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Development of a new method to measure moisture content for wood with moisture gradients with ultrasonic method.

开发了一种利用超声波法测量具有水分梯度的木材水分含量的新方法。

基本信息

批准号：
03660162
负责人：
MISHIRO Akiyoshi
金额：
$ 1.09万
依托单位：
Niigata University (1992)The University of Tokyo (1991)
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

项目摘要

The properties of ultrasonic velocity through wood were examined to estimate moisture content of wood with moisture gradients by ultrasonic method.Following results were obtained.1)The simple and good bonding methods were devised to get an accurate ultrasonic velocity. 2) When moisture gradient exists against the forward direction of ultrasound,the law of composite was applicable. When moisture gradient exists parallel to the forward direction of ultrasound, ultrasonic velocity was more dependent on the parts with the faster velocity. 3) Below the fibersaturation, ultrasonic velocity increased curvilinealy as moisture content decreased and the change percentage in ultrasonic velocity per unit moisture content was much more in the longituidnal direction than in the radial. The patterns of ultrasonic velocity-moisture content curves on a graph in a longitudinal and a radial for vapor-saturated specimens during drying were not so different with species. The patterns of ultrasonic velocity-moisture content curves in a longitudinal and a radial for water-saturated specimens during drying depended on the species,and could be divided into three groups. Consider the wood during drying as a composite material of woods with different moisture contents and the law of composite was applied,and the calculations agreed with measured valued. 4) In the LR and LT planes, ultrasonic velocity decreased as grain angle increased in softwoods and hardwoods,but in the RT plane the tendency of ultrasonic velocity on the annual rings in softwoods was different from that in hardwoods. 5) Ultrasonic velocity in a longitudinal was directly proportional to density in some speices, and in some it was inversely proportional to density, and in some no correlation was found between them.

为了利用超声波法测量木材的含水率，研究了木材中的超声波传播速度特性，得到以下结果：1）设计了简单有效的胶合方法，以获得准确的超声波传播速度。2)当逆超声前进方向存在水分梯度时，复合定律适用。当水分梯度与超声前进方向平行时，超声速度对速度较快的部位有较大的依赖性。3)在纤维饱和度以下，超声速随含水率的降低呈曲线上升，且单位含水率超声速的径向变化率远大于径向变化率。在干燥过程中的超声速-含水率曲线的模式在纵向和径向的饱和蒸汽试样的图形没有那么不同的物种。在干燥过程中的超声波速度-含水量曲线的模式在纵向和径向的水分饱和的标本取决于物种，并可分为三组。将干燥过程中的木材视为不同含水率木材的复合材料，应用复合定律，计算结果与实测值吻合较好。4)在LR和LT平面上，针叶材和阔叶材的声速随纹理角的增大而减小，但在RT平面上，针叶材和阔叶材的声速在年轮上的变化趋势不同。5)在某些物种中，纵向声速与密度成正比，在某些物种中，纵向声速与密度成反比，在某些物种中，它们之间没有相关性。