Effect of Temperature and Electric Field on the Damping and Stiffness Characteristics of ER Fluid Short Squeeze Film Dampers

H P Jagadish,L Ravikumar

doi:10.1155/2013/526428

Abstract

Squeeze film dampers are novel rotor dynamic devices used to alleviate small amplitude, large force vibrations and are used in conjunction with antifriction bearings in aircraft jet engine bearings to provide external damping as these possess very little inherent damping. Electrorheological (ER) fluids are controllable fluids in which the rheological properties of the fluid, particularly viscosity, can be controlled in accordance with the requirements of the rotor dynamic system by controlling the intensity of the applied electric field and this property can be utilized in squeeze film dampers, to provide variable stiffness and damping at a particular excitation frequency. The paper investigates the effect of temperature and electric field on the apparent viscosity and dynamic (stiffness and damping characteristics) of ER fluid (suspension of diatomite in transformer oil) using the available literature. These characteristics increase with the field as the viscosity increases with the field. However, these characteristics decrease with increase in temperature and shear strain rate as the viscosity of the fluid decreases with temperature and shear strain rate. The temperature is an important parameter as the aircraft jet engine rotors are located in a zone of high temperature gradients and the damper fluid is susceptible to large variations in temperature.

Highlights

The application of controllable fluids in engineering is an area which began to be explored in the early 1980s and fluids of interest in this study are materials that respond to an applied electric field with a remarkable change in its rheological behavior
Since the available literature regarding the effect of temperature on the stiffness and damping characteristics of ER Fluid squeeze film dampers is very scanty, this paper investigates these aspects on a short squeeze film damper using the relation obtained between viscosity and temperature for a particular ER fluid which is a suspension of diatomite in transformer oil
The theoretical results are discussed under two headings: (a) effect of temperature on the viscosity and dynamic characteristics, (b) effect of electric field intensity and shear strain rate on the viscosity and dynamic characteristics

Summary

Introduction

The application of controllable fluids in engineering is an area which began to be explored in the early 1980s and fluids of interest in this study are materials that respond to an applied electric field with a remarkable change in its rheological behavior. The essential characteristic of these controllable fluids is their capability to change from a liquid state into a solid-like gel under the action of an electric field. These materials are commonly called electrorheological (ER) fluids and are normally low-viscosity colloidal suspensions. The change in the field induced shear stress produces a change in their apparent viscosity and this property is successfully utilized in applications involving valves, dampers, clutches, and adaptive structures but applications in rotor dynamics are far from satisfactory and require considerable attention [1–3]. Since the available literature regarding the effect of temperature on the stiffness and damping characteristics of ER Fluid squeeze film dampers is very scanty, this paper investigates these aspects on a short squeeze film damper using the relation obtained between viscosity and temperature for a particular ER fluid which is a suspension of diatomite in transformer oil

The Herschel-Bulkley Model

Temperature Effect on Viscosity of ER Fluid

Methodology Proposed

Results and Discussions

Conclusions