蠕变疲劳交互作用下裂纹萌生的有限元模拟

Numerical simulation of crack initiation under creep-fatigue interaction in P92 steel

通过结合初始应力应变场与连续损伤力学理论以及单元失效和裂纹萌生准则,构建了蠕变-疲劳交互作用下裂纹萌生的预测模型,将模型编写为UMAT耦合到ABAQUS有限元分析软件中,实现了初始无缺陷结构蠕变-疲劳交互作用下裂纹萌生的有限元模拟,并分析了影响裂纹萌生寿命的因素.通过与线性累计损伤理论对比发现,裂纹萌生位置蠕变损伤和疲劳损伤具有相互促进作用,蠕变疲劳的交互作用使裂纹萌生寿命减小;蠕变和疲劳载荷加载顺序对损伤的累积具有很大影响,模拟发现承受蠕变载荷的结构在承受后续循环载荷下总损伤值更大,裂纹萌生寿命更短.

By combining the theory of continuum damage mechanics with initial stress and strain fields and criteria for element failure and crack initiation,a predictive model of crack initiation under creep-fatigue interaction was constructed. Based on the model,a user defined material subroutine( UMAT) was compiled and creep-fatigue damage accumulation was investigated by the finite element method using ABAQUS codes. Crack initiation was simulated in a structure without initial defects under a creepfatigue interaction. Factors affecting the time of crack initiation were investigated. In contrast to linear cumulative damage( LCD) theory,mutually promoting effects exist between creep damage and fatigue damage at crack initiation locations. Interaction between creep and fatigue shortens the time to crack initiation. The sequence of creep and fatigue loading greatly influences accumulation of damage at the crack initiation location.Cyclic loads cause larger damage after long periods of creep load compared with periods without creep load,hence time to crack initiation is shorter.