Effect of notch root angle on fatigue behavior of aluminum to steel resistance spot welds

Aluminum was resistance spot welded to steel with varying electrode polarity on the aluminum sheet to produce different notch root angles but maintain the same weld nugget diameter and intermetallic layer thickness. Fatigue life was longer in negative polarity welds having larger notch root angle owing to the reduced maximum principal strain at the notch root. In fatigue, pull-out fracture was observed in negative polarity welds while interfacial fracture occurred in the positive polarity welds because of reduced tensile and shear stress at the notch root and the position of maximum tensile stress moving away from the notch root tip.