冻结状态下应力波在长白落叶松立木中传播速度的研究

Stress wave propagating velocity in Larix olgensis standing trees under a freezing condition.

为进行冬季活立木健康检测和伐后原木内部缺陷无损检测,该文在冻结状态下,研究了应力波在长白落叶松活立木中的传播速度,以及光照条件对含水率及应力波在活立木中传播速度的影响。在室外温度0℃以下,利用FAKOPP Microsecond Timer等仪器测试了应力波在30棵树干通直且无缺陷的长白落叶松活立木中的纵向和径向传播速度。经过软件包SPSS统计分析,得出阴阳两面应力波的纵向传播速度分别为4 238.7和4 210.6 m/s,径向传播速度均值为1 834.5 m/s。同时,利用成对t检验法分析了光照条件对含水率及应力波在活立木中纵向传播速度的影响,并建立了回归方程。结果表明:①光照条件对含水率和应力波纵向传播速度有一定的影响,阴面含水率均值比阳面含水率均值低约1.6%,阴面应力波纵向传播速度均值比阳面的高约28.1 m/s。②含水率与应力波纵向传播速度呈显著负相关,阴阳两面的负相关系数分别为0.90和0.91。含水率每增加1%,阴阳两面应力波的纵向传播速度分别减小25.1和22.9 m/s。

In order to make practical non-destructive evaluation on the health of standing trees or to detect the inner defects in logs after tree felling during the winter period, the stress wave velocities propagating in Larix olgensis standing trees under a freezing condition, and the effects of light and moisture content on stress wave velocities were investigated under low temperature （below 0 ℃ ）. The original survey data were from 30 healthy standing trees with straight trunks by using FAKOPP Microsecond Timer. The survey results showed that the longitudinal stress wave velocities of the sunny and shade sides were 4 238.7 and 4 210.6 m/s respectively, and the radial stress wave velocity was 1 834.5 m/s. Meanwhile, the paired t-test was employed to analyze the effects of light on moisture content and longitudinal stress wave velocities. Then, a linear regression model was used to relate moisture content, longitudinal stress wave velocities, and radial stress wave velocities. Results showed that： 1 ） the effects of light on moisture content of standing trees and longitudinal velocities of stress wave propagating in standing trees were significant, and the average moisture content in standing trees in shade was 1.6% lower than that of sunny side while the longitudinal stress wave velocity in standing trees in the shade was 28.1 m/s higher than that of the side exposed to the sun; 2） the moisture content was negatively related to longitudinal stress wave velocities with a correlation coefficient of 0.90 and 0.91 for shade and suny sides, respectively. The longitudinal stress wave velocities measured in the shade and sunny sides decreased by 25.1 and 22.9 m/s respectively with a 1% increase in moisture content of standing trees.