Improvement of Fatigue Strength of Resistance Spot Welded Joints in High Strength Steel Sheets by Shot Blast Processing

摘要

This paper discusses the effect of shot blast processing on the fatigue strength of resistance spot welded joints in 980 MPa steel sheets. The fatigue limit load of shot blasted spot welded joints increased to approximately twice that of non-blasted specimens. While high compressive residual stress was conferred to the outer surface of the shot blasted steel sheets, there was little variation in the residual stress on the side of the overlapped surface. Shot blasting on the outer sheet surface increased the initiation life of fatigue cracks that occurred on the overlapped surface and reduced the propagation speed of the cracks that grow from the overlapped surface toward the outer surface. The initiation and propagation of fatigue cracks were affected in the region where compressive residual stress by shot blasting was not conferred.