CHARACTERISATION OF THE COMPLEX SHEAR MODULUS PROPERTIES OF ELECTRO-RHEOLOGICAL FLUIDS BY THE DIRECT STIFFNESS AND MASTER CURVE TECHNIQUES

Abstract

The direct stiffness technique was employed to characterise the complex modulus properties of a silicone oil-based electrorheological fluid over a frequency range from 30Hz to 300Hz and a temperature range from 0°C to 60ºC. The ER fluid device utilised was a set of concentric cylinders possessing a radial gap of 3mm between adjacent cylinders. Electric field strengths of between 0kV/mm and 2kV/mm were applied across the ER fluid. The results show that the shear modulus of the ER fluid decreased monotonically as the temperature was increased from 0ºC to 60ºC. Overall, the shear modulus decreased by a factor of up to 20. On the other hand, the shear loss factor increased from a low value of about 0.05 at 0ºC to a high value of about 1.0 at 60ºC. Conversely, as the electric field strength was increased from 0kV/mm to 2kV/mm, the shear modulus increased whereas the loss factor decreased. At all temperatures and electric field strengths of these investigations, both the shear modulus and loss factor increased in value as the excitation frequency was increased. The sets of measured temperature- and frequency-dependent data were converted, using the master curve technique, to master curves of shear modulus and loss factor which vary with frequency over several decades at a constant reference temperature and for varying levels of the electric field strength.