Stress-strain relation of CuAlNi SMA single crystal under biaxial loading - Constitutive model and experiments

In the previous work of two of the authors, a generalized micromechanics constitutive model was developed to describe thermoelastic martensitic transformation. In order to verify the theory and to investigate basic properties of thermoelastic martensitic transformation in shape memory alloys (SMA), uni-axial and biaxial loading tests under different combined loads at a constant temperature were performed on cruciform specimens of a SMA CuAlNi single crystal. The crystallographic theory for martensitic transformation has been employed to calculate the orientations of martensite variants and the transformation plastic strain. Experimental data were compared with theoretical calculation by the generalized constitutive model based on micromechanics. The results show that the constitutive theory can describe the complex thermodynamic processes, such as the forward transformation, reverse transformation and reorientation happening simultaneously, and the theoretical predictions consist well with experiments.