The Rheological Characteristics of Electrorheological Fluids in Dynamic Squeeze

This paper is concerned with an experimental and theoretical determination of the rheological performance of an electrorheological (ER) fluid when subjected to time-dependent applied loads. The experimental facility was built as a squeeze cell in which the fluid is sandwiched between two electrodes, one fixed and the other moving, which permits the instantaneous measurement of the mechanical and electrical responses of the fluid. The transient rheological characteristics of the fluid were assessed for various mechanical force levels and for constant voltage excitation of the fluid. Input and output stress levels across the fluid were monitored enabling the dynamic response of the fluid to be determined using a combination of displacement, force, velocity and acceleration transducers. The experimental results were compared with the results from a modified theoretical analysis, which employs a bi-viscous shear stress/shear strain characteristic of the electrically stressed fluid together with a fluid yield stress, which has a strain-direction dependence on the electric field.