Experimental Characterization of an Electrorheological Material Subjected to Oscillatory Shear Strains

Abstract

The coupled electrical and mechanical dynamic properties of electrorheological (ER) materials comprised of alumino-silicate in fluorinated liquids are experimentally studied to gain insight into their effectiveness for application in the area of vibration control. A prototype test device is built to subject the test materials to oscillatory shear strains over a frequency range of 1 to 50 Hz. Energy dissipation in the material is determined as a function of volume fraction, electric field, strain amplitude, and frequency. Both the pre-yield and post-yield dynamic characteristics of the material under electric field are evaluated. Results of dynamic testing showed linear visco-elastic solid behavior for the pre-yield state with the shear modulus independent of the electric field and frequency. Post-yield energy dissipation of the materials tested is found to parallel that of Coulomb damping in which the energy dissipated is independent of frequency and increases linearly with increasing strain. The method of equivalent linearization is applied to determine equivalent viscous damping and stiffness expressions in terms of the device geometry, electric field, frequency of oscillation, and amplitude of oscillation for the nonlinear post-yield behavior.