PSI - Issue 66

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2025) 000–000

www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 66 (2024) 38–48

8th International Conference on Crack Paths Elucidation of small fatigue crack initiation and propagation behavior on polycrystal Ti-22V-4Al Jinta Arakawa a *, Koki Hirazumi a ,Takeshi Uemori a , Yoshito Takemoto a a Okayama University, Okayama-shi 3-1-1 Tsushimanaka, Kita-ku, Okayama, 700-8530, Japan Abstract In this study, the quantitative evaluation of small fatigue crack initiation was performed using Ti-22V-4Al to ensure the safety and reliability of β -type titanium alloys for long-term use. This study showed that cracks occur from the slip system which has the maximum value of Schimd factor in the grain where the crack occur at first. So that, Schmid factor can approximately predict the slip system, which generate crack for single crystals. When we conducted that the comparison of Schmid factors for different grains around the crack initiation site, fatigue crack did not initiate from the grain with the largest Schmid factor. This result indicates that the Schmid factor cannot predict crack initiation in polycrystalline materials. Furthermore, small fatigue crack initiation and propagation was evaluated by crystal plasticity analysis (CP-FEM) considering grain interactions. The results indicated that the grain where fatigue crack initiates and its path could be predicted by CP-FEM. Therefore, in order to predict fatigue crack initiation site and its path, in addition to the Schmid factor, it will be necessary to use crystal plasticity analysis considering the grain interactions. © 2025 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 CP 2024 Organizers Keywords: Fatigue crack initiation; Small crack path; Schmid factor; Crystal plasticity FEM 1. Introduction Industrial α+β titanium alloys are difficult to machine due to the presence of the α phase, which hinders their application in small precision parts. Therefore, to significantly improve workability, a β -type titanium alloy consisting © 2025 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 CP 2024 Organizers

* Corresponding author.. E-mail address: jarakawa@okayama-u.ac.jp

2452-3216 © 2025 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 CP 2024 Organizers

2452-3216 © 2025 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 CP 2024 Organizers 10.1016/j.prostr.2024.11.053