A study of transient elastic wave propagation in a bimaterial modeling the thorax

The transient response of an elastic bimaterial, made out of a ‘‘hard’’ medium and a ‘‘soft’’ medium, welded at a plane interface, have been investigated by using an integral transform technique that permits isolation of the pressure and shear waves contributions to the wave-field. The method, often referred to as the generalized ray/Cagniard-de Hoop method (GR/CdH), is briefly presented. The wave motion is generated alternatively by a buried point source of strain rate and by a point force perpendicular to the free surface of the bimaterial. New simplified solutions are derived for points located on the axis perpendicular to the interfaces and passing through the source. Owing to the formalism, an approximation to the strain energy is shown to be readily obtained. The numerical schemes for the implementation of the exact three-dimensional GR/CdH are presented. Numerical examples are concerned with the propagation of an impact wave in the thorax modeled as a bimaterial (thoracic wall–lung). The effects of the weakcoupling between the thoracic wall and the lung are investigated. The distributions of transient strain energies, respectively carried by the pressure and the shear waves in the media representing the lung, are plotted