Effects of asymmetric material response on the mechanical behavior of porous shape memory alloys

The demand for lightweight devices attracts attention toward porous materials. Among them, porous shape memory alloys are of interest due to superior mechanical and biological properties. High cost related to fabrication and characterization of such materials makes it necessary to model their mechanical properties before fabrication. Experimental observations of dense shape memory alloys show tension–compression asymmetry which in turn can affect the mechanical response of porous ones. In this article, the effects of this asymmetric response on the mechanical response of porous shape memory alloys are investigated by comparing three models: asymmetric, symmetric with tensile, and symmetric with compressive material parameters. To this end, a constitutive model considering asymmetric material response is proposed based on microplane theory. Then, this model is used to simulate the stress–strain response of porous shape memory alloys. The results are compared with available experimental and numerical data, and a good agreement is observed. It is concluded that in comparison with the asymmetric model, the symmetric model with tensile material parameters under-predicts the stress level while the model with compressive one over-predicts the stress level. In addition, the effects of porosity on the asymmetric response as well as hysteresis of stress–strain curve in tension and compression are assessed.