一种改进的Cockroft-Latham断裂准则及其在液固挤压中的应用  

Modified Cockroft-Latham Fracture Criterion and Its Application to Liquid-Solid Extrusion

作　　者：刘健[1] 齐乐华[2] Liu Jian Qi Lehua(Xi＇an University of Technology, Xi＇an 710048, China Northwestern Polytechnical University, Xi＇an 710072, China)

机构地区：[1]西安理工大学,陕西西安710048 [2]西北工业大学,陕西西安710072

出　　处：《稀有金属材料与工程》2016年第11期2902-2906,共5页Rare Metal Materials and Engineering

基　　金：国家自然科学基金(51305345);陕西省自然科学基金(2014JQ6228);西安理工大学科技新星科学研究计划项目(104-211404)

摘　　要：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。Both deformation temperature and strain rate are important factors for the damage behavior of magnesium matrix composites in the liquid-solid state. In the present paper, Zener-Hollomon parameter, which incorporates a combined effect of temperature and strain rate, was introduced to Cockroft-Latham fracture criterion as a correlation coefficient. The correlation coefficient, which equals facture strain under uniaxial tensile stress state, was determined by a series of tensile tests of Csf/Mg composites in the high temperature solid state and semi-solid state, and fitted into a nonlinear function of lnZ, thereby obtaining a modified Cockroft-Latham fracture criterion. Furthermore, the modified Cockroft-Latham fracture criterion was applied to the simulation of liquid-solid extrusion, and the predicted results show a good agreement with experimental observations in both the direction and length of surface cracks.

关 键 词：表面裂纹 液固挤压 韧性断裂准则 镁基复合材料 有限元模拟 

分 类 号：TB333[一般工业技术—材料科学与工程] TG376[金属学及工艺—金属压力加工]