Journal of the Korean Wood Science and Technology

The Korean Society of Wood Science & Technology (한국목재공학회)
권호 표지
DOI QR코드

DOI QR Code

Determination of Air-dry Density of Wood with Polychromatic X-ray and Digital Detector

  • Kim, Chul-Ki (Department of Forest Products, National Institute of Forest Science) ;
  • Kim, Kwang-Mo (Department of Forest Products, National Institute of Forest Science) ;
  • Lee, Sang-Joon (Department of Forest Products, National Institute of Forest Science) ;
  • Lee, Jun-Jae (Department of Forest Sciences, Seoul National University)
  • Received : 2017.10.16
  • Accepted : 2017.11.08
  • Published : 2017.11.25
Download PDF
⟨ Previous Next ⟩

Abstract

Gravimetric method is usually used to evaluate air-dry density, which is governing physical or mechanical properties of wood. Although it had high evaluation accuracy, the method is time consuming process. Thus, this study was conducted to estimate air-dry density of wood with high accuracy by using polychromatic X-ray and digital detector as alternative of gravimetric method. To quantify polychromatic X-ray projection for evaluating air-dry density, Lambert-Beer's law with the integral value of probability function was used. The integral value was used as weighting factor in the law, and it was determined by conducting simple test at various penetration depths and tube voltage. Mass attenuation coefficient (MAC) of wood also calculated by investigating polychromatic X-ray projection according to species, penetration depth and tube voltage. The species had not an effect on change of MAC. Finally, an air-dry density of wood was estimated by applying the integral value, MAC and Lambert-Beer's law to polychromatic X-ray projection. As an example, the relation of the integral value (${\alpha}$) according to penetration depth (t, cm) at tube voltage of 35 kV was ${\alpha}=-0.00091t{\times}0.0184$ while the regression of the MAC (${\mu}$, $cm^2/g$) was ${\mu}=0.5414{\exp}(-0.0734t)$. When calculation of root mean squared error (RMSE) was performed to check the estimation accuracy, RMSE at 35, 45 and 55 kV was 0.010, 0.013 and $0.009g/cm^3$, respectively. However, partial RMSE in relation to air-dry density was varied according to tube voltage. The partial RMSE below air-dry density of $0.41g/cm^3$ was $0.008g/cm^3$ when tube voltage of 35 kV was used. Meanwhile, the partial RMSE above air-dry density of $0.41g/cm^3$ decreased as tube voltage increased. It was conclude that the accuracy of estimation with polychromatic X-ray and digital detector was quite high if the integral value and MAC of wood were determined precisely or a condition of examination was chosen properly. It was seemed that the estimation of air-dry density by using polychromatic X-ray system can supplant the gravimetric method.

Keywords

References

  1. Brooks, R.A., Di Chiro, G. 1976. Beam hardening in x-ray reconstructive tomography. Physics in medicine and biology 21(3): 390. https://doi.org/10.1088/0031-9155/21/3/004
  2. Bucur, V. 2013. Nondestructive characterization and imaging of wood, Springer-Verlag Berlin Heidlberg, New York, USA.
  3. Goy, B., Martin, P., Leban, J.-M. 1992. The measurement of wood density by microwave sensor. Holz als Roh-und Werkstoff 50(4): 163-166. https://doi.org/10.1007/BF02663259
  4. Hoffmeyer, P., Pedersen, J. 1995. Evaluation of density and strength of Norway spruce wood by near infrared reflectance spectroscopy. European Journal of Wood and Wood Products 53(3): 165-170. https://doi.org/10.1007/BF02716418
  5. Kaelble, E.F. 1967. Handbook of X-rays, McGraw-Hill Education, New York, USA.
  6. Kim, C.-K. 2016. Nondestructive Evaluation of Wood with Reconstructed Polychromatic X-ray Image. Doctoral dissertation, Seoul National University Korea.
  7. Kim, C.-K., Oh, J.-K., Hong, J.-P., Lee, J.-J. 2014. Density calculation of wood by portable X-ray tube with consideration of penetrating depth. Journal of Wood Science 60(2): 105-110. https://doi.org/10.1007/s10086-013-1381-z
  8. Kim, G.-M., Lee, S.-J., Lee, J.-J. 2006. Development of portable X-ray CT system 1 - evaluation of wood density using X-ray radiography. Journal of the Korean Wood Science and Technology 34(1): 15-22.
  9. Lifton, J.J., Malcolm, A.A., McBride, J.W. 2013. The application of beam hardening correction for industrial x-ray computed tomography. Singapore, Proc. 5th Internatioal Symposium on NDT in Aerospace.
  10. Lindgren, L. 1991. Medical CAT-scanning: X-ray absorption coefficients, CT-numbers and their relation to wood density. Wood science and technology 25(5): 341-349. https://doi.org/10.1007/BF00226173
  11. Malan, F., Marais, P. 1992. Some notes on the direct gamma ray densitometry of wood. Holzforschung-International Journal of the Biology, Chemistry, Physics and Technology of Wood 46(2): 91-97.
  12. Nishihata, T., Ohtake, Y., Suzuki, H., Moriguchi, M. 2012. A Non-Iterative Data-Driven Beam Hardening Correction for Single-Material Objects. In: Kastner, J. (ed) Maastricht, Netherlands, Proc. Conf. Industrial Computed Tomography, pp. 135-142.
  13. Olson, J.R., Liu, C., Tian, Y., Shen, Q. 1988. Theoretical Wood Densitometry: II. Optimal X-ray Energy For Wood Density Measurement. Wood and fiber science 20(2): 187-196.
  14. Phillips, E. 1960. The beta ray method of determining the density of wood and the proportion of summer wood. Journal of the Institute of Wood Science 5: 16-28.
  15. Poludniowski, G., Landry, G., DeBlois, F., Evans, P., Verhaegen, F. 2009. SpekCalc: a program to calculate photon spectra from tungsten anode x-ray tubes. Physics in medicine and biology 54(19): N433. https://doi.org/10.1088/0031-9155/54/19/N01
  16. Waggener, R.G., Levy, L.B., Rogers, L.F., Zanca, P. 1972. Measured X-Ray Spectra from 25 to 110 kVp for a Typical Diagnostic Unit 1. Radiology 105(1): 169-175. https://doi.org/10.1148/105.1.169