Study Of Constitutive Relationship Of NiMnGa Ferromagnetic Shape Memory Alloys

Ferromagnetic shape memory alloys (FSMAs) is a new functional material with large magnetic field induced strain and high frequency , and it is one of the focuses in the field of smart materials. Ni₂MnGa ferromagnetic shape memory alloy, because of its characteristics of high ferromagnetism, large magnetostriction , thermoelastic and magnetic shape memory effect, high response frequency and large strain-stress output, has attractived the considerable interests from material and physical scientists.The magnetic field-induced strain in ferromagnetic shape memory alloys arises not from any effect of the magnetic field on the austenite-martensite transformation, but rather from the field-induced motion of twin boundaries in the martensite state. According to the characteristics of magnetism and crystallography, magnetic shape memory effect is compared to the conventional thermoelastic shape memory effect and contrasted with the more familiar phenomenon of magnetostriction .A thermo-magneto-mechanical coupled model of Ni₂MnGa ferromagnetic shape memory alloys is presented ,which captures the ferromagnetic shape memory effect, hysteresis effect i. e,with the simple expressions and general references. In the model, considering the effects of thermoelastic energy, mechanical energy,Zeeman energy, magnetocrystalline anisotropy energy and magnetostatic energy,we give the numerical simulations of magnetic flied-induced strain, magnetic flied-induced stress, magnetization and hysteresis effect.