Analysis of wave scattering from non-symmetric discontinuities in one-dimensional waveguides

Predicting the scattering from waves that are incident on a damaged section of structure is of importance in structural health monitoring and nondestructive testing techniques to detect dam-age. High frequency waves are generally involved, and simple models which cannot capture the dynamic behaviour of the waveguides at high frequency, can result in experimental failure and misinterpretation of the results. Moreover, damage is generally non-symmetrical with respect to the neutral axis of the structure, resulting in wavemode conversion and different reflected and transmitted waves propagating with different velocities. The aim of this work is to investigate wave reflection and transmission over a wide frequency range due to non-symmetric discontinuities in a one-dimensional waveguide. These can be either fluid-filled pipes or plates or beams with point discontinuities or finite length damage. In this work, wave propagation analysis for the undamaged waveguide is carried out using the wave finite element method, where a small segment of the waveguide is modelled using a number of solid or plane elements which can describe both rich wave behaviour and wavemode conversion. Continuity and equilibrium conditions are imposed at the interfaces using a wave-matrix based approach and the scattering matrix is obtained, together with the power reflection and transmission ratios. These provide valuable information about the effect of damage on the propagating waves. A numerical example is presented which consists of a change of cross-sectional area.