Theory and numerical calculation of the acoustic field produced in metal by an electromagnetic ultrasonic transducer

Abstract

The equations for calculating the acoustic field produced within a nonmagnetic metal by an interaction of eddy current with a static magnetic field were obtained on the assumptions that (1) an ultrasonic wave is generated by the electromagnetic force through classical and macroscopic phenomena; (2) the electric, magnetic, and elastic properties of the metal are linear, isotropic, and homogeneous throughout the metal, which occupies semi-infinite space; (3) the whole system is axially symmetric; and (4) eddy currents and elastic waves show a steady-state sinusoidal variation. The acoustic field produced by a specific electromagnetic ultrasonic transducer with axial symmetry was calculated numerically, and the results showed a well-defined ultrasonic wave beam, which was narrower than had been expected from the size of the transducer. Subject Classification: [43]35.60; [43]85.48.