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Experimental and numerical investigation of effect of sawn timber dimensions in ultrasonic velocity measurements of Spanish softwoods

D. F. LLana, S. J. Sanabria, G. Iñiguez-Gonzalez, F. Arriaga, P. Niemz
Proc. 18th International Symposium on Non-destructive Testing and Evaluation of Wood
Madison, WI, USA 2013

Abstract

Ultrasonic sound velocity measurements with hand-held equipment remain due to their simplicity among the most used methods for non-destructive grading of sawn woods, yet a dedicated normalization effort with respect to strength classes for Spanish species is still required. As part of an ongoing project with the aim of definition of standard testing methods, the effect of the dimensions of commonly tested Scots pine (Pinus sylvestris L.) timbers and equipment testing frequency on ultrasonic velocity were investigated. A dedicated full-wave finite-difference time-domain software allowed simulation of pulse propagation through timbers of representative length and section combinations. Sound velocity measurements vL were performed along the grain with the indirect method at 22 kHz and 45 kHz for grids of measurement points at specific distances. For sample sections larger than the cross-sectional wavelength ?RT, the simulated sound velocity vL converges to vL = (CL/?)0.5. For smaller square sections the sound velocity drops down to vL = (EL/?)0.5, where CL, EL and ? are the stiffness, E-modul and density, respectively. The experiments confirm a linear regression between time of flight and measurement distance even at less than two wavelength <2?L distance, the fitted sound speed values increased by 15% between the two tested frequencies.


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@InProceedings{eth_biwi_01115,
  author = {D. F. LLana and S. J. Sanabria and G. Iñiguez-Gonzalez and F. Arriaga and P. Niemz},
  title = {Experimental and numerical investigation of effect of sawn timber dimensions in ultrasonic velocity measurements of Spanish softwoods},
  booktitle = {Proc. 18th International Symposium on Non-destructive Testing and Evaluation of Wood},
  year = {2013},
  pages = {710},
  publisher = {USDA Forust Products Laboratory},
  keywords = {}
}