PSI - Issue 71

Available online at www.sciencedirect.com

ScienceDirect

Procedia Structural Integrity 71 (2025) 4–9

5 th International Structural Integrity Conference & Exhibition (SICE 2024)

Crack Initiation and Propagation Behaviors in Rotating Bending Fatigue of Al-Si-Mg Cast Aluminum Alloy Containing Artificial Defects and Applicability of the √ Parameter Model Shohei Matsuda a , Tohru Hashimoto b , Kota Takamatsu b , Takashi Matsuo c,d , Masahiro Endo c,d and Junichiro Yamabe c,d

a Graduate School of Engineering, Fukuoka University, Jonan-ku, Fukuoka 814-0180, Japan b HINODE Holdings Co. Ltd, Hakata-ku, Fukuoka 812-8636, Japan c Department of Mechanical Engineering, Fukuoka University, Jonan-ku, Fukuoka 814-0180, Japan d Institute of Materials Science and Technology, Fukuoka University, Jonan-ku, Fukuoka 814-0180, Japan

Abstract Natural defects in cast aluminum alloys, such as gas and shrinkage porosities, significantly reduce the fatigue strength. It is essential to understand how these defects relate to fatigue limits to develop a practical fatigue strength prediction model. This study investigated the fatigue crack behaviors in a cast aluminum alloy A356-T6 by performing rotating bending fatigue tests using specimens containing an identical artificial defect of 287 μ m in √ . The obtained S-N data exhibited large scatter, and the √ parameter model gave a non-conservative prediction for the fatigue limit. The fracture surface was macroscopically normal to the loading direction but microscopically composed of many smaller facets with different inclinations. The size and orientation variations of the grains greater than the artificial defect are supposed to be related to creating these facets and causing the scatter in fatigue strength. Unsatisfactory fatigue limit prediction based on the √ parameter model may be attributed to the misestimation of effective defect size and the cracks microscopically extending in a mixed-mode manner. © 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 SICE 2024 organizers

Keywords: Age-hardened Al alloy; Fatigue life; Fatigue limit; Scatter; Prediction method

1. Introduction Al-Si-Mg cast aluminum alloys are an excellent material with characteristics of high specific strength,

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 SICE 2024 organizers 10.1016/j.prostr.2025.08.002