Damage analysis in mechanical clinching: Experimental and numerical study

A numerical model describing the evolution of ductile damage was developed to predict the onset of fracture during the clinch joining of thin aluminium AA6082-T6 sheets. The damage model was calibrated and validated using instrumented punch-out tests in order to increase the reliability and robustness of the damage parameter. An inverse analysis was performed (by varying the damage parameter) by minimizing the difference between the experimental and numerical prediction concerning the load-stroke curves and the geometries of punched cross-sections. Then, a numerical model of mechanical clinching using the damage parameter was developed and compared with experimental clinched connections. The results show that the model enables the onset of cracks in critical regions to be predicted. The critical regions are the punch-sided sheet neck and die-sided sheet bulge. The established numerical model of clinching provides a viable means for optimizing the geometry of the clinching tools so as to improve the mechanical behaviour of the joints (by maximizing the undercut and reducing the neck thinning) other than preventing the onset of cracks on the joints.