常规干燥过程中桉木薄板的水分迁移和流变特性  

Moisture Transfer and Rheological Characteristics of Thin Eucalyptus Specimens during Conventional Drying

作　　者：殷勤 王克民 刘洪海 YIN Qin;WANG Kemin;LIU Honghai(College of Furnishings and Industrial Design,Nanjing Forestry University,Nanjing 210037,China;Dandong Little Ant Knowledge-Action Education Technology Co.,Ltd.,Dandong 158000,China)

机构地区：[1]南京林业大学家居与工业设计学院,南京210037 [2]丹东市小蚂蚁行知教育科技有限公司,丹东158000

出　　处：《家具》2023年第1期10-14,共5页Furniture

基　　金：江苏省苏北科技专项(SZ-SD2017014);南京林业大学大学生创新实践项目(2021NFUSPITP0688,2021NFUSPITP0700)。

摘　　要：为探索桉木干燥应力和应变对于减少干燥缺陷和提高木材质量的重要意义,对纤维方向3 mm厚的尾巨桉进行常规窑干,测试了终含水率为25%,18%和8%时试件的含水率分布,并通过数字图像解析了其干燥应变规律。结果表明:木材在初始和8%含水率阶段时各层含水率的分布最均匀。干燥初期,表层干燥应力小,转变快,芯层受干燥应力作用时间较长。最大的实际干缩应变发生在边材位置,并且在3个含水率阶段,应变都沿着心材方向变小。弹性应变状态呈现先拉伸后压缩的趋势。黏弹性蠕变应变受含水率、试件取材位置的影响很大,与干燥应力没有明显的相关性。机械吸附蠕变应变与干燥应力对应明显,在干燥后期更接近弦向变化的规律。发生在干燥早期的皱缩可能会影响应力、应变,尤其是应力转向的时机。Eucalyptuswood is hard-to-dry. Drying defects,such as checking,deformation and collapse,often occur due to internal stress in wood as eucalyptus wood undergoing convention kiln drying,resulting wood quality degrading. Thus,exploring the drying stress and strain of eucalyptus wood during drying is important to reduce drying defects and improve wood quality. In this study,3mm thin specimens of Eucalyptus urophylla × E.grandis wood were dried in a convention kiln,the moisture content(MC)distribution and drying strain were measured at the average MC of specimens was 25%,18%,and 8% respectively.The results show that:the distribution of MC in each layer in initial and final stages(8%MC)of wood is uniform,but became much more uneven at 25% MC,showing a 10% difference between surface and center layers. In early drying stage,the drying stress in the surface layer is small,the transform is fast and the employ of drying stress on the central layers of wood is much longer. The greatest actual shrinkage strains occurred in the sapwood layer and became smaller toward to heartwood at three MCs stage. The elastic strain shows a tendency of tensile strain firstly and then compressive strain. The combined effect of tangential and radial stress complicates the rheological characteristics of the specimen. The viscoelastic creep strain is affected greatly by MC and tangential or radial specimens,showing non-obvious correlation with drying stress. However,the mechano-sorptive creep strain corresponds significantly to the drying stress,showing tangential strain in later drying stage. The collapse occurred in the early drying stage may affect the stress,strains and timing of stress transform in especial.

关 键 词：尾巨桉 含水率分布 干燥应力 流变特性 

分 类 号：TS664[轻工技术与工程]