基于平均应变能密度准则的裂纹断裂扩展特性分析

Crack fracture and growth behavior based on averaged strain energy density criterion

考虑裂纹尖端应力场常数项T应力对裂纹断裂特性的影响,对平均应变能密度准则进行修正,建立混合型裂纹扩展条件计算式。在此基础上,系统分析常数项T应力对Ⅰ型、Ⅱ型、Ⅰ-Ⅱ混合型裂纹断裂判据的影响。结果表明,常数项T应力降低了材料裂纹起裂阻力,且参数|Bα|越大裂纹断裂极限值越低,|Bα|相同时,正T应力要比负T应力更容易发生断裂。基于修正平均应变能密度准则,预测双轴疲劳载荷作用下平板表面Ⅰ型裂纹扩展寿命。结果表明,考虑常数项T应力影响后的疲劳裂纹扩展寿命约为传统疲劳裂纹扩展寿命的49%。

The averaged strain energy density criterion is modified by considering the constant term T-stress. The crack onset propagation formulation of mixed mode Ⅰ-Ⅱ-Ⅲ crack were then given. The mode Ⅰ, mode Ⅱ and mixed mode Ⅰ-Ⅱ crack onset propagation behavior were investigated thoroughly. The analysis results show that the crack onset propagation limit will be reduced by considering T-stress. The greater the parameter |Bα| is, the easier the fracture will take place. Fracture will more easily happen when the T-stress is positive at a given parameter |Bα|. The crack growth life of the plate surface mode Ⅰ crack under longitudinal tensile load and lateral compressive load simultaneously were analyzed based on the traditional reference variable ΔKΙ and the proposed reference variable ΔKeq. The analysis results show that T-stress has a significant effect on mode Ⅰ surface crack growth life, the crack growth life will be overestimated by neglecting the T-stress effect.