A Review of the Fatigue Properties of Spot-Welded Sheet Steels 830033

Over the past several years, the automotive industry has used increasing amounts of high-strength sheet steels to reduce vehicle weight for improved fuel economy. It is important that these high strength steels exhibit spot-weld fatigue characteristics at least equal to those of previous lower strength low-carbon steels. This study reviews the spot-weld fatigue performance of uncoated sheet steels with respect to material strength, spot-weld diameter, sheet thickness, and the number and array of spot welds. Models used to describe the state of stress around the spot weld are also reviewed. Selected results contained in the literature are reevaluated using fracture-mechanics concepts. Comments are given regarding fatigue-crack growth in spot welds with respect to the cyclic-stress ratio and threshold-fatigue limit. Limitations of current theories used to evaluate fatigue performance of spot welds are discussed, and an alternative approach to interpreting such data is recommended.