香椿木材物理力学性质及抽提物含量研究

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%。     

进口辐射松木材主要物理性能径向变异研究

为了提高进口辐射松木材加工利用效率,扩展其使用范围,参照国家标准对新西兰辐射松木材的气干密度、干缩性、湿胀性径向变异进行了研究。结果表明:辐射松木材近树皮、中部和近髓心的气干密度分别为0.502,0.480和0.452 g/cm~3,自树皮至髓心气干密度呈现出逐渐减小的趋势,并且在0.05水平达到了显著差异,平均气干密度为0.478 g/cm~3,属于低密度木材;辐射松木材在气干状态下,其径向、弦向及体积干缩率自近树皮至近髓心呈现出逐渐减小的趋势,并且弦向和径向干缩率在0.05水平上达到了显著差异,体积干缩率在0.01水平上达到了极显著差异;辐射松木材在全干至气干状态下,其径向、弦向及体积湿胀率自近树皮至近髓心呈现出逐渐减小的趋势,并且径向湿胀率在0.05水平达到了显著差异,弦向和体积湿胀率在0.01水平达到了极显著差异。在同一环境条件下,辐射松径向的干缩率和湿胀率均小于弦向。研究结果为进口辐射松木材的加工利用及径向不同部位木材尺寸稳定性能评价提供了重要的数据支撑。     

抽提处理对尾巨按木材干缩性的影响

为了抑制桉木干缩,采用全因子试验方法研究抽提工艺对尾巨桉木材干缩性的影响.试验结果表明:碱抽提对尾巨桉木材线性干缩率(径向、弦向)、体积干缩率的影响规律不一,但第6、8,9组方案的碱抽提试样的差异干缩率趋近于1;冷水抽提对尾巨桉木材线性干缩率(径向、弦向)、体积干缩率的影响规律比热水抽提明显,热水抽提材的差异干缩波动幅度比冷水抽提材大,效果较好的工艺组合也明显少;第3,4、7、8、11、12组方案的冷水抽提试样的差异干缩趋近于1,而仅第12组方案的热水抽提试样的差异干缩趋近于1.因此,碱抽提和水抽提可以降低尾巨桉木材干缩性的各向异性.     

长江滩地杨木密度和干缩性的研究

对安庆段长江滩地I-72杨的密度和干缩性进行了研究。结果表明:I-72杨的气干密度、全干密度和基本密度分别为0.454 g/cm3、0.415 g/cm3和0.364 g/cm3;I-72杨木材密度的径向变异为自髓心向外,最初递减,然后再向外层递增;轴向变异为沿树干向上逐渐增加;I-72杨的径向、弦向和体积全干缩率分别为3.917%、8.093%和12.138%,体积干缩系数为0.169,差异干缩为2.107;I-72杨5.3 m高度处的径向、弦向和体积全干缩率测量值均大于1.3 m高度处的测量值。     

油茶木材物理力学性质分析

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。     

莎丽格木材解剖学特征及物理力学性能研究

以莎丽格木材为研究对象,对其解剖特征、密度、干缩率及关键力学性能等材性指标进行测试和分析,并与改良处理前的山杨做了对比,以期为莎丽格木材的应用提供理论依据。实验结果表明,莎丽格木材纤维长度和宽度平均分别为1 284.26、25.91μm,纤维长宽比为50.62,纤维的壁腔比和腔径比分别为0.27、0.67。莎丽格木材基本密度、气干密度和全干密度分别为0.41、0.49、0.46 g/cm~3。莎丽格木材弦向、径向、体积的气干干缩系数为0.322%、0.128%、0.476%;弦向、径向、体积的全干干缩系数为0.054%、0.031%、0.385%,气干差异干缩为2.612、全干差异干缩为1.818。莎丽格木材的抗弯强度为72.85 MPa、抗弯弹性模量为10 984.17 MPa、顺纹抗拉强度为89.66 MPa。综合来看,莎丽格木材主要物理力学性能优良,具有在木器企业广泛应用的基础。     

无性系杉木木材物理性质研究

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.     

