The electrorheology of a zeolite/silicone oil suspension (

Dielectric and conduction effects in electrorheological (ER) fluids with ohmic conductivity of the host liquids and with an applied AC electric field are considered. It is found that the conductivity ratio Γσ, the dielectric constant ratio Γε and the applied field frequency fare three important parameters which determine the ER effect. If Γσ>Γε, a stronger ER response is obtained with a low applied field frequency than with a high frequency. If Γσ<Γε, the opposite occurs. Empirical equations are given for the attractive force between the particles in an ER fluid and for the shear yield stress. The calculated current density is independent of the applied field frequency when the frequency is smaller than a critical value, but becomes a linear function of the frequency beyond the critical value. The predicted attractive force of two nearly touching polymer spheres inmineral oil is in good agreement with that measured; also the predicted shear yield stress of some common ER suspensions is in accord with measurements.

Dielectric and conduction effects in electrorheological (ER) suspensions with non-Ohmic conductivity of the host liquid and with ac applied electric field are investigated. It is found that the conductivity ratio Гб, the non-Ohmic conductivity parameters A and Ec of the host oil, the dielectric constant ratio Гб, and the applied field frequency are important parameters that determine ER response. The effects of these parameters are more complex than in the case of host liquids with simple Ohmic conductivity. If the ac field frequency is high, the conductivity effect disappears; if the frequency is low the dielectric effect disappears. The current density is independent of the frequency below a critical value, but it increases with frequency beyond the critical value. The critical frequency is larger for ER suspensions having non-Ohmic conductivity of the host liquid than with Ohmic conductivity. Good agreement occurs between experimental measurements of the current density and attractive force between particles (including shear yield stress) and predictions by our model.

Hydrodynamic lubrication of a bilinear rheological fluid plays an important role in the so-called electrorheological (ER) smart' bearings. There may not. however, be a reliable and efficient algorithm for the non-Newtonian lubrication problem of bilinear rheological fluids. In this paper, a finite element trethod (FEM), together with a mathematical programming solution technique, are proposed for solving such a non-Newtonian lubrication problem. This method was used to study the hydrodynamic lubrication of a journal bearing lubricated by a bilinear rheological lubricant. The computed results were compared with Tichy's work for the Bingham rhcological model. It was shown that the Bingham model should be regarded as a limiting case of the bilinear rhcological model.

This paper presents a new scheme of time stepping for solving non-linear dynamic problems. By expanding variables in a discretized time interval, FEM-based recurrent formulae are derived leading to a self-adaptive algorithm for different sizes of time steps. There will be no requirement of iteration for the non-linear solutions. Numerical validation shows satisfactory results.