Material Characterization of Contact Springs for Finite Element Analysis

The contact normal force (CNF) is one of the crucial parameters to ensure electrical contact reliability. Generally, such contacts are stamped and formed from rolled copper alloys. The rolling process introduces anisotropy and leads to different material behaviors in the rolling direction and transverse to the rolling direction. Thus, it is essential to characterize contact spring materials in different orientations for better prediction of the CNF and understanding of the spring behavior. Existing bending tests can be used for characterization, like the Piet van Dijk bend test (PD-bend test) [2], [3]. However, the elastic modulus is overestimated which results in reduced accuracy. This paper introduces an improvement in the elastic modulus formulation of the PD-bend test and a method to treat the test data for large plastic deformation. The PD-bend test is a 3-point bending test that helps to determine both elastic and plastic flexural material properties of the copper alloys. The stress-strain curve obtained from the test provides input for finite element analysis (FEA), and the results are verified against the test data. Further, the FEA results obtained from the previous formulation and the standard uniaxial tensile test are also compared. The findings highlight the significance of using flexural material properties due to its accuracy and better alignment with the application of contact springs.