Rolling shear modulus and damping factor of spruce and decayed spruce estimated by modal analysis

Modal analysis was used to determine the rolling shear modulus of Norway spruce samples that were either untreated or inoculated with fungi. The resonance frequencies of centimeter-range cuboids were measured using contact-less laser interferometry. A three-dimensional theoretical model describing the orthotropic behavior of the material was used to calculate the resonance frequencies. Using an iterative scheme based on the least-squares method, the value of the rolling shear modulus was then extracted. In this first investigation, the decrease in the rolling shear modulus and the weight loss of Norway spruce inoculated with white-rot fungi Heterobasidion annosum and Ganoderma lipsiense were studied for three different exposure times ranging from 4 to 12weeks. Comparison of measured and theoretical resonance frequencies confirmed that operation was in the applicable range of the theoretical model for the inoculated specimens. A decrease in rolling shear modulus of up to 10% (H. annosum) and 50% (G. lipsiense) was foun

A simple anisotropy correction procedure for acoustic wood tomography

Anisotropy of acoustic propagation velocities is a ubiquitous feature of wood. This needs to be considered for successful application of travel time tomography, an increasingly popular technique for non-destructive testing of living trees. We have developed a simple correction scheme that removes first-order anisotropy effects. The corrected travel-time data can be inverted with isotropic inversion codes that are commercially available. Using a numerical experiment, we demonstrate the consequences of ignoring anisotropy effects and outline the performance of our correction scheme. The new technique has been applied to two spruce samples. Subsequent inspection of the samples revealed a good match with the tomogram

A simple anisotropy correction procedure for acoustic wood tomography

ISSN:0018-3830ISSN:1437-434