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) 113–122

Fatigue Design 2019 Defect Analysis for Additively Manufactured Materials in Fatigue from the Viewpoint of Quality Control and Statistics of Extremes Yukitaka Murakami a,c, * , Hiroshige Masuo b , Yuzo Tanaka c , Masanori Nakatani c a Emeritus Professor, Kyushu University, Fukuoka, Japan Fatigue Design 2019 Defect Analysis for Additively Manufactured Materials in Fatigue from the Viewpoint of Quality Control and Statistics of Extremes Yukitaka Murakami a,c, * , Hiroshige Masuo b , Yuzo Tanaka c , Masanori Nakatani c a Emeritus Profess r, Kyushu University, Fukuoka, Japan Abstract Additive manufacturing (AM) is expected to be a promising new manufacturing process for components having complex geometry. However, the disadvantage or challenge of AM is the presence of defects and surface roughness which are inevitably produced by the manufacturing process. Without strict and reliable quality control of components regarding defects and surface roughness, we cannot positively admire the advantages of AM as the new technology. In this paper, the method of quantitative evaluation of defects with complicated shapes and configurations, is explained from the viewpoint of small 3D cracks. First of all, the ideal fatigue strength (goal) to be attained by AM is discussed. Use of Fatigue-Grades from 5 (ideal strength) to 1 (lowest grade) is proposed for mutual comparison of fatigue performance of AM materials. The factors which decrease fatigue strength and degrade tensile properties are quantitatively analyzed. It is verified that the fatigue limit of AM materials is determined by the presence of nonpropagating crack emanating from defects. The reasons are made clear for fatigue fracture from surface defects even by tension-compression fatigue test as due to the difference of population of defects and increase in stress intensity factor for surface crack compared to internal cracks. Practical guides will be presented for the fatigue design and development of high quality AMmaterials, based on the combination of the 3D defect analysis, the statistics of extremes on defects, and the  area parameter model. It is shown that fatigue notch effect in AM materials is influenced by probability of presence of defects at notch root. Abstract Additive manufacturing (AM) is expected to be a promising new manufacturing pro ss for components havi g complex geometry. However, the disadvantage or c allenge of AM is the presence f defects and surface roughness whi h re inevitably produced by the manufacturing process. Without strict and reliabl quality control of components regarding defects and surface roughness, we cannot ositively admire the advant ges of AM as the new technology. In this paper, the method of quantitative evaluation of d fects with complicated shapes and configurations, i explained from the viewpoint of small 3D cracks. First of all, the ideal fatigue strength (goal) to be att ined by AM is discussed. Use of Fatigue-Grades from 5 (ideal strength) to 1 (lowest grade) is proposed for mutual comparison of fatigue performance of AM materials. The factors which decrease fatigue strength and degrade te sile properties are quantitatively analyzed. It is verified that the fatigue limit of AM materials is determined by the presence of onpropagati g crack emanating from efects. The reasons are made clear for fatigu fracture from surface defects even by tension-compression fatigue test as due to the ifference of population of defects and increase in stress intensity factor for surface crack compared to internal cracks. Practical guides will be pr sented for the fatigue design and development of high quality AMmaterials, based on the combination of the 3D defect analysis, the statistics of extremes on defects, and the  area parameter model. It is shown that fatigue notch effect in AM materials is influenced by probability of presence of defects at notch root. b Metal Technology Co.Ltd., Ebina, Kanagawa, 243-0424, Japan c Kobe Material Testing Laboratory Co. Ltd, Kako-gun, Hyogo, Japan b Metal Technology Co.Ltd., Ebina, Kanagawa, 243-0424, Jap n c Kobe Material Testing Laboratory Co. Ltd, Kako-gun, Hyogo, Japan

© 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.

Keywords: Additive manufacturing; Fatigue; Defects; Fatigue-Grades; √area parameter model ; Statistics of extremes Keywords: Additive manufacturing; Fatigue; Defects; Fatigue-Grades; √area parameter model ; Statistics of extremes

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. * Correspon ing author. Tel.: +81-79-435-5010; fax: +81-79-435-5102. E-mail address: murakami.yukitaka.600@m.kyushu-u.ac.jp * Corresponding author. Tel.: +81-79-435-5010; fax: +81-79-435-5102. E-mail address: murakami.yukitaka.600@m.kyushu-u.ac.jp

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. 10.1016/j.prostr.2019.12.014