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.

Monitoring of resistance spot weld quality using electrode vibration signals

“…As shown in figure 4, the repeatability of the amplitude curves of electrode vibrations is good, which indicated that the changing law of electrode vibrations during the welding process is steady and reliable. Compared with the extraction method of the electrode displacement fluctuation characteristics in [17], it is faster and more effective using the band-pass filtering method. The changing law of the amplitude curve of electrode vibrations is consistent with that of the DFP curve in [17] except the first two half cycles.…”

“…Compared with the extraction method of the electrode displacement fluctuation characteristics in [17], it is faster and more effective using the band-pass filtering method. The changing law of the amplitude curve of electrode vibrations is consistent with that of the DFP curve in [17] except the first two half cycles. This difference is caused by the filtering method.…”

“…Cho et al [16] used the half-section truncated dome-type electrode and digital high-speed camera to study the nugget formation mechanism, and they found that owing to the pulsing phenomenon during the nugget growth caused by 60 Hz ac, the nugget size expanded in all directions with an oscillation frequency twice that of the welding current, and the pulsing variations of the nugget size are greater at the beginning of the 10th cycle and less at the end of the 12th cycle. Wang et al [17] used the Heidenhain-Specto length meter to measure the electrode displacement and manually extracted its displacement fluctuation peak (DFP) caused by ac resistance pulse heating in every half cycle during the RSW process, and they found that a DFP is strongly related to the nugget formation process and shows different changing laws at different welding currents. Therefore, electrode vibrations induced by ac resistance pulse heating can be used to monitor the resistance spot weld quality.…”

Quality evaluation in small-scale resistance spot welding by electrode voltage recognition

“…Fortunately, the weld quality information could be reflected from monitored process signals. Researches on this aspect are ranged over dynamic resistance, [1][2][3][4][5] electrode displacement, [6][7][8] electrode force, 9,10 etc. Non-destructive weld quality evaluation could be realised through above methods.…”

Image-based electrode tip displacement in resistance spot welding

“…The automotive industry, however, is the major user due to its high efficiency, low cost and high degree of automation. There are thousands of spot welds on an automobile body [2,3] and in a steel car body; in general, 90% of assembly work is performed with RSW [4]. As the properties of the spot welds significantly affect the durability and crashworthiness of the vehicle [5], improving their quality is an ongoing process in RSW research [6][7][8][9][10].…”