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Monitored assessment of structural integrity of multilayered glued laminated timber beams with air-coupled ultrasound and contact ultrasound imaging

S. J. Sanabria, R. Furrer, J. Neuenschwander, P. Niemz, U. Sennhauser
Proc. 17th International Symposium on Non-destructive Testing and Evaluation of Wood
Sopron, Hungary 2011

Abstract

Air-coupled ultrasound inspection of bonding defects in up to 520 mm high glulam was for the first time demonstrated. A careful system design with off-the-shelf transducers and electronics, together with specific signal processing achieve the required signal-to-noise ratio. For well-defined annual ring orientations (T, R) the lateral resolution was found to be anisotropic and higher in beam width (RT plane) than in beam length (L) directions. Bonding defects in commercial 395 mm and 520 mm thick glulam were assessed with 100 kHz and 50 kHz transducers. Ther repeatability error was +-0.6 dB even for 395 mm high glulam. ACU images of the same beam, before and after introduction of lamination defects, were compared. The main wave propagation phenomena were discussed with the help of analytical and numerical models. In the second part of the work, an automated dry contact shear wave imaging system was developed for single-sided inspection of bonding defects in individual glue lines, the amplitude repeatability error was <10%, surface waves were found to be most sensitive to bonding defects at beam width edges.


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@InProceedings{eth_biwi_01119,
  author = {S. J. Sanabria and R. Furrer and J. Neuenschwander and P. Niemz and U. Sennhauser},
  title = {Monitored assessment of structural integrity of multilayered glued laminated timber beams with air-coupled ultrasound and contact ultrasound imaging},
  booktitle = {Proc. 17th International Symposium on Non-destructive Testing and Evaluation of Wood},
  year = {2011},
  pages = {359-366},
  publisher = {University of West Hungary},
  keywords = {}
}