Strength of three-sheet spot welds with critical nugget sizes in tensile shear, cross tension, peel and fatigue tests

Plug failures have been observed in three-sheet spot welds, where the weld nugget did not penetrate into outer sheet. Such solid-state bonds were found to be formed as a result of high contact pressure and temperature during welding. The strength single welds was studied combination (0.61 mm DX54 on two 1.21 DP600) with penetrations thin sheet below 40%. static evaluated by tensile shear, cross tension mechanized peel testing, fatigue tests carried out shear configuration at 30 Hz mean load 2 kN. It that loading specimens leads plug failure ductile fracture is correlated penetration but determined area bonded interface, instead, shown tests. Fatigue revealed break failure. mechanism for highest range after approximately 33 000 cycles. At lower ranges, evidence crack sheet, leading higher stress concentration subsequent fracture. estimated 940 N 10 6