Prediction of spot weld fatigue life using finite element approach

Abstract

Resistant spot welding is predominantly used in automotive industry for joining sheet metal. Mostly automobile fatigue failure occurs in and around spot welding (80%). So, accurate prediction of the deformation, stresses and fatigue life of spot weld is necessary. In this work finite element model of spot weld and experimental study of coach peel test of spot welded low carbon steel sheets are presented. The property change in various zones of spot weld is found by nano-indentation test followed by inverse finite element modelling. Spot weld failure happens at the interface between nugget and heat affected zone due to the geometric stress concentration and property change that occurs during the welding process. Solid elements are successful in capturing the geometric stress concentration, but they increase the simulation cost and hence a model with combined shell and solid elements is used. For nugget solid elements are used and tore present all other parts of spot weld shell elements are used. Tensile and fatigue tests on coach peel specimen are done as per ASTM standardD903-98. The simulation results are found to be in close agreement with experimental results.