THE INFLUENCE OF INHOMOGENEITY ON THE PROPAGATION OF ULTRASOUND IN WOOD

The use of ultrasound for determining the elastic constants of materia ls is a well-established science for homogeneous materials such as met als. However, its extension to anisotropic, inhomogeneous materials su ch as wood has proved more problematic. Wood is modelled as an orthorh ombic material with the influence of inhomogeneities generally being n eglected. For this paper the potential influence of inhomogeneities on waves propagating in the radial direction was considered. Within ring density and ultrasonic velocity measurements were made. A model for u ltrasound propagation in the radial direction was then constructed whi ch treats the annual ring structure in the radial direction as a layer ed structure and predicts the occurrence of stop bands in the frequenc y domain. Evidence for the existence of such stop bands is considered. (C) 1998 Elsevier Science B.V.