Non destructive evaluation of mechanical properties by vibration

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The mechanical properties of wood were investigated by mode analysis, vibration intensity analysis and sound intensity analysis. The possibility of material evaluation of lumber examined from the shape of natural vibration mode and vibration/sound energy flow. The following results were obtained.(1) With the existence of a knot in a lumber, the shape of natural vibration mode changed largely.(2) Vibration energy spread toward periphery in the counterclockwise direction from a impacting force position. In the case of lower vibration modes, the flows of vibration energy vector draw the swirl shape and traveled cross the vibration nodal lines. On the other hand, in the case of higher vibration modes, vibration intensity mainly occurred in the abdomen of vibration mode. Accordingly, the flow of vibration energy corresponded to a characteristic vibration mode and a situation of occurrence and spread and consumption of vibration energy might be shown. A vibration intensity analysis could be suggested that there was the possibility of material evaluation.(3) The sound intensity corresponded to the natural vibration mode very well. The material evaluation of wood could be evaluated by the sound intensity method. The sound energy radiated cross the nodal lines and the flows of sound energy from wide radiation area to narrow radiation area in the case of higher vibration mode. It was guessed to be the one that is able to evaluate a sound characteristic such as the radiation the efficiency, the directivity of a musical instrument by the sound intensity method.