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由于变形温度和应变速率是影响液固态C_sf/Mg复合材料损伤行为的重要因素,因此将与变形温度和应变速率相关的Zener-Hollomon参数作为一个修正系数引入Cockroft-Latham断裂准则。采用高温及半固态单轴拉伸试验方法得到不同lnZ下C_sf/Mg复合材料的断裂应变,通过非线性拟合确定了模型中的修正系数,从而得到改进的Cockroft-Latham断裂准则。将该断裂准则应用于液固挤压成形过程中的数值模拟,发现模拟结果与试验结果基本吻合。表明该断裂准则可以很好地应用于镁基复合材料液固挤压表面裂纹的预测。
Since deformation temperature and strain rate are important factors affecting the damage behavior of liquid-solid C_sf / Mg composites, the Zener-Hollomon parameters related to deformation temperature and strain rate are used as a correction factor to introduce the Cockroft-Latham fault criterion. The fracture strain of C_sf / Mg composites with different lnZ was obtained by high temperature and semi-solid uniaxial tensile test. The correction coefficient in the model was determined by nonlinear fitting, so that the improved Cockroft-Latham fracture criterion was obtained. The fracture criterion was applied to the numerical simulation of liquid-solid extrusion forming process. It was found that the simulation results were in good agreement with the experimental results. It is shown that the fracture criterion can be applied to the prediction of surface cracks on liquid-solid extrusion of Mg-based composites.