Recovery Stress of TiNi Shape Memory Alloy : Cyclic Characteristics under Constant Maximum Strain

Abstract

The cyclic behavior of recovery stress under constant maximum strain in TiNi shape memory alloy is investigated experimentally. The influence of maximum strain and the heating temperature in the thermal cycle on cyclic characteristics of recovery stress is discussed. The main results are summarized as follows. Both stresses at high temperature and at low temperature decrease gradually with the number of cycles, but the recovery stress is almost constant. Recovery stress under the thermal cycle decreases with maximum strain. Both recovery stress and stress at high temperature increase with the heating temperature, but stress at low temperature is almost constant. The amount of decrease in stress at high temperature under the thermal cycle is less than that in yield stress of stress-induced martensitic transformation in the pseudoelastic region. The infiuence of a rate of temperature variation on cyclic characteristics of recovery stress is slight.