Finite element simulation on investigations, modeling, and multiobjective optimization for clinch joining process design accounting for process parameters and design constraints

Abstract

Clinch joining is a complexed mechanical behavior influenced by both process parameters and geometry parameters. The present clinch joining optimizations are more dedicated on geometry parameters, and except some property objectives of optimization, the other design properties of clinching process are not considered as constrained conditions. Therefore, the multiobjective optimization in the paper takes clinching process parameters such as punch speed, bottom thickness, and blank holder force into consideration besides geometry parameters, and then sets two thinning rates as constrained conditions. In the paper, a sufficient and systemic procedure for high-quality clinched joint based on FEA (finite element analysis), PS (parameter study), RSM (response surface methodology), and NSGA-II (non-dominated sorting genetic algorithm-II) is developed. Parameter study is conducted to choose significant parameters from both process and geometric parameters for neck, interlock, and tensile force. Then, mathematical models of nine selected parameters with responses are built based on RSM, and the interactions on interlock and tensile force are clearly identified by the model. Finally, three objectives neck, interlock, and tensile force and two constraints thinning rates of side face of joint are applied on multiobjective optimization using NSGA-II, which could obtain comprehensive high-quality joint, and the Pareto sets reveal negative relations of both tensile force to neck and interlock to neck, as well as the positive relation between interlock and tensile force. The result shows that the presented procedure performs well in optimization of clinch joining process and the use of finite element simulation model is valuable for complex optimization design.