Papers by Author: Guan Suo Dui

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Authors: Bing Fei Liu, Guan Suo Dui, Yu Ping Zhu
Abstract: A micromechanical constitutive model for responding the macroscopic behavior of porous shape memory alloys (SMA) has been proposed in this work. According to the micromechanical method, the stiffness tensor of the porous SMA is obtained. The critical stresses are calculated by elastic mechanics. Based on the general concept of secant moduli method, the effective secant moduli of the porous SMA is given in terms of the secant moduli of dense SMA and the volume fraction of pores. The model takes account of the tensile-compressive asymmetry of SMA materials and the effect of the hydrostatic stress. Only the material parameters of dense SMA are needed for numerical calculation, and can degenerate to dense material. Examples for the uniaxial response of porous SMA materials at constant temperature are then used to illustrate one possible application of the constitutive model. The numerical results have been compared with the experiment data for porous SMA, which show that the modeling results are in good agreement with the experiments.
Authors: Bing Fei Liu, Guan Suo Dui, Yu Ping Zhu
Abstract: According to micromechanics, consider the porous shape memory alloy (SMA) as a composite-sphere model. Isolate a constant thickness spherical shell which is composed of SMA, and is traction free on its inner surface and subjected to the uniform hydrostatic pressure and the deviatoric stress on its external surface. Then, a constitutive model for porous SMA considering hydrostatic stress is proposed by elasticity solution. The stress distribution of the spherical shell was calculated. Corresponding to different applied stresses, the spherical shell is divided into different regions of pure austenite, pure martenite, and austenite/martensite mixture under isothermal circumstances. The martensite volume fraction is then obtained. The predicted results have been compared with the obtained experimental data by Zhao and Sia Nemat-Nasser. It shows that the modeling results are in good agreement with the experiments and the initial phase transition point for porous SMA is lower than the dense SMA.
Authors: Yun Zhang Wu, Yu Ping Zhu, Guan Suo Dui
Abstract: Based on thermodynamic theory, a phenomenological model of shape memory alloy is provided. Simulations under different loading illustrate the influence of large-strain deformation and small-strain deformation on the characteristics of the model. The results indicate that the difference between the two methods is small under uniaxial tension case, while the influence is very large under shear deformation case.
Authors: Yu Ping Zhu, Guan Suo Dui
Abstract: A constitutive model for magnetic shape memory alloys is developed through a combined consideration of micromechanical and thermodynamic theories. Of special concern is the influence of different temperatures on field-induced reorientation strain for a NiMnGa single-crystal specimen. The theoretical results are found to be in general agreement with experimental data. It is shown that the method is accurate and simple.
Authors: Yu Ping Zhu, Guan Suo Dui
Abstract: In this paper, combined the micromechanical and the thermodynamic theory, a three phase model for the SMA composite is developed, in which the composite is considered as the austenitic phase, the product phase (martensite) and the matrix phase. In the present model, the interaction among the three phases is analyzed. From the micromechanical analysis, the macroscopic free energy function is found. Then macroscopic transformation strain, effective elastic compliance, macroscopic constitutive model are derived.Compared with the traditional two-phase method, non-linearity of SMA need not be considered. The method is not only simply but also the interaction among the three phases is considered. As an application of above model, we consider the case of a composite with NiTi/epoxy, illustrate the predicted stress-strain response of it under isothermal loading and unloading conditions and analyses the effects of temperature and fiber volume on macroscopic mechanical property. By comparing with references, it is shown that the results are credible. It is helpful to design the intelligent composite.
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