钛合金绝热剪切带出现时临界塑性剪切应变的估算方法

基于曲线的最小二乘拟合方法,计算了Ti-6Al-4V绝热剪切带出现时的临界塑性剪切应变。根据梯度塑性理论,获得了绝热剪切带内部的局部塑性剪切变形分布曲线的理论表达式,用于拟合Liao及Duffy的实验数据。在不同的绝热剪切带宽度取值条件下,估算了绝热剪切带出现时的临界塑性剪切应变。当绝热剪切带的宽度取值在1~2mm时,计算出的临界塑性剪切应变在0.1~0.47之间。绝热剪切带内部的局部变形分布曲线的理论表达式可以很好地描述流线的非线性特征。当绝热剪切带的宽度取值较大时,绝热剪切带内部的流线的理论结果在两端较弯曲;而当其取值较小时,这些流线比较平直,仅稍微弯曲。

A Method for Assessing the Critical Plastic Shear Strain Corresponding to the Onset of Adiabatic Shear Band for Titanium Alloy

The critical plastic shear strain corresponding to the onset of adiabatic shear band for Ti-6Al-4V alloy is calculated based on the curve-fitting least-squares method. Using gradient-dependent plasticity, the local plastic shear deformation distribution in the adiabatic shear band is obtained theoretically to fit the experimental flow lines by Liao and Duffy (1998). The critical plastic shear strains at different values of the adiabatic shear band width are assessed. When the width is assigned to be in the range of 1-2 mm, the predicted critical plastic shear strain is in the range of 0.1-0.47. It is found that the theoretical expression for the local plastic shear deformation distribution in the adiabatic shear band can well describe the nonlinear characteristics of flow lines. When the width is assigned to be a higher value, the theoretical flow lines in the adiabatic shear band are more curved at the two ends of the band, while when the width is assigned to be a lower value, the theoretical flow lines are straighter and only slightly curved.