应力波在原木中传播理论的研究

Study on the Propagation Theories of Stress Wave in Log

对原木中微小单元进行动力学分析,确定应力波沿原木轴向传播的波动方程,应用分离变量法,得出应力波沿原木轴向传播的位移、速度、应力和应变方程。根据波动学理论中的反射和透射原理,从传播方向与界面垂直和不垂直2个方面得出界面两侧位移、速度、应力、应变的关系式。在此基础上,建立传播方向与界面垂直情况下的应力波沿原木径向或弦向传播的位移、速度、应力和应变方程。从这些方程可以得出:微小单元的位移、速度、应力和应变不仅与原木试件的弹性模量、密度有关,而且与小锤的敲击力、小锤与原木试件作用时间、敲击方向有关。

By dynamics analysis of microunit, the mathematical models of propagation of stress wave along the axis-direction of a log were founded. The displacement equation, velocity equation, stress equation and strain equation were established by using the method of separation of variables. After this, the relations of displacement velocity, stress and strain at both sides of interface were presented according to the reflection and transmission principles of stress wave. On the basis of this, the transmission equations of displacement, velocity, stress and strain of stress wave alone the diameter-direction or string-direction of a log were founded as the propagation direction is vertical on the interface. The results of analysis and experiments showed that the propagation of stress wave in a log was affected by not only the wood physical properties but also the shocking force strength, shocking area, shocking direction and response time to shockings. All these equations will be theoretical references for testing log properties by using stress wave method.