A Micromechanically Motivated Constitutive Model for Magnetostrictive Materials With Rate Effects

A micromechanically motivated uniaxial model with least number of state variables is presented in this paper to capture nonlinear hysteresis behavior of polycrystalline magnetostrictive materials, in particular Galfenol, with rate effects. This model is formulated based on the classical thermodynamic framework and relies on the domain rotation phenomenon occurring at the microscopic level. The macroscopically averaged domain rotation events are considered as the material state variables. The driving force required for the transformation of one state variable into another is extracted from the derived dissipation inequality equations. A special case, wherein two transformation systems activated simultaneously, is also taken into consideration in the model development. Back fields, accounting in a way the averaged inter-domain and inter-grain effects, are introduced in the proposed model. Rate-dependent effects are also set into the model in a straightforward way without compromising the core idea of this model development, i.e., a simplified approach, yet capturing most of the material responses. Finally, the proposed model, despite the reduced number of state variables, demonstrates its ability to collaborate well with many complex experimental observations of Galfenol reported in the literature.