Fatigue Crack Propagation Path and Life Prediction Based on XFEM

Longlong He,Kunfa Men,Jinliang Wang,Junjie Gu,Zhifang Liu

doi:10.1051/jnwpu/20193740737

Abstract

Based on the theory of linear elastic fracture mechanics, the relationships between material constants c3, c4 required in Abaqus and constants C, m in Paris formula are derived. Then extended finite element method (XFEM) of Abaqus software is used to is used to predict the crack propagation path and life of the plate with center inclined through crack and typical stiffened wing spar with initial crack under the constant amplitude fatigue load. The results show that the predicted crack propagation path is in good agreement with the experimental results, and the crack propagation life error is less than 6.3%. It also shows that this method can accurately predict the fatigue crack growth path and life of two-dimensional and three-dimensional complex structures under constant amplitude loads. This study can provide an effective way for damage tolerance analysis of structures and has certain engineering application value.

Highlights

Based on the theory of linear elastic fracture mechanics, the relationships between material constants c3, c4 required in Abaqus and constants C, m in Paris formula are derived
Extended finite element method ( XFEM) of Abaqus software is used to is used to predict the crack propagation path and life of the plate with center inclined through crack and typical stiffened wing spar with initial crack under the constant amplitude fatigue load
The results show that the predicted crack propagation path is in good agreement with the experimental results, and the crack propagation life error is less than 6.3%

Summary

Abaqus 中提供了亚临界循环载荷作用下部件

纹尖端的能量释放率 ΔG 相关联。 Paris 法则通过 ΔG 表示,其中 Gmax 和 Gmin 分别为结构最大载荷 Pmax 和最小载荷 Pmin 对应的应变能释放率,ΔG = Gmax - Gmin 。 Gthresh 为应变能释放率门槛值,Gpl 为应变能释放率上限值,GC 为临界应变释放率,GequivC 为基于用户指定的混合模式断裂准则计算得到的临界等效应变能释放率。 Paris 法则以 Gthresh 和 Gpl 为上下界,低于 Gthresh,疲劳裂纹不扩展; 高于 Gpl , 疲劳裂纹将快速扩展至破坏;介于 Gthresh 和 Gpl 的中间直线区域,是疲劳裂纹稳定扩展区域,也是 Paris 法则控制区域。只是说明在计算时需要的 c3,c4 为材料常数,但是没有任何其他关于 c3,c4 取值的说明。因此,这给使用该方法解决工程问题带来了困惑。原始的 Paris 公过对图 2 中间线性段裂纹扩展数据进行线性拟合, 得到裂纹扩展速率的 Paris 公式如下 da = 1.093 7 × 10 -11( ΔK) 2.855 6 参数见表 1:

Paris 参数

Findings

Pmin P max