Prediction of Tensile-Shear Strength of Spot Welds Based on Fracture Modes

Abstract

Assessment of the strength of spot welds is a key process in the design of spot welded structures. Moreover, the prediction method to be used to evaluate the strength of specimens is not always clear, even for static loading. This is because the strength of spot welds depends upon various factors such as nugget diameter, plate width and thickness, material strength, number and location of spot welds and different fracture patterns. In this study, three formulae were proposed for the prediction of the tensile-shear strength of spot welds, which are based upon the relationship between the maximum stress and material strength in three fracture modes; plug type fracture, shear type fracture and fracture across the base metal. In these formulae, two parameters were used for the assessment of maximum stress in the uneven stress distribution around a spot weld. Assuming that fracture takes place at the weakest portion of the structure, the tensile-shear strength is given by the minimum value of the fracture load evaluated for the three fracture modes. It was shown by comparing the predictions and experiments that the predicted fracture load and real fracture mode are in close agreement for both single- and multi-spot welds.