Variation of Electrical Resistance and the Elastic Modulus of Shape Memory Alloys under Different Loading and Temperature Conditions

Abstract

Shape memory alloys (SMA) have recently been proposed and demonstrated for several active control applications. However, there is only limited experimental information available on the properties of the SMA. The present paper focuses on variations of the dynamical Young's modulus, the damping characteristics, and the electrical resistance as a function of the various parameters, such as temperature and applied stresses and strains. Tests were performed to measure the dynamic Young's modulus and damping characteristics of various Smas using the Dynamical Mechanical Analysis (DMA) method. The experimental results show that the curve of the dynamic Young's modulus exhibits a trough shape, while the damping curve has a maximum peak during the martensite = austenite transformation. The variation of the electrical resistance of the SMAS was also measured during the phase transformation under the action of an applied stress. The results show that the applied stress plays a significant role on the electrical resistance, which not only affects its value, but also changes the phase transformation sequence. Furthermore, the effect of the strain on the electrical resistance of the SMA at different phase states (martensite, austenite, and stress induced martensite transformation) was observed. In the initial stage of deformation,, the electrical resistivity decreases as the strain increases, and demonstrates a unique functional relationship.