A macro-constitutive model of polycrystalline NiTi SMAs including tensile–compressive asymmetry and torsion pseudoelastic behaviors

Experimental results show that material component and loading modes may affect the properties of shape-memory alloys (SMAs) markedly. In order to investigate the influence of loading modes on pseudoelasticity behaviors fully, some experiments of NiTi specimens under pure tension, compression and torsion with the same material component are investigated. In terms of the phenomena observed in experiments, a macro-constitutive model is presented for considering the tension–compression asymmetry of polycrystalline NiTi SMAs. In this study, the macroscopic strain is taken account of elastic strain, macro-transformation strain and macro-temperature strain. The volume fraction of martensite is governed by the reduction in Gibbs’ free energy of the system. In the present model, the fewer experimental data which are used to determine model parameters are needed. The model is not only simple but also fit for using in engineering. The theoretical results are found to be in good agreement with experimental data.