Spatial analysis of torsional wave propagation in a cylindrical waveguide.Application to magnetostrictive generation

A spatial analysis of the generation and propagation of torsional waves in a cylindrical rod is presented. Starting from the classical linear equation of propagation and assuming a linear medium of propagation, the eigenfunct ions of the propagation operator are calculated. Under the hypothesis of se paration-of-variables type of solution, two ways of deriving the associated modes are performed. Given the normal mode basis, the behavior of a wavefr ont generated into the rod is examined. The application to the magnetostric tive generation of torsional waves is studied. Including the influence of e ddy currents on the excitation and the geometry waveguide effects on the wa ve propagation, an analytical expression of mechanical losses during the fi rst steps of propagation is given. A basic model of the interaction between a defect and the torsional guided waves is also proposed. (C) 2001 Acousti cal Society of America. [DOI: 10.1121/1.1323717].