| The shear stress response of an electrorheological (ER) material composed of aluminosilicate powder dispersed in paraffin oil was modified by the application of an electric field. Shearing studies showed that the ER material behaved as either a linear viscous, a linear viscoelastic, or a nonlinear viscoelastic material. The transitions between the different rheological behaviors were dependent on the applied electric field strength, shear strain amplitude, and shear strain frequency. Furthermore, different analytical techniques were used to calculate the energy storing and energy dissipating properties of the ER material as functions of several experimental parameters.;Small amplitude, high frequency shearing studies were performed to observe the linear viscoelastic properties of the ER material. Both the shear storage modulus and the shear loss modulus increased in magnitude with increasing field strength, with the shear storage modulus showing a stronger dependence on the strength of the electric field. Increasing the field strength also caused the tangent of the phase angle to decrease.;Moderate frequency shearing studies were conducted with moderate and large shear strain amplitudes to observe the nonlinear viscoelastic response of the ER material. Analysis of the rheological properties during nonlinear deformation was conducted by Fourier analysis and the generating of shear stress-shear strain loops.;Fourier analysis was performed on the recorded shear strain signal and the shear stress response signal of the ER material to calculate the fundamental shear storage modulus, fundamental shear loss modulus, and tangent of the fundamental phase angle. Also, the Fourier spectrum of the shear stress response of the ER material was generated to observe the deformation mode transition, which was noted with the appearance of the third harmonic within the Fourier spectrum.;Shear stress-shear strain loops were generated to determine the energy dissipated by the ER material per volume, per shear strain cycle, and to observe the transition from linear damping to nonlinear damping. Linear damping was observed at low electric field strengths and low shear strain amplitudes, while nonlinear damping was observed during the application of high electric field strengths and high shear strain amplitudes. |
