Spectral Analysis of Elastic Waves Scattered by Objects with Smooth Surfaces

This is a summary of the research on NDE performed during the last two years by the authors and Professor W. Sachse and Messrs . S. Sancar and G. C. C. Ku of the Department of Theoretical and Applied Mechanics at Cornell University. The report is divided into three parts: (1) Theoretical Spectra-Results based on the method of wave function expansion and the method of transition matrix (T-matrix) will be presented for the scattering by a circular cylindrical, elliptic cylindrical, spherical, and spheroidal (prolate or oblate) inclusions in solids. Additional results for the scattering by two circular cylindrical inclusions will also be shown. (2) Interpretation of Spectra - Spectra of a fluid inclusion may be interpreted on the basis of the theory of normal modes, and those of a cavity from the principle of interference. Spectra for two cylindrical cavities exhibit new features which are related to the interferences of waves diffracted by each cavity. (3) Comparison with Experiments - Some of the theoretical spectra are compared with experimental results obtained by Professor W. Sachse and his associates