含水率和密度对木材应力波传播速度的影响

为了用应力波检测木材含水率,采用ARBOTOM 应力波测试仪测量了木材径向不同位置上的试件在不同含 水率(0 ~65%范围内)条件下的应力波纵向传播速度。结果表明:木材中应力波传播速度随含水率的下降而增加; 当含水率低于纤维饱和点时,传播速度随含水率下降增加较大,其中山毛榉的增幅为17.4% ~19.5%,落叶松的增 幅为18.2% ~20.8%;当含水率高于纤维饱和点时,传播速度随含水率下降增加较小,其中山毛榉的增幅为6.0% ~ 7.9%,落叶松的增幅为8.0% ~10.6%。当含水率相同时,应力波在同一树种木材不同位置上的传播速度不同,这 与木材不同位置的基本密度差异有关。应力波传播速度随木材基本密度的增大而增大,其中山毛榉木材的增幅为 17.5% ~20.8%,落叶松木材的增幅为12.7% ~ 14.5%。同一树种内的任意含水率下,基本密度不同时应力波传 播速度之间差异显著,传播速度和基本密度之间存在较好的正相关线性关系。不同树种之间,传播速度和基本密 度之间没有明显关系,这可能与不同树种之间的成分差异有关。 

Effects of moisture content and density on the stress wave velocity in wood

In order to measure the moisture content of wood by stress wave, the longitudinal stress wave velocities of wood samples in different radial locations with different moisture content (0% -65%) were examined by a ARBOTOM commercial equipment. The results revealed that the stress wave velocity in wood increased with the decrease of moisture content. Wave velocity increased greatly with the decrease of moisture content when the moisture content was less than the fiber saturation point, the increasing rate was 17.4% -19.5% for beech (Fagus longipetiolata) and 18.2% -20.8% for larch (Larix gmelinii) wood, and the increasing rates were 6.0% - 7.9% for beech and 8.0% - 10.6% for larch when the moisture content was higher than the fiber saturation point. When the moisture content was the same, the stress wave velocity increased with increasing the basic density of wood, and the increase rate for beech wood was 17.5% -20.8% while that of larch wood was 12.7% -14.5%. For the same wood species, a good positive linear correlation between the stress wave velocity and the basic density was found under any moisture content. However, there was no similar correlation among different wood species, which might be due to the differences in the chemical compositions.