林业工程学报2024，Vol.9Issue(4)：34-39,6.DOI:10.13360/j.issn.2096-1359.202308028
受拉面节子对杉木幼龄材抗弯性能的影响
The effect of knots in tension face on bending properties of Cunninghamia lanceolate juvenile wood
摘要
Abstract
This work was aimed at revealing the effect of knots'features and distribution locations on wood bending strength and investigating the variation of this effect on tree growth direction.In this study,the specimens made from Cunninghamia lanceolate juvenile wood were obtained from three different heights of tree stems and divided into two groups,including specimens with and without knots.The locations of knots at the bottom of the specimens were examined.The modulus of rupture(MOR)and modulus of elasticity(MOE)of the specimens were measured using the three-point bending test.After the bending test,the images of the failure regions were collected.Knot information,including knot to specimen thickness ratio,knot area and knot to loading distance was recorded.The influence of knot features on MOR and MOE was statistically analyzed.The results showed that the size of knots increased as the increase in height of tree stem.MOR of the specimens with knots decreased as the increase in height of tree stem.The influence of knots on MOE of the specimens was trivial and knots significantly decreased MOR of the specimens.The knot to specimen thickness ratio and knot area negatively related to MOR,and knot to loading distance and MOE posi-tively related to MOR.Knot to loading distance had extremely significant influence on MOR and MOE.The knot to specimen thickness ratio,knot area,knot to loading distance and MOE can explain MOR with R2=0.580.Knot to specimen thickness ratio,knot area,knot to loading distance and MOE can explain MOR with R2=0.658 when the specimens are failure only at knots.The linear relationship between MOE and MOR of the specimens with knots was R2=0.580.Knot to specimen thickness ratio,knot area,knot to loading distance and MOE can explain MOR with R2=0.851 when the specimens with knots are not failure at knots.Because there is a strong linear relationship between MOE and MOR(R2=0.856),the influence of knot to specimen thickness ratio,knot area,knot to loading distance on MOR was slight when the specimens with knots were not failure at knots.The structural failure of specimens with-out knots was tearing of fibers.Shear strain can effectively transfer along fiber direction of wood without knots.The structural failure of specimens was sharp fractures or rupture around knots.Shear strain accumulation was prone to occur in knots when the specimens fail at knots.The effect of knots of bending properties of Cunninghamia lanceolate juvenile wood was statistically analyzed.The key knot parameters affecting bending properties of the specimens were found.关键词
杉木幼龄材/节子/节径比/节面积/节距/静曲强度/弹性模量Key words
Cunninghamia lanceolate juvenile wood/knot/knot to specimen thickness ratio/knot area/knot to loading distance/modulus of rupture/modulus of elasticity分类
农业科技引用本文复制引用
孙辉波,李万兆,张勰,何功秀,石江涛..受拉面节子对杉木幼龄材抗弯性能的影响[J].林业工程学报,2024,9(4):34-39,6.基金项目
国家重点研发计划(2021YFD2201302-2) （2021YFD2201302-2）
江苏高校"青蓝工程"资助(2022). （2022）
