Metrological Performance of Hybrid Measurement Technique Applied for the Lamb Waves Phase Velocity Dispersion Evaluation

The work presents the metrological evaluation of the modified hybrid spectrum decomposition and zero-crossing technique. The presented technique enables to reconstruct the phase velocity dispersion curve part of Lamb wave modes using only two signals. This is set to consequently simplify the of complex guided wave signals analysis. Experimentally measured asymmetric A0 mode Lamb wave signals propagating in 4 mm thickness non-homogeneous Glass Fibre Reinforced Plastic (GFRP) plate are used for assessment of the proposed technique. The phase velocity dispersion curve (DC) segments are obtained using three different filter bandwidths as reference using the DC obtained by the semi-analytical finite element method SAFE. The proposed technique quantitative and qualitative characteristics are presented. Using this technique and employing various band-pass filters it is shown that the DC segments are reconstructed in approximately 50% - 88% bandwidth of the incident signal frequency spectrum. The average of the calculated expanded uncertainties for all filter bandwidths is equal to approximately 2%. The narrower filter bandwidth has produced smaller systematic errors equal to 1.8%, yielding to wider reconstructed dispersion curve segments.