说明：  ABAQUS 用户子程序 UMAT 的开发方法，采用 FORTRAN 语言编制了各向同性硬化材料模型的接口程序，研究该类材料的弹塑性本构关系极其实现方法
(Based on the development method of user subroutine UMAT of ABAQUS, the interface program of isotropic hardening material model is compiled by FORTRAN language, and the elastic-plastic constitutive relation of this kind of material and its realization method are studied)