Analytical modelling of electrode wear occurring during resistance spot welding

Abstract

Electrode wear during resistance spot welding of galvanised steels has been modelled using an analytical thermomechanical approach. Thermal profiles in the spot weld and electrode are estimated using a one-dimensional solution. The thermal profile in the spot weld is based on a thermal balance between the material stack-up, nugget penetration and electrode geometry. Thermal profiles in the electrode are based on the results from the spot weld, as well as its relative conductivity and geometry. Results for a single weld cycle allowed prediction of a forge zone at the electrode face. Deformation of this zone under the applied stress then defined the wear and relative resultant changes in electrode geometry. Electrode life could then be predicted as a summation of these deformations from weld to weld. This was done by repeated applications of the defined equations in a spreadsheet format. Initial results were shown consistent with representative electrode life tests. The equations were then used to understand underlying physical phenomena associated with electrode wear. A discussion is also provided defining limitations to the model, and its ability to predict actual electrode life.