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The large compressive deformation of wood in the transverse direction

木材横向压缩变形较大

基本信息

批准号：
05660188
负责人：
MOROOKA Toshiro
金额：
$ 1.22万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05660188/
关键词：
compressive test large deformation transverse direction yield stress wood 圧変ひずみ降げ値圧密歪

项目摘要

The stress strain diagrams of wood in compression in the transverse direction are known to be quite different from those in the longitudinal direction since in the transverse direction they depend on cell porous structure or cell arrangement. In the present report, we aimed at finding out universal expression for the stress strain diagrams of wood in the transverse direction. For this purpose, the compressive tests in the radial direction for seventeen kinds of hardwoods were conducted in three conditions, in the air-dried condition at 20ﾟC,in the wet condition at 20ﾟC and in the wet condition at 100ﾟC.Although the stress (sigma) -strain (epsilon) diagrams obtained were different in the different conditions, they could be expressed by the following expressions with two parameters of b and K.epsilon*epsilony sigma=Eepsilonepsilon>epsilony sigma/sigmay=1+b{epsilond/ [epsilond- (epsilon-sigmay/E) ] -1}epsilond=1-K (rho/rhos)where sigmay, epsilony, E,rho, and rhos refer to yield stress, yield strain, Young's modulus, specific gravity of wood, and specific gravity of the cell wall, respectively. The value epsilond is a measure of the strain at which all the pore space in wood is squeezed. The parameter b indicates the extent of the increase of stress with strain above the yield point. The parameter K is related to poisson's ratio in the large deformation. Although both parameters are little affected by the viscoelastic properties of the cell wall, they were shown to be affected by the water flow in wood during compression.

木材在横向受压时的应力应变图与纵向的应力应变图有很大的不同，因为在横向上，应力应变图取决于木材的细胞多孔结构或细胞排列。本文旨在寻求木材横向应力应变图的普遍表达式。为此，对17种硬木在20 ℃风干条件、20 ℃湿态条件和100 ℃湿态条件下进行径向压缩试验。虽然在不同条件下获得的应力（σ）-应变（σ）图不同，它们可以由具有两个参数B和K的以下表达式来表示。其中σ、ε、E、ρ和ρ分别指屈服应力、屈服应变、杨氏模量、木材的比重和细胞壁的比重。值ε是木材中所有孔隙空间被挤压时的应变的量度。参数B表示在屈服点以上应力随应变增加的程度。参数K与大变形时的泊松比有关。虽然这两个参数的细胞壁的粘弹性的影响很小，他们被证明是由木材中的水流动在压缩过程中的影响。