无刺刺槐木材基础材性研究及其品质评定

以‘皖槐1号’刺槐(Robinia pseudoacacia)人工林木材为对象,对其解剖构造、密度、干缩率及物理力学性质进行研究,并对其木材品质进行评估。结果表明:‘皖槐1号’木材纤维形态均匀,纤维平均长度、宽度分别为1 232.97、21.56μm,长宽比57.18,腔径比0.56;导管平均长度、宽度分别为226.13、154.31μm;微纤丝角为15.85°;气干密度、全干密度、基本密度分别为0.79、0.71、0.65g/cm~3;弦向、径向、体积的气干干缩率分别为3.85%、2.15%、6.47%,弦向、径向、体积的全干干缩率分别为7.53%、4.88%、12.86%,气干和全干差异干缩分别为1.79和1.54;抗弯强度、顺纹抗压强度、抗弯弹性模量分别为152.71 MPa、52.94 MPa、12.07 GPa;品质系数为316.37 MPa。综合分析表明,当为制浆造纸和纤维板原料时,‘皖槐1号’木材属优等木材;作为结构用材时,综合强度及品质系数均属"高"级。     

三倍体毛白杨新无性系木材干缩性的遗传分析

利用 9a生三倍体毛白杨测定林的 9个无性系为试材 ,着重研究了木材干缩率的遗传学问题。结果表明 :木材干缩率在无性系间的差异都达到了极显著水平 ,并受到强度遗传控制 ;木材干缩在株内纵向的变异模式是随树高增加而降低 ;全干体积 ,径向、弦向干缩率和气干体积 ,径向、弦向干缩率无性系重复力分别为 0 89,0 95 ,0 84 ,0 6 7,0 84和 0 6 8。     

杨树浸渍改性处理材尺寸稳定性研究

利用聚乙烯醇缩甲醛改性剂对杨树木材进行浸渍改性,对其改性材的尺寸稳定性进行研究。结果表明:改性材的径向、弦向和体积干缩率与素材相比均有不同程度的下降;从全干到吸水饱和状态的过程中,当改性剂达到一定浓度时,改性材的径向、体积湿胀率与素材相比有明显下降,弦向线湿胀率下降不明显。从气干到吸水饱和状态的过程中,改性材的径向、弦向湿胀率与素材相比均有不同程度的下降;改性材体积湿胀率随着改性剂浓度的上升而呈下降趋势,当改性剂浓度为30%时,改性材体积湿胀率为6.85%,与素材相比下降了5.54%。改性材吸水率随改性剂浓度的上升而下降,最低可达159%;改性材的抗干缩系数(ASE)随改性剂浓度上升而增加,最大可达47.8%。改性材的尺寸稳定性能要明显优于杨树素材。     

人工林落羽杉力学性能研究

对江汉平原人工林落羽杉物理力学性能进行了研究,结果表明:落羽杉的气干密度为0.413 g/cm3,气干密度等级为轻;综合强度为74 MPa,强度等级为Ⅰ级;径向横纹抗压强度略大于弦向横纹抗压强度;端面硬度最高,弦面硬度与径面硬度差别不大。落羽杉南北面近树皮处木材的密度、抗弯强度、弹性模量、顺纹抗压强度均大于近髓心处,南北方向对落羽杉的密度、顺纹抗压强度在5%水平上差异均不显著,而对其抗弯强度、弹性模量在1%水平上差异显著。     

Dielectric anisotropy of oven- and air-dried wood evaluated using a free space millimeter wave

To evaluate the dielectric anisotropy caused by wood structure at a millimeter wave frequency of 100 GHz, the dielectric parameters for flat-sawn specimens of nine wood species at 0 and 11 % moisture content (MC) were measured using a free space method devised for reducing the multiple reflections under an electric field of millimeter waves parallel to longitudinal and tangential directions of wood, and those in radial direction were estimated using a conventional approximation theory. The dielectric parameters in the tangential and radial directions were almost identical and constantly smaller than those in the longitudinal direction. All the dielectric parameters increased with wood density and were larger at 11 than 0 % MC. The dielectric parameters in the longitudinal and transverse directions and the dielectric anisotropy between them were well fitted to the regression lines based on a dielectric mixture model composed of pores and dielectric isotropic wood substance, and a parallel capacitor and Lichtenecker’s exponential formulas were employed to represent the dielectric parameters of the mixture in the longitudinal and transverse directions, respectively. It was concluded that the dielectric anisotropy at 100 GHz is caused by the pore alignment and that the dielectric parameters are almost unaffected by anatomical structures, such as the rays. It was also confirmed that the free space method was effective for the measurement of the dielectric parameters for the flat-sawn specimens.     

