A new characterization approach of weld nugget growth by real-time input electrical impedance

The in-process changes of weld nugget growth during the Resistance Spot Welding were investi- gated based on the resistance of input electrical impedance. To compute the time varying resis- tance of input electrical impedance, the welding voltage and current signals are measured simul- taneously and then converted into complex-valued signals by using Hilbert transform. Comparing with the dynamic contact resistance as reported in literature, it showed that the time varying re- sistance of input electrical impedance can be accurately correlated with the physical changes of weld nugget growth. Therefore, it can be used to characterize the in-process changes of weld nug- get growth. Several new findings were reported based on the investigation of spot welds under no weld, with and without weld expulsion conditions.

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