超声波在原木内部传播理论研究

超声波技术在木材无损检测中已有广泛的应用,尤其是一些研究表明超声波在原木内部的传播规律对无损检测效果产生重要影响.根据弹性波在固体介质中的传播理论,通过对微小单元体的受力分析,得出弹性动力学运动微分方程,并在此基础上,根据正交各向异性介质的弹性常数,应力与应变之间的相互关系,几何方程（应变和位移的关系）以及超声波传播（无旋波）的方向向量,最终得出以位移表示的运动微分方程;然后利用分离变量法,建立超声波在原木内部传播过程中的位移方程和速度方程.

The Study on the Propagation Law of Ultrasonic Wave in Log

The ultrasonic technology has been widely applied in the field of nondestructive testing of wood and the propagation law of ultrasonic wave in log has been proved to have important influence on the evaluation efficiency. According to the theory of elastic wave transmitting in solid medium, differential equations of motion of elastic dynamics were derived through the stress analysis of tiny unit. Furthermore, based on the elastic constants of the orthogona] anisotropic medium, the relationship between stress and strain, geometric equations of the relationship between strain and displacement, and the direction vector of ultrasonic transmission（ irrotational wave）, differential equations of motion expressed by displacement were obtained. At last, the displacement equation and velocity e- quation of the propagation process of ultrasonic wave in log were established using the method of variable separation.