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Since the structure of oil palm wood varies dramatically, the property gradients of oil palm wood within a trunk are of great interest. In this study, the physical (density, water uptake and swelling in the radial direction) and mechanical properties (bending modulus of elasticity and strength, compressive modulus of elasticity and strength in the direction parallel to the fiber, compressive strength in the direction perpendicular to the fiber and shear strength in the direction parallel to the fiber) of oil palm wood for a whole trunk were examined. The water uptake, compressive strength in the direction perpendicular to the fiber, shear strength in the direction parallel to the fiber, bending modulus of elasticity and strength and compressive modulus of elasticity and strength in the direction parallel to the fiber appeared to be independent of trunk height but tended to be related to the relative distance from surface or density by a single master curve. However, the swelling in the radial direction of the oil palm wood was not correlated with the relative distance from the surface, trunk height or density. Finally, property map of oil palm wood for a cross section at any height was prepared for practical use. 相似文献
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人工林杉木和杨树木材物理力学性质的株内变异研究 总被引：4，自引：0，他引：4
按照中国国家标准研究杉木和I-214杨树木材的抗弯弹性模量、抗弯强度、顺纹抗压强度和密度,同时按照日本国家标准研究2个树种的顺纹抗剪强度.结果表明:杉木的抗弯强度、顺纹抗压强度和密度由胸高直径处向上呈波浪形增加,抗弯弹性模量则稳定降低,但不同高度间杉木的物理力学性质没有显著差异;近树皮处木材的物理力学性质高于近髓心处木材,并有极显著差异.对于I-214杨树,只有抗弯弹性模量从髓心到树皮逐渐增加,其他的物理力学性质,最小值在从髓心到树皮的过渡区,最大值在近树皮处,从髓心到树皮,杨树的物理力学性质有极显著的差异.杉木和杨树的径面顺纹抗剪强度从髓心到树皮有极显著差异,并且近树皮的高于近髓心的木材,而弦面顺纹抗剪强度从髓心到树皮没有显著差异.木材密度与力学性质有很好的线性相关关系,木材密度是一个很好的力学强度的预测手段. 相似文献
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Yoshitaka Kubojima Seiichi Kanetani Takeshi Fujiwara Youki Suzuki Mario Tonosaki Hiroshi Yoshimaru Hiroharu Ikegame 《Journal of Wood Science》2008,54(6):443-450
A dead tree of Pinus armandii Franch. var. amamiana (Koidz.) Hatusima (abbreviated to PAAm) was obtained from a natural habitat on Tanega-shima Island and various properties
of its wood were investigated. Grain angle was measured and soft X-ray analysis was undertaken to obtain the density in each
annual ring. Unit shrinkage and dynamic properties were measured by shrinkage, bending, and compression tests. Variations
of wood properties in the radial direction, relationships of wood properties to density, and annual ring width were examined.
Roughly speaking, variations in the radial direction of the grain angle, twist angle by drying, Young’s modulus and strength
in static bending, absorbed energy in impact bending, compressive Young’s modulus, compressive strength, and compressive proportional
limit corresponded to the variation of annual ring width. As a result, it was determined that if PAAm is afforested artificially
for the purposes of lumber production and conservation, the annual rings of logs should not be too widely spaced. Wood properties
of PAAm were similar to those of Japanese black pine (Pinus thunbergii Parl.), which is another representative pine on Tanegashima Island.
