Damping properties of some tropical wood species determined by free transverse vibration method

This article describes a non-destructive method for determining the damping properties of wood. It was based on the analysis of the attenuation of the free transverse vibrations of a fixed support-free specimen following excitation. Cameroonian forests abound important species that were much in demand for structural applications and were often subjected to dynamic loads. However, in the literature and in the available databases, very little information was available on the vibration properties of these wood species. To solve this problem, three specimens of twenty-four wood species with a cross-section of 10 x 20 mm, with a length of 1600 mm were prepared and subjected to a free vibration test in the fixed support-free configuration. The accelerations as a function of time were obtained. By transforming the recorded accelerations into displacements, it was allowed to determine the logarithmic decrement by mean the first twenty-one amplitudinal peaks. Thanks to the interrelationships, the viscous damping ratio, loss factor, quality factor and specific damping ratio were deduced. The results obtained were relatively variable between species. Compared with the data available in the literature for the same species, there was a considerable difference.