摘要
【目的】刺槐作为我国重要的速生用材树种,被广泛应用于北方人工林种植,深入研究刺槐木材的物理力学性质,为刺槐人工林建设经营以及木材的高效精细化利用提供科学依据。【方法】本文对采自于山东省东营市刺槐林场的4株不同树龄人工林刺槐沿树干等分成0.65 m长若干小段并顺序编号,测定和分析每段木材的物理性质(气干密度、全干密度、基本密度)、力学性质(顺纹抗压强度、横纹径向全部抗压强度、横纹弦向全部抗压强度、抗弯强度、抗弯弹性模量)以及化学组分(纤维素、半纤维素、木质素)含量,并通过SEM电镜扫描图对各段木材的微观构造进行对比分析。【结果】刺槐木材的气干密度、全干密度、基本密度、顺纹抗压强度、横纹全部抗压强度(径向、弦向)、抗弯强度、抗弯弹性模量均随树龄的增大而增加,随树干位置增高呈现先增大后减小的规律。将木材气干密度与顺纹抗压强度、横纹(径向、弦向)全部抗压强度、抗弯强度、抗弯弹性模量分别进行线性和幂函数拟合,两种模型均能很好地拟合试验结果,拟合度R2值为0.865~0.895。各段木材化学组分中纤维素含量随树龄及树干高度位置的变化规律与木材各项力学性质的变化规律相似。木材的微观构造中导管占比率随树龄增大而减少,随树干高度位置增加呈现出先减后增的变化规律。【结论】10年生、15年生、20年生、25年生刺槐木材的气干密度、顺纹抗压强度、抗弯强度、抗弯弹性模量均为中级以上,是良好的家具和建筑用材。在利用时应充分考虑不同树龄木材和树干不同位置的差别。密度作为影响木材力学性质的直接要素,可根据相关方程通过刺槐木材的密度值估算部分力学性质的数值。刺槐木材纤维素含量与木材各项宏观力学性质相关度很高,而木材导管占比率的差异则从微观构造上揭示了木材密度变化的内在机理。
[Objective]Robinia pseudoacacia,as an important fast-growing timber tree species in China,is widely used in plantation in northern China. In order to provide a scientific basis for the construction and management of Robinia pseudoacacia plantation and efficient and meticulous utilization of wood,it is very necessary to further study the physical and mechanical properties of Robinia pseudoacacia wood.[Method] In this paper,4 different tree-age plantations of Robinia pseudoacacia collected from the coastal forest farm of Dongying,Shandong Province of eastern China were divided into 0. 65 m longsegments along the tree trunk and numbered in sequence. The physical properties( air-dry density,absolute-dry density and basic density) and mechanical properties( compressive strength parallel to grain, radial compression entire strength perpendicular to grain, the tangential compression entire strength perpendicular to grain,bending strength,bending elastic modulus) and chemical components( cellulose,hemicellulose and lignin) content of wood in different ages and varied heights were measured and analyzed. The microscopic structure of each section of wood was compared and analyzed by scanning electron microscope. [Result]The results showed that wood air-dry density,absolute-dry density,basic density,compressive strength parallel to grain and compression( entire) strength perpendicular to grain( radial and tangential), bending strength, bending elastic modulus all increased with tree age increasing,and with the increase of trunk height position,the above variables increased first and then decreased. The wood air-dry density was fitted by linear and power functions fitting to the compressive strength,the transverse compressive strength,the bending strength and the bending modulus of elasticity.It was found that the two models can fit the experimental results well,and the fitting R2 was 0. 865-0. 895. The changing rules of cellulose content in chemical components of each wood segment with tree age and trunk height position were similar to those of each mechanical property of wood. In the microstructure of wood,the ratio of duct decreased with the increase of tree age,and showed a rule of decreased first and then increased with the increase of trunk height position. [Conclusion] The results show that the air-dry density,compressive strength parallel to grain,bending strength,bending elastic modulus of 10 years old,15 years old,20 years old and 25 years old Robinia pseudoacacia wood were all above intermediate level and these are good furniture and building wood. The difference in varied tree age and varied trunk height position should be taken into full consideration when utilizing wood. As a direct factor influencing the mechanical properties of wood,density can be used to estimate partial mechanical properties of Robinia pseudoacacia wood according to the relevant equations. The cellulose content of Robinia pseudoacacia wood is highly correlated with the macro mechanical properties of wood,while the difference of wood duct occupation ratio reveals the intrinsic reason of wood density change from microscopic structure.
作者
孙恒
冀晓东
赵红华
杨茂林
丛旭
Sun Heng;Ji Xiaodong;Zhao Honghua;Yang Maolin;Cong Xu(Key Laboratory of Soil and Water Conservation of State Forestry Administration Beijing Forestry University,Beijing 100083,China)
出处
《北京林业大学学报》
CAS
CSCD
北大核心
2018年第7期104-112,共9页
Journal of Beijing Forestry University
基金
国家自然科学基金项目(31570708)
关键词
刺槐
密度
力学性质
化学组分
微观构造
Robinia pseudoacacia
density
mechanical property
chemical composition
micro structure