Superelasticity description based on the combined model of shape memory alloys deformation considering development of the martensitic elements | Mekhanika | kompozitsionnykh | materialov i konstruktsii
> Volume 26 > №4 / 2021 / Pages: 441-454

Superelasticity description based on the combined model of shape memory alloys deformation considering development of the martensitic elements

Abstract:

The article considers a constitutive model for shape memory alloys, which allows to take into account the differences between phase and structural transformation. The model reflects the fact that hardening effect is typical for structural transformation, but not for phase transformation. Deformation due to structural transformation is described with the use of loading surface by analogue of the plasticity theory with isotropic hardening. The deformed state is determined by one parameter, which can be changed by phase or structural deformation. Inelastic deformation due to structural transformation in the active process is subject to the associated flow rule. The article examines the possibilities of the model for describing the phenomenon of superelasticity. The temperature of the phase transition in shape memory alloys depends on the operating stress, so the phase transition can occur at the constant temperature. In a certain range of stresses, dependence of deformations on stresses becomes nonlinear. This phenomenon can be explained by a phase-structural transition. In this paper, a proportional monotonic loading at a constant temperature and phase transitions caused by increasing and decreasing stresses. The model is extended to the case of the development of martensitic elements during the phase and structural transition. Phase-structural and phase deformations plots are provided. It is shown that the model allows to describe the phenomenon of superelasticity correctly. The obtained results are compared for different material functions that determine the relationship between the processes of origin and development of martensitic elements. It is shown that under the considered loading conditions, phase deformations increase with temperature. The values of phase deformations are higher for material functions that take into account the development of martensitic elements.

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