A parametric study of FE modeling of die-less clinching of AA7075 aluminum sheets

Die-less clinching process is a relatively new process for joining two sheet materials and aspects of this process are being optimized for many sheet materials. Die-less clinching tool optimizing by conducting many experimental trials with different tool design can be quite expensive and time consuming. Tool optimization via numerical simulations can be an effective and economical alternative provided material and other characteristics during clinching are adequately captured by the models. Also, there are several material, process and simulation parameters that can affect the simulation accuracy. In the present work a finite element (FE) modeling investigation of the influence of different numerical, material and tool stiffness conditions on die-less clinch characteristics is carried out with a goal towards clarifying and optimizing die-less clinching simulations for improved and efficient predictions. The numerical parameters include element size and aspect ratio, adaptive re-meshing criterion, tool stiffness and material parameters (such as non-linear work hardening behavior and friction between mating tool-sheet surfaces respectively). Adaptive re-meshing technique is required to avoid excessive element distortion as the strain is very large in die-less clinching. A mass scaling factor of less than 150 is suggested for acceptable accuracy from the model. Extended-Voce constitutive material model has been shown to accurately capture the large strain behavior of AA7075-O sheet for die-less clinching simulations. Inter-sheet as well as punch-sheet friction are shown to primarily influence geometric interlock.