Effects of panel density and particle type on the ultrasonic transmission through wood-based panels

Air-coupled ultrasonic inspection for the detection of delaminations inside panels is a widely applied technique in the wood-based panel industry. Additionally, the ultrasonic signal is used to monitor the constancy of the production process as unsteady material properties and process parameters cause variations in the transmitted ultrasonic signal. This article examines the physical effects of air-coupled ultrasonic testing and analyses the influences of panel density and particle type on the transmitted ultrasonic signal. The experiments were carried out for a broad range of wood-based panels. The experimental results indicate that the tested properties influence the transmission in two ways. Firstly, density affects the reflection and transmission factors at the material boundaries, and secondly, particles and pores act as scattering centres inside the material, leading to an attenuation of the ultrasonic signal. The results of this study may be used to efficiently include the ultrasonic signal into a trending system for the wood-based panel production process.