Study on Moisture Movement in Wood with X-ray CT scanner.

用x线CT对干燥过程中的水分分布进行无损检测。在本研究的第一阶段，研究了将CT扫描仪直接获得的CT数与仅归属于水分的CT数区分的方法，并提高了在样品周围使用硅橡胶袋测量水分的准确性。内部截面的含水率可以在1% ~ 40%的范围内进行无损测量。第二阶段，应用该方法对道格拉斯杉木厚四分木（6cm厚度）干燥过程中的水分分布进行检测，测量水分在厚度方向上的分布变化。样品可能具有水分运动的均匀性。同时，假设扩散系数随含水率连续变化。在此假设下，由扩散系数与含水率的关系反求试样表面含水率。用有限差分法求解菲克第二定律时，表面含水率应设定在高含水率范围内高于平衡含水率6%左右，在低含水率范围内高于平衡含水率3-4%。以含水率为驱动力的水分运动，扩散系数随含水率的变化基本不变。

Moisture distribution in drying were non-destructively detected with X-ray CT scanner. In the first stage of this research, methods were investigated to distinguish CT number attributed the moisture only from total CT number obtained directly with CT scanner and to improve the accuracy of moisture measurment using silicon rubber bags surrounding the sample. Moisture contents on internal cross section could be non-destructively measured in the finest of 1% below 40% range.In the second stage, applying the method to detect the moisture distribution of Douglas-fir thick quarter sawn lumber (6 cm thickness) in drying, change of moisture distribution in thickness direction was measured. The sample had probbably a homogeneous property for moisture movement. Also, it was assumed that the diffusion coefficient was continuously changing with moisture content. On this assumption, moisture contents on the surface of sample were reversely calculated from the relationship between diffusion coefficient and moisture content. Moisture content on the surface should be set the higher value of about 6% in high moisture content range and the higher value of 3-4% in low range than equilibrium moisture contents, in solving the Fick's 2nd law with the finite difference method. Describing moisture movement with moisture content as driving force, the diffusion coefficient was almost constant with moisture content change.