On Combined Tensile-Shear Performance of Laser-Welded Dissimilar Overlap Joints Made of Austenitic Stainless Steel and Low-Carbon Steel

This paper addresses the mechanical characterization of dissimilar overlap joints made by autogenous laser welding between thin sheets of low-carbon steel (CS) and austenitic stainless steel (SS) with an optimized welding technology able to produce sound overlap joints. This involved applying the laser beam from the CS-side to reduce the SS overheating. The research is focused on the analysis of combined tensile-shear behavior of the weld and of the heat-affected zones. During testing, the applied tensile-shear load rotates the weld connecting the CS and SS plates. The rotation angle transmitted to the free ends of the plates, together with relevant strain fields, were measured by using a digital image correlation system, VIC-2D. Thus, it was found that the weld acts as a non-linear hinge which experiences a sudden loss of stiffness when strain concentrations develop from the weld ligament edges towards the loaded sides of the plates. The welded joint fails by yielding localization and necking in the CS plate, far from the weld. This mode of failure is a consequence of the weld and heat-affected zone strength mismatches of 1.09 and 1.33, respectively. These values are consistent with the hardness profile and the documented microstructural heterogeneities.