Predicting of strength and stiffness of wood using acoustic measurement in trees

Author(s)

Cinthya Bertoldo Pedroso

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Agrícola
• Defense date: 2014-07-25

Examining board members

Raquel Gonçalves; Esther Merlo Sánchez; Cláudio Henrique Soares Del Menezzi; Cristiane Camargo Zani de Lemos; Julio Soriano

• Advisor: Raquel Gonçalves

Abstract

The use of wave propagation methods to access the wood quality in standing tree has been one of the current focuses of research in this area. However, one of the problems for the application of this technology directly in standing trees is the influence of different mechanisms of wave propagation, which occurs according to the characteristics linked to the type of measurement, geometry of the piece and other parameters that affect the results. Consequently the wave propagation velocity obtained from measurements in trees differs from that obtained from measurements in freshly felled logs or on beams in green condition removed from the log. Additionally, the velocity obtained in log or in beam is better correlated with mechanical properties than the velocity obtained in standing tree. Thus, the aim of the this research was examine parameters that allows better prediction of log velocity and beam velocity from velocity obtained from measurements in standing trees. As a consequence, allow better prediction of properties of strength and stiffness of wood from the tree acoustic measurement. To achieve the objectives, wave propagation measurements were performed in standing trees, in freshly felled logs obtained from these trees and in beams removed from the logs. The beams were submitted to the bending tests, in equilibrium moisture content, for later correlation of the strength (fm) and stiffness (EM) with acoustic properties obtained on trees. The bulk green density (?), the diameter at breast height (DBH), the acoustoelasticity coefficient and the Poisson's ratio (?) were the parameters adopted for the analysis. The differences between tree/log velocities and tree/beam velocities were minimized by inserting the Poisson ratio and the diameter at breast height. The coefficient of determination of the models to predict the mechanical properties from tree velocities, corrected for green density, diameter at breast height and Poisson's ratio, were similar or superior to those obtained by prediction models of these properties (fm and EM) from the velocities obtained directly from logs or from beams. This result allows prove the viability of the anticipation of wood properties from measurements in standing tree (AU)

• FAPESP's process: 11/00904-1 - Wood stiffness obtained by acoustic evaluation on the tree
• Grantee: Cinthya Bertoldo Pedroso
• Support Opportunities: Scholarships in Brazil - Doctorate