PSI - Issue 77

5

Andreas Fezer et al. / Procedia Structural Integrity 77 (2026) 229–236 Andreas Fezer / Structural Integrity Procedia 00 (2026) 000–000

233

12

10

8

6

4

Spot diameter [mm]

2

0

30kA, 5kN

35kA, 5kN

40kA, 5kN

45kA, 5kN

30kA, 6kN

35kA, 6kN

40kA, 6kN

45kA, 6kN

30kA, 7kN

35kA, 7kN

40kA, 7kN

45kA, 7kN

30kA, 8kN

35kA, 8kN

40kA, 8kN

45kA, 8kN

Al6-HDI

MIN (VDA)

TARGET (VDA)

Figure 4. Spot diameter of AL6-HDI at different currents and electrode forces

This figure shows that the spot diameter increases with increasing current at each force level. Furthermore, the spot diameter decreases with increasing electrode force. This trend can be used to reduce the number of tests required to determine the welding range, avoiding the need to test all possible parameter variations. However, this trend may sometimes not occur in the limiting ranges, for example, when high currents or low forces are used, which lead to weld spatter. Alternatively, when low currents or high forces are used, this can result in very small spots whose fluctuations can be very large. However, in areas with acceptable spot diameters, this tendency can be assumed. 3.2. Influence of Adhesive In body-in-white, RSW is primarily used with adhesive. The applied adhesive also influences the joining process with RSW. Figure 5 shows the effect of the BETAMATE™ 1640 adhesive on the spot diameter. It can be seen that when welding with adhesive and using the same welding parameters, the spot diameters are larger than without adhesive. This is due to the additional resistance created by the adhesive between the sheets. Figure 5 also clearly shows the previously described trend, independent of the adhesive used. With increasing electrode force, the spot diameter decreases, while with increasing current, the spot diameter increases.