Characterisation of guided wave dispersion in isotropic tubes based on damping finite element boundaries

Guided waves are suitable for non-destructive testing and structural health monitoring of tube-like structures. However, the dispersion phenomenon impedes the application of guided waves. Although the finite element (FE) method can simulate the guided wave propagation and help to study the dispersion phenomenon, boundary reflections can contaminate the wave field of interest and impede the FE simulation. In this paper, damping boundaries are developed as a set of FE frames with gradually increasing damping coefficients to alleviate boundary reflections. The wave signals simulated through the FE model with the damping boundaries only contain the waves from the transmitter to the receiver, without the interferences of the boundary reflections. The energy distribution on the frequency-velocity spectrum of the simulated signals agrees well with the analytical dispersion curves, indicating that the boundary reflections are effectively alleviated. The analytical solution of the guided wave equation and the FE modelling method presented in this paper can facilitate both research and applications of guided waves for tube-like structures.