MATHEMATICAL MODELING OF TRANSMISSION CHARACTERISTICS OF PIEZOELECTRIC TRANSDUCERS IN THE REGIME OF LAMB WAVES EXCITATION

Abstract

The calculation scheme of the transducer of a contact type with a piezoelectric element of a disk-form was considered. The transducer radiates the elastic waves in a massive metal plate through the layer of matching liquid. The  coefficient of transmission from the electrical to the mechanical side of the piezoelectric disc was calculated. It was shown that for the effective operation of the radiator at high frequencies, it is necessary to choose the discs with the smallest possible diameter. The motion of material particles in the layer of the matching liquid was researched. It was shown that this layer is a peculiar resonator, which significantly modifies the spectral structure of the pulse pressure, which is formed on the metal plate surface. The conclusion was made about the need to consider the existence of the matching liquid layer as well as the  thickness of this layer. The expressions for calculating the amplitudes of normal Lamb waves, which are excited by the normal stresses acting on one side of the sheet were obtained. For the first time there were obtained the calculated relations that take into account the effect of geometrical,  physical and mechanical properties of all the elements of the ultrasonic transducer of a contact type on the efficiency of excitation of normal Lamb waves in a given frequency range. This relations can be used in the design of new devices for nondestructive testing of metalrolling.