Abstract
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.
Highlights
In recent years, the ultrasonic guided waves (UGW) are used in many industrial fields and applications due to possibility to detect defects and delaminations and to evaluate their parameters in large structures
Guided wave inspection is a convenient tool for the evaluation of the non-homogeneities in composite materials owing to sensitivity of propagation velocity to the material surface and internal defects and capability to propagate long distances with reasonable attenuation [10]–[15]
On the other hand, using the wide-band filters a small number of the filters is needed to cover the bandwidth of the signal but the phase velocity dispersion curve is reconstructed in a narrower frequency range
Summary
The ultrasonic guided waves (UGW) are used in many industrial fields and applications due to possibility to detect defects and delaminations and to evaluate their parameters in large structures. Identification of different modes offers the possibility to determine more accurately the defect location and size and/or estimation of the material properties [11] To resolve these tasks, the hybrid spectrum decomposition and zero-crossing technique for the evaluation of phase velocity dispersion relations of the Lamb wave’s fundamental modes presented in previous work was proposed [28]. B) On a non-homogeneous medium using signals obtained by 3D finite element model of Carbon Fiber Reinforced Plastic (CFRP) plate In both cases, the obtained results have verified suitability the proposed hybrid measurement technique to evaluate the Lamb waves phase velocity dispersion properties and to reconstruct the segment of dispersion curve. The processing of the selected two signals is performed and the obtain results are presented
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