Behavior Of Polycrystalline Shape Memory Alloys Research Articles

A comprehensive description for shape memory alloys with a two-phase mixture modelincorporating the conventional theory of plasticity

A comprehensive description for the constitutive behavior of polycrystalline shape memoryalloys (SMAs) is proposed based on a two-phase mixture model incorporating theconventional theory of plasticity. An SMA is composed of austenite and martensite phases,and its constitutive behavior should be the combination of the individual behavior of eachof the two phases. In the interested ranges of stress and temperature, the behavior of theaustenite is assumed to be linearly elastic while that of martensite is assumed tobe elastoplastic. The main features of SMAs, such as shape memory effect andpseudoelasticity, can be successfully replicated with the proposed constitutive model. Theconstitutive behavior of SMA Au–47.5 at.% Cd subjected to uniaxial forward and reverseloading and the pseudoelasticity of Cu–Al–Zn–Mn SMA polycrystal subjected toproportional and nonproportional complex stress or strain histories are simulated andcompared with the experimental results.

Modeling of the Mechanical Behavior of Polycrystalline Shape-Memory Alloys by a Homogenization Method

We obtain a micromechanics-based Helmholtz free energy and then in the framework of irreversible thermodynamics, a kinetic relation, a martensitic nucleation criterion and the reorientation criterion of martensitic variants are obtained. These relations are valid for a three-dimensional proportional and non-proportional loadings and for a combination of mechanical and thermal loading. From the simulated pseudoelastic stress-strain relation of a single crystal with loading rate effect, polycrystalline behavior in case of proportional and non-proportional loading is predicted by a homogenization method. The obtained results are compared quantitatively with experimental results.