This paper examines the transition area between elastic and viscous behavior for a conventional electro-rheological (ER) fluid and a state-of-the-art magneto-rheological (MR) fluid through the use of oscillatory rheometry techniques. A comparison between the yield behavior (strain and stress) measured for these two different types of controllable fluids is presented. The data obtained for MR fluids represents the initial characterization of the pre-yield properties exhibited by this type of material. Finally, a recommendation as to a key area for future R&D is highlighted.
Acoustical scattering resulting from a high-frequency plane-wave incident upon an infinite aluminum circular cylindrical shell immersed in and filled with water is determined by applying the Sommerfeld-Watson transformation to the classical Rayleigh normal-mode series solution. The resulting contour integrals are computed by both the saddle point method and by summing residues over poles which correspond to the zeros of a 6 X 6 determinant resulting from satisfying the necessary boundary conditions. The Bessel functions and their derivatives which appear in the 6 X 6 determinant are evaluated using asymptotic representations of both the Airy and Debye type depending upon the region of the complex plane. Emphasis is placed on the transitions in the scattering characteristics as the shell goes from a solid cylinder to a thin-walled shell. This dual behavior will be discussed in terms of the number and trajectories of allowed modes of the scatterer, the dispersion curves of various modes, and the contributions of the various modes to the scattered pressure field.
Coefficients for the prolate spheroidal solution of Laplace’s equation are derived in terms of a line of magnetization extending between the focal points of a spheroid. The present paper applies Havelock’s formula to obtain the magnetization corresponding to terms of a prolate spheroidal inverse model. Knowledge of the relationship of the prolate spheroidal coefficients to the equivalent magnetization distribution is required when mathematically modeling distinctly nonspherical static magnetic sources in the near field.
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