Analysis of Radiation Absorption of Acoustic Lamb Waves in Plates Loaded with Inviscid Nonconducting Liquid

The dependence of radiation losses in a liquid on the value of displacement component U3 normal to the plate on the surface of a piezoelectric plate for Lamb waves of various orders has been experimentally investigated. The waves whose phase velocity Vn in the plate is greater than velocity Vl of the longitudinal volumetric acoustic wave in the liquid are considered. It is shown that at low values of U3, there is no radiation into the liquid and the value of radiation losses is close to zero even at Vn > Vl, at high values of U3, the value of radiation losses is large and for Lamb waves in the YZ–LiNbO3 plate with a normalized wavelength thickness of 1.75 and a frequency of 16.97 MHz, it reaches a value of 4 dB/mm, comparable to the radiation losses of surface acoustic waves in the same material.