Experimental and Calculated Cyclic Elasto-Plastic Deformations of Copper-Based Spring Materials

Yasuhiro HATTORI  Kingo FURUKAWA  Fusahito YOSHIDA  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E96-C   No.9   pp.1157-1164
Publication Date: 2013/09/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E96.C.1157
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Development of Electro-Mechanical Devices — Papers selected from International Session on Electro-Mechanical Devices 2012 (IS-EMD2012) and other recent research results —)
Category: 
Keyword: 
spring material,  stress-strain response,  Bauschinger effect,  Yoshida-Uemori model,  FEM,  

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Summary: 
The reliability of a connector depends on the contact force generated by the spring in the terminal of a connector. The springs are commonly formed by stamping from a strip of spring material. Therefore, the prediction of the force — displacement relation by the finite element (FE) method is very important for the design of terminals. For simulation, an accurate model of stress-strain (s-s) responses of the materials is required. When the materials are deformed in the forward and then the reverse directions, almost all spring materials show different s-s responses between the two directions, due to the Bauschinger effect. This phenomenon makes simulation difficult because the s-s response depends on the prior deformation of the material. Hence, the measurement of the s-s response is the elementary process, by cyclic tension and compression testing in which materials deform elastically and plastically. Then, the s-s responses should be described accurately by mathematical models for FE simulation. In this paper, the authors compare the experimental s-s responses of copper-based materials with conventional mathematical models and the Yoshida-Uemori model, which is a constitutive model having high capability of describing the elastic and plastic behavior of cyclic deformation. The calculated s-s responses only by Yoshida-Uemori model were in very good agreement with the corresponding experimental results. Therefore, the use of this model for FE simulation would be recommended for a more accurate prediction of force-displacement relation of the spring.