Torsional Stress Waves in a Circular Cylinder With a Modulated Surface

The paper describes a theoretical and experimental study pertaining to torsional stress wave motion in an axisymmetric waveguide whose cross-sectional area varies periodically as a function of the axial coordinate. Dispersion relations for the phase speed are obtained for both nonresonant and resonant conditions, using perturbation techniques for small amplitude, sinusoidal modulation. Resonant conditions exist when the modulation wave number is proportional to the sum or difference of wave numbers corresponding to various modes of the torsional stress wave. The experiments consist of measuring the stress wave speed in waveguides with threaded surfaces. The experimental observations verify the general trends predicted by the theory.