Three-Dimensional Finite Element Analyses of Local Stress Intensity Factor Solutions for Kinked Cracks of Spot Welds in Commonly Used Specimens 2019-01-1110

Local stress intensity factors (LSIFs) for kinked cracks of spot welds in four specimens, lap-shear, cross-tension, U-shaped, and coach-peel, were studied by three-dimensional finite element analyses. Finite element models for spot welds without and with kinked cracks were developed. Semi-elliptical cracks with various kinked crack lengths were assumed. Two dominant cracking modes for each specimen were considered. The global stress intensity factor (GSIF) solutions for spot welds without kinked cracks were first obtained to determine the analytical LSIF solutions for spot welds with infinitesimal kinked cracks. The LSIF solutions for spot welds with finite kinked cracks were then obtained. The LSIF solutions of the four specimens show similar general trends. As kinked crack length increases, the mode I LSIF solutions gradually increase and then decrease, while the mode II LSIF solutions show inverse trends. Finally, the applications of LSIFs for fatigue life estimations of various types of spot welds or spot joints are discussed.