Predicting the Strength of Sawn Products by X-ray Scanning of Logs: A Preliminary Study


  • Johan Oja
  • Stig Grundberg
  • Anders Grönlund


Grading, modulus of elasticity (MOE), modulus of rupture (MOR), partial least squares (PLS), scanning, saw logs, X-ray


The aim of the study was to investigate the possibility of predicting the strength of centerboards from Norway spruce (Picea abies (L.) Karst.) saw logs, based on simulated X-ray LogScanner measurements. The study was based on eight logs. The logs were scanned using computed tomography (CT), four centerboards were sawn from each log, and the bending stiffness (MOE) and strength (MOR) of the boards were measured. The CT-images were used for simulations of the industrial X-ray LogScanner, resulting in simulated measurements of knot volume and the green density of heart-wood. Finally, multivariate models were calibrated using Partial Least Squares (PLS) regression. These models predict bending strength and stiffness based on the variables measured by the simulated X-ray LogScanner. Both bending strength and modulus of elasticity were defined as the mean value of the four boards from each log.

The results were very promising, with strong models for prediction of both MOR (R2 = 0.73) and MOE (R2 = 0.94) mean values for all four boards from each log. The results indicate that the X-ray LogScanner can be used for the sorting of saw logs according to strength and stiffness. The next step should be to repeat the study on a larger sample of material.


Boström, L. 1997. Proof-loading, en method for hållfasth-etsklassificering av konstruktionsvirke. Projektrapport: Höghållfast konstruktionsvirke, optimering av föräd-lingskedjan med ny mätteknik och förbättrade logistiksystem, Section C, M. Perstorper, ed. 12 pp. Division of Steel and Timber Structures, Chalmers University of Technology. Göteborg, Sweden.nGeladi, P., and B. R. Kowalski. 1986. Partial least-squares regression: A tutorial. Analytica Chimica Acta 185(1986):1-17.nGrundberg, S. 1994. Scanning for internal defects in logs. Licentiate thesis 1994:14 L, Luleå University of Technology, Luleå. Sweden. 121 pp.nGrundberg, S., and A. Grönlund. 1995. The development of a LogScanner for Scots pine. Pages 39-50 in O. Lindgren, ed. Proc. 2nd International Seminar/Workshop on Scanning Technology and Image Processing on Wood. Technical Report 1995:22 T, Luleå University of Technology. Luleå, Sweden.nGrundberg, S., and A. Grönlund. 1997. Simulated grading of logs with an X-ray LogScanner—Grading accuracy compared with manual grading. Scand. J. For. Res. 12:70-76.nGrundberg, S., and A. Grönlund. 1998. Feature extraction with the aid of an X-ray LogScanner. Pages 39-49 in A. Grönlund, O. Hagman, and O. Lindgren, eds. Proc. 3rd International Wood Scanning Seminar, August 17-19, 1998. Lövånger, Sweden. Technical Report 1998:27, Luleå University of Technology. Luleå, Sweden.nKliger, I. R., M. Perstorper, G. Johansson, and P. J. Pellicane. 1995. Quality of timber products from Norway spruce, part 3. Influence of spatial position and growth characteristics on bending stiffness and strength. Wood Sci. Technol. 29:397-410.nKollman, F. F. P., and W. A. Côté. 1968. Principles of wood science and technology, vol. 1. Solid wood. Springer-Verlag, Berlin, Germany. Pp. 292-375.nOja, J., S. Grundberg, and A. Gronlund. 1998a. Simulated control of sawing position based on X-ray LogScanner measurements. Pages 51-58 in A. Grönlund, O. Hagman, and O. Lindgren, eds. Proc. 3rd International Wood Scanning Seminar, August 17-19, 1998. Lövånger, Sweden. Technical Report 1998:27, Luleå University of Technology. Luleå, Sweden.nOja, J., S. Grundberg, and A. Gronlund. 1998b. Measuring the outer shape of Pinus sylvestris saw logs with an X-ray LogScanner. Scand. J. For. Res. 13:340-347.nRoss, R. J., K. A. McDonald, D. W. Green, and K. C. Schad. 1997. Relationship between log and lumber modulus of elasticity. Forest Prod. J. 47(2):89-92.nSandoz, J. L. 1996. Ultrasonic solid wood evaluation in industrial applications. Pages 147-153 in J. L. Sandoz, ed. Proc. 10th International Symposium on Nondestructive Testing of Wood, Lausanne, Switzerland, August 26-28, 1996. Swiss Federal Institute of Technology, Chair of Timber Construction. Lausanne, Switzerland.nWang, X. 1998. Pulp log sorting based on growth rings and wood density obtained by image analysis of X-ray and optical data. Dr. Scient thesis, Image Processing Laboratory, Department of Informatics, University of Oslo, Norway. 103 pp.nANON. 1995. SS-EN 408, Timber structures—Structural timber and glued laminated timber: Determination of some physical and mechanical properties. SIS Förlag AB, Stockholm, Sweden.nANON. 1998. User's guide to SIMCA Version 7.0. Umetri AB. Umeå, Sweden. 230 pp.nAratake, S., T. Arima, T. Sakoda, and Y. Nakamura. 1992. Estimation of modulus of rupture (MOR) and modulus of elasticity (MOE) of lumber using higher natural frequency of log in pile of logs. Mokuzai Gakkaishi 38(11):995-1001.n






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