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Grunde Waag

Bio: Grunde Waag is an academic researcher from Vestfold University College. The author has contributed to research in topics: Resonance & Shear waves. The author has an hindex of 2, co-authored 4 publications receiving 35 citations. Previous affiliations of Grunde Waag include Buskerud and Vestfold University College.

Papers
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Journal ArticleDOI
TL;DR: Air-coupled ultrasonic through-transmission measurements on a steel plate with thicknesses 10.15 mm; 10.0 mm; 9.8 mm show that the resonances could be clearly identified after transmission through the steel plate, and that the frequencies of the resonance could be used to distinguish between the three plate thicknesses.

36 citations

Posted Content
TL;DR: In this paper, a method of measuring the thickness of steel plates using through transmission of an acoustic pulse is demonstrated using a stainless steel plate with regions of thickness 10:0 mm, 9:8 mm, and 9:6 mm.
Abstract: 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.

7 citations

Proceedings ArticleDOI
01 Oct 2012
TL;DR: In this article, a frequency domain model was developed using the wavenumber integration method to explain the deviation of the lowest pressure wave resonance peak from the plane wave theory, and predicted its position within 2%.
Abstract: 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.

2 citations

Proceedings ArticleDOI
23 Oct 2014
Abstract: 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.

1 citations


Cited by
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Journal ArticleDOI
TL;DR: The applications of ACU to wood characterization with reference to wood quality aspects are summarized andCorrelations between the ACU parameters and the wood properties as well as the wood defects are dealt with in detail.

64 citations

Journal ArticleDOI
TL;DR: In this paper, a non-contact set-up based on laser excitation of ultrasound and detection with a broadband, air-coupled optical microphone is presented and tested on flax/PLA laminates.

30 citations

Journal ArticleDOI
TL;DR: This work presents two high‐frequency ultrasonic non‐destructive testing technologies, including piezoelectric pulse‐echo and laser‐ultrasonic methods, for detecting corrosion of Ni superalloy from the opposite side, and demonstrates the determination of corrosion layer thickness below ˜100&mgr;m.

23 citations

Journal ArticleDOI
TL;DR: In this paper, the authors proposed to apply polyphase coded pulse compression technique to air-coupled ultrasonic testing system, which showed that the received signal is effectively improved, the transmission initial wave can be effectively identified, and the compressed signal has a good response to debonding defect.
Abstract: The finite models of honeycomb sandwich composite with intact and embedded debonding defects are constructed. The sound pressure in fluid domain and the stress strain problem in solid domain are related by acoustic-structure coupling method, which visually shows the propagation process and modal characteristics of the acoustic wave inside the honeycomb sandwich composite. The simulation results show that the transmission longitudinal wave T1 (transmission initial wave) can effectively characterize debonding defects of honeycomb sandwich composite. However, in the actual detection of honeycomb sandwich composite, there are some problems, such as poor Signal-to-noise ratio (SNR) of received signal, incognizable transmission initial wave. In order to solve these problems, this paper proposes to apply polyphase coded pulse compression technique to air-coupled ultrasonic testing system. The actual test results show that the SNR of received signal is effectively improved, the transmission initial wave can be effectively identified, and the compressed signal has a good response to debonding defect. The air-coupled ultrasonic testing C scan result of honeycomb sandwich composite verifies the rationality and correctness of the theoretical simulation and signal processing technique, which promotes industrial application of air-coupled ultrasonic testing technique in the aerospace field.

18 citations