Stress Intensity Factor for Aluminum and Copper Spot Weld Joints

For decades, resistance spot welding (RSW) between aluminum and copper has encountered difficulties; however, it remains essential for modern applications. Additionally, crack propagation and the stress intensity factor (SIF) of dissimilar RSW have not been extensively investigated. The welding parameters used for Al-Al joints were as follows: welding current, time, and electrode force were set at 14,000 Amps, 0.8 seconds, and 7,000 N, respectively. Conversely, for Al-Cu joints, 14,000 Amps, 1 second, and 8,800 N were determined. The similar joints exhibited an average weld nugget size of 6 mm, whereas the dissimilar joints had a nugget size of 5.2 mm. The tensile shear force was 690 N and 780 N for dissimilar and similar joints, respectively. Accordingly, the fatigue load, as a percentage of the tensile force, was utilized at 414 N and 468 N for Al-Cu and Al-Al, respectively. Finite Element Analysis (FEA) was employed to determine the SIF. The initial crack length was determined to be 0.1 mm. The numerical solution was then compared with theoretical solutions for the opening SIF-KI, such as the equations proposed by Pook and Zhang. The FEA results showed higher values of SIF compared to those from theoretical solutions. Additionally, crack propagation was investigated for both dissimilar and similar joints at a determined failure load. Cracks tended to develop close to the heat-affected zone (HAZ) around the weld nugget diameter (dn). SIF and crack path have been verified.