基于材料非均匀性铝厚板预拉伸残余应力的预测方法

Prediction approach of residual stress distribution in aluminum alloy pre-stretched thick plate based on material non-uniformity

引入离散化思想将铝厚板划分为若干层,依据淬火残余应力定义各层的等效塑性应变;通过各层材料应力-应变曲线的线性近似后,根据等效塑性应变推导出误差不超过2%的屈服极限分布模型。此外,根据弹性模量随塑性变形进展而不断变化的实验数据,拟合出弹性模量的变化曲线。以淬火7075铝厚板的预拉伸为例,考虑淬火所引起的屈服极限与弹性模量的非均匀性,分别进行预拉伸率为1.8%、2.2%和2.5%的残余应力有限元仿真,无论是分布曲线还是应力的大小,残余应力仿真值与实验测量值均比较吻合,分布曲线拐点处残余应力的平均误差仅为13.5%。

The discretization method was employed to separate the aluminum alloy thick plate into several levels. The equivalent plastic strain was defined for each level according to the residual stress during quenching. With the linear approximation of the stress-strain curve, the yield strength model with less than 2% difference was formulated as a function of the equivalent plastic strain. Moreover, the curve of elasticity modulus according to the variation of elasticity modulus with plastic deformation was fitted. Finally, by considering the non-uniformity of yield strength as well as elasticity modulus, the pre-stretching of the 7075 quenched aluminum alloy thick plate was simulated for the residual stresses when the pre-stretching rates are 1.8%, 2.2% and 2.5%, respectively. Whether the distribution curve or the stress magnitude, the simulated residual stresses obtained by the proposed method are in good agreement with the experimental data. The average error of the simulated residual stresses at the inflection points of the distribution curve is only 13.5%.