Thick hollow cylindrical waveguides: A theoretical, numerical and experimental study

The paper investigates elastic waves guided by thick-walled, hollow cylindrical structures. Theoretical, numerical and experimental investigations are presented to facilitate understanding of various wave propagation phenomena in thick-walled cylinders for potential damage detection applications. Semi-analytical analysis of dispersion characteristics is performed, revealing a repetitive pattern of coupled pairs of higher-order longitudinal modes. This behaviour is found to be analogue to terrace-like structures formed by interlacing high-frequency symmetric and antisymmetric plate mode curves. A hyperbolic behaviour of curves and modeshape transitions is observed due to mode coupling. The work presented demonstrates analytically how solutions for a thick-walled hollow cylinder correspond to the Lamb wave theory. The relevant pseudo-symmetry relations for mode displacement patterns are obtained using asymptotic approximations of Bessel functions. Theoretical solutions of dispersion characteristics are compared with numerical simulations that are based on the local interaction simulation approach. The results are validated experimentally using laser vibrometry.