Estimation of Bending Stress in Earlywood and Latewood Growth Rings of Oil Thermally Treated Wood by Near Infrared Spectroscopy

摘要

This paper focuses on the estimation of bending strengths in earlywood and latewood growth rings of three refractory wood species such as white spruce (Picea glauca), eastern hemlock (Tsuga canadensis L.) and soft maple (Acer rubrum) wood samples by near infrared (NIR) spectroscopy. Wood samples were heat thermally treated in the deep fryer with vegetable oil at 220oC during 120 minutes. For earlywood zones, calibration R2 achieved 0.44 and 0.63 in Spruce and Hemlock, respectively. The root mean square error (RMSE) ranging from 9.25 to 12.90MPa for all the species and relative percent difference (RPD) ranging from 1.0 to 1.6 in Spruce, Hemlock and Maple. For latewood zones, validation statistics R2 achieved 0.27 and 0.32 in Spruce and Hemlock, respectively. RMSE ranging from 10.177 to 18.27MPa for all the three wood species, and RPD ranging from 1.2 to 1.5 for all the species. The NIR prediction results confirm that chemical reactions in wood sites resulting from the heat treatment account for the maximum amount of flexure stress that were related to main peaks of spectra data using 1100-2200nm region of the three wood species, while the oil absorbed by wood reduces the sensitivity of NIR reflectance.