屈服准则及切线模量修正的弹塑性计算模型

为提高不同应力状态下金属弹塑性行为的模拟精度,采用含应力三轴度修正的von Mises屈服准则,材料弹塑性本构关系在等效应力-等效应变曲线基础上,提出一个切线模量为主应力函数的理论修正项.将这两个修正项结合,以子程序形式编程嵌入ABAQUS主程序,以此模拟几种不同形状试样的弹塑性行为,并将其他屈服准则在单一曲线假设下编程与之对比.模拟结果与真实试验结果对比发现,对于屈服而言,含应力三轴度修正的von Mises屈服准则比其他屈服理论准确;对于弹塑性阶段计算而言,提出的切线模量为主应力函数这一假设比单一曲线假设更加接近真实试验.

A NEW COMPUTATIONAL MODEL OF METAL PLASTICITY BASED ON VON MISES CRITERION CORRECTION AND TANGENT MODULUS CORRECTION

The simulation precision of metal plasticity is closely related to yield criteria and constitutive law which are used in computational model. In order to improve this precision under complex stress state, tensile tests with five kinds of samples, such as smooth round bar, round bar with small notch, round bar with large notch, thin plate with central hole and thick plate with central hole, were conducted. Parallel finite element models were built for each test and solved in ABAQUS. In these simulations, von Mises yield criterion, Tresca criterion, Twin-Shear criterion were separately used based on equivalent stress-strain curve as the constitutive law. The results showed that none of them had a satisfying precision for all these different tests. So Von Mises criterion with stress triaxiality dependence was used as yield function. Tangent modulus with principal stresses correction based on equivalent stress-strain curve was used as elasto-plastic constitutive law. With this theory, the above tests were recomputed. The results further showed that, comparing with other criterions, von Mises criterion with stress triaxiality correction has a better precision than other yield functions. The tangent modulus with principal stresses correction which is first postulated in this paper has a better estimation of 2A12-T4 Aluminum Alloy's Elasto-plastic behavior than the assumption with unique equivalent stress-strain curve.