Yaitskova Natalia, van de Kuilen Jan Willem
Holzforschung München, Technische Universität München, Winzererstraße 45, D-80797, Munich, Germany.
J Acoust Soc Am. 2014 Jun;135(6):3409-15. doi: 10.1121/1.4873519.
Time-of-flight is a time for an ultrasonic pulse to cross a sample. It contains valuable information about the mechanical properties of a material. For the ultrasonic pulse propagating in wood perpendicular to the grain the relation between the time-of-flight and the elastic constants is rather complex due to the strong anisotropicity of wood. With the help of some assumptions this relation can be established from the elastic theory. The analytical calculation results in a function which represents a change of time-of-flight when the direction of propagation shifts from the radial to the tangential direction while scanning a board crosswise. The function takes into account the location of the pith and the geometry of the growth rings. The measurement performed on a sample of European spruce confirms the theoretical prediction.
飞行时间是超声脉冲穿过样品所需的时间。它包含有关材料机械性能的宝贵信息。对于在木材中垂直于纹理传播的超声脉冲，由于木材的强各向异性，飞行时间与弹性常数之间的关系相当复杂。借助一些假设，可以从弹性理论建立这种关系。解析计算得出一个函数，该函数表示在横向扫描板材时传播方向从径向转变为切向时飞行时间的变化。该函数考虑了髓心的位置和年轮的几何形状。对欧洲云杉样品进行的测量证实了理论预测。
