PSI - Issue 51

Liting Shi et al. / Procedia Structural Integrity 51 (2023) 102–108 L. Shi et al. / Structural Integrity Procedia 00 (2022) 000–000

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Fig. 4. Fatigue test result of three resistance spot weld stack-ups for (a) tensile-shear specimens; (b) coach-peel specimens.

Using the structural stress method based on the Rupp’s approach (Rupp et al. (1995)), all fatigue life of the three stack-ups of tensile shear and coach peel configurations fell onto one master curve with the fitting coefficient of 0.8371 (Fig. 5), indicating that the aluminum-steel weld nugget diameter dominates the fatigue life.

Fig. 5. Relationship between structural stress range of fatigue life for all resistance spot welds studied.

4. Conclusions Three-sheet aluminum-steel-steel RSW of 1.2 mm thick AA6022 to 0.65 mm thick HSLA and 1.4 mm thick CR780T was successfully resistance spot welded using MRD electrodes and multiple solidification weld schedules. Tensile load capacity and fatigue behavior were analyzed and compared with the two-sheet aluminum-steel RSW, which has nearly same steel thickness as the total thickness in three-sheet RSW. The stack-ups aluminum to itself was also presented in this research as a base line. A thin layer of intermetallic compound formed between the aluminum steel interface and a much smaller but completely melted weld nugget between the two steels, achieving an acceptable joint strength compared to RSWs of 1.2 mm thick AA6022 to itself and 1.2 mm thick AA6022 to 2.0 mm thick HSLA. The three-sheet RSWs reached comparable fatigue behavior to that of 1.2 mm AA6022 to 2.0 mm HSLA. Using