The effect of wall discontinuities on the propagation of flexural waves in cylindrical shells

Abstract

The transmission of flexural waves through various discontinuities in the walls of cylindrical shells is theoretically investigated. The discontinuities consist of changes in wall thickness or wall material. The solution employs matching boundary conditions with all propagating and evanescent waves provided by the Flügge solution of the cylindrical shell problem. The curves obtained predict high transmission losses at the cut‐on frequencies of various axial and torsional waves and at high frequencies approach the flat plate solution. It is also shown that, due to the strong generation of nonflexural waves, the evaluation of transmission losses at a discontinuity by measurement of radial vibrational velocity alone can give a highly misleading result. The attenuation produced by a change in wall material was found to depend more strongly upon the ratios of phase speeds of the materials than their relative stiffnesses, and falls markedly at the ring frequency of the incident pipe due to improved coupling of flexural waves in both materials. The inclusion of damping in the analysis was found to increase the transmission losses. [Work supported by MOD].