The investigation of shear elasticity of liquids at low-frequent shear influence

In this paper shear properties of visco-elastic fluids have been investigated using an acoustic resonance method. The tested fluid is placed between the X-18 degrees cut piezoquartz resonator and the solid cover-plate at rest. Piezoquartz performed tangential oscillations at resonance frequency (74 kHz). The liquid layer undergoes shear strain and shear standing waves are excited therein. The parameters of the resonance curve of the piezoquartz depend on the thickness of the liquid layer and allow finding visco-elastic parameters of the studied liquid. The solution of the problem of interaction of piezoquartz-liquid layer-cover-plate gives three methods of determination of the real shear modulus (G) and the tangent of mechanical loss angle (tan theta). The first method is realized at smaller thickness of the liquid layer than the wavelength. Liquids of different classes have been studied using this method: polymer liquids, oils, glycols and alcohols. The second method is connected with the propagation of the shear wave in liquid layer, parameters of which determine G and tan theta. And the third method is based on the determination of the limiting shift of resonance frequencies at complete damping of the shear wave in thick layers of liquid. All these three methods give satisfactory agreement of results. The investigated low-frequency shear elasticity of liquids is a bulk property of liquids. (C) 2006 Elsevier B.V All rights reserved.