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1.
木材导热系数的理论表达式(英文) 总被引：7，自引：0，他引：7
本文从木材的微观结构出发，应用物理力学导出木材弦向和径向导热系数的理论表达式 ，计算20种左右木材导热系数并与相同条件下的实验值比较，平均误差在5%附近，两者吻合 程度令人满意。 相似文献
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古建筑旧木材腐朽状况皮罗钉检测结果的定量分析 总被引：1，自引：0，他引：1
以故宫武英殿维修时替换下来的局部腐朽的落叶松、软木松旧木构件为材料,用目测法将试材划分为未腐朽及4级腐朽,共5个等级,对不同腐朽等级木材进行皮罗钉径向、弦向检测后,测定木材密度.应用统计学方法分析密度与皮罗钉径向、弦向打入深度间的关系,建立木材密度与皮罗钉打入深度的回归模型,以探讨应用皮罗钉检测方法定量评估古建筑木材材质状况的方法和途径.结果表明:随着木材腐朽程度的加深,木材密度降低,径向、弦向打入深度显著加大,各腐朽等级间差异极显著.2个树种因腐朽引起的密度及径向和弦向打入深度变化趋势表现出高度的一致性,达到"4"级腐朽时,与未腐朽材相比,密度降低20%左右,径向和弦向打入深度增加110%～136%;皮罗钉径向打入深度与弦向打人深度之间存在极显著的线性函数关系,密度与皮罗钉弦向打入深度及径向打入深度之间均存在着极显著的幂函数关系,决定系数均在0.01水平显著(P<0.01);落叶松和软木松密度与弦向打入深度的相关系数分别为-0.67和-0.76,均大于密度与径向打入深度的相关系数-0.55和-0.69. 相似文献
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杉木和I-72杨人工林木材干缩性质的研究 总被引：2，自引：0，他引：2
通过对杉木和I-72杨人工林木材南北向、不同高度位置、不同径向位置横向干缩(弦、径向)的测量,研究上述3个因素对2种木材横向干缩(弦、径向)的影响规律。结果表明:南北向的不同对杉木和I-72杨人工林木材的干缩均无显著影响;高度位置的不同对杉木和I-72杨木的弦向干缩均有显著影响,而对径向干缩则无显著影响;径向位置的不同对杉木和I-72杨人工林木材的径、弦向干缩均有极显著影响:从树皮到髓心,木材径、弦向干缩逐渐减小,与其基本密度的变化趋势一致。 相似文献
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油茶木材物理力学性质分析 总被引：1，自引：0，他引：1
《广西林业科学》2021,50(3)
为给油茶(Camellia oleifera)木材的综合利用提供理论参考,以37年生油茶木材为研究对象,对其主要物理力学性质进行测定,并将其与气干密度相近的木材进行对比分析。结果表明,油茶木材的基本、气干和全干密度分别为0.669、0.870和0.839 g/cm3。弦向、径向和体积气干干缩率分别为9.30%、4.80%和14.10%,差异干缩为1.94;弦向、径向和体积全干干缩率分别为13.30%、7.20%和20.20%,差异干缩为1.85;弦向、径向和体积干缩系数分别为0.339%、0.226%和0.667%。端面、弦面和径面硬度分别为11 100、9 470和9 280 N;木材抗弯强度、抗弯弹性模量、顺纹抗压强度和冲击韧性分别为118.0 MPa、8 910 MPa、49.2 MPa和208 kJ/m2;品质系数为2 499.2×105Pa。油茶木材干缩均匀性中等,尺寸稳定性中等;有较高的密度和品质系数以及中等的抗弯和顺纹抗压强度,虽然短小,但可采用指接或拼接等方式加以利用;柔韧性非常好,在弯曲成型方面有显著优势,适用于制作弯曲构件或弯曲木家具,可采用木材弯曲成型技术对其进行加工。 相似文献
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无性系杉木木材物理性质研究 总被引：1，自引：0，他引：1
对金洞林场杉木无性系19年生(不含苗龄)的木材物理性质研究,结果表明:杉木优良无性系木材的基本密度、径向干缩率、弦向干缩率、体积干缩率分别是0.279 g.cm-3、2.90%、5.10%和7.85%;整个无性系的基本密度、径向干缩率、弦向干缩率、体积干缩率分别是0.301 g.cm-3、3.28%、5.26%和8.27%;而对照CK的基本密度、径向干缩木材基率、弦向干缩率、体积干缩率分别是0.275 g.cm-3、2.80%、5.10%和8.00%.研究证明:杉木优良无性系不但木材产量高,而且木材质量也并不比当地实生苗差.选用杉木优良无性系造林,不但能增加木材产量,而且材质也不会因速生而变劣. 相似文献
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对香椿木材的物理力学性质及抽提物含量进行了系统研究。结果表明:香椿木材为轻质木材,气干密度0.45 g/cm3;气干材径向、弦向、体积干缩率分别为1.53%、3.21%、4.85%;全干材径向、弦向、体积干缩率分别为3.33%、6.56%、10.46%;饱水径向、弦向、体积湿胀率分别为3.45%、7.01%、11.67%;香椿木材顺纹抗压强度25.64 MPa,抗弯强度75.01 MPa,抗弯弹性模量6331.24 MPa,端面、径面、弦面的硬度分别为2.90 k N、1.91 k N、2.08 k N;香椿木材的热水抽提物含量为5%、苯醇抽提物含量为4.47%、1%No OH抽提物含量为20%。 相似文献
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分析和讨论了影响马尾松木材横向液体渗透性及其各向异性的机理.对马尾松木材的径向液体渗透性和弦向液体渗透性进行了测量.结果表明,马尾松木材的径向液体渗透性大于弦向液体渗透性,并且,马尾松木材的径向液体渗透性和弦向液体渗透性都是从边材向心材逐渐减小,并随着含水率的下降而升高.其原因是径向液体流动的主要通道是木射线和水平树脂道,弦向主要是管胞壁和交叉场上的纹孔. 相似文献
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Brief report on theoretical research upon wood thermal property 总被引：2，自引：0，他引：2
lntroductionThermaIpropertiesofwoodsuchasspecificheat,thermalconductivityandsoonareparameterswhichisrequiredinscientificresearchandheattreatmentofwood.BecausewoodisakindofnaturaIpolymerorganismwhosechemicaleIementandmicrostruc-tureareverycomplicated,it'sverydif=ficulttostudyitsthermaIpropeFtytheoreticalIy,therefOre,foraImostonecentury,itwasbymeansofexperimentthatthescientistsathomeandabroadstudiedthethermalpropertyofwooddirectIy(Dunlap19121KotImann1968,Cheng1985,Gao1985,Zhang1986)Buttheq… 相似文献
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Study on the specific heat of wood by statistical mechanics 总被引：2，自引：0，他引：2
Introduction12Sincewoodisanaturalmacromolecularorganism,andchemicalcomposition,structureandbiologicalcellstructureofwoodareextremelycomplicated,thesecausegreatdifficultytothetheoreticalstudyonthespecificheatofwood.Sofar,anyresearchachievementhasnotbeenreportedonit.Wetrytheoreticallytofindouttheinternalrelationandessentiallawsbetweenthespecificheatofwoodandthemicrostructureofwood,revealtheinternalfactorsandtheexternalconditionsofaffectingthespecificheatofwood,andfinallyderiveatheoreticalexpress… 相似文献
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Thermal conductivity and diffusivity of wood 总被引：5，自引：0，他引：5
Summary Transient simultaneous measurements of thermal conductivity and diffusivity of Swedish wood have been performed with the
plane source technique on oven-dry hardwood (birch) samples at room temperature and at 100 °C. The influences of temperature,
