Abstract Fracture of an anisotropic rare-earth-containing magnesium alloy (ZEK100) sheet is investigated at different stress states and strain rates. A variety of sample geometries, loading conditions, and loading orientations are used to achieve different stress triaxiality and deformation mechanisms. Digital image correlation (DIC) technique is used to measure the surface strains up to fracture for all the specimens. We show that ZEK100 exhibits larger strain at fracture across the gage section of the test specimens aligned with the transverse direction (TD) than specimens aligned with the rolling direction (RD); however, the opposite is shown for the local strain measurements at fracture. With an increase in the strain rate, the strains at fracture decrease for all loading paths. A crystal plasticity finite element model is used to simulate the local stress state and deformation mechanisms for each loading condition. ZEK100 exhibits an anisotropic fracture behavior that is a function of the stress triaxiality and Lode parameter. We show that extension twinning also plays an important role in the fracture response of ZEK100. Overall, the local effective strain at fracture is lower for the specimens that exhibit the largest volume fraction of extension twinning. A novel anisotropic extension to the Hosford-Coulomb (HC) fracture model is then developed to account for the effect of extension twinning on the anisotropic fracture response of ZEK100.

中文翻译：

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各向异性含稀土镁合金 (ZEK100) 在不同应力状态和应变率下的断裂：实验和建模

摘要 研究了各向异性含稀土镁合金 (ZEK100) 板在不同应力状态和应变率下的断裂。各种样品几何形状、加载条件和加载方向用于实现不同的应力三轴性和变形机制。数字图像相关 (DIC) 技术用于测量所有试样直至断裂的表面应变。我们表明，与与轧制方向 (RD) 对齐的试样相比，ZEK100 在与横向 (TD) 对齐的试样的应变片断面处表现出更大的断裂应变；然而，对于断裂处的局部应变测量则相反。随着应变率的增加，所有加载路径的断裂应变都减小。晶体塑性有限元模型用于模拟每种加载条件下的局部应力状态和变形机制。ZEK100 表现出各向异性断裂行为，该行为是应力三轴性和 Lode 参数的函数。我们表明，延伸孪晶在 ZEK100 的断裂响应中也起着重要作用。总体而言，对于表现出最大拉伸孪晶体积分数的试样，断裂时的局部有效应变较低。然后开发了 Hosford-Coulomb (HC) 断裂模型的新型各向异性扩展，以解释扩展孪生对 ZEK100 各向异性断裂响应的影响。ZEK100 表现出各向异性断裂行为，该行为是应力三轴性和 Lode 参数的函数。我们表明，延伸孪晶在 ZEK100 的断裂响应中也起着重要作用。总体而言，对于表现出最大拉伸孪晶体积分数的试样，断裂时的局部有效应变较低。然后开发了 Hosford-Coulomb (HC) 断裂模型的新型各向异性扩展，以解释扩展孪生对 ZEK100 各向异性断裂响应的影响。ZEK100 表现出各向异性断裂行为，该行为是应力三轴性和 Lode 参数的函数。我们表明，延伸孪晶在 ZEK100 的断裂响应中也起着重要作用。总体而言，对于表现出最大拉伸孪晶体积分数的试样，断裂时的局部有效应变较低。然后开发了 Hosford-Coulomb (HC) 断裂模型的新型各向异性扩展，以解释扩展孪生对 ZEK100 各向异性断裂响应的影响。