TRANSIENT WAVES IN A THICK DISK

Transient elastic waves in a free thick disk are analyzed by a modal method. Eigenfunctions are determined by applying the Galerkin technique to trial functions which satisfy the differential equations and shear free conditions on all boundaries. The disk is forced concentrically by a trapezoidal pulse of short duration. The excitation is treated in two ways. The first approximates normal pressure by a body force acting over a vanishingly thin layer adjacent to the boundary. The second superimposes an inhomogeneous static problem on a homogeneous dynamic problem. In this way, stress close to the excitation is modeled accurately. Transient stress history matches closely that from a finite element and a finite difference simulation.