This study was presented in part at the 56th Annual Meeting of the Japan Wood Research Society, Hiroshima, August 2007 相似文献
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Boštjan Lesar Miha Humar Frederick A. Kamke Andreja Kutnar 《Wood Science and Technology》2013,47(5):977-992
Hybrid poplar (Populus deltoides × Populus trichocarpa) and Douglas-fir (Pseudotsuga menziesii) wood specimens were densified with three variations of thermo-hydro-mechanical (THM) treatment. The THM treatments differed in the steam environment, including transient steam (TS), saturated steam (SS), and saturated steam with 1-min post–heat treatment at 200 °C (SS+PHT). The bending properties, FTIR spectra, and colour of the THM wood specimens were studied before and after exposure to two different wood decay fungi, brown rot Gloeophyllum trabeum, and white rot Trametes versicolor. The results showed that the performance of densified hybrid poplar wood was considerably poorer than the performance of Douglas-fir heartwood. The FTIR spectra measurements did not show changes in the densified hybrid poplar wood, while some changes were evident in densified Douglas-fir specimens. After fungal degradation, the most prominent changes were observed on the SS+PHT specimens. Colour is one of the most important parameter predominantly influenced by the wood species and the intensity of the densification process for both wood species, while after fungal exposure, the colour of all densified Douglas-fir specimens obtained more or less the same appearance, and densified hybrid poplar specimens resulted in lighter colour tones, indicating that the pattern of degradation of the densified and non-densified specimens are similar. The 3-point bending test results determined that the THM treatment significantly increased the modulus of rupture (MOR) and modulus of elasticity (MOE) of the densified wood specimens, while fungal exposure decreased the MOE and MOR in hybrid poplar and Douglas-fir specimens. 相似文献
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Effects of short-term thermomechanical densification on the structure and properties of wood veneers
Pavlo Bekhta Stanisław Proszyk Tomasz Krystofiak Jan Sedliacik Igor Novak Miroslava Mamonova 《Wood material science & engineering》2017,12(1):40-54
The effects of short-term thermomechanical (STTM) densification temperature and pressure on the changes in surface roughness, wettability, mass loss (ML), thickness and density of alder, beech, birch, and pine wood veneer with low moisture content (~5%) were investigated. The anatomical structure of veneers was also observed. Veneer sheets were densified using pressure levels of 4, 8 and 12 MPa at three temperatures: 100°C, 150°C and 200°C for 4 min. The results were compared with those of the non-densified veneers. The obtained results show that STTM densification of veneers similarly to long-term densification of solid wood causes irreversible changes in their properties. The STTM-densified veneer surfaces became smoother and more hydrophobic, ML increased slightly while roughness and thickness values decreased significantly, the cell lumens collapsed and a certain amount of fractures in cell walls developed with increasing densification temperature and pressure. All of the investigated wood species showed higher density values after densification. It was found that an even STTM densification of veneers provides stable properties under normal atmosphere conditions; in particular, the thickness and contact angle values were stable for 24 hours after densification, which is an important consideration for industrial applications. 相似文献
