Finite Element Model for Predicting Modulus of Elasticity of Lumber Measured by Stress-Grading Machines

Authors

  • Marcel Samson

Keywords:

Machine stress-rating, grading machines, lumber

Abstract

Development of a finite element model to predict modulus of elasticity of lumber as measured by bending-type stress-grading machines is discussed. The model is general in that lumber characteristics critical in machine grading, such as natural bow and local stiffness variations, can be taken into account. Simulations are carried out to compare the performance of two constant deflection machines employing different testing geometries. Results show that, depending on support conditions, grading machines may vary substantially in their ability to locate low stiffness zones along the length of lumber and identify the value of modulus of elasticity at these zones. Ability of the grading machines to test end portions of the lumber is also discussed, along with the influence of span on machine accuracy.

References

Cook, J. D. 1981. Concepts and applications on finite element analysis. John Wiley and Sons, NY.nEndersby, H. J. 1969. Survey of machine stress grading. Proceedings from IUFRO meeting, Working Group on Structural Utilization, vol. II, For. Prod. Res. Lab., Princes Risborough, England. Pp. 149-176.nGalligan, W. L., D. V. Snodgrass, and C. W. Crow. 1977. Machine stress rating: Practical concerns for lumber producers. USDA For. Serv. Gen. Tech. Rep. FPL 7, For. Prod. Lab., Madison, WI.nGlos, P. 1982. Die maschinelle Sortierung von Schnittholz, Stand der Technik-Vergleich der Verfahen. (The mechanical sorting of lumber, status of the technique-Comparison of the processes.) Holz-Zentralblatt 108:153-155.nGlos, P., and H. Schultz. 1980. Stand und Aussichten der maschinellen Schmittholzsortierung. (The state and prospects of mechanical sawn timber grading.) Holz Ron- Werkst. 38(11):409-417.nKorneev, V. I. 1980. Investigation of devices for grading lumber according to strength. Lesnoi Zhurnal 3:98-104. (In Russian.)nLogan, J. D. 1978. Machine stress rating. Proceedings of the 4th nondestructive testing of wood symposium. Vancouver, WA. Pp. 285-303.nMüller, P. H. 1968. Mechanical stress-grading of structural timber in Europe, North America and Australia. Wood Sci. Technol. 2:43-72.nThunell, B. 1969. On the premises for mechanical grading of timber. Paper and Timber 51(4):373-377.n

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Published

2007-06-28

Issue

Number 4 / October 1985

Section

Research Contributions

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