Assessment of flexural properties of different grade dimension lumber by ultrasonic technique

Abstract

The dimension lumber (45mm×90mm×3700mm) of plantation Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) was graded to four different classes as SS, No.1, No.2 and No.3, according to national lumber grades authority (NLGA) for structure light framing and structure joists and planks. The properties of apparent density was determined at 15% moisture content, bending strength and stiffness were tested according to American Society for Testing and Materials (ASTM) D198-99, and dynamic modulus of elasticity (E_usw) was measured by ultrasonic technique, for predicting the flexural properties of different grade lumbers. The results showed that E_usw was larger than the static MOE. The relationship between E_usw and static MOE was significant at 0.01 level, and the determination coefficients (R²) of the four grade lumbers followed the sequence as R² _No.2 (0.616)> R² _SS (0.567)> R² _No.1 (0.366)> R² _No.3 (0.137). The R² of E_usw and MOR were lower than that of the E_tru and MOR for each grade. The E_usw of all the grade lumbers, except No.3-grade, had significant correlation with the static MOE and MOR, thus the bending strength of those grade lumbers can be estimated by the E_usw. The E_tru values of four grade lumbers followed a sequence as No.2-grade (10.701 GPa) > SS-grade (10.359 GPa) > No.1-grade (9.840 GPa) > No.3-grade (9.554 GPa). For the same grade dimension lumber, its E_usw value was larger than static MOE. Mean values of MOR for four grade lumbers follow a sequence as No.2-grade (48.67 MPa) > SS-grade (48.16 MPa) > No.3-grade (46.55 MPa) > No.1-grade (43.39MPa).

Keywords

Dimension lumber / Lumber grade / Ultrasonic technique / Dynamic modulus of elasticity / Static modulus of elasticity / Modulus of rupture

References

[1] American Society for TestingMaterials. D 198-98 Test method of static tests of timbers in structural sizes, 2002, 4(10): 59-78.

[2] Bao F., Jiang Zehui. Wood properties of main tree species from plantation China, 1998 Beijing: China Forestry Publishing House

[3] Barrett, J.D., Lau, W. 1994. Canadian Lumber Properties. Canadian Wood Council.

[4] de Oliveira, F.G..R., de Campos, J.A.O., Pletz, E., Sales, A. 2002, Assessment of Mechanical Properties of Wood Using an Ultrasonic Technique. In: 13th International Symposium on Nondestructive Testing of Wood, USA, 75–78.

[5] Duju, A., Nakai, T., Nagao, H. 2000. Nondestructive evaluation of mechanical strength of sarawak timbers. In: 12^th International Symposium on Nondestructive Testing of Wood, Hungary, 131–137.

[6] Huang Anming. Modeling wood properties of Chinese fir plantation using near infrared spectroscopy, 2006 China: Chinese Academy of Forestry

[7] Kretschmann, D.E., Evans, J.W. 1999. Monitoring of visually graded structural lumber. Forest Products Laboratory, United States Department of Agriculture.

[8] Robert, R.J., Wang Xiping. 2000, Comparison of several nondestructive evaluation techniques for assessing stiffness and MOE of small-diameter logs. 12^nd International Symposium on Nondestructive Testing of Wood, Hungary, 155–163.

[9] Standard Grading Rules for Canadian Lumber. 2003. National lumber grades authority (NLGA). Approved by the American lumber standard board of review and the Canadian lumber standards accreditation board.

[10] Yin Sici. Wood qualify and defect, 1990 Beijing: China Forestry Publishing House

[11] Yin Y., Lu J., Ni C., Ren Haiqing. Evaluating static bending elastic properties of full-size lumbers by using transverse vibration method Journal of Beijing Forestry University, 2005, 27(5): 107-110.