluminum structures. One main effect is detected as the surface condition. Therefore, miscellaneous test series involving the as built surface as well as machined and polished surface topographies are experimentally investigated. In addition, the impact of different post treatments on the fatigue strength is researched. The microstructure of selected samples is studied utilizing SEM images of micrographs whereby microstructural features are assessed. Additionally, the axial residual stresses at the surface of selected specimen are measured using X-Ray diffraction, with the aim to assess influencing factors on the fatigue strength more properly. The fatigue characteristic is evaluated by tension compression high cycle fatigue tests under a load stress ratio of R=-1. Subsequently to the testing, a fracture surface analysis for each tested specimen is carried out in order to study the failure mechanism and evaluate the fatigue crack initiating imperfection. The results revealed that for specimens that possess an as-built surface, the high cycle fatigue strength is significantly influenced by surface related characteristics. It is also found that the microstructure affects the fatigue behavior as well. Fatigue Design 2019 Influencing factors on the fatigue strength of selectively laser melted structures Wolfgang Schneller a,* , Martin Leitner a , Sebastian Springer a , Florian Beter a , Florian Grün a a Montanuniversität Leoben, Department of Product Engineering, Chair of Mechanical Engineering, 8700 Leoben, Austria Abstract This research focusses on influencing factors on the fatigue strength of selectively laser melted (SLM) aluminum structures. One main effect is detected as the surface condition. Therefore, miscellaneous test series involving the as built surface as well as machined and polished surface topographies are experi entally investigated. In addition, the impact of different post treatments on the fatigue strength is researched. The microstructure of selected samples is studied utilizing SEM images of micrographs whereby microstructural features are assessed. Additionally, the axial residual stresses at the surface of selected specimen are measured using X-Ray diffraction, with the aim to assess influencing factors on the fatigue strength more properly. The fatigue characteristic is evaluated by tension compression high cycle fatigue tests under a load stress ratio of R=-1. Subsequently to the testing, a fracture surface analysis for each tested specimen is carried out in order to study the failure mechanism and evaluate the fatigue crack initiating imperfection. The results revealed that for specimens that possess an as-built surface, the high cycle fatigue strength is significantly influenced by surface related characteristics. It is also found that the microstructure affects the fatigue behavior as well.

© 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers.

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1. Introduction High performance, lightweight components are fabricated more frequently by generative manufacturing processes. Such additively manufactured, especially selectively laser melted, structures find application in various fields, for example aviation, motorsport and medical purposes [1–5]. Hence, it is of upmost importance to characterize cyclic material properties, and respective influencing factors, in order to safely design failure critical parts. Aluminum is one of the most commonly used materials for powder-bed based AM [6]. Several influencing factors on the fatigue strength 1. Introduction High performance, lightweight components are fabricated more frequently by generative manufacturing processes. Such additively manufactured, especially selectively laser melted, structures find application in various fields, for example aviation, motorsport and medical purposes [1–5]. Hence, it is of upmost importance to characterize cyclic material properties, and respective influencing factors, in order to safely design failure critical parts. Aluminum is one of the most commonly used materials for powder-bed based AM [6]. Several influencing factors on the fatigue strength

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. 2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers.

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. 10.1016/j.prostr.2019.12.060