Modeling of residual strain accumulation of NiTi shape memory alloys under uniaxial cyclic loading

For shape memory alloys (SMA) to be usable in engineering applications, it must be possible to simulate the degradation of the material when subjected to cyclic loading. This paper presents an adaptation of Likhachev's micromechanical model capable of such a degradation, concentrating on strain accumulation. The proposed model, based on a cellular automata algorithm and on the Ramberg-Osgood theory of plasticity, is easy to characterize, with the material constants reduced to a minimum. Further, a thermal model is coupled to the micromechanical formulation in order to allow the thermal exchanges with the surroundings to be taken into account. A series of numerical validations demonstrate the potential of the model to reproduce SMA-related effects: superelasticity, thermal cycling and shape-memory effect. An experimental validation is carried out using a superelastic NiTi wire and a good agreement with experimental data is found. (C) 2009 Elsevier B.V. All rights reserved.