Abstract
Corrosion detection using a pulsed laser scanning system can be performed via ultrasonic wave propagation imaging. This method outputs illustrations of the wave field within the host structure; thus, it can depict wave–corrosion area interactions. Additionally, post-processing can be performed to enhance the visualization of corroded areas. The wavefield energy computed using RMS (Root Mean Square) is a validated post-processing tool capable of displaying the location and area of corrosion-damaged regions. Nonetheless, to characterize corrosion, it is necessary to determine its depth. The measurement of depth in conjunction with that of the corroded area via the RMS distribution enables the determination of all dimensions of corrosion damage. Thereafter, the flaw severity can be evaluated. This study employed a wavefield within a plate on which corrosion was developed artificially to generate frequency–wavenumber dispersion curves. The curves were compared with their counterparts from a corrosion-free plate. Alternatively, they could be compared with dispersion curves drawn using the depth and material properties of a pristine plate via a computer program. Frequency–wavenumber pairs were extracted from the dispersion curves produced using the portion of the wavefield within the corroded area. These were inserted into the Rayleigh–Lamb equation, from which depths were calculated and averaged.
Highlights
In an ultrasonic wave-based NDE (Non Destructive Evaluation), damages on plates and plate-like structural components are assessed primarily using ultrasonic guided waves rather than other types of ultrasonic waves
This study focused on corrosion damage sizing, which is based on UWPI, to determine area information and experimental dispersion curves for obtaining depth
The weight was applied because the magnitude of the propagating wave decreases with distance from the excitation; larger root mean square (RMS) values are exhibited near the excitation [35]
Summary
In an ultrasonic wave-based NDE (Non Destructive Evaluation), damages on plates and plate-like structural components are assessed primarily using ultrasonic guided waves rather than other types of ultrasonic waves. Lamb waves are generally known as plate waves because they exist in a thin plate-like isotropic material and are guided by free upper and lower surfaces. Such waves are capable of traversing a relatively large distance, compared to other types of waves, before attenuation [1,2,3]. The structural response of a plate can be measured either through a laser Doppler vibrometer [5] or a PZT (Lead Zirconate Titanate) sensor [6] These actuation-sensing pairs can be employed to scan a predefined area of a specimen by introducing a galvanometer into the Materials 2020, 13, 1436; doi:10.3390/ma13061436 www.mdpi.com/journal/materials
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