Abstract:

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.

Key words: stress wave, log, propagation theories, method of separation of variables