Strain hardening effects on Cu springs

Abstract

It is increasingly important to understand the characteristics of Cu wires and springs as their instructional value increases. This paper examines the effects of strain hardening on Cu springs by stretching the spring plastically; and by stretching the wire plastically and coiling and uncoiling the wire before the spring is made. It is found that plastically stretching the springs hardens it to some extent to yield consistent elastic deformation below its elastic limit. Stretching the wire does not significantly alter the elastic limit of the spring but limits the amount of plastic deformation it undergoes. Coiling and uncoiling the wire yields the same effect as stretching the wire but the hardening tends to be non-uniform depending on how the springs are coiled. The effects on spring geometry are also considered.