Boundary resonance in a semi-infinite elastic rigidly fixed waveguide

On the basis of a numerical analysis, a boundary resonance in a semi-infinite elastic waveguide with mixed boundary conditions, when a part of the surface is rigidly fixed while a force which is harmonically dependent on time is imposed on the other part, is found and analysed. Here, the frequency found for the boundary resonance lies below the first stopping frequency of the waveguide so that the boundary resonance in the situation being considered is of the same nature as a resonance in a system without damping: an unlimited increase is observed in the amplitudes of the characteristics of the wave field as the frequency of the vibrations tends to a value Ω_e, unlike the conventional form of a resonance with finite amplitudes [1–3]. The specific behaviour of the amplitude of excitation of a normal wave with a purely imaginary propagation constant in the neighbourhood of the frequency of the boundary resonance Ω_e is found.