Experimental Results of Stress Wave Investigations

Abstract

Experimental work plays two distinct rôles in the study of stress wave propagation in solids. The first of these is to verify conclusions which have been reached as a result of the mathematical analysis of a dynamic elastic type of loading, or to find the wave pattern in situations where mathematically the problem is a perfectly well-posed one with well-defined initial or boundary conditions, but where the complexity of the mathematical analysis is such that it is impossible to obtain a solution in analytic form. In either of these situations the stress wave experiments are acting as analog computers solving known partial differential equations with well-defined boundary conditions. This type of experiment is a dynamic counterpart of the use of stress analysis techniques to the static elastic loading of engineering structures, where by the use of photoelastic models or of electrical strain gages on elastic models, the strains are measured under conditions of quasi-static loading. The geometry of these structures is generally too complicated to be treated analytically, and although the constitutive relations between the stress and strain tensors is well-established, (the material is assumed to obey Hooke’s Law), and the boundary conditions are perfectly well-defined, an analytic solution cannot in general be obtained, and experiments have to be carried out to determine the form of the elastic solution.