Numerical Investigation of the Tool Load in Joining by Forming of Dissimilar Materials Using Shear-Clinching Technology

Abstract

Modern developments in the automotive sector are motivated by the objective of lowering the emission of pollutants. In contrast, growing demands for safety and comfort lead to a potential increase of the weight of vehicles. Thus, the consequent use of lightweight design is indispensable. This includes the use of different materials for the construction of car bodies. Because of various material properties, joining of dissimilar materials is challenging and requires often the application of non-thermic processes like riveting or clinching. These processes are limited by the mechanical properties of the joining partners. Especially the increasing use of ultra-high strength alloys, like the hot stamped steel 22MnB5, makes the development of new joining technologies necessary. One of these innovative technologies is shear-clinching. By combining shear-cutting and clinching in one process, this technology produces durable and tight connections of dissimilar materials with high differences regarding strength and formability. In contrast to shear-cutting the die-sided material has no contact with the punch. Since the process of shear-clinching is a combination of cutting and joining using the same tool, the tool loads differ from common shear-cutting. Especially cutting hot stamped steels is a challenge due to their high ultimate strength which leads to high tool loads. Thus, the analysis of the load condition is essential for the dimensioning of durable and wear resistant tools. Hence, the scope of this paper is a numerical investigation of the tool loads during the indirect cutting process and the subsequent step of joining by forming during shear-clinching. Since an experimental investigation of the occurring tool loads in the closed process is not practicable, the finite element method has to be used. Therefore, a damage-based numerical model is set up to enable the coupled simulation of the combined cutting and joining process and the resulting tool loads. This allows the analysis of the loads during the whole process, identifying the influences of materials and sheet thicknesses.

The State of the Art of Finite Element Analysis in Mechanical Clinching

“…With the development of clinching technology, the concept of clinching connection technology is constantly expanding. Based on this technology, hole-clinching [7][8][9], shear-clinching [10][11][12][13][14][15][16], friction-stir clinching [17][18][19][20][21], clinching-welding technology [22][23][24], and clinch-bond composite technology [25,26] have been developed and applied. The materials have been extended from carbon steel and aluminum alloy to new types of refractory materials such as high-strength steel [27][28][29][30][31][32][33], titanium alloy, and magnesium alloy, which present special advantages in the connection between a metal and a non-metal (carbon fiber and polymer [34][35][36][37][38][39][40][41][42][43][44][45][46]).…”