抄録
The natural frequency of longitudinal vibration due to sound emitted by hitting the cross section of lumber with hammer was measured to determine the modulus of elasticity (Et) and weight change. And its application for mechanical grading of lumber and quality control for drying in the mill was discussed.
Et was recognized to be highly linear to the modulus of elasticity determined by static bending test (Es). Et was hardly affected by the length and section of lumber as compared with Es, and practically represented the average value of Et of components.
Since the change of natural frequency during drying process was associated with Et and weight loss due to desorption of water, it might be used as an effective rough classification method for mechanical grading and quality control in drying. Especially, as the third lowest natural frequency of longitudinal wave was hardly affected by piling, measurements of longitudinal vibration after sawing and weight change during drying process could be considered as a reasonable quality control system.
