Deformation Properties Associated with the Martensitic and R-Phase Transformations in TiNi Shape Memory Alloy.

In TiNi shape memory alloy, the shape memory effect and pseudoelasticity appear due to the martensitic transformation and the R-phase transformation, and the recovery stress associated with both transformations is utilized in many practical applications. In order to describe these properties of the material, a thermomechanical constitutive equation considering the volume fractions of induced phases associated with both transformations is developed. The proposed constituve equation expresses well the properties of the shape memory effect, pseudoelasticity and recovery stress. The proposed theory is useful for design of shape memory alloy elements in which the working stroke, the working force and the working start and completion temperatures are specified.