This paper presents a novel mesoscopic damage model to characterize the low-cycle fatigue damage evolution of an extruded AZ31 magnesium (Mg) alloy, taking into account the effect of twinning. The damage caused by the slip bands (SBs)–twin boundaries (TBs) and SBs–grain boundaries (GBs) interactions is treated based on the Tanaka–Mura model and the Eshelby inclusion theory. Strain energy values at the TBs and GBs are defined as the TB and GB damage variables, respectively. Explicit formulae for the TB and GB damage evolution are derived from the characteristics of the {$10\overline{1}2$} extension twin and the basal texture. A fracture energy-based crack initiation criterion is established, and the proposed damage model is validated against the existing experimental results. The model demonstrates its ability to reproduce the damage evolution processes, and the predictions of the crack initiation life are within the twice error band.

本文提出了一种新的细观损伤模型来表征挤压 AZ31 镁 (Mg) 合金的低周疲劳损伤演变，同时考虑孪晶效应。基于 Tanaka-Mura 模型和 Eshelby 夹杂理论处理由滑移带 (SBs)-孪晶界 (TBs) 和 SBs-晶界 (GBs) 相互作用引起的损伤。TB 和 GB 处的应变能值分别定义为 TB 和 GB 损伤变量。TB 和 GB 损伤演化的显式公式源自 {$10\overline{\mathrm{1个}}\mathrm{2个}$} 扩展孪生和基底纹理。建立了基于断裂能量的裂纹萌生准则，并根据现有实验结果验证了所提出的损伤模型。该模型展示了其重现损伤演化过程的能力，并且裂纹萌生寿命的预测在两倍误差范围内。