单轴压缩金属粉末材料屈服准则研究

Study on yield criterion of powder metal under uniaxial compression

基于塑性泊松比与相对密度的关系,在单轴压缩受力状态下建立金属粉末材料的致密化模型,探讨材料的致密化过程.通过对椭球体屈服准则几何性质研究,推导了屈服准则扁率、第一偏心率和第二偏心率等椭球体几何参数的表达形式.将单轴应力屈服准则与多种经验屈服准则进行对比,分析椭球体几何参数随相对密度的变化趋势.结果显示:单轴压缩致密化过程中,致密化模型预测相对密度与试验结果的最大相对误差为1.27%;单轴应力屈服准则和经验屈服准则的椭球体几何参数表现出一致的强化规律.

A densification model,which was based on the relationship of plastic Poisson′s ratio and relative density,was established for powder metal under uniaxial compression.Densification behavior of powder metal was predicted by the model.Geometric interpretation for yield criterions of powder metal was also studied.Expressions of ellipsoid geometric parameters,such as flattening,the first and second eccentricity,were deduced.Effects of relative density on ellipsoid geometric parameters were investigated by comparison of uniaxial stress yield criterion and experimental criterions.The results show that the maximum relative error of the densification model is about 1.27%for powder metal under uniaxial compression.The prediction results agree well with experiment.Densification hardening behavior of ellipsoid geometric parameters is very similar for both uniaxial stress yield criterion and experimental criterions.