The dependence of Lamb wave stimulation parameters on the impedance difference between upper and lower liquid

Abstract

It is known that inhomogeneous plane waves are better capable of stimulating Lamb waves in a solid plate than homogeneous plane waves. For each Lamb mode there exists an angle of incidence and an inhomogeneity parameter that maximizes its stimulation. If for example a solid plate separates two different liquids (a lower liquid and an upper liquid), then the angle of incidence, for stimulating the same Lamb mode, is unchanged, whereas the inhomogeneity differs compared with the situation where both liquids are equal to each other. If for a given upper liquid and for a given Lamb mode this inhomogeneity difference is plotted as a function of the impedance of the lower liquid, then a linear dependence is noticed. It is noticed that all physical liquids follow this linear tendency. Furthermore, this linearity depends on the generated mode and also on the properties of the solid plate. [Work supported by The Flemish Institute for the Encouragement of the Scientific and Technological Research in Industry (I.W.T.).]