Sheet Metal Forming and Crimping Simulation in ANSYS
Crimping is a widely used assembly method to attach a metal fitting (crimp-nut) to a sheet metal structure. This method mechanically locks the fitting and the sheet metal together by means of a crimp die. For some applications, this mechanical joint must be leak proof. For a leak-proof joint, 3-layer-crimp form (fitting flange-sheet metal flange-sheet metal, shown in Figure 11) must be achieved. However, achieving 3- layer crimp form is not easy. It requires the right combination of the flange lengths, sheet metal thickness and most importantly crimp-die profile. Historically, trial and error was the only way to determine these parameters correctly. This used to be a time consuming and expensive process since several prototypes and pilot runs were necessary until the right combination is found. Fortunately some commercial finite element packages are capable of handling contacts, plasticity and large strains and displacements efficiently and accurately. Thus, the computer simulation of such a crimping process is possible now. In this paper, the authors modeled the several combinations of a crimp-nut, a metal shell and a crimp-die in ANSYS 8.0. To obtain the correct stressstrain curve for the already work hardened low carbon steel metal shell, a simple and practical method was developed and used.