M&M材料力学カンファレンス
Online ISSN : 2424-2845
セッションID: OS1419
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AZ31マグネシウム合金における疲労き裂発生の数値解析
*ブリフォ ファビャン白岩 隆行榎 学
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The present study aims at investigating the fatigue behavior of AZ31 Mg alloys through crystal plasticity finite element simulations of statistically representative polycrystalline aggregates. A crystal plasticity model including twinning, detwinning and slip in the twinned region is presented and calibrated against cyclic experiments conducted on rolled AZ31 Mg alloys. Fatigue experiments under load-controlled conditions are conducted with in situ optical microscopy observation in order to identify the appearance of fatigue cracks with regards to the number of applied cycles. Fatigue simulations of two-dimensional periodic microstructures are then performed with similar loading conditions than in experiments. Mesoscopic non-local fatigue criteria for slip and twin-induced crack initiation are presented, investigated and compared to experimental data. The results indicate that basal slip and deformation twinning are the main mechanisms occurring during fatigue conditions as the low applied stress prevents the onset of prismatic and pyramidal slip. In addition these deformation modes appear to take place in different grains. The analysis of the fatigue criteria shows that the twin-induced crack initiation criterion exhibits a better trends in terms of mean behavior, scattering and sensitivity against loading conditions compared with the slip-induced criterion. It suggests that under fully-reversed conditions, the appearance of a fatigue crack is intimately related to the presence of twins within the microstructure.

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