Lamb wave propagation method for nondestructive characterization of the elastic properties of wood

Abstract

Nondestructive evaluation (NDE) of the mechanical properties of structural wood is of great importance for quality control purposes in wood industries and construction applications. The currently used ultrasonic and stress wave methods fail to accurately estimate the elastic properties of wood. The present study aimed to propose an NDE method for accurate characterization of the elastic properties of wood using the Lamb wave propagation method. Lamb wave propagation and mechanical three-point-bending tests were performed on the green poplar wood specimens with different moisture content (MC) levels. The fundamental antisymmetric Lamb wave mode was propagated in specimens using an ultrasonic actuator, and an ultrasonic sensor was used to acquire the wave signal at different locations of the specimens along the propagation direction. The Lamb wave velocity was measured for the wood specimens with different MC and found to be in very good agreement with those from semi-analytically obtained dispersion curves. Afterwards, the corresponding inverse Lamb wave propagation problem was solved and the modulus of elasticity (MOE) of the specimens was estimated. The maximum difference between the MOE calculated by the proposed Lamb wave propagation method and that measured from the three-point bending test was less than 2%, proving the validity of the proposed method for nondestructive characterization of wood.