Improved Description of the Flow Characteristics of Copper for the Finite Element Simulation of the Cold Joining Process for High Current Electrical Contacts

Abstract

Cold‐joined connectors (CJC) are widely used, owing to the simplicity of the assembly process, the low initial investment, and the possibility to join several contacts in parallel. Due to the fast‐growing number of high power applications in the automotive industry, increasing efforts are made in order to make these advantages of the cold joining technology (CJT) suitable for high currents. New finite element method (FEM) models are still developed for supporting the new design cycle. The preferred technology to produce the assembly parts for high current CJC is die‐cutting. Two punched edges will come in contact during the joining process to form a high power connector (HPC). Therefore, accurately describing the material properties at punched edges is crucial for a correct understanding and finite element (FE) modeling of the cold‐joining process (CJP). Die‐cutting causes a strong strain hardening in the contact zone and changes the material properties significantly. Thus, the material properties of the bulk material cannot be assumed at punched edges for the FE‐simulation. This paper presents a new method for an improved material description of punched edges. The hardening mechanisms caused by die‐cutting are studied by means of electron backscatter diffraction (EBSD) and quantified with nanoindentation experiments. The hardness distributions at punched edges are correlated to flow curves, building a new inhomogeneous material law for the cold‐joining simulation. The new material description is validated by means of a small‐punch test on a real assembly part and shows a significant improvement of the component's material characterization.