Evaluation of Stress Intensity Factor-Based Predictive Technique for Fatigue Life of Resistance Spot Welds

This paper summarizes the results of a recent study on a fatigue predictive technique for spot-welded automotive structures. The technique makes use of an equivalent stress intensity factor (K_eq) as fatigue parameter for life predictions. A series of fatigue tests were conducted by using different types of fatigue specimens and weld arrangements. Using the raw test data collected, fatigue properties were processed in the form of ΔK_eq versus fatigue life by a fracture mechanics based stress intensity factor technique. It is demonstrated that the fatigue properties are consistent among all the specimens tested and relatively geometry-independent. With the stress intensity factor based fatigue properties, the predictive technique was applied to more complex specimens with non-symmetric weld configurations and non-uniform loading conditions (resulting in mixed-mode loading on each weld). The results indicate good correlation between life predictions and test data. Finally, the results of a series of sensitivity studies are presented concerning the effects of various FE modeling details on the accuracy of the predictive technique.