Orbital-type trapping of elastic Lamb waves

• Capturing of the Lamb wave by an axially symmetric acoustic trap has been studied.
• Results of numerical simulation, theoretical calculation and experiment are compared.
• Incident Lamb wave was converted into the wedge wave and orbital wave.
• Stroboscopic interferometer has been used to picture the wave field.

The interaction of laser-generated Lamb waves propagating in a plate with a sharp-angle conical hole was studied experimentally and numerically. Part of the energy of the incident wave is trapped within the conic area in two ways: the antisymmetric Lamb wave orbiting the center of the hole and the wave localized at the acute edge. Parameters and conditions for optimal conversion of the incident wave into the trapped modes were studied in this work. Experiments were performed using the laser stroboscopic shearography technique, which delivers the time evolution of the acoustic field in the whole area of interest. The effect of trapping can be used for efficient damping, similar to the one-dimensional acoustical black hole effect.