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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.

Air-coupled ultrasonic through-transmission thickness measurements of steel plates

A method of measuring the thickness of steel plates using through transmission of an acoustic pulse is demonstrated. This study has been done on a stainless steel plate with regions of thickness 10:0 mm, 9:8 mm, and 9:6 mm, using broadband pulses with energy in 200 kHz to 600 kHz band. Ultimately the goal is to perform similar air-coupled thickness measurements in a single sided pitch-catch measurement setup. 
The spectra of the transmitted pulses show the first and second harmonics of the compressional waves in the plate. When compared to a plane wave model of a fluid layer embedded in air, the second harmonic of the plate resonance fits well with the expected value. However, the first harmonic deviates such that the plate appears thicker at this resonance. This is believed to be caused by the finite aperture of the transmitting transducer, causing deviations from a plane wave. Thickness differences of 0:2 mm between the different regions of the plate were shown to be resolved. 
A third peak was found in the spectra. The origin of this peaks has not been verified, but is believed to come from the third harmonic of the shear wave in the steel plate.

Air-coupled thickness measurements of stainless steel

A long-standing challenge in integrity management of gas pipelines is stress corrosion cracking (SCC). Such cracks are difficult to detect, calling for sensitive detection methods with good coverage. Recent advances in gas-coupled broad band ultrasound provide a potential method that is based on guided plate waves. The objective of this work is to describe and experimentally evaluate this method based on Halfwave's ART Scan® tool. A water-immersed 12 mm thick steel plate with machined crack-like, spark eroded notches (SEN) of 2 and 6 mm depth, and 10 and 20 mm lengths, were acoustically investigated with broadband (0.3–1.3 MHz) transducers in a pitch-catch setup. Received signals were acquired at 2D grid locations, and pointwise processing parameters were extracted. Summed signal power and a spectral parameter demonstrated the detection of the SENs. The received energy in a selected frequency band was 2.5 and 5.5 dB lower for the 2 and 6 mm deep SENs, respectively, compared to that of an undamaged part of the plate. Using a tomographic image inversion method, the received signals were combined and converted into images. Results of the 6 mm deep SEN showed good agreement with the actual size and location of the SEN. In conclusion, the potential to detect SCC by using an ART Scan® based set-up, combined with pointwise and image formation processing, was successfully demonstrated on test plates with machined crack-like defects.

Ultrasonic detection of spark eroded notches in steel plates

Stress corrosion cracking (SCC) is a serious problem in gas pipelines. The detection of such cracks are difficult with currently available in-line inspection technologies. Recent work demonstrated the crack detection potential of using guided waves and gas-coupled broad band ultrasound by experimental detection of machined crack-like defects based on Halfwave's ART Scan® tool [1]. The present study experimentally investigated the detection of real SCC, with crack depths of up to 4.3 mm, on a real pipe, with a nominal wall thickness of 12.7mm, using broadband (0.3-1.3 MHz) transducers in a pitch-catch set-up. Acoustic signals were received by eight transducers, surrounding the transmitter, at cylindrical scan locations, and different processing parameters were extracted. 2D parameter scans displayed the crack and pitting corrosion areas. The summed power parameter resulted in signal differences of up to 8 dB for the crack area as compared to the surrounding area. In conclusion, the detection of real SCC by using an ART Scan® based set-up was successfully demonstrated on a real pipe section in water.

Ultrasonic Detection of Stress Corrosion Cracks in Pipe Samples Using Guided Waves

Stress corrosion cracking (SCC) is a serious threat to gas pipelines. Current in-line inspection tools have issues with the detection and sizing of small cracks. Advances in gas-coupled broadband ultrasound enable new detection methods based on Guided Ultrasonic Waves (GUW). Recently, the potential to detect SCC using Halfwave’s ART Scan® tool was successfully demonstrated on real pipe samples with SCC, submerged in water [1]. In this study, the ultrasonic detection of SCC is experimentally demonstrated, using pressurized gas at 60 bar as acoustic coupling medium. A custom-made test scanner with 32 transmit/receive channels was developed to perform circumferential scans of 425 mm × 60° from the inside of pipe samples of diameters close to 36 inches. The gaseous atmosphere of 60 bar (nitrogen) required the experiments to be conducted inside a pressure tank that contained both the test scanner and pipe samples. Broad-band pulses were transmitted, and signals were received from all scan positions. Processed parameters like spectral power and wall thickness estimates were calculated. 2D plots of processed parameters and reconstructed image results demonstrated the detection and sizing potential for real cracks, crack fields, and other surface irregularities.

Petter Norli

Papers

Air-coupled ultrasonic through-transmission thickness measurements of steel plates

Air-coupled thickness measurements of stainless steel

Ultrasonic detection of spark eroded notches in steel plates

Ultrasonic Detection of Stress Corrosion Cracks in Pipe Samples Using Guided Waves

Ultrasonic detection of stress corrosion cracks in pipe samples in gaseous atmosphere