A new approach to the numerical fatigue‐life prediction of spot‐welded structures

From the numerical evaluation of the experimental data for the double-cup specimens (DC specimens) under cross-tension, a new and simple fatigue parameter is derived which is based on the nominal radial stress at the tip of the spot weld and the thickness of the sheets. The new parameter is especially suitable for use in the context of a FE calculation. The relation of the proposed fatigue parameter to the stress intensity factor is shown by a simple example. The results show that, instead of the nominal stress, the notch effect (or the singularity due to a spot weld) has to be considered in order to characterize the fatigue behaviour of the weld. This is supported by the evaluation of the same test data using notch stresses. A FE model for the spot weld is presented which can be used to determine the nominal stress around a spot weld. Using this model, the experimental results for H-type specimens under tensile-shear can be evaluated subsequently, and hence the viability of the new parameter demonstrated.