Effect of Pore Shape on Mechanical Properties of Porous Shape Memory Alloy.

Porous shape memory alloys (SMAs) have been widely used in the aerospace, military, medical, and health fields due to its unique mechanical properties such as superelasticity, biocompatibility, and shape memory effect. In this work, the pore shape was considered in the constitutive model of the porous SMAs by respectively introducing the parameter of aspect ratio and for different pore shapes including oblate, sphere, and prolate shapes, so the expression of Young's modulus for the porous SMA can be derived. Then, the constitutive model for such a porous shape memory alloy was established. When the porosity was zero, the model can be degenerated to the dense case. The stress-strain curves for the porous SMA with a porosity of 13% with different aspect ratio are then given. Numerical results showed good agreement with the published experimental data that proved the validation of the model. Based on the proven constitutive model, the properties of porous SMA with different porosity and pore shapes are discussed. The results showed that the pore shapes and the porosities had a big effect on the stress-strain curves for the porous shape memory, while with the increasing porosities, the Young's modulus and the hysteresis both decreased. With the same porosities, the Young's modulus and hysteresis loop of SMA with round pores were the largest, while the Young's modulus and hysteresis loop were the smallest when r=0.1, and they were greater when r=0.75 than when r=10. It can be seen that the closer to the circle, the better the performance of the material.