Fatigue behavior of spot-welded joints in air and under corrosive environments

Abstract

The main aim of the project was to evaluate the influence of combined effects of fatigue loading and exposure to cyclic corrosion testing on the corrosion and the fatigue resistances of coated thin sheet steel joined by spot welding. Seven types of steel including cold rolled mild steels, high-strength steels, and press-hardened steels (PHS) were selected and provided by steel suppliers for fatigue strength evaluation of resistance spot welding (RSW) assemblies. Panels were joined using conventional resistance spot welding in both lap-shear and T-peel designs. Joined samples were painted by e-coating following the industrial process. Metallographic characterization of the steels revealed that microstructures and metallic coating composition and thickness were as expected. Cross-section of spot welds showed good quality and typical evolutions of hardness. Tensile tests performed on reference samples (non-exposed to corrosion) showed tensile which were obviously configuration and material dependent. For each configuration, three replicates were tested and did not show significant scatter. The results were and will be used to evaluate the influence of corrosion on tensile strength of the joined samples. Fatigue tests were performed “in air”, meaning without corrosion exposition, leading to typical SN-lines. The results will be used to evaluate the influence of corrosion on the fatigue resistance of the joined samples.