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林业科学 ›› 2004, Vol. 40 ›› Issue (3): 111-116.doi: 10.11707/j.1001-7488.20040319

• 论文及研究报告 • 上一篇    下一篇

X射线直接扫描法研究毛竹材密度的径向变异规律

王朝晖 江泽慧 阮锡根   

  1. 中国林业科学研究院木材工业研究所,北京100091;南京林业大学,南京210037
  • 收稿日期:2004-01-15 修回日期:1900-01-01 出版日期:2004-05-25 发布日期:2004-05-25

Studies on Radial Variation in Density of Moso Bamboo Using X-ray Scanning

Wang Zhaohui,Jiang Zehui,Ruan Xigen   

  1. Nanjing Forestry University Nanjing210037;Research Institute of Wood Industry,CAF Beijing100091
  • Received:2004-01-15 Revised:1900-01-01 Online:2004-05-25 Published:2004-05-25

摘要:

采用单色X射线直接扫描法测定了竹材密度径向连续变化曲线,以到竹青外皮的相对距离为自变量,以基本密度为因变量建立非线性经验回归方程为y=ax2-bx +c(x≤1) ,相关系数都在0.8~0.9以上,提出径向分层劈篾的可行性。分析了不同年龄和不同高度竹材密度径向变异规律,在竹子生长过程中,竹青部位密度变化小,竹肉部位密度变化大,是决定竹材平均密度的主要因子;随着高度的增加,各密度组成分量均提高,最小密度提高幅度比最大密度提高幅度略大,由于竹片的竹壁厚度减小使得竹片的密度梯度(密度差/距离)绝对增大。平均基本密度与中点密度相关性最高,相关系数达0.973。竹材径向密度梯度与最大密度具有正相关性。对于同一高度竹秆,密度梯度主要取决于最小密度,随最小密度的减小而增加;对于不同高度的竹秆,径向最大密度、最小密度随着高度增加而增加,密度梯度主要取决于竹壁厚度,随竹壁厚度的减小而绝对增加。与木材相比,竹材的密度梯度是杨木的3~4倍,在竹材加工时应采取各种措施减少或避免因密度梯度大引起的干缩不均而导致的表面开裂。

关键词: X射线直接扫描法, 竹材径向密度变异, 密度梯度

Abstract:

The bamboo test pieces could be scanned by the X-ray densitometer to get the successive profile on radial variation in density.The profile on radial variation in density of bamboo timber might be accordance with the equation of y=ax2-bx +c(x≤1),x is relative distance from bamboo green to yellow,moreover the regression coefficient beyond 0.8~0.9.It is possible to classify the bamboo slivers from different parts for improving value of the bamboo slivers.With age changing density of bamboo pulp change distinctly while density of bamboo green keep little variation.Density of bamboo pulp is the main factor to bamboo average density.With the height of culms increasing the density components and density grades(density gap/distance)in the radial direction also increase.The bamboo average density has excellent correlation with its middle density.The bamboo density grades have good correlation with its maximum density.As for the bamboo at the same height the minimum density is the main factor to its density grades while as for the bamboo at the different heights the culms thickness is the key effect on the density grades.The density grades of bamboo culm in the radial direction are normally 3 or 4 times bigger than that of wood.Because that characteristic might lead to an uneven shrinkage to produce the surface crack of bamboo,some protections should be done to reduce the effect.

Key words: X-ray scanning, Radial variation in bamboo density, Density grades