FOURIER-TRANSFORM ANALYSIS - NONLINEAR DYNAMIC-RESPONSE OF AN ELECTRORHEOLOGICAL MATERIAL

A fast Fourier transform algorithm is used to generate the Fourier spectrum of the shear stress response of an electrorheological (ER) material, composed of aluminosilicate powder in paraffin oil, during the application of a sinusoidal shear strain. The Fourier spectrum of the shear stress response of the ER material demonstrates the existence of the first harmonic for electric field strengths up to some critical value above which higher harmonics appear within the Fourier spectrum. The appearance of the higher harmonics suggests the onset of a transition in the mode of deformation of the material. Furthermore, the observation of this deformation transition necessitates the use of Fourier analysis to determine the nonlinear viscoelastic parameters: the first-harmonic shear storage and loss moduli.