Vibration Based NDT Methods to Verify Wood Drying Efficiency

The capability of application of flexural vibration test in nondestructive evaluation of wood drying was studied. Poplar timbers were conventionally kiln dried under three different drying schedules down to the final moisture content of 12 ±2 %. Dynamic Modulus of Elasticity, damping (internal friction), acoustic coefficient, and acoustic converting efficiency of each sample were evaluated using free flexural vibration test of both-ends free bars before and after the drying, while dynamic responses in each individual step were also monitored. Results revealed that emerging of some defects in the dried timber caused signifi cant changes through the studied parameters of samples by different extents. Cracks were amongst the most prevalent defects influencing the studied factors. The desired schedule, which caused the least abundance of defects in the dried timber, was then identified using this technique. It can be stated that the existing destructive and traditional methods could be replaced by the free vibration method to evaluate the final drying quality accurately.