Characteristic of Coil Spring of TiNi Shape Memory Alloy

Abstract

This paper is concerned with a coil spring of TiNi shape memory alloy. Three basic models (condition of constant temprature, condition of constant load, condition of constant deflection) can be taken for the study of both SMA spring itself and the combined application with a bias coil spring. The spring characteristics in each model were tested, and the relationship of the characteristic between each models was obtained.
The main conclusion can be shown as follows:
(1) As for three basic models for SMA spring, the characteristic value obtained from one model, is not always the same with that obtained from the other model.
(2) When in the combined use with a bias coil spring, if the spring-rate of bias coil spring is relatively small, the characteristic of the SMA spring can be estimated by the loading characteristic at constant temprature.
(3) The hysteresis of the P-δ, δ-T, and T-P planes in the combined condition, coresponds to that of the SMA coil spring.