Proposal of new crack-tip-opening-displacement as a mechanical driving force of elastic-plastic fracture mechanics

Abstract

In this study, the current status of linear and nonlinear fracture mechanics was surveyed, and the conditions required for elastic–plastic fracture mechanics (EPFM) as the next step of fracture mechanics were listed. Then, the imaginary crack tip opening displacement (I-CTOD), expressed by the integral of the plastic strain in a two-dimensional plastic zone, was proposed as a driving force of EPFM. Elastic-plastic FEMs of cracked solids in various work-hardened materials were performed under both the plane stress and plane strain states to understand the singular field characteristics of elastic and plastic strains near a crack tip. The I-CTOD was found to represent the intensity of the plastic strain singular field, the elastic strain singular field, and the imaginary plastic deformation field near the crack tip in elastic–plastic solids under both the plane stress and plane strain states. This I-CTOD is promising as a mechanical driving force parameter of EPFM because the analyzable and visualizable characteristics of the behavior and its clear relationship to actual material behavior make it easy to develop prediction methods for the actual crack behavior.