Performance evaluation of electrorheological fluids under mixed shear and squeeze mode

Electrorheological (ER) fluids are capable of providing continuously variable damping forces in response to an electrical stimulus. Most ER dampers have exploited the variable shear or flow characteristics of ER fluids. Greater potential application in vibration control may be sought if these fluids are utilised in the squeeze flow mode.This paper is concerned with an experimental assessment of the comparative performance of an ER fluid in dynamic shear, squeeze, and combined shear and squeeze mode. The ER cell comprises a cylinder, which provides the reservoir for the fluid, and a piston. The cylinder is subjected to an oscillatory sinusoidal motion while the piston is fixed. This motion simultaneously subjects the fluid sandwiched between the parallel circular-planes of the cell to a compressive and tensile loading, and the fluid contained in the cylindrical gap to a shear loading. The cell is designed to permit the fluid contained in the cylindrical and circular gaps to be energised either separately to simulate a single shear or squeeze mode or simultaneously to simulate the combined shear and squeeze mode.It is seen that the force transmitted across the fluid in squeeze is greater than that transmitted when the fluid is in simple shear. The transmitted force level was further enhanced under mixed shear and squeeze mode of operation. In addition, the implications of the results to vibration control, where the ER fluid is employed in an engine mount, are discussed.