Torsional dispersion relations of waves in an infinitely long clad cylindrical rod

The dispersion relations of torsional waves propagating in a system consisting of an elastic rod of radius a embedded in a linear elastic medium are investigated. Phase speeds of waves of wavelength λ which propagate under steady‐state conditions are determined. The dispersion relations are found to be dependent on the geometric ratio a/λ, as well as on nondimensional ratios of the rod‐medium properties. The frequency equation obtained is analyzed and upper and lower bounds on the phase speed are determined. It is shown that torsional waves can propagate freely only if the propagation speed of torsional waves in the corresponding free rod is less than that of shear waves propagating in the medium. Results are presented by means of dispersion curves and surfaces.