Studies on Estimating Moulus of Elasticity and Strength of Standing Trees and Lumbers by Ultra Sonic Propagation Method

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At the present time, no technique has been generally accepted that accurately measures the mechanical properties of standing tree or lumbers, and the research for such a nondestructive test for mechanical properties has been hampered by a lack of fundamental knowledge on which to base the method, but some promise has been shown by empirical relationships between mechanical properties of wood and other properties that can be measured nondestructively. Accordingly in this research, to estimate nondestructively the mechanical properties (modulus of elasticity and strength) of standing trees and lumbers, some methods of applying acoustic wave velocity or resonant frequency were tried. Furthermore, factors affecting acoustic wave velocity or resonant frequency were investigated.The results obtained were as follows:(1)The case of applying ultra sonic testerStable acoustic wave velocity was obtained in the frequency of 50KHz, and the measurable distance was less than 40cm. The effect of moist … More ure content and temperature on acoustic wave velocity was remarkable in the radial direction. The relationship between acoustic wave velocity and grain angle/annual ring angle was much the same as that in modulus of elasticity.(2)The case of applying the method of hitting one position of lumber with hammerThe measurement of acoustic wave velocity and resonant frequency of stress wave developed, when a position of pillar was hit with hammer, was more easy in the longitudinal wave than in the transverse wave. The values of acoustic wave velocity and resonant frequency of stress wave were not affected by the position of accelerator and the position hit with hammer (except for the center of length of pillar), and the art of support. And in this case, especially in resonant frequency, the reproducible values were obtained.(3)The correlations between dynamic modulus and static modulus were high in either methods, but superior in the method of resonant frequency.(4)To apply the measurement of standing trees, the operation that a small block of wood was tied or pasted on the surface of pillar was devised. Less