density, porosity and anisotropy on thermal conduction were investigated. The measurements were done in longitudinal (parallel
to the grain) and transverse (intermediate between radial and tangential) directions. As the temperature increased from 20
to 100 °C, the thermal conductivity of each sample increased slightly for both longitudinal and transverse directions. The
effect of density and porosity on the thermal conductivity may be related to the presence of other scattering mechanisms such
as voids and cell boundaries. It seems that the dominant mechanism of heat transfer across the cell lumina in these types
of wood is the heat conduction through the voids. An attempt was made to explain the behaviour of the effective thermal conductivity
by adopting a model based on the ratio between heat conduction in parallel and serial layers of gas, liquid, and solid phases.
Received 7 May 1997 相似文献
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The thermal diffusivity, specific heat, and thermal conductivity of 13 species of wood were measured by means of the laser flash method to investigate the thermal properties of wood during the heating process. The temperature ranged from room temperature to 270°C in air or under vacuum. The thermal diffusivity varied little during the heating process up to 240°C. The values in air were larger than those under vacuum. There was a linear relation between the specific heat and the ambient temperature, and the specific heat under vacuum was larger than that in air at high temperature. The thermal conductivity increased with density and the ambient temperature. To discuss the effects of the atmospheric conditions on the thermal constants of wood, a theoretical model of thermal conductivity was proposed and its validity examined, where the wood was assumed to be a uniformly distributed material composed of cell walls and air.Part of this paper was presented at the 47th annual meeting of Japan Wood Research Society at Kochi, April 1997 相似文献
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Summary A technique was developed for the determination of the effective dissolved oxygen diffusivity in liquid-saturated softwood in a diffusion cell under ambient pressure. From the measurements in the temperature range 2° to 50°C, the activation energy of diffusion was found to be 4.6 kcal/mole. The diffusivity in summerwood is about one half of that in springwood. The diffusivity of dissolved oxygen through composite springwood and summerwood layers was based upon samples of two Douglas fir sapwood blocks saturated with water. In the radial and tangential directions, diffusivity was 1.4 to 2.3x10-6cm2/s, which is about 6 to 10% that of dissolved oxygen diffusivity in water. The diffusivity in the longitudinal direction is about 5.5 times that in the other two directions.The diffusivity of dissolved oxygen through liquor-saturated wood and the effect of delignification on oxygen diffusion were also determined.The authors are grateful to Weyerhaeuser Company and Air Products and Chemical Inc., for the financial support of this research. 相似文献
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The effect of heat treatment on the surface colour and hygroscopic properties of pine wood were investigated in this study. Boards of Scots pine wood (Pinus sylvestris L.) were subjected to thermal treatment at 200°C, for 4, 6, and 8 h. The change of equilibrium moisture content and density values of the specimens in order to facilitate the understanding of the treated material behavior. The colour parameters L*, a* and b*, used to depict the total colour change (Δ E) of wood surface, were shown to change proportionally to the treatment intensity. Moreover, swelling in the tangential and radial directions and absorption of the specimens appeared to be enhanced in great extent by the thermal treatment process. The mean value of swelling percentage in the tangential direction decreased 10.26%, 17.22%, and 19.60% for specimens treated for 4, 6, and 8 h, respectively, referring to the final measurement after 72 h of immersion. In radial direction, mean value of swelling percentage decreased 19.56%, 32.75%, and 34.65% for treated for 4, 6 and 8 h, respectively, after 72 h immersion, which attests the decrease in swelling and improvement in the hygroscopic behavior of Scots pine wood. 相似文献