摘要
木材细观损伤不仅是木材受外力而产生的宏观破坏,还包括由于载荷所引起的微观裂纹的萌生与扩展。通过汽蒸-模压弯曲杨木,运用对比分析的方法研究其物理力学性能与弯曲性能。结果表明:110℃蒸汽处理杨木的绝干密度和气干密度均有所增加,但最大载荷、抗弯强度、弹性模量却明显下降;而最大变形量增加到杨木素材最大变形量的196.85%,说明汽蒸处理杨木的弯曲性能很好。显微镜观察其微观构造发现,蒸汽处理木材中所有的导管分子均没有发生开裂和损伤,但均有不同程度的变形;导管壁上纹孔变形变扁和变平拉长,也有少数纹孔保持原型;导管射线间纹孔基本保持原状;无论在弯曲木的受拉侧还是受压侧,木纤维细胞壁中均受挤压、剪切出现细胞分离和细胞之间撕裂或隆起的现象,并向纹孔口方向和木纤维主轴方向扩展、延伸、开裂;木射线形状完好,没有受到破坏,说明木材弯曲对木射线影响不大。
The meso-damage of wood is not only the macro fracture caused by external force,but also the initiation and propagation of micro cracks caused by the load.The poplar wood was bent by steam treatment and mould pressing,and its physical-mechanical properties and bending properties were investigated.The results indicated that the oven-dry density and air-dried density of poplar wood could be improved after steam treatment at 110°,but the maximum load,MOR,MOE were reduced.Meanwhile,the maximum deformation is 196.85%higher than the natural poplar wood,indicating that the bending performance of the steam treated poplar is very good.All the vessel element in the steam treated wood did not crack and damage by microstructure observation,but there are different degrees’deformation.The pits on the wall are flattened and elongated,and a few pits remain the prototype.The vessel–ray pits remain original micro-morphology.Regardless of whether it is on the tension side or the pressure side of the bent wood,the cell wall of the wood fiber were squeezed and sheared to cause cell separated and tearing between the cells.And expand,extend and crack toward the direction of the groove and the main axis of the wood fiber.The micro-morphology of the bent wood ray is intact and has not been damaged,indicating that the wood bending has little effect on the wood rays.
作者
杨玉山
沈华杰
王宪
王云龙
邱坚
YANG Yushan;SHEN Huajie;WANG Xian;WANG Yunlong;QIU Jian(College of Materials Science and Engineering,Southwest Forestiy University,Kunming 650224,China)
出处
《山东林业科技》
2019年第5期1-5,共5页
Journal of Shandong Forestry Science and Technology
基金
云南省应用基础研究计划项目青年项目（2017FD102）
973/863项目
国家重点研究计划（2016YFD0600702）
关键词
汽蒸处理
弯曲
杨木
物理力学性能
细观损伤
steam treatment
bend
poplar lumber
physical-mechanical properties
meso-damage