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This study investigated the densities, average width of annual rings, and partial compression stresses at 5 % strain perpendicular to the grain of air-dried wood specimens, which were continuous in the radial direction from the pith and were obtained from Japanese larch (Larix kaempferi) trees with different diameters at breast height in the same stand, to evaluate the radial variations in partial compression properties perpendicular to the grain. The air-dried densities of the wood increased with the distance from the pith. The average width of annual rings of the wood tended to decrease with increasing distance from the pith and those of medium- and large-diameter trees seemed to increase near the pith. The partial compression stresses at 5 % strain in the tangential loading direction tended to increase with the distance from the pith and with air-dried wood density. However, in the radial loading direction, this tendency was not observed. The partial compression stresses at 5 % strain in the radial loading direction tended to be low in wood with a small average width of annual rings. These results indicate that the factors affecting the radial variations in the partial compression stress at 5 % strain differ depending on the loading directions. 相似文献
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毛竹竹材物理力学性能研究 总被引：5，自引：0，他引：5
为了解不同竹龄毛竹生材含水率、线性干缩率、气干密度、抗弯强度、抗弯弹性模量和顺纹抗压强度等物理性能,对其加工应用的影响,笔者以2-7年生毛竹为材料进行研究,结果表明：竹材的生材含水率、气干干缩率（弦向、径向、纵向）和全干缩率（弦向、径向、纵向）随着竹龄的增加呈减小的趋势;从基部到梢部竹材的生材含水率、线性干缩率均减小;竹材线性干缩率弦向＞径向＞纵向.竹材气干密度、抗弯强度、抗弯弹性模量和顺纹抗压强度均随着竹龄的增加呈增大的趋势,尤其是3年生竹材的这些物理力学性能与2年生差异显著,但3年后生竹材差异不大;从基部到梢部竹材的气干密度、抗弯强度、抗弯弹性模量和顺纹抗压强度逐渐增加.综合考虑毛竹的物理力学性能和竹林的经济效益,适合采伐的是3年后生竹材,锯截之后的竹材也应根据部位不同进行区分,以便于加工应用过程中合理利用,提高产品的理化性能和质量的稳定性. 相似文献
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Eylem Dizman Tomak Elif Topaloglu Nurgul Ay Umit C. Yildiz 《Wood Science and Technology》2012,46(5):905-918
The objective of this study was to investigate the effect of accelerated aging on compression strength, modulus of rupture, modulus of elasticity, color change, volumetric swelling, and volumetric shrinkage of bamboo specimens with and without node sections. In the study, these properties were compared with those of Scots pine and beech wood specimens. Depending on bamboo sections, the aging procedure reduced modulus of rupture, modulus of elasticity, and compression strength. Bamboo specimens showed relatively high strength properties compared to wood specimens due to having high density. Strength properties increased from bottom to top of bamboo culms. The presence of nodes in the specimens reduced compression strength and modulus of rupture but affected modulus of elasticity slightly. Remarkable color changes in specimens were observed after aging. Volumetric swelling and shrinkage of bamboo specimens exposed to aging decreased probably due to heat effect of aging procedure. 相似文献
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竹节对竹材力学强度影响的研究 总被引：9，自引：2，他引：9
本文对毛竹和刚竹的带节材与不带节竹材的主要力学性质研究表明,带节竹材的抗弯强度、顺纹抗压、抗剪、抗拉强度和冲击韧性都有一定程度降低的趋向,但抗劈开强度和横纹抗拉强度却有明显提高。影响竹材力学强度的主要因素是维管束数量、维管束排列方向及维管束中纤维的力学强度,了解这些规律,对复合材料的结构仿生有重要参考作用。 相似文献
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研究了不同培育措施(初植密度、间伐强度、坡向、坡位)对人工林樟子松(Pinus sylvestris var.mongolica)木材的密度和力学性质(横纹抗弯强度、抗弯弹性模量、顺纹抗压强度、冲击韧性、端面硬度)的影响。初植密度(1.5m×1.0m,1.5m×2.0m和1.5m×2.5m)对木材密度和抗弯弹性模量有显著的影响。初植密度为1.5m×1.0m时,木材主要力学指标值最大。适当间伐可提高木材的抗弯弹性模量和顺纹抗压强度,但重度间伐则会降低木材的力学强度。坡向(阳坡和阴坡)对木材的抗弯弹性模量影响显著,阳坡高于阴坡。坡位(上坡位和下坡位)对除端面硬度外的木材力学性质指标影响都显著,各项力学指标值均是坡下高于坡上。表5参9。 相似文献
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对天目铁木进行物理力学性质测试与分析,结果表明,天目铁木木材的气干密度为0.721g.cm-3,弹性模量11.2Gpa,弦向抗弯强度104.9Mpa,顺纹抗压强度46Mpa,顺纹抗拉强度126.7Mpa,综合强度为150.9MPa,物理力学性能属于中等。 相似文献
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正交胶合木（CLT）在木结构建筑中应用越来越广泛,特别是在中高层建筑物中。CLT作为楼盖构件使用时,承受柱或墙体施加的垂直荷载,因此CLT产品的设计及应用需要其横纹承压弹性模量和强度方面的参数;改善CLT横纹承压性能,也可以提高整体结构强度和建筑安全系数。文中主要介绍目前CLT横纹承压性能测试方法,总结CLT横纹承压性能影响因素方面的研究进展,以期为国内CLT研究提供参考。 相似文献
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Acoustic emissions of pine wood samples (Pinus sylvestris L.) previously infected with the soft-rot fungi (Chaetomium globosum Kunze) and brown-rot fungi (Coniophora puteana (Schum. ex Fr.) Karst.) were measured in the perpendicular to grain compression test, in the radial direction. It was found
that even a minimum mass loss (below 1%) caused by enzymatic deterioration of the wood substance resulted in an increase in
acoustic emission level in the compression test measured perpendicular to grain in the radial direction. A particularly sensitive
indicator of wood enzymatic destruction were cumulative counts of acoustic emission related to the value of the applied compression
load.
