Analysis of the strength difference effect on tailor welded blanks’ springback

Abstract

Tailor welded blanks (TWBs) are becoming widespread in the automotive industry due to their advantages, such as the possibility of weight reduction or the material usage optimising, resulting from the application. However, their main disadvantage is that the construction design and the simulation of the mechanical processes (like weld line movement, sheet springback, etc) are more complex. Predicting the mechanical response can only be done by accurately estimating the weld properties, which greatly increases the material testing requirements. Moreover, it often does not coincide with the matter of the field of material forming. In this study we focus on the simplified description of the springback of TWBs, to reveal which parameters have the primary influence on this process. Three kinds of DP steels with different strengths were welded to a mild steel grade one by one. Using these pairs we have varied both the strength difference between each sides and the average strength of the blanks, too. Uniaxial tensile tests were performed for the mechanical characterisation of each material, as well as right-angled bends perpendicular to the weld line were carried out to monitor the springback tendency of the samples. Our results show that a transition zone develops near to the weld line, independently from the strength difference between the TWB’s components. This zone is well-defined by linear functions, in which, the parameters are consistent with the physical content of the springback phenomenon.