Experimental study on electrode displacement fluctuation characteristics during resistance spot welding

Abstract

Electrode displacement has been used to monitor resistance spot weld quality for long, but the fluctuation of the electrode displacement has not been well studied. This paper analysed the mechanism of the displacement fluctuation by collecting the welding current and electrode displacement during welding process and extracted the incremental pulse expansion of the electrode displacement, which was named as the displacement fluctuation peak. Through metallurgical experiments, the relationship of the displacement fluctuation peak with the weld nugget growth during resistance spot welding process was analysed. The whole process can be divided into four successive stages, and five characteristic points of the displacement fluctuation peak curve were selected to online predict the weld quality. The variation in the displacement fluctuation peak curve under different welding currents was studied, and the results showed that the displacement fluctuation characteristics can be used to effectively evaluate the weld quality.

Keywords:

• Resistance spot welding
• Electrode displacement
• Displacement fluctuation
• Process monitoring

The authors would like to acknowledge the support of the National Natural Science Foundation of China (grant no. 50705059). The authors also want to thank the support of SMC of Japan. Besides, the authors would like to thank Professor Z. J. Feng, Senior Engineer W. H. Xie, Associate Professor Q. Ye and Dr L. Gong for help.