Impact strength measurement of spot welds

Abstract

The impact strength of spot welds is a very important quality index in the automotive industry. However, impact testing is not routinely performed for weld quality testing because of its complexity, cost and relatively low reliability and repeatability. In this paper, the impact strength of steel spot welds was measured using a newly designed impact tester. Besides the impact energy of the welds, detailed impact process characteristics, such as impact force and displacement profiles, which may be important to understanding the impact performance of a weld for vehicle design and analysis, were also recorded. A brief description of the new impact tester and experimental results on welded joints using this device are presented. A sensitivity study of testing results to specimen size has been conducted, prior to experiments on the influence of weld size, shape and orientation on the impact strength of resistance spot-welded joints. Results of impact testing were also compared with those of static tensile shear tests. The correlation between weld attributes and impact performance also provides important information for the quality definition of spot welds. Initial tests using this impact tester show promise that it can be used to measure impact strength of a large variety of welds (spot welded, laser welded, brazed, etc.), and other joints (such as mechanical fasteners and adhesion).