Evaluation of multiaxial spot weld fatigue parameters for proportional loading

The authors have conducted set of experiments to study the effects of combined tension and shear loads on the fatigue life of spot welded joints. The fatigue life of the specimens depended on the applied load amplitude, the ratio of shear to normal loading, and spot weld nugget diameter. The lower load amplitudes had longer fatigue lives, as did the cases which contained a higher amount of shear loading and specimens with a larger nugget diameter. Based on the test results, Swellam and co-workers' model, Sheppard's model, Rupp and co-workers' model, and an interpolation/extrapolation model are evaluated. The four approaches were correlated with the experimental fatigue life for the multiaxial test results with reasonable accuracy. The success of Swellam and co-workers' method relies heavily on determining the appropriate parameters beta and b(0). Sheppard's structural stress method agreed reasonably well for mutiaxial test results, although the maximum structural stress range is sensitive to the variation of the sheet thickness, and the determination of Delta M* is a complex procedure. Rupp and co-workers' method is suitable for application to large structural models because mesh refinement is not necessary for modeling the spot weld connection. (C) 2000 Elsevier Science Ltd. All rights reserved.