含裂纹木梁的弯曲性能.pdf

_______________________________________________________________________________ 论文学科类别 220 含裂纹木梁的弯曲性能 王丽宇 鹿振友 （北京林业大学材料科学与技术学院，北京100083） 摘要 木材的抗弯弹性模量和抗弯强度是木材的主要力学性质。本文对木梁无疵小试样和含裂纹试样的抗 弯弹性模量和抗弯强度分别做对比实验，分析含裂纹木梁的弯曲特点及裂纹对弯曲性能的影响。研究结果 表明，切向裂纹对 LT 木梁弹性模量影响不大，因此可忽略不计，但切向裂纹的尺寸要有限制，即保证在线 弹性范围内，裂纹体是稳定的且裂纹没有扩展，在进行弹性模量测试的最高载荷作用下，不改变梁的弯曲 形态。裂纹的存在会降低木梁的抗弯强度，裂纹扩展时的载荷远远小于木材断裂时的载荷。所以对于含裂 纹的木梁来说，其承载能力的分析应同时考虑裂纹的稳定性，应该用断裂力学理论进一步分析和研究其安 全性、设计和预测其承载能力。 关键词 木梁，裂纹，弯曲性能 4、（英文）题名、作者姓名及所在单位、摘要、关键词： Wang Liyu ；Lu Zhenyou. Bending performance of wooden beam with crack. College of Material Science and Technology ，Beijing Forestry University ，100083，P.R.China. Bending strength and modulus are main mechanics characteristic，properties and stress indexes for wood. This paper carried on the contrast experiments about bending elastic modulus and bending strength for wooden beam containing no fault （crack ）small specimens and crack specimens respectively, analyzed the bending characteristic of wooden beam with crack and crack effect on bending performance. The experiments showed that the influence of tangential crack on LT wooden beam elastic modulus was not big and could be neglected. But the tangential crack size must have the limit, namely in linear elastic scope the crack body was guaranteed stable，crack did not propagate, and bending shape of wooden beam did not change under the highest load. The crack existence would reduce wooden beam bending strength because crack expansion load was far smaller than fracture load. Therefore for wooden beam containing crack，its load-bearing capacity analysis should simultaneously consider the crack stability, should further analyze and study its security, design and forecast l