Focusing on the recent studies that the fatigue strength can be improved by using rectangular electrodes, the voltage and temperature distribution in resistance spot weldments were simulated for the various rectangular electrodes which have the different W/L ratio(width vs. length ratio) of the contact area.
Because the electrode shape is not axi-symmetric, the solution domain for simulation was three dimensional. From the calculation results, it could be shown that there is no evident difference in the voltage distribution for different types of the electrode, although a slight variation of distribution was resulted according to the W/L ratio of the contact area. It is probably caused by the assumption that the pressure distribution is uniform on the contact area.
A series of experiments were carried out to verify the analytically obtained temperature distribution in the weldment. From the calculational and experimental results, it could be revealed that the nugget took the form of ellipsoid although both of the result shows a considerable discepancy for the high W/L ratio.
In spite of the advantage of rectangular electrodes, some problems were discovered by experiments. Because the large W/L ratio increases the nonuniformity of the pressure distribution at the contact area, the melting occurred at the perimeter of the contact area. But it was proved from the experiment that this problem can be solved by rounding the edge of the electrode.
