3-Dimentional Elucidation of Fatigue Characteristics and Fracture Morphologies in Spot Welding Joints of High Strength Steel

Abstract

In order to investigate the three-dimensional fatigue properties of resistance spot welded joints made of high strength steel, this study was carried out observed three-dimensional fatigue cracks and calculated stress intensity factors using fem analysis. In addition, this study was conducted under shear mode and pure shear mode to investigate the influence of loading mode during fatigue testing. As a result, it was found that a new crack growth behavior branched in the welding circumferential and width direction under the low loading force range. However, all the cracks leading to final fracture were of the same type, and it was confirmed that the fatigue strength was not affected by a new crack growth behavior. Moreover, the results of observed initial fatigue crack growth angles and the calculated stress intensity factor, K_Iθ, were in close agreement, which proved that the fatigue crack growth behavior was strongly influenced by the fracture mechanics.