Ultrasonic and Viscoelastic Studies on Liquids at Different Pressures

Ellis, J 1976, Ultrasonic and Viscoelastic Studies on Liquids at Different Pressures , PhD thesis, University of Salford.

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This thesis describes experimental researches in ultrasonic and viscoelastic relaxation in pure liquids, mixtures and a polymer solution. The measurements were made over a range of temperatures and pressures in the frequency range 5 to 78 MHz. Density, steady flow viscosity, real part and imaginary part of the shear impedance were measured on five liquids. Four of the liquids obeyed the Time-Temperature Superposition principle and could be described by the Barlow, Erginsav and Lamb (B. E. L, ) model. The fifth liquid did not obey the Time-Temperature Superposition principle and deviated from the model. This was attributed to the distribution of relaxation times wideningas the temperature is decreased. The shear compliance for all five liquids varied linearly with temperature at atmospheric pressure. At higher pressures it was the shear modulus that varied linearly with pressure. Both low and high frequency longitudinal velocities were found to vary linearly with temperature at atmospheric pressure, while at higher pressures only the low frequency velocity varied linearly with pressure, the high frequency velocity results were too scattered. Values of the bulk moduli obtained from the longitudinal moduli and shear moduli were normalised and the variation with reduced I frequency was found to be of the same shape as for the shear moduli but displaced along the reduced frequency axis. Therefore the shear and bulk relaxation properties have a common origin. From this displacement and the values of G(w) and the relaxing part of the bulk modulus K(O)) the ratio of volume to shear viscosity was calculated for three liquids at atmospheric pressure and two liquids at higher pressures. The ratio Tlv/T), varied from 2.7 to 4.2 at atmospheric pressure with slightly lower values at higher pressures but the difference was notstatistically significant. Measurements of density and velocity were made on solutions of a surfactant at elevated pressures. The density measurements were fitted to the linear secant modulus equation. Investigation of the shear properties of a gel-soap solution showed that it was thixotropic. ' Finally, a conformati onal analysis at pressures above atmospheric pressure showed that the relaxation frequency was not significantly changed by increasing the pressure.

Item Type: Thesis (PhD)
Contributors: Hawkes, JC (Supervisor) and Thomas, WJO (Supervisor)
Themes: Subjects outside of the University Themes
Depositing User: Institutional Repository
Date Deposited: 22 Jul 2011 15:33
Last Modified: 27 Aug 2021 22:37
URI: http://usir.salford.ac.uk/id/eprint/14883

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