A constitutive model of porous SMAs considering tensile-compressive asymmetry behaviors

A constitutive model of the macroscopic behaviors of porous shape memory alloys (SMA) is developed in this work. A yield function for porous SMAs considering both the effect of hydrostatic stress and the tensile-compressive asymmetry is proposed. Combining the constitutive model of dense SMAs and the macroscale and microscale analysis, the evolution equation for the overall transformation strain is then derived. Examples for the response of both dense SMA and porous Ni-Ti SMA subjected to uniaxial tension and compression loads are supplied. Good agreement between the numerical prediction results and the published experimental data is observed. Numerical result shows that the yielding stresses, loop width and length, strain-hardening behaviors of porous SMAs under pure tensile and pure compressive are different. Importantly, the transformation initiation stress is much closer to the experiment result than simulated by Zhao et al. (2005).