Parametric investigation into fatigue life behaviour of spot welded tensile shear test samples

Abstract

Resistance spot welding is a widely used joining process in the structural components of various engineering products such as white goods, aerospace equipment and especially automobiles. Hence it is crucial that the mechanical performance of such joints be well understood in order to design and manufacture reliable engineering products. In service, Spot-welded joints undergo fatigue failure under cyclic loadings. In order to examine and improve the fatigue life of spot welded structures, various assessment methods have been used on standardized test samples such as tensile shear (TS), modified tensile shear (MTS), coach peel (CP) and modified coach peel (MCP) specimens. The fatigue life studies have shown that among the most important design variables for spot-welded structures influencing joint strengths, sheet thickness, spot weld nugget diameter, number of spot welds and the joint type can be counted. In this study, a numerical examination was carried out to observe the effects of sheet thickness and nugget diameter on the fatigue life of tensile shear (TS) samples. In the analysis both Morrows mean stress and Coffin Manson approach were utilized. The performance of both methods was verified on the basis of experimental data available in literature. The elastic and plastic strains necessary for the calculations were found out by means of finite element method. The results presented herein provide variation of fatigue life predictions according to selected geometry parameters along with valuable interpretations that can be used as guidelines for designers.