Stress Intensity Factor Solutions for Kinked Cracks in Spot Weld Specimens 2019-01-1110

In this paper, the local stress intensity factor solutions for kinked cracks near spot welds in four commonly used specimens, lap-shear, cross-tension, U-shaped, and coach-peel, were investigated by finite element analyses. Based on the experimental observations, three-dimensional finite element models for spot welds with finite kinked cracks were established to investigate the local stress intensity factor solutions for kinked cracks emanating from the main crack. Semi-elliptical cracks with various kinked crack lengths were assumed in the three-dimensional finite element analysis. The local stress intensity factor solutions for kinked cracks were obtained. The computational local stress intensity factor solutions for various kinked crack lengths were expressed in terms of those for vanishing kinked cracks based on the analytical local intensity stress solutions for vanishing kinked cracks, global stress intensity factor solutions for main crack, and kinked crack angle. The computational results showed that the general trends of local stress intensity factor solutions for kinked cracks in the four specimens are quite similar. The local mode I stress intensity factor solutions increase and then decrease as the kinked crack length increases. The local mode II stress intensity factor solutions decrease and then increase as the kinked crack length increases. When the kink depth approaches to zero, the local mode I stress intensity factor solution tends to approach to that for vanishing kinked cracks. Finally, the implications of the local stress intensity factor solutions for kinked cracks on fatigue life prediction are discussed.