EXPERIMENTAL CHARACTERIZATION OF AN ELECTRORHEOLOGICAL MATERIAL SUBJECTED TO OSCILLATORY SHEAR STRAINS

The coupled electrical and mechanical dynamic properties of electrorhe ological (ER)) materials comprised of alumino-silicate in fluorinated liquids are experimentally studied to gain insight into their effectiv eness for application in the area of vibration control. A prototype te st device is built to subject the test materials to oscillatory shear strains over a frequency range of I to so lit. Energy dissipation in t he material is determined as a function of volume fraction, electric f ield, strain amplitude, and frequency. Both the pre-yield and post-yie ld dynamic characteristics of the material under electric field are ev aluated. Results of dynamic testing showed linear viscoelastic solid b ehavior 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 whic h the energy dissipated is independent of frequency and increases line arly with increasing strain. The method of equivalent linearization is applied to determine equivalent viscous damping and stiffness express ions in terms of the device geometry, electric field, frequency of osc illation, and amplitude of oscillation for the nonlinear post-yield be havior.