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

目前，还没有一种技术被普遍接受来准确地测量立木或木材的力学性质，而且由于缺乏作为该方法基础的基本知识，这种力学性质的无损测试的研究一直受到阻碍，但木材的力学性质与其他可以无损测量的性质之间的经验关系已经显示出一些希望。因此，在本研究中，为了无损地估计立木和木材的力学性质(弹性模数和强度)，尝试了一些施加声波速度或共振频率的方法。研究了影响超声波波速或共振频率的因素，得到了以下结论：(1)在50 kHz频率下获得了稳定的超声波波速，可测距离小于40 cm。湿润…的效果在径向上，较高含量和温度对声波速度的影响是显著的。声波速度与木质角/年环角的关系与弹性模量法基本相同。(2)用锤子击打木材某一位置时，纵波比横波更容易测量声波速度和应力波的共振频率。应力波的声波速度和共振频率不受加速器位置、锤击位置(柱长中心除外)和支承工艺的影响。在这种情况下，特别是在共振频率下，得到了可重现值。(3)两种方法的动静模值相关性都很高，但共振频率法的相关性更好。(4)为了应用于立木的测量，设计了在立木表面捆绑或粘贴一小块木块的操作。较少

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