PSI - Issue 77

4

Andreas Fezer / Structural Integrity Procedia 00 (2026) 000–000

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

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The current and force profile shown in Figure 3 was always used as the welding profile. The preheating current remained constant throughout all tests, while the welding current intensity (t = 670 – 760 ms) varied. The force remained constant at a preset value throughout welding. The force varied from 5 to 8 kN and the current from 30 to 45 kA.

Figure 3. Current and force profile of the welds

In this study, several parameters were varied to investigate their influence on the diameter of the spot weld. The following parameters were varied: (A) welding current, (B) electrode force, (C) with and without adhesive, and (D) sheet thickness. The number of tests conducted for each variation is listed below: • (A) + (B) Welding current + Electrode force: A total of 480 weld spots / 16 sheet pairs on 2 mm thick sheets; for each welding current and force, one sheet pair with 30 weld spots was welded.  Welding current: 30, 35, 40, 45 kA; Electrode force: 5, 6, 7, 8 kN  With adhesive • (C) With and without adhesive BETAMATE™ 1640: A total of 2x 480 weld spots / 2x 16 sheet pairs on 2 mm thick sheets • (D) Sheet thickness (3 different sheet thicknesses): A total of 3x 480 weld spots / 3x 16 sheet pairs  With adhesive

3. Results und Discussion This chapter presents the various results of the influence studies and describes their findings.

3.1. Influence of Welding current and Electrode force Figure 4 shows the measured spot diameter for the respective welding current and electrode force. Each bar consists of a pair of sheets and thus 30 weld spots. The red line represents the minimum spot diameter for a good weld, as recommended in VDA 238-401 (Verband der Automobilindustrie e. V. 2020), while the green line indicates the recommended spot diameter (Verband der Automobilindustrie e. V. 2020).