Theoretical and experimental research on moisture content and wood property indexes based on nondestructive testing

Abstract

A set of reformulated theoretical formulas was developed to measure the relationships between moisture content (MC) and stress wave propagation velocity, dynamic modulus of elasticity ( “E” _”d” ), and modulus of stress-resistograph of the wood. The theory of wood science, elastic mechanics, wave science, and stress wave propagation were used as the theoretical basis. Using larch as the material, both stress wave and micro-drilling resistance technologies were used to study the timber property changes under different moisture contents. The results showed that when the MC of wood did not reach the fiber saturation point (FSP), the wood property decreased sharply with increased MC. However, the study also found that when the MC of wood was higher than the FSP, the wood property decreased with increased MC. In addition, the experimental results showed that the variation trend calculated by the new set of theoretical formulas was consistent with the numerical variation trend measured by the experiment, and the coupling effect of stress wave and micro-drilling resistance was high. This set of theoretical formulas can provide a reference for the research on nondestructive testing and performance evaluation of ancient building timber.