Received 4 March 1997 相似文献
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Semi-isostatic densification is a useful method to increase the density and to improve the mechanical properties of fast-grown
softwood species like radiata pine. A major disadvantage of this method is the almost complete recovery of the original dimensions
when densified wood is exposed to moisture. Heat treatment improves the dimensional stability of wood and might be a useful
method to prevent this shape-recovery after densification. However, no or only a limited effect on the shape-recovery was
found when densified radiata pine was exposed to moisture. 相似文献
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Compression of wood under saturated steam, superheated steam, and transient conditions at 150°C, 160°C, and 170°C 总被引：1，自引：1，他引：0
In this paper, the compressive deformation of hybrid poplar wood (Populus deltoides?×?Populus trichocarpa) at high temperature (150, 160, and 170°C) and under various conditions of steam pressure was studied. Temperature and conditions of steam environment affected the relative density change and creep deformation during compression, as well as properties of the resulting densified material. While the temperature significantly affected the compression deformation of specimens compressed under transient and superheated steam conditions, temperature within the range studied had little effect on the compressive deformation in saturated steam. In all tested conditions, compression deformation was achieved without cell wall fractures. Higher temperature of compression, regardless of steam condition, resulted in lower equilibrium moisture content. In specimens compressed under saturated steam, the modulus of rupture (MOR) and modulus of elasticity (MOE) were increased proportionally to the increase in density, while the compression under superheated steam produced lower increase in the MOE and MOR than expected based on the increase in density. Compression in transient steam conditions at 170°C produced densified wood with higher MOE and MOR than expected based on the increase in density. 相似文献
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Variations in compression strength and surface roughness of heat-treated Turkish river red gum (Eucalyptus camaldulensis) wood 总被引：1，自引：0，他引：1
This article reports the effects of heat treatment on compression strength parallel to the grain, the surface roughness [average roughness (Ra)], and the air-dry den-sity of wood from the river red gum tree (Eucalyptus camaldulensis Dehn.) planted in Turkey. Eucalyptus wood was heat-treated at temperatures varying from 120° to 180°C for durations of 2–10 h. Samples cut from the heat-treated wood were tested for air-dry density, compression strength parallel to grain, and surface roughness properties. Roughness measurements by the stylus method were made in the direction perpendicular to the fiber. Based on the findings in this study, the results showed that density, compression strength, and surface roughness values decreased with increasing treatment temperature and treatment times. Eucalyptus wood could be utilized by using proper heat treatment techniques without any losses in strength values in areas where working, stability, and surface smoothness, such as in window frames, are important factors. 相似文献
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对3种追肥处理1(N300P200K200)、处理2(N200P100K150)和处理3(N100P50K50),从12、27、42、50、62、75、88、99、110、144到192月生的尾巨桉生长量数据进行了统计分析,并在198月生时对每种施肥处理取7株样木进行了木材的基本密度、抗弯强度、弹性模量、硬度、干缩率以及皱缩率等指标开展研究,结果如下:追肥量与生长量成正相关关系.追肥量越多,生长量越大,这种差距从追肥后就开始产生,一直到192月生时都存在;但是,这种差距在大部分时间里都未达到显著水平:达到显著差距的只有施肥处理1和处理3之间,27月生时DBH达到0.01的显著性差异、平均高在12、27和37月生时达到0.05的显著性差异、蓄积量在27、37、42和50月生时达到0.05的显著性差异.材性指标上,大径材木材材性与追肥量的关系密切,增大施肥会影响木材材性,包括降低抗弯强度,增加弹性模量,降低端、径面和弦面硬度,降低基本密度,增加木材含水率等;达到显著差异的有:木材的抗弯强度、径面硬度被显著降低,达到了0.05的显著水平.木材边材基本密度降低更大,达到了0.01的极显著水平.经过多重比较的分析,都是常规施肥处理3与处理2和常规施肥处理3与处理1两两之间差异显著.处理1和2比处理3的抗弯强度平均分别降低了12％和14％、径面硬度分别降低了11.7％和14.1％,而边材基本密度分别降低了8.6％和8.1％;因此,在培育桉树大径材时,一定要考虑合理施肥量. 相似文献