Modelling spot welded joints in elastic-plastic field

In this paper two analytical approaches for the evaluation of spot weld joints behavior in elastic plastic conditions are presented and compared. The procedures are based on two new theoretical models of spot weld region: a circular plate, with a central rigid nugget, having two variable thickness profiles. The complex closed-form solutions allow to describe the displacement of a rigid nugget while plasticity and moderately large deflections are present. These approaches allow to reach a reliable spot weld region model which can be used as the basis to develop a spot weld element in FE analysis even when plasticity and large deflections are in effect. The correct evaluation of the spot stiffness is the basis of a reliable evaluation of fatigue resistance or failure mode of the joint and, consequently, allows to correctly simulate the behavior of an actual multi-spot structure