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Principles Of Optics Electromagnetic Theory Of Propagation Interference And Diffraction Of Light

Review of the use of air-coupled ultrasonic technologies for nondestructive testing of wood and wood products

/pdf/acoustics-of-layered-media-i-plane-and-quasi-plane-waves-l-m-4s6ss9tr1q.pdf

Acoustics of layered media I. Plane and quasi-plane waves L. M. Brekhovskikh and O. A. Godin, Springer Series on Wave Phenomena, vol. 5, Springer-Verlag, Berlin, 1990, x + 240 pp, hardcover ISBN 3-540-51038-9, DM 128.

https://hal.archives-ouvertes.fr/hal-03026118/document

Impact damage assessment in biocomposites by micro-CT and innovative air-coupled detection of laser-generated ultrasound

High-frequency ultrasonic methods for determining corrosion layer thickness of hollow metallic components.

Stress corrosion cracking (SCC) is a serious threat to gas pipelines that is challenging to detect with current in-line inspection technologies. Recently, the potential to detect SCC with Guided Ultrasonic Waves (GUW) using Halfwave's ART Scan® tool was successfully demonstrated in pressurized gas on real pipe samples. In this work, the ultrasonic detection of SCC is demonstrated by 3-meter-long pull-through experiments with a modified ART Scan® tool consisting of 132 broad-band transducer inside a pressure tank with pressurized gas at 60 bar as acoustic coupling medium. Mechanical translation and rotation from inside 4.6 meter long test spools allowed the acquisition of C-scans with resolutions down to $1.6\ \mathrm{mm}\times 0.2^{\circ}$ . Acoustic signals were received in pitch-catch mode and processed to calculate different parameters like spectral power. Processed 2D scan results demonstrated the detection of crack regions and artificial notches. Resulting plots also demonstrated the sensitivity to undesired low-energy areas, of which some highly correlated with misalignment between the tool and the inner pipe wall. The crack sizing potential was successfully demonstrated by initial sizing algorithms applied to artificial notches that were machined one of the test pipes.

Ultrasonic detection of crack defects in pipe samples with a 132-channel test scanner in gas

Previously reported measurement have shown how air-coupled ultrasound transmission measurements can be used to measure the thickness of steel plates, resolving thickness variations down to 0.2 mm. Simple plane wave theory predicts that at normal incidence, the steel plate is excited into compressional resonances when the plate thickness is an integer number of halfwavelengths. No shear waves are excited at normal incidence. The plate investigated previously had thickness 10.15 mm, with half-wave resonances expected at 288.18 kHz and 576.35 kHz. Transmission measurements on this plate showed resonance peaks at 267.33 kHz, 464.63 kHz and 571.98 kHz. The former and latter values deviate by 7% and 0.7%, respectively, from the values predicted by the plane wave model. The peak at 464.6 kHz was assumed to be due to the third harmonic resonance of the shear wave, but this was not confirmed. The aim of this work is to investigate whether this deviation can be explained by using a more realistic model for the plate, including shear waves and the finite extent of the source and receiver. A frequency domain model was developed using the wavenumber integration method. The transducer is modeled as a plane piston in an infinite planar baffle and the sound field is decomposed into plane waves over a range of angles. The stainless steel plate is modeled as an elastic layer, including compressional and shear waves, immersed in a fluid. The impulse response of this system was found by multiplying the plane wave decomposition of the sound field from the transducer with the transmission coefficient for the stainless steel plate and integrate over all angles. The transmitted sound pulse was then found by convolving this impulse response and the transmitted pulse, a chirp covering the frequency range from 200 kHz to 800 kHz Compared to the previously reported experimental results, the developed model was able to explain the deviation of the lowest pressure wave resonance peak from the plane wave theory, and predicted its position within 2%. The existence of the shear wave resonance was confirmed, and the position of the observed peak explained within the accuracy of the shear wave velocity of the steel plate.

Model for thickness measurements of steel plates using half-wave resonances

Air-coupled ultrasound (ACU) is an attractive option in non-destructive testing when the target of inspection is affected by the coupling liquid, or when the target is too big to be immersed in the coupling liquid. The challenge with ACU is the huge impedance mismatch between the air and the target. In pulse-echo measurements this mismatch causes a huge difference in level between the first reflection, from the air-target interface, and the tail, from multiple reflections inside the target. This can cause the first reflection to mask the tail signal.

Petter Norli

Papers

Ultrasonic detection of crack defects in pipe samples with a 132-channel test scanner in gas

Model for thickness measurements of steel plates using half-wave resonances

Feasibility of pulse-echo thickness measurements in air with a laterally displaced receiver