Phase velocity measurement of dispersive wave modes by Gaussian peak-tracing in the f-k transform domain

The measurement of guided wave phase velocity is vital for the successful implementation of the guided wave technique for defect detection and material characterization. In this paper, an algorithm for quantitative phase velocity measurement based on f-k (frequency-wavenumber) transformation with a Gaussian fit peak-tracing is proposed. The versatility of the algorithm is demonstrated using numerically simulated data for a wide range of case studies, including non-dispersive, dispersive, dispersive with viscoelasticity, overlapping modes, and highly attenuative materials. It is further validated utilizing two experimental datasets. The maximum error in measuring phase velocity using experimental and numerical data is less than 0.8% when compared to the analytical value obtained using DISPERSE. The phase velocity values obtained with the proposed f-k transformation with a Gaussian fit peak-tracing algorithm are also compared with the conventional methods and found to be superior. Further, the proposed algorithm is suitable for evaluating the phase velocity of the coexistence of forward and reflected wave modes. Hence, the proposed algorithm is appropriate for measuring phase velocity where separation of modes or reflected signal is difficult to achieve, such as for a smaller specimen or even longer specimens with higher-order faster mode.