Stress Intensity Factor Solutions for Semi-Elliptical Weld-Toe Cracks in Tubular K-Joints

摘要

Stress intensity factors (SIFs) are generally used to predict the remaining life of cracked tubular K-joints used in the offshore structures. The accuracy of SIFs depends very much on accurate modelling of the surface crack. In this paper, a new mesh generation method is proposed for any cracked tubular K-joint where five types of elements are adopted in modelling the surface crack so as to avoid high elements aspect ratio around the crack front. The mesh of any K-joint is obtained by merging the mesh of several distinct regions, and each region is generated separately according to different requirements. To check the accuracy of the computed SIFs, two large scale K-joint specimens were tested to failure under fatigue loading conditions. The alternating current potential drop (ACPD) technique is used to monitor the rate of crack propagation of the surface crack located at the crown position. The experimental test results are then used to validate the numerical results. Generally, they agree well and the relative errors are acceptable.