适用于UH模型的单元破坏修正方法

Element failure correction method for UH model

在采用UH模型的用户材料子程序(UMAT)进行有限元计算过程中时常会出现局部单元破坏的情况,主要包括拉裂和剪坏,这种破坏应力状态的存在不仅会使得计算结果不合理,也会降低有限元计算的稳定性。针对采用UH模型UMAT进行有限元计算时遇到的局部单元破坏问题,根据一定的假设条件,并结合不同坐标系下的应力变换关系,推导得到适用于UH模型的三维问题单元破坏修正公式;采用FORTRAN语言编写出相应的子程序,将其嵌入UH模型UMAT中,以消除采用UH模型进行有限元计算时出现的不合理的破坏应力状态,提高UH模型UMAT有限元计算的稳定性,并通过有限元模拟基坑开挖的例子验证本文所提的单元破坏修正方法的有效性和合理性。

The problem of some elements＇ damage often appears when finite element calculation of using UH model UMAT is conducted, including tension failure and shear failure. The failure stress state not only makes the results unreasonable, but also reduces the stability of calculation. To solve the problem generated by unreasonable failure stress state when the UH model＇ s UMAT is used to conduct finite element analysis, based on certain assumptions and combined with stress transformation relationship under different coordinates, three-dimensional element failure correction formulas for UI-I model can be elicited. Then FORTRAN language is used to write the subroutine of element failure correction, and it is embedded in the UH model＇ s UMAT to eliminate the unreasonable failure stress state and improve the stability of finite element calculation. Finally, an example of foundation pit excavation is used to verify the validity and rationality of this method.