A spot weld finite element for structural modelling

A new finite element assembly, to account for the structural behaviour of the region surrounding a spot weld, is developed. The formulation derives from the analytic solution of two circular sheets externally clamped, with a central rigid core connecting them (representing the spot weld). The effective modelling strategy of the above mentioned region makes use of equivalent beam elements; therefore, the implementation is possible in any structural code. The aim is to use this assembled element for the region around the spot: two assembled elements, connected by a link, form the spot weld connection between two metal sheets. The analytic solution is provided for any possible typology of loading acting on a spot weld (shear, bending and orthogonal loads). Moreover, the link connecting the two sub elements may be considered rigid as well as deformable, this can be very useful to evaluate fatigue damage evolution in structures jointed with many spot welds. Using these assembled elements for the spot weld region, an important increase in the accuracy is reached, as demonstrated in the example. However, the accuracy does not imply an increase in the total number of degrees of freedom of the whole model.