Computational Modelling of Deformation of NiTi Plates with Circular Holes

This study presents a numerical model for deformation behaviour of near-equiatomic NiTi holey plates using finite element method. Near-equiatomic NiTi alloy deforms via stress-induced AM martensitic transformation, which exhibits a typical hystoelastic mechanical behaviour. In this model, the transformation stress is decomposed into two components: the hyperelastic stress, which describes the main reversible aspect of the deformation process, and the hysteretic stress, which describes the irreversible aspect of the process. It is found that with increasing the level of porosity of the holey plate, the nominal stress for the AM transformation decreases and the strain increases. In addition, the stress-strain slope over the stress plateau also increases with increasing the porosity. While the porosity level has a strong effect on global stress-strain behaviour of the holey plate, regularity of the arrangement of the holes is found to have negligible effect.