Comparison between three-point and four-point flexural tests to determine wood strength of eucalyptus specimens
Keywords:
Acoustic vibration, density, Eucalyptus grandis, static bending test, stiffness, strengthAbstract
Comparison between flexural wood strength values obtained from three-point and four-point bending tests in wood were only reported in few previous works, but remains unclear. Thus, the aim of this study was to determine the relationship between wood strength (MOR) obtained by 4-point and 3-point bending tests in Eucalyptus. Two or three specimens were cut from the same scantling (thus considered as twin) and submitted to flexural vibration tests. Then 190 wood specimens were tested by 4-point bending tests and 138 twin specimens were submitted to 3-point bending tests. Wood strength determined from 3-point bending test presented significantly higher mean value (76.8 MPa) than that from 4-point bending test (73.0 MPa). A linear regression for converting MOR from 3-point to 4-point bending test was proposed for these Eucalyptus specimens: MOR4p = 0.889 × MOR3p + 5.14 in MPa (R²=0.74). The correlation of MOR in 3-point bending with density was higher (R²=0.57) than in 4-point bending (R²=0.45). The correlations between dynamic elastic moduli and moduli of rupture were similar (circa R²=0.57 for MOR3p and R²=0.65 for MOR4p).
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References
Brancheriau, L.; Baillères, H. 2002a. Natural vibration analysis of clear wooden beams: a theoretical review. Wood Science and Technology 36:347-365.
Brancheriau, L.; Baillères, H.; Guitard, D. 2002b. Comparison between modulus of elasticity values calculated using 3 and 4 point bending tests on wooden samples. Wood Science and Technology 36:367-383.
Brancheriau, L. 2014. An alternative solution for the determination of elastic parameters in free-free flexural vibration of a Timoshenko beam. Wood Science and Technology 48 (6):1269-1279.
Chitchumnong, P.; Brooks, S.C.; Stafford, G.D. 1989. Comparison of three- and four-point flexural strength testing of denture-base polymers. Dental Materials 5:2-5.
Gibson, L.J.; Ashby, M.F. 1997. Cellular solids. Cambridge University Press. Second edition. p. 387-428.
Gustafsson, S. I. 2001. Mechanical Properties of some Swedish hard wood species. Proceedings of the Institution of Mechanical Engineers 215:125-131.
Haines, D.W.; Leban, J.M.; Herbe, C. 1996. Determination of Young’s modulus for spruce, fir and isotropic materials by the resonance flexure method with comparisons to static flexure and other dynamic methods. Wood Science and Technology 30:253-263.
Hein, P.R.G.; Lima, J.T.; Gril, J.; Rosado, A.M.; Brancheriau, L. 2012. Resonance of structural timbers indicates the stiffness even of small specimens of Eucalyptus from plantations. Wood Science and Technology 46 (4): 621-635.
Igartúa, D.V; Moreno, K.; Piter, J.C.; Monteoliva, S. 2015. Densidad y propiedades mecánicas de la madera de Acacia melanoxylon implantada en Argentina. Maderas-Cienc Tecnol 17(4): 809-820.
Ilic, J. 2001. Relationship among the dynamic and static elastic properties of air-dry Eucalyptus delegatensis R. Baker. Holz als Roh- und Werkstoff 59:169-175.
Kollmann, F.F.P.; Côté, W.A. 1968. Principles of wood science and technology. Solid wood. Springer-Verlag. p. 359-363.
Kumar, M.P.; Murthy, V.B. 2012. Effect of Specimen Dimensions on Flexural Modulus in a 3-Point Bending Test. International Journal of Engineering Research & Technology 1 (8):1-6.
Hayat, M.A.; Suliman, S.M.A. 1998. Mechanical and structural properties of glass reinforced phenolic laminates. Polymer Testing 17:79-97.
Mujika, F. 2006. On the difference between flexural moduli obtained by three-point and four-point bending tests. Polymer Testing 25:214-220.
Naylor, A.; Hackney, P.; Perera, N. 2012. Determination of wood strength properties through standard test procedures. Proceedings of the 10th International Conference on Manufacturing Research 372-377.
Riyanto, D.; Gupta, R. 1998. A comparison of test methods for evaluating shear strength of structural lumber. Forest Products Journal 48 (2):83-90.
Sales, C. 1977. The rheological study of tropical woods: Modulus of elasticity. Bois et Forêts des Tropiques 176:47-65.
Yoshihara, H.; Fukuda, A. 1998. Influence of loading point on the static bending test of wood. Journal of Wood Science 44 (6):473-481.
Yoshihara, H.; Kubojima, Y.; Ishimoto, T. 2003. Several examinations on the static bending test methods of wood using todomatsu (Japanese fir). Forest Products Journal 53. 39-44.
