NEW TECHNIQUE FOR EVALUATING DAMPING OF LONGITUDINAL FREE-VIBRATION IN WOOD-BASED MATERIALS

Classical log-decrement techniques have been used to evaluate the damp ing property of materials. However, the consistency and repeatability of the methods when applied to wood and wood-based materials have been found lacking. A different way to view the free vibration of a single -degree-of-freedom system in the x - (x) over dot plane is presented. A new method that uses all sample points and does not require a knowle dge of the initial conditions to determine the damping properties is d eveloped. A comparison between the new method and the classical method is made for three wood-based materials: solid wood, medium density fi berboard (MDF), and particleboard. The results show that the new metho d is more consistent and repeatable in measuring damping than the clas sical method. For the six cases examined, there was an absolute averag e difference of 3.8% in measuring log-decrement between the methods.