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Quantification of knots in dimension lumber using a single-pass X-ray radiation
Journal of Wood Science volume 55, pages 264–272 (2009)
Abstract
The knot depth ratio (KDR) evaluation method was designed to quantitatively evaluate the amount of knot in dimension lumber by a single-pass X-ray radiation. To verify the proposed method, KDR values for 38-mm-thick specimens were predicted, and they were compared with the actual measured KDR values. The knot is surrounded by the transition zone, and the density of the knot and the transition zone is higher than the clear wood. Because the average density of the transition zone was similar to the knot density, it was found that the proposed method gives the KDR values for the knot area including the transition zone. The coefficients of determination between the predicted and measured KDR values were 0.87 and 0.83 for Japanese larch and red pine specimens, respectively. Using the KDR information, the ratio of knot area including transition zone to cross-sectional area was calculated. The presence of latewood and earlywood in the same path of the X-ray radiation caused discrepancies in the estimation of KDR values because the density of latewood is much higher than that of earlywood. Fortunately, latewood and earlywood are repeated in a cross section, so the amount of overestimation and underestimation was expected to be nearly identical. As expected, the relationship between the predicted area ratio and the real area ratio of knot and transition zone was strong with R 2 values of 0.89 and 0.93 for Japanese larch and red pine specimens, respectively.
References
Riberholt H, Madsen PH (1979) Strength of timber structures, measured variation of the cross sectional strength of structural lumber. Report R 114, Structural Research Laboratory, Technical University of Denmark
Schniewind AP, Lyon DE (1971) Tensile strength of redwood dimension lumber II. Prediction of strength values. Forest Prod J 21:45–55
Johansson CJ, Brundin J, Gruber R (1992) Stress grading of Swedish and German timber. A comparison of machine stress grading and three visual grading systems. Swedish National Testing and Research Institute, SP Report 1998:38
Machado JS, Sardinha RA, Crus HP (2007) Feasibility of automatic detection of knots in maritime pine timber by acousto-ultrasonic scanning. Wood Sci Technol 38:277–284
Baradit E, Aedo R, Correa J (2006) Knots detection in wood using microwaves. Wood Sci Technol 40:118–123
Gerhards CC (1982) Effect of knots on stress waves in lumber. Research Paper FPL-RP-384. USDA Forest Products Laboratory, Madison, WI, USA
Hu C, Tanaka C, Ohtani T (2004) Location and identifying sound knots and dead knots on sugi by the rule-based color vision system. J Wood Sci 50:115–122
Lam F, Barrett D, Nakajima S (2005) Influence of knot area ratio on the bending strength of Canadian Douglas fir timber used in Japanese post and beam housing. J Wood Sci 51:18–25
Madsen B (1992) Structural behaviour of timber. Timber Engineering, pp 52–79
Institute of Isotopes of the Hungarian Academy of Sciences (1986) Industrial application of radioisotopes. Elsevier, Amsterdam, pp 232–239
Kim KM, Lee SJ, Lee JJ (2006) Development of portable X-ray CT system I - evaluation of wood density using X-ray radiography. J Korean Wood Sci Technol 34:15–22
Sahlberg U (1995) Influence of knot fibers on TMP properties. TAPPI J 78:162–168
Oh JK, Kim KM, Shim K, Park JH, Kim WS, Yeo H, Lee JJ (2007) Prediction of bending performance for Japanese larch lumber: Xray scanning. Proceedings of the Korean Society of Wood Science and Technology Annual Meeting, Yeosu, pp 71–72
Kim KM, Lee SJ, Lee JJ (2006) Development of portable X-ray CT system II - CT image reconstruction of wood using density distribution. J Korean Wood Sci Technol 34:23–31
Lee SJ, Kim KM, Lee JJ (2006) Application of the X-ray CT technique for NDE of wood in field. Key Eng Mater 321-323:1 172-1176
Rojas G, Condal A, Beauregard R, Verret D, Hernandex RE (2006) Identification of internal defect of sugar maple logs from CT images using supervised classification methods. Holz Roh Werkst 64:295–303
Korean Standards Association (2002) Softwood structural lumber, KS F 2162
Western Wood Products Association (2005) Western lumber grading rules 05. pp 143–148
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Oh, JK., Shim, K., Kim, KM. et al. Quantification of knots in dimension lumber using a single-pass X-ray radiation. J Wood Sci 55, 264–272 (2009). https://doi.org/10.1007/s10086-009-1031-7
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DOI: https://doi.org/10.1007/s10086-009-1031-7