海洋平台中KK管节点表面裂纹应力强度因子的有限元计算方法

Finite element analysis of stress intensity factor of a surface crack for tubular KK-joints in offshore platforms

海洋平台中的KK管节点由于长期承受循环载荷而容易在焊缝处产生疲劳表面裂纹。对包含表面裂纹的KK节点的残余寿命的评估依赖于对表面裂纹应力强度因子的准确估算。本文首先提出了KK节点中表面裂纹的有限元网格产生方法,然后采用线弹性断裂力学理论,通过裂纹前缘的位移外推插值法分析了KK节点在轴向力作用下沿着表面裂纹的应力强度因子的分布情况。最后,通过对22个KK节点的模型分析,研究了节点的几何参数和裂纹形状参数对应力强度因子的影响情况。

Fatigue surface crack will initiate along the weld toe when tubular KK-joints in offshore platforms are subjected to cyclic loading for a long time. The assessment of the residual life of the KK-joints containing surface cracks is dependent on the accurate estimation of the stress intensity factor of the surface cracks. The finite element mesh generation method is firstly presented in this study. Thereafter, the stress intensity factor distribution along the surface crack in tubular KK-joints under axial loading was analyzed using displacement extrapolation method based on linear elastic fracture mechanics theory. Finally, the effect of the geometrical parameters and the crack shape parameters on the stress intensity factors was studied from the parametric study of 22 KK-joint models.