PSI - Issue 42

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

www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 42 (2022) 730–737

© 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the 23 European Conference on Fracture – ECF23 Abstract ISO 12135 provide a unified method of test for the determination of quasistatic fracture toughness. This test is conducted by using three-point bending specimen with a notch and fatigue pre-crack, and with regards to the fatigue pre-crack, ISO 12135 and ISO 15653 require some requirements such as minimum length and straightness. A base material specimen often meets the requirements without any special techniques, however, welds specimen cannot meet them due to welding residual stress. In order to meet the requirements, the local compression technique is used in general and ISO 15653 provides the recommended conditions. However, some interested parties have reported that the recommended conditions decrease the fracture toughness values. Based on the above, the authors developed prediction method for fatigue pre-crack straightness and fracture toughness evaluation value with numerical analysis and searched the good local compression condition, such as shape, size and location, with Bayesian optimization. As a result, we found that the area and location significantly effect on the fatigue pre-crack straightness and fracture toughness evaluation value and proposed new recommended local compression condition, which securing a straight fatigue pre-crack while maintaining the fracture toughness evaluation value. This proposed condition is validated through fracture toughness test and the fracture toughness evaluation values were compared with ISO recommended condition and so on. These experimental results also showed the effectiveness of proposed condition. © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of 23 European Conference on Fracture - ECF23 Keywords: Fracture toughness, Local compression, Bayesian optimization 23 European Conference on Fracture - ECF23 Search for Good Local Compression Condition with Bayesian Optimization Takumi Ozawa a *, Tomoya Kawabata b , Yoshiki Mikami c a National Maritime Research Institute, 6-38-1 Shinkawa, Mitaka, Tokyo, 181-0004, Japan b Graduate School of Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo, 113-8656, Japan c Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka, 567-0047, Japan

* Corresponding author. Tel.: +81-422-41-3732; fax: +81-422-41-3112. E-mail address: ozawa-t@m.mpat.go.jp

2452-3216 © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of 23 European Conference on Fracture - ECF23

2452-3216 © 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the 23 European Conference on Fracture – ECF23 10.1016/j.prostr.2022.12.092