Spot welds fatigue life prediction with cyclic strain range

Even though spot welds have been used widely in automotive manufacturing for years, fatigue life prediction methods for estimating life have been based on welds connecting sheets of the same thickness. A validated fatigue life prediction method for spot welds connecting sheets of different thicknesses has yet to be published. In this study, the stresses and strains at the notch of a spot weld nugget were studied in detail. It was found that significant yielding occurs in spot welds even under relatively low loads. A fatigue life prediction method based on strain is proposed. The work here shows that a strain-based approach does a very good job of describing the fatigue life of mixed-thickness spot welds.