PNNL

Abstract

This chapter discusses the relationship between fusion zone size and weld performance for aluminum resistance spot welds. Weld performance in terms of failure modes, static strength and energy absorption are examined using a combined experimental, statistical and analytical approach. The main failure modes for aluminum spot welds are nugget pullout and interfacial fracture. First, static strength tests for joint populations with a controlled fusion zone size are carried out using three coupon configurations: lap shear, cross tension and coach peel. Thirty replicate static strength tests were performed for each coupon configuration. The resulted peak load and energy absorption levels associated with each failure mode are studied using statistical models. Next, an analytical model is developed to determine the failure mode of an aluminum resistance spot weld based on limit load analyses. It is found that fusion zone size, sheet thickness, and the level and location of weld porosity/defects are the main factors influencing the cross-tension failure mode of an aluminum spot weld. Two additional spot weld populations with different fusion zone sizes are used to validate the analytical failure mode model.