Extended Irreversible Thermodynamics Approach to Magnetorheological Fluids

Abstract

Magnetorheological (MR) fluids have the unique ability to change properties from those of a fluid to those of a solid in the presence of a magnetic field. In this paper, we present a phenomenological theory for MR fluids within the framework of extended irreversible thermodynamics (EIT), which relates the dynamics of the fluxes to the form of the nonequilibrium equation of state and introduces the elasticity of MR fluids in a natural way. The Gibbs equation and the entropy inequality are derived to present the energy transfer and dissipative mechanisms. In particular, the viscoelastic behavior of the pre-yield regime and the fluid behavior of the post-yield regime are discussed in depth. Finally, according to the entropy inequality, we propose a mechanical model of MR fluids that can characterize the duplicate phenomena of the fluid-solid transition. The results of a numerical analysis of this model correspond with those of the functional tests of an MR damper.