Prediction of the Best Electrode Geometry of Resistance Spot Welding RSW Theoretically by FEM and Experimentally

Abstract

The present research studies five spot welding electrodes (RSW) of different geometries. The design of each electrode considerers contacts shape and area of the welding spot. The considered welding electrodes are (Flat, Round, Project, PunchFlat, Cross Flat). A simplified mathematical 2D-axisymmetric model is used to study the behavior of each electrode. It is solved numerically using Finite Element Method (FEM). The model describes the nature of welding contact in terms of contact locations, contact pressure and stress distribution. The model is validated by performing tensile shear tests on the welded specimens resulted from each electrode. Results show good agreement between the estimated behavior and the performed tests. The strength of welding appeared to be proportional to welding time for all five electrodes considered. The type (Project) gives the highest shear strength and the type (PunchFlat) gives the lowest shear strength. The tests show that the electrode of the type (PunchFlat) produces a hole in the welding area. This is caused by the electric spark in the gap between the upper electrode and the plate. The same defect is noticed in the type (Round). In both types, this phenomenon is attributed to the stress concentration in a narrow area which eventually causes the punch.