Iranian Journal of Wood and Paper Industries (May 2014)
Evaluation of Modulus of Elasticity in Standing Trees and Sawn Wood in Populous deltoids using Nondestructive Stress Wave Testing
Abstract
The aim of this paper was to evaluate relationship between dynamic modulus of elasticity (MOEd) in healthy standing trees of Populus deltoides and static modulus of elasticity (MOEs) of sawn lumber from the same standing trees, using nondestructive stress wave testing (NDT). For this purpose, NDT stress wave technique was used. The study was performed on 10 healthy standing trees of Populus deltoides. The diameter of trees at the breast height was selected at two categories, namely 25-30 cm and 30-35 cm. Measurement of wave velocity in standing trees were done transversely in radial direction at two geographical directions as North-South and East-West at the breast height, namely 130 cm and longitudinal measurements were done on the height between 80 and 180 cm. Then, standing trees were cut following by measurements of wave velocity in their logs. Logs were kept for two months after cutting in order to reduce moisture content. Then, they were cut into the clear specimens for statistical bending test and their MOE were evaluated according to ASTM standard. The results showed that the stress wave velocity and dynamic modulus of elasticity in longitudinal direction of standing trees and logs were more than those in transverse directions. Also, stress wave velocity and dynamic modulus of elasticity of the logs were higher than those in their standing trees at both directions. Finally, regression analysis indicated that the correlation coefficient between MOEd in standing trees and logs at diameter 30-35 cm is (r= 0.94), which is statistically significant.
