Ⅲ型裂纹裂尖应力场的内聚力模型

Cohesive Zone Modeling for Model Ⅲ Crack Based on Near Tip Stress Field

针对幂指数硬化材料,在小范围的屈服条件下,建立了Ⅲ型裂纹的内聚力模型,获得了内聚区和塑性区中的应力-应变场及内聚区中的内聚力和张开位移的本构关系.结果表明:对于中等硬度的材料,如果内聚力的峰值小于2.5倍的屈服应力,那么内聚力对塑性区中的应力分布起决定性的作用,传统的弹塑性断裂力学方法和内聚力方法之间存在着差别;当牵引力的峰值变为无穷大时,无论有否内聚力,应力分布都会趋于收敛.

A cohesive zone model for model Ⅲ crack in power-law hardening was studied under small scale yielding conditions. The cohesive traction-separation displacement in the cohesive zone and the stress- strain fields were obtained. The results show that the stress distribution in a large portion of the plastic zone is significantly altered with the introduction of the cohesive zone, for a modest hardening material, if the peak cohesive traction is less than 2.5 times yield stress, which implies that the disparity in terms of the fracture prediction between the classical approach of elastic-plastic fracture mechanics and the cohesive traction becomes infinitely large. When the peak cohesive traction becomes infinitely large, the stress dis- tribution with and without the cohesive zone converges.