Propagation of ultrasonic waves in porous ceramics

Theoretical problems concerning the propagation of ultrasonic waves in a porous medium are outlined. The propagation velocity of longitudinal ultrasonic waves in an elastic medium with spherical gaseous inclusions is considered in detail. The calculation method adopted consists of determining equivalent elasticity moduli of the porous medium. The calculation of these moduli is based on the work of H. Mackenzie on media containing spherical gaseous inclusions of various diameters. The theoretical results obtained for the propagation velocity of ultrasonic waves, are compared with those measured on electrical porcelain, the latter constituting a model of a porous medium. Also a method allowing for the effect of composition of the porcelain mass to be taken into account, is described. The results of measurements of the propagation velocity of a longitudinal wave are found to be in good agreement with theoretical data. This conformity allows for non-destructive tests of products containing spherical gaseous inclusions.