A rate-dependent constitutive model incorporated in two-dimensional PolyFEM for Galfenol sensors

A micromechanical model with rate effects is developed to constitute the nonlinear hysteresis sensor behaviour of Galfenol and embedded into a numerical framework, the polygonal finite element method. The model stems from the domain rotation events taking place at microlevel in response to the external magnetomechanical loads. The internal variables of the model to represent the material state at any instant are the volume fraction of the domains, and their evolution equations are derived using thermodynamic principles. Inter-domain effects within each grain are accounted in the form of back fields that act as hardening or softening parameters. The constitutive model is extended further to include the rate effects and then incorporated into a hybrid-magnetomechanical-formulation with Voronoi-based-discretization to study the behaviour of Galfenol. The Voronoi discretizations closely resemble the microstructure of Galfenol with each finite element specifying a random grain in the polycrystalline Galfenol. The developed framework is shown to simulate the major and minor loop sensor responses of the material with rate effects under complex loading conditions.