A numerical simulation of electrorheological fluids in oscillatory compressive squeeze-flow

Abstract

This paper is concerned with the theoretical analysis of the compressive squeeze performance of an electrorheological (ER) fluid sandwiched between two parallel circular electrodes, the upper one fixed and the lower one oscillating sinusoidally normal to its own plane. It is shown how the force transmitted through the fluid on the upper electrode varies with amplitude and frequency of oscillation together with applied potential difference and also how the fluid, modelled by a bi-viscous characteristic, responds when electrically stressed compared with its unstressed, Newtonian counterpart. Finally, the relevance of the theoretical results to the determination of the mechanical properties of an ER fluid in squeeze is discussed.

Transient response of compressed electrorheological fluid

“…In the following, we will propose a normalized method to deal with compressive stress to achieve the transient time constant. As in the investigation by Gartling and Phan-Thien [29] and continued by Williams and co-workers [30], ER fluids under fields could be looked as a plastic fluid, the compression can be looked as a transferred shear flow. At very low compressive speeds, the contribution of the viscous force to the compressive stress can be neglected.…”

“…At very low compressive speeds, the contribution of the viscous force to the compressive stress can be neglected. The compressive stress can be derived from the lubrication theory and approximated by [30] (3)…”

“…For low mechanical output of ER fluids working in shearing mode, to achieve higher mechanical performance, recently, compression and elongation of ER fluids have been experimentally and theoretically carried out [23][24][25][26][27][28][29][30][31][32]. These investigations indeed show that compression and elongation of ER fluids could bring much higher mechanical outputs than that working in shearing mode.…”

“…Gartling and Phan-Thien [29] have modeled the compressive flow of plastic fluids. Sproston et al [30] employed a biviscous model and lubrication equations to describe the oscillatory squeezing flow of ER fluids. Their analysis showed that compressive stress is tightly related to the geometric parameters of the compressive plates.…”

Optimal Design Methodology of Magnetorheological Fluid Based Mechanisms

“…Bingham parameters tested from shear mode are not well-founded for the calculation of the squeeze mode behaviour. Sproston et al [63] characterized the performance of ER fluids in dynamic squeeze mode using a bi-viscous model under a constant potential difference or by a constant field. Later on, Sproston and El Wahed [64] utilized the model to assess the fluid's response to a step-change in the applied field and the influence of the size of solid phase.…”