Quantitative Interpretation of Dynamic Resistance Signal in Resistance Spot Welding

Dynamic resistance is one of the most common and important signals used to monitor and control the resistance spot welding (RSW) process. However, existing studies on the signal evolution mechanism are limited to qualitative analysis, resulting in an ambiguous interpretation of the formation mechanism for the signal features. In this paper, a collaborative simulation approach was applied for the RSW of bare DP590 steel to obtain high-precision computation of the temperature and potential distributions inside the weld. On this basis, an analytical mapping model between the dynamic resistance signal and the weld profile was developed based on basic physical laws, and the signal evolution mechanism was quantitatively revealed through the model. It was found that the main factors determining the signal evolution trend are average sheet temperature and electrode/sheet contact diameter rather than the nugget growth process. The peak resistance feature was attributed to the bilinear relationship between sheet resistivity and temperature rather than nugget formation. The resistance drop after the peak mainly arose from the increase of the electrode/sheet contact diameter rather than nugget growth. This study can help improve the comprehension of the dynamic resistance signal and the interpretability of some data-driven methods used for RSW quality monitoring and control.