Micromechanical modelling of void nucleation in ductile metals indicates that strain required for damage initiation reduces exponentially with increasing stress triaxiality. This feature has been incorporated in a continuum damage mechanics (CDM) model, providing a phenomenological relationship for the damage threshold strain dependence on the stress triaxiality. The main consequences of this model modification are that the failure locus is predicted to change as function of stress triaxiality sensitivity of the material damage threshold strain and that high triaxial fracture strain is expected to be even lower than the threshold strain at which the damage processes initiate at triaxiality as low as 1/3. The proposed damage model formulation has been used to predict ductile fracture in unnotched and notched bars in tension for two commercially pure α‐iron grades (Swedish and ARMCO iron). Finally, the model has been validated, predicting spall fracture in a plate‐impact experiment and confirming the capability to capture the effect of the stress state on material fracture ductility at very high stress triaxiality.

中文翻译：

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包含应力三轴效应对延性损伤萌生的连续损伤力学建模

韧性金属中空核形核的微机械模型表明，损伤引发所需的应变随应力三轴性的增加而呈指数下降。此功能已合并到连续损伤力学（CDM）模型中，为损伤阈值应变对应力三轴性的依赖性提供了现象学关系。这种模型修改的主要结果是，预计破坏轨迹将随着材料损伤阈值应变的应力三轴敏感性而变化，并且预期高三轴断裂应变甚至会低于损伤过程开始时的阈值应变。在三轴性低至1/3。所提出的损伤模型公式已用于预测两种商业纯α-铁等级（瑞典和ARMCO铁）的无缺口和有缺口钢筋的拉伸断裂。最后，该模型已经过验证，可以在板冲击实验中预测剥落断裂，并确认能够在非常高的应力三轴性条件下捕获应力状态对材料断裂延展性的影响。