Stress conditions and strength of spot-welds under cyclic loading - a design procedure

Abstract
By investigations on component-like hat profile specimens of different sheet steels it is demonstrated, that the fatigue strength of spot welds can be described in terms of the particular local stress conditions. The computed and measured stresses refer to the actual failure modes and crack locations as well as to the local material conditions. For the different loading conditions of a spot welded structure the maximum damage in the area of the investigated spot weld is computed and can be used during the design procedure. The calculation of the stresses is based on the cross-sectional forces and moments computed by Finit-Element-Analysis, which are state of art in the automotive industry. The calculated stresses at spot welds of components are used to establish the design spectra under the representative loading conditions. The stresses of the spot welded specimens are used to obtain the appropriate endurable stresses for the damage calculations on the spot welded component.