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 co nstitutive model was developed to describe thermoelastic martensitic transf ormation. In order to verify the theory and to investigate basic properties of thermoelastic martensitic transformation in shape memory alloys (SMA), uniaxial and biaxial loading tests under different combined loads at a cons tant temperature were performed on cruciform specimens of a SMA CuAlNi sing le 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 theoret ical calculation by the generalized constitutive model based on micromechan ics. The results show that the constitutive theory can describe the complex thermodynamic processes, such as the forward transformation, reverse trans formation and reorientation happening simultaneously, and the theoretical p redictions consist well with experiments. (C) 1998 Acta Metallurgica Inc. P ublished by Elsevier Science Ltd. All rights reserved.