Fatigue behaviour of clinched joints in a steel sheet

Clinch joining has been used in sheet metal work owing to its simplicity and because it facilitates the joining dissimilar metal sheets. In this study, monotonic and fatigue tests were conducted using coach-peel and cross-tension type specimens to evaluate the fatigue strength of clinch joints in a cold-rolled mild steel sheet. The monotonic experimental results reveal that the coach-peel specimen exhibits the lowest monotonic strength among the three specimen configurations. The coach-peel and cross-tension specimen geometries exhibit very low fatigue ratios, compared with the tensile-shear specimen. The maximum von Mises and principal stresses at the fatigue endurance limit are much higher than the engineering tensile strengths of the steel sheet used to determine the three specimen geometries. Compared with the effective stress and maximum principal stress, the Smith-Watson-Topper fatigue parameter can be used for an appropriate prediction of the current experimental fatigue life. With regard to the coach-peel specimen geometry, all samples exhibit pull-out failure mode in the fatigue testing range. However, for the cross-tension specimen geometry, mixed (pull-out and interface) and interface failure modes occurred, depending on the number of cycles to failure.