Comparative experimental study on constitutive mechanical models of magnetorheological fluids

Abstract

Accurate and feasible mechanical constitutive models of magnetorheological (MR) fluids can facilitate the design of MR devices. Therefore, the purpose of this article is to compare which of the three models can better describe the mechanical behavior of the MR fluids, and the experiments were implemented to measure the shear stress and apparent viscosity of a representative MR fluid under varying shear rates and different applied magnetic field conditions. The obtained rheological properties of the MR fluid are then fitted to the Bingham, Casson, and Herschel-Bulkley models to test the constitutive mechanical performance and accuracy. The results demonstrate that, although the models above appropriately describe the approximate Newtonian fluid properties of the MR fluid in the absence of a magnetic field, the Bingham and Casson models are difficult to describe the nonlinear characteristics of the MR fluid in the pre-yield region under an excited magnetic field. Meanwhile, the Casson are not sensitively responsive to equation forms change and can only be suitable to describe the mechanical behavior of the MR fluids roughly. However, the Herschel-Bulkley model can closely describe the constitutive mechanical behaviors of shear stresses varying nonlinearly with the external excited magnetic field. Especially in the pre-yield region, the model can reflect the peristaltic mechanical behaviors of MR fluids. These findings could provide theoretical guidance for the design of MR devices.