Experimental and simulated force-displacement relations under cyclic bending deformation of copper-based spring materials

The reliability of connector is depending on the contact force, generated by the spring in terminals of connectors. The springs are commonly formed by stamping from a strip of the spring material. Therefore, the prediction of its force-displacement relation by the finite element method (FEM) is very important for the design of terminals. For the simulation, the accurate model of stress-strain (s-s) responses of the materials is required. When the materials are deformed in forward and the following reverse directions, almost all the spring materials show different s-s responses between the two directions, due to the Bauschinger effect. This phenomenon makes the simulation difficult because the s-s response depends on the prior deformation of the material. The authors reported the mathematical description of s-s responses of the materials by the Yoshida-Uemori model, which is a constitutive model having high capability of describing the elastic and plastic behavior of cyclic deformation. In this paper, a new measurement method for cyclic bending of actual strips of the materials will be presented. The experimental force-displacement relations were in good agreement with the corresponding simulation results using Yoshida-Uemori model. Therefore, the use of this model for the FE simulation would be recommended for the more accurate prediction of force-displacement relation of the spring.