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A Developmental Study of Drying System Applying RF-Heating/Vacuum Method to The Boxed-Heart Heavy Timbers Like Logs.

射频加热/真空法对箱心重材（如原木）干燥系统的开发研究。

基本信息

批准号：
08556029
负责人：
MATAKI Yoshihiro
金额：
$ 6.98万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1998
项目状态：
已结题

项目摘要

In Japan, sugi is very often used as a boxed- heart timber of log or square column. It is difficult to dry these timbers in a short time, as having a big cross section and large aria of heart wood. It connects with the increase of the drying cost. And the severe checks occur easily for the boxed heart timbers of sugi during drying , because of anisotropic shrinkage. RE/vacuum drying method is wellknown for an effective means of rapid and checkless drying. But When the moisture distribution became approximately uniform after drying, surface check often occurred.In this research, measurment of internal stress and drying set was performed on the sugi log and boxed-heart square timber dried with RE/vacuum method and it's combination with heat treatment or transpirational drying. As a result of these investigations, it became clear as follows. (1) These stresses of Sugi logs dried with RE/Vacuum method were relatively large tension , when the moisture distribution in the cross section became approximately uniform after drying. By the heat treatment of 80ﾟC for 1 day, these large tensile stresses at the surface layer disappeared and surface checks were improved. (2) The conbination method of kiln- drying and RE/Vacuum drying improved these drying time and surface check for the boxed-heart square timbers. It seems that one of the reason for surface check decrease is drying set made at the former stage of kiln- drying. (3) By the transpirational drying, moisture content of only sap wood was decreased. So the moisture contents of outer part in the cross section of the boxed-heart square timbers became approximately lower than inner part during RE/Vacuum drying, and surface checks were decreased comparing with untreated.

在日本，Sugi经常被用作原木或正方形立柱的盒心材。这些木材很难在短时间内干燥，因为它们的横截面很大，心材的咏叹调也很大。这与干燥成本的增加有关。而且，由于各向异性收缩，Sugi的盒装心材在干燥过程中很容易出现严格的检查。Re/真空干燥法是一种快速、无阻碍的有效干燥方法。本研究以杉木原木和盒心方材为研究对象，采用RE/真空干燥法及其与热处理和蒸腾干燥相结合的方法，对其进行了内应力和干燥永久变形的测量。作为这些调查的结果，情况变得清晰如下。(1)用稀土/真空干燥方法干燥的杉木原木，当横截面水分分布基本均匀时，这些应力较大。经80ﾟC热处理1d后，表层的这些大的拉应力消失，表面质量得到改善。(2)采用窑法干燥和稀土/真空干燥相结合的方法，提高了箱心方材的干燥时间和表面质量。表面质量下降的原因之一似乎是在窑炉烘干的前一阶段制作的烘箱。(3)蒸腾干燥只降低了树干的含水率。因此，在RE/真空干燥过程中，箱心方材横截面外层的含水率基本低于内部，表面缺陷也较未处理前有所减少。