Effect of isotropic and anisotropic damage and plasticity on ductile crack initiation

In this article, the effects of plastic anisotropy and damage on ductile crack initiation (ductile failure) are studied in a thermodynamically consistent framework. First, isotropic and anisotropic continuum damage models of Lemaitre are modified to incorporate anisotropic plasticity. In the next stage, a subroutine is developed to add the damage formulation to Abaqus finite element package. A highly ductile material with anisotropic plastic behavior, API 5L X100 pipeline steel, is selected for this study. Finite element analyses are done to simulate isotropic/anisotropic plasticity coupled with isotropic/anisotropic damage. Finite element results are compared with the result of tests on smooth and notched specimens, and the effects of anisotropic plasticity, anisotropic damage, geometry changes, triaxiality in stress and their mutual effects and interactions on post yield behavior and crack initiation are studied.