In order to research the damage and wall thickness distribution of 3A21 thin-wall rectangular tube with different fillet in the bending process, the material parameters of Lemaitre criterion were obtained through cyclic loading-unloading tensile tests by using the method of Young's modulus weakening. A user-defined VUMAT subroutine combined Lemaitre criterion was developed based on ABAQUS/Explicit platform. Furthermore, 3D finite element models for bending process of rectangular tube with different fillet were built and the reliability was validated. The results show that the maximum wall-thinning and damage value locates at the section of 50° , and the wall-thinning and damage value increases with the fillet radius decreases. In other words, the tube is more prone to rupture with the cross-section of tube tending to be rectangular.%为获得不同圆角过渡3A21铝合金薄壁矩形管弯曲的壁厚变化和损伤情况,采用弹性模量变化法,通过对拉伸进行试样反复加载、卸载试验,获取了Lemaitre断裂准则中的损伤参数.基于ABAQUS/Explicit的VUMAT二次开发平台,开发了耦合Lemaitre准则的用户材料子程序,建立了相同弯曲半径条件下不同圆角过渡的矩形管弯曲损伤预测三维有限元模型,并对模型的可靠性进行了验证.基于所建模型,研究发现管材壁厚减薄率与损伤最大值均出现在弯曲后截面50.左右,并且管材截面的圆角半径越小,其弯曲后中性层外侧壁厚减薄越严重,损伤值越大,即管材截面形状越趋向于矩形,弯曲过程中越容易发生破裂.
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