Details
| Original language | English |
|---|---|
| Pages (from-to) | 1-12 |
| Number of pages | 12 |
| Journal | NDT and E International |
| Volume | 99 |
| Early online date | 25 May 2018 |
| Publication status | Published - Oct 2018 |
Abstract
In this work, we model ACU transmission in delaminations, with focus in the interference effects resulting from multiple ultrasonic reflections within the delamination layers and the resulting changes in the amplitude and time of flight. For this purpose, we propose a simplified analytical model, which we cross-validate with full-wave finite-difference time-domain (FDTD) simulations. Both models show a very high agreement on the predicted ultrasound waveforms, with amplitude deviations less than 0.15 dB and time deviations below 0.1 μs. The reduction of ultrasound signal amplitude at debonding was validated with experiments. A simple engineering formula in function of delamination gap and transducer frequency was sufficient to model experimental transmission values for a gap thickness range from 70 to 2000 μm with an uncertainty below 2 dB. Furthermore, consistent resonance frequencies were identified in both experiments and simulations. The use of pulsed ultrasound signals reduces undesired resonances and provides a consistent amplitude reduction across the full range of delamination gaps. Apart from interference effects, the effect of the finite size of the ultrasound transducers as well as diffraction effects were empirically investigated. As a result of these, the lateral resolution is reduced and the sound tends to propagate through the bonded region next to the delamination. Diffraction effects are strongly influenced by wood anisotropy, with lower lateral resolution in the grain direction.
Keywords
- Air-coupled ultrasound, Composite materials, Debond, Experiment, Ultrasonic modeling
ASJC Scopus subject areas
- Materials Science(all)
- Physics and Astronomy(all)
- Condensed Matter Physics
- Engineering(all)
- Mechanical Engineering
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In: NDT and E International, Vol. 99, 10.2018, p. 1-12.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Modeling of delamination detection utilizing air-coupled ultrasound in wood-based composites
AU - Marhenke, Torben
AU - Neuenschwander, Jürg
AU - Furrer, Roman
AU - Twiefel, Jens
AU - Hasener, Jörg
AU - Niemz, Peter
AU - Sanabria, Sergio J.
N1 - Publisher Copyright: © 2018 Elsevier Ltd Copyright: Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2018/10
Y1 - 2018/10
N2 - In this work, we model ACU transmission in delaminations, with focus in the interference effects resulting from multiple ultrasonic reflections within the delamination layers and the resulting changes in the amplitude and time of flight. For this purpose, we propose a simplified analytical model, which we cross-validate with full-wave finite-difference time-domain (FDTD) simulations. Both models show a very high agreement on the predicted ultrasound waveforms, with amplitude deviations less than 0.15 dB and time deviations below 0.1 μs. The reduction of ultrasound signal amplitude at debonding was validated with experiments. A simple engineering formula in function of delamination gap and transducer frequency was sufficient to model experimental transmission values for a gap thickness range from 70 to 2000 μm with an uncertainty below 2 dB. Furthermore, consistent resonance frequencies were identified in both experiments and simulations. The use of pulsed ultrasound signals reduces undesired resonances and provides a consistent amplitude reduction across the full range of delamination gaps. Apart from interference effects, the effect of the finite size of the ultrasound transducers as well as diffraction effects were empirically investigated. As a result of these, the lateral resolution is reduced and the sound tends to propagate through the bonded region next to the delamination. Diffraction effects are strongly influenced by wood anisotropy, with lower lateral resolution in the grain direction.
AB - In this work, we model ACU transmission in delaminations, with focus in the interference effects resulting from multiple ultrasonic reflections within the delamination layers and the resulting changes in the amplitude and time of flight. For this purpose, we propose a simplified analytical model, which we cross-validate with full-wave finite-difference time-domain (FDTD) simulations. Both models show a very high agreement on the predicted ultrasound waveforms, with amplitude deviations less than 0.15 dB and time deviations below 0.1 μs. The reduction of ultrasound signal amplitude at debonding was validated with experiments. A simple engineering formula in function of delamination gap and transducer frequency was sufficient to model experimental transmission values for a gap thickness range from 70 to 2000 μm with an uncertainty below 2 dB. Furthermore, consistent resonance frequencies were identified in both experiments and simulations. The use of pulsed ultrasound signals reduces undesired resonances and provides a consistent amplitude reduction across the full range of delamination gaps. Apart from interference effects, the effect of the finite size of the ultrasound transducers as well as diffraction effects were empirically investigated. As a result of these, the lateral resolution is reduced and the sound tends to propagate through the bonded region next to the delamination. Diffraction effects are strongly influenced by wood anisotropy, with lower lateral resolution in the grain direction.
KW - Air-coupled ultrasound
KW - Composite materials
KW - Debond
KW - Experiment
KW - Ultrasonic modeling
UR - http://www.scopus.com/inward/record.url?scp=85053704505&partnerID=8YFLogxK
U2 - 10.1016/j.ndteint.2018.05.012
DO - 10.1016/j.ndteint.2018.05.012
M3 - Article
AN - SCOPUS:85053704505
VL - 99
SP - 1
EP - 12
JO - NDT and E International
JF - NDT and E International
SN - 0963-8695
ER -