A Note on Critical Reflections of Elastic Waves at Free Surfaces

Abstract

The wave motion in an elastic solid given by the theory of reflection at a free surface is evanescent for certain conditions—a P (plane irrotational) wave at grazing incidence and also an SV (plane equivoluminal) wave at grazing incidence. It is shown that by the application of suitable limiting processes wave motions can be obtained for these critical circumstances. The relation of these motions to the noncritical motions is analogous to the relation of critically damped to noncritically damped vibrations.