Characteristics of shunting effect in resistance spot welding in mild steel based on electrode displacement

Shunting effect of resistance spot welding is evaluated based on the electrode displacement signals. The shunted welds in mild steel with different weld spacing were produced. The results showed that the weld spacing and nugget diameter were polynomial-correlated, and the minimum welding spacing of 20 mm can be derived from the results. Both the peak value and gradient of electrode displacement in the weld stage indicated strong correlations with the nugget diameters of shunted welds. Additional shunt path was found to further aggregate the shunting, suggesting the decline in the values of profile features. Furthermore, it is found that the shunting effect led to the decline of the dynamic resistance curves, which is contradictive to the trends between acceptable-sized and undersized welds claimed based on the single weld study. The paper shows that electrode displacement curves of shunting can be incorporated into existing quality monitoring system.