Resumo

DAVALOS SOTELO, Raymundo  e  LIMON GODINA, Roberto. Efecto de los nudos sobre la resistencia y rigidez en flexión de la madera de pino. Rev. Cien. For. Mex [online]. 2009, vol.34, n.106, pp.205-212. ISSN 1405-3586.

This study was conducted to establish the influence of several parameters such as the knot area ratio (KAR), the basic density or specific gravity (SG) and the modulus of elasticity (MOE) on the bending properties of a sample of 17 pieces of Durango pine wood supplied by a local company. Bending strength (MOR) and modulus of elasticity test results on 50 × 50 × 760 mm specimens are presented in this paper. Test results were adjusted to (MC) of 12%. The test results indicate that both the basic density and the knot area ratio have similar ability to predict bending strength and thus, both have similar potential to develop grading rules that could be reasonably applied to structural pine wood. The statistical correlation improves if the stress is measured in the section where the largest knot is present. The prediction model improves substantially if in addition to KAR, the specific gravity is included in the regression equation and, even better results are obtained if modulus of elasticity is also included in a multiple regression equation. This suggests that a combination visual-mechanical grading method might be the best option for grading Mexican pine wood.

Palavras-chave : Moisture content; specific gravity; modulus of elasticity; Mexican pine; knot area ratio; bending strength.