PSI - Issue 19

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

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Procedia Structural Integrity 19 (2019) 520–527

Fatigue Design 2019 Effect of Hydrogen on Fatigue Limit of SCM435 Low-Alloy Steel Masanobu Kubota a *, Mio Fukuda b , Ryosuke Komoda c a International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan b Graduate School of Engineering, Kyushu University, , 744 Motooka, Fukuoka 819-0395, Japan c Department of Mechanical Engineering, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka, 814-0180, Japan Fatigue Design 2019 Effect of Hydrogen on Fatigue Limit of SC 435 Low-Alloy Steel Masanobu Kubota a *, Mio Fukuda b , Ryosuke Komoda c a International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan b Graduate School of Engineering, Kyushu University, , 744 Motooka, Fukuoka 819-0395, Japan c Department of Mechanical Engineering, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka, 814-0180, Japan The objective of this study is to gain a basic understanding of the effect of hydrogen on the fatigue limit. The material was a low alloy steel modified to be sensitive to hydrogen embrittlement by heat treatment. A statistical fatigue test was carried out using smooth and deep-notched specimens at a loading frequency of 20 Hz. The environment was laboratory air and hydrogen gas. The hydrogen gas pressure was 0.1 MPa in gauge pressure. The fatigue limit of the smooth specimen was higher in the hydrogen gas than that in air, although the material showed severe hydrogen embrittlement during the SSRT (Slow Strain Rate Test). The fatigue limit of the deep-notched specimen in the hydrogen gas was the same as that in air. For the smooth specimen, the fatigue limit was determined by whether or not a crack was initiated. For the deep-notched specimen, the fatigue limit was determined by whether or not a crack propagated. The results can be interpreted as that hydrogen has no significant effect on crack initiation in the high cycle fatigue regime and affected the threshold of the crack propagation. Abstract Abstract The objective of this study is to gain a basic understanding of the effect of hydrogen on the fatigue limit. The material was a low alloy steel modified to be sensitive to hydrogen embrittlement by heat treatment. A statistical fatigue test was carried out using smooth and deep-notched specimens at a loading frequency of 20 Hz. The environment was laboratory air and hydrogen gas. The hydrogen gas pressure was 0.1 MPa in gauge pressure. The fatigue limit of the smooth specimen was higher in the hydrogen gas than that in air, although the material showed severe hydrogen embrittlement during the SSRT (Slow Strain Rate Test). The fatigue limit of the deep-notched specimen in the hydrogen gas was the same as that in air. For the smooth specimen, the fatigue limit was determined by whether or not a crack was initiated. For the deep-notched specimen, the fatigue limit was determined by whether or not a crack propagated. The results can be interpreted as that hydrogen has no significant effect on crack initiation in the high cycle fatigue regime and affected the threshold of the crack propagation.

© 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Fatigue Design 2019 Organizers. © 2019 The Authors. Pu lished 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: Hydrogen; Fatigue; Fatigue limit; Keywords: Hydrogen; Fatigue; Fatigue limit;

1. Introduction 1. Introduction

For the design of high-pressure gas containment systems, the design-by-rule approach is the most common. Kobayashi (2015) and Yamabe et al. (2016) reviewed this design approach and explained that the allowable stress is determined based on the ultimate tensile stress (UTS) of the material and safety factor. The safety factor is designated For the design of high-pressure gas containment systems, the design-by-rule approach is the most common. Kobayashi (2015) and Yamabe et al. (2016) reviewed this design approach and explained that the allowable stress is determined based on the ultimate tensile stress (UTS) of the material and safety factor. The safety factor is designated

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. * Corresponding author. Tel.: +81-92-802-6720 E-mail address: Kubota.masanobu.304@m.kyushu-u.ac.jp * Corresponding author. Tel.: +81-92-802-6720 E-mail address: Kubota.masanobu.304@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.2019.12.056