A phase velocity filter for the measurement of lamb wave dispersion

The complex, multi-modal and dispersive nature of guided waves makes them extremely effective in the non destructive evaluation of plate-like structures. Knowledge of the dispersion relation of a material is a prerequisite to many guided wave experiments. A frequency-phase velocity map is by far the most useful representation of dispersion. These phase velocity curves can be obtained numerically by solving the Lamb equations, however instabilities and unfamiliarity with the specimen's parameters makes experimentally obtained dispersion relation desirable. Transformations can be applied to an experimentally obtained frequency-wave number map but it requires prohibitively high number of sampling points in space to resolve modes across the full bandwidth of the transducer. The phase velocity filter described here is able to extract wavelets of a particular phase velocity irrespective of frequency. When applied to the acquisition of dispersion relation, the technique exhibits reduced artefacts and is able to extract modes across the full bandwidth of the excitation. Results show a bandwidth increase of approximately 58%. © 2016, IEEE. This is an author produced version of a paper published in IEEE International Ultrasonics Symposium, IUS. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works. Uploaded in accordance with the publisher’s self-archiving policy.