The effect of fatigue properties on the load mode ratio in Spot Welded Joints.

Abstract

In the automotive industry, it is required to improve fuel consumption such as lightweight body in order to solve environment issues, the increasing use of high-strength steel is expected. However, high-strength steel spot welds have problems of reducing the fatigue strength, moreover, for the conventional shear-type joints, which subject to mode I loading may cause the welded part inclined. Therefore, evaluation of fatigue strength by considering purely shearing loading may lead to inaccuracy prediction. Thus, this study investigated the effect of loading mode on the fatigue characteristics of spot welded joint by restraining the jigs for suppressing the rotational deformation of the joint. As a result, there is no difference between the fatigue strength of low- and high-strength steel in the conventional shear-type joints. However, in the shear-type under mode II loading only using restrained jigs, the fatigue strength of the high-strength steel tended to improve because of the difference in the fatigue crack propagation path.