Numerical analysis of the robustness of clinching process considering the pre-forming of the parts

Clinching is a conventional cold forming process in which two or more sheets of materials can be joined without any auxiliary parts. To achieve the required geometrical characteristics of the joint, it is essential to use the desired joining tools. The motivation of this study is to investigate the influence of forming steps prior to the joining process on the joint quality. The influences of strain hardening and the variation of sheet thickness on the joint characteristics are to be studied. In this regard, a metamodel-based analysis of the clinching process is performed to investigate the robustness of the clinching process with respect to the different material prestains. Three different material combinations made of steel and aluminium sheets (HCT590x; t = 1.5 mm, EN AW-6014, T4; t = 2.0 mm) are examined to illustrate the influence of different material properties on the joint characteristics. The numerical FEM-Simulation is used to predict the geometrical properties of the joint during the simulation of clinching process. For this purpose, an optimization software is used to conduct varieties of simulations and to create a meta-model, which is able to describe the relationship between the pre-straining and the quality relevant parameters of the clinched joint. To validate the model, the results of simulation and experiment are compared. It is shown that there is a good agreement between the simulation and the experiment concerning the geometrical parameters and force-displacement diagram. Finally the joinability of the investigated material-geometry combinations with regard to a tolerable pre-forming is described.