نوع مقاله : مقاله پژوهشی
دانشکده مهندسی مکانیک- دانشگاه صنعتی شریف
عنوان مقاله [English]
Magnetic shape memory alloys (MSMAs) are a new category of smart materials that have attracted significant interest in recent years for their special properties, such as;\ large\ magnetic-field-induced \ strains \ up \ to \ 10\%.\ \ Magnetic-field-induced strains in MSMAs are created due to austenite-martensite phase transformation, as well as martensitic variant reorientations. MSMAs have the ability to perform at high frequencies (up to 1kHz), contrary to non-magnetic types, which perform at low frequencies, due to the time involved in heat transfer (up to 5Hz). Major limiting aspects of MSMAs are low blocking stress (about 6-10 MPa) and low output stress (about 10MPa). Considering these features, MSMAs are unique choices in sensor and actuator applications.In this paper, using the incremental approach, which is a useful method in the analysis of nonlinear behavior of materials, the behavior of Ni-Mn-Ga MSMA single crystal is modeled. This method utilizes a different secant module for different parts of the stress-strain curve, so, it is applicable to a large variety of problems related to MSMAs and ppropriate for implementing in the finite element method.In addition, the stress-strain curve of MSMA is approximated with an analytical relation, whose parameters can be obtained from an experimental stress-strain curve under the effect of a reference field. The incremental model is used in predicting the magnetic-field-induced strain, either under the influence of mechanical stress or in the absence of stress, by means of relating the magnetic field to an equivalent mechanical stress. Furthermore, calculation of the magnetic field equivalent stress is modified to predict the superelastic behavior of MSMA under constant field and variable stress. Results obtained from the incremental model show good correlation with experimental observations.