Speed Effect on a Fast Propagating Crack Based on a Modified Cohesive Zone Model

摘要

A modified cohesive zone model based on von Mises yielding criterion is proposed to study speed effect on a mode-I steady-state moving crack or self-similar expanding crack.The present model predicts that ahead of a steady-state moving crack tip,the traction force in the cohesive zone is a constant.A relationship is derived which relates the length of cohesive zone to the crack speed,remote loading and yielding strength of material.Our results show that the cohesive zone size depends on the crack speed for a steady-state moving crack,contradicting with the classical moving crack Dugdale model which predicts the zone size independent of the crack speed.Comparison with experimental data shows that the present model gives a more reasonable fracture energy especially at higher crack speed.This modified cohesive zone model is further employed to study a self-similar expanding crack problem.Results predict that the cohesive zone size decreases with crack speed for a self-similar expanding crack,in agreement with the existing dynamic Dugdale model.These results suggest that the present cohesive zone model is plausible to capture the speed effect on a fast propagating crack in a ductile material.