LXII. Reflection of elastic waves from a free boundary

A dilatation wave incident on a free surface produces reflected dilatation and distortion waves. The relation between the amplitudes of these waves has already been calculated when the reflection occurs at the surface of an elastic half-space. It is shown in this paper that a similar relation holds for a plane pulse travelling in a plate and reflected from a free edge. An experimental method is described for investigating this reflection problem, together with the results obtained. Agreement between experiment and the classical reflection theory is found to be good, provided that care is taken in defining the observed variables. At glancing incidence the phenomenon should be considered as one of diffraction ; however Roesler (1954) has shown that by suitable choice of variables an explanation is possible in terms of reflection theory. His results are found to be in agreement with experiment.