Experimental Study of the Nugget Diameter Effect on Tensile-Shear Strength in AISI 1008 Spot Welding Specimens

The spot welding is widely used for joining thin sheets in different industries; such as automotive industry. This method of welding is very easy to automate and maintain. In this study, the effect of nugget diameter on the tensile-shear strength of the spot welding joints was investigated. The specimens were manufactured from AISI 1008 HR sheets with 1.0 mm thickness. The eight different electrodes with different active face diameters (3-10 mm) were employed. Tensile tests of the prepared specimens indicated that both ultimate tensile strength (UTS) and yield strength increased to a certain level and then remained constant. The comparison between specimen failure modes showed that in specimens with lower nugget diameter, tearing occurred in nugget. However with increasing the diameter, failure location moved to nugget edge with tearing in base sheet. Interestingly, the specimens with change in failure location were those that UTS and yield strength were remained almost constant. This was also the case where the elongations of these specimens were studied.