杉木浸渍改性材的尺寸稳定性研究

利用聚乙烯醇缩甲醛改性剂对杉木木材进行浸溃改性，对其改性材的尺寸稳定性进行研究。结果表明：改性材的弦向、径向和体积干缩率与素材相比均有不同程度的下降；改性材的弦向、径向和体积湿胀率与素材相比也均有不同程度的下降，但当改性剂浓度超过20％时，下降才较明显；改性材吸水率随改性剂浓度的上升而下降，最大可由改性前的197％下降到改性后的155％；改性材的抗干缩系数（ASE）随改性剂浓度上升而增加，最大可达18．8％。杉木改性材的尺寸稳定性能要明显优于素材。     

Stiffness of normal, opposite, and tension poplar wood determined using micro-samples in the three material directions

Mechanical tests on micro-samples were performed in the three material directions in normal, opposite, and tension wood collected from a poplar tree. Two custom micro-devices were designed and built in the laboratory to test samples under pure tension in the transverse direction and under 4-point bending conditions in the longitudinal direction. Both devices were designed to handle samples with a small transverse section (a few square mm), which allowed to select zones with homogenous anatomical features. The results indicate a very high longitudinal stiffness in tension wood (up to 35 GPa compared to an average of 18 GPa for normal wood). Considering wood density, the value represents a specific modulus that is nearly 70 % crystalline cellulose. However, tension wood is slightly less stiff in the tangential and radial directions (1,150 vs. 1,500 MPa for normal wood in the radial direction and 430 vs. 530 MPa in the tangential direction).     

Variability in physical properties of plantation-grown progenies of Melia composita and determination of a kiln-drying schedule

Plantation-grown progenies of Melia composita Willd.were studied for variability in several physical properties: density,radial and tangential shrinkage,longitudinal permeability of heartwood and sapwood.Furthermore,flat-sawn planks from each of the progeny were subjected to a quick-drying test for determination of kilndrying schedule.The mean density of the species was 0.39 g cm~(-3) and the wood may be categorized as light wood.Mean radial shrinkage(%) for the species was 2.8% with progeny-wise variation in radial shrinkage from 1.56 to 4.11%.Mean tangential shrinkage(%) for the species was 5.54% with progeny-wise variation in tangential shrinkage from 3.69 to 7.71%.The resultant tangentialradial shrinkage ratio was 1.98(less than two),which suggests that the wood is relatively stable with respect to drying behavior.Mean sapwood and heartwood longitudinal permeability of the species were 3.38 and 2.02 Darcy,respectively.Higher longitudinal permeability of sapwood and heartwood indicate better drying and preservative properties of the species.Terazawa quick-drying test method suggests that the species is less susceptible to drying defects.During the test,only moderate checks and cracks were observed.A tentative kiln-drying schedule was recommended based on these results.     

Changes in physical properties of tropical and temperate hardwoods below and above the fiber saturation point

Changes in physical and mechanical properties of wood were analyzed using sorption tests combined with dimensional measurements and perpendicular-to-the-grain tangential compression tests. In order to determine the influence of wood structure on these changes, three hardwood species (Fagus grandifolia, Brosimum alicastrum and Cariniana domestica) presenting different anatomical structures were studied. Two experimental techniques were used to perform moisture sorption tests at 25°C. The first technique used saturated salt solutions (from 33 to 90% relative humidity) and the second used the pressure membrane method (above 96% relative humidity). Special attention was given to the “fiber saturation region”, where changes in wood properties started to take place. Results showed that at equilibrium moisture content (EMC), radial, tangential and volumetric shrinkage, as well as changes in transverse strength occurred above the fiber saturation point (FSP). This behavior can be explained by the effect of hysteresis at saturation on wood properties. This hysteresis indicates that loss of bound water takes place in the presence of liquid or capillary water, which contradicts the concept of FSP. The initial EMC at which bound water starts to be removed varied largely among the wood species.     

闽楠天然林与人工林木材物理力学性质研究

对闽楠人工林和天然林木材物理和力学性质进行了测定和比较分析,结果表明:闽楠天然林木材气干密度和全干密度分别为0.721 g.cm-3和0.680 g.cm-3,人工林木材气干密度和全干密度分别为0.572 g.cm-3和0.535 g.cm-3,闽楠天然林木材密度大于人工林且差异达到极显著水平,但人工林木材密度变异系数却小于天然林。闽楠人工林和天然林木材气干状态下体积干缩率分别为4.935%和6.439%,全干状态下分别为9.330%和11.376%,闽楠人工林木材的尺寸稳定性稍差于天然林,但从木材的差异干缩来看,闽楠天然林和人工林相近,分别为1.75和1.76。闽楠天然林木材端面、径面和弦面硬度分别为7 583 N、6 183 N和6 625 N,稍大于人工林,但差异不显著。闽楠天然林与人工林旋切板背面裂隙率分别为53%和67%,单板厚度的偏差人工林和天然林分别为0.08mm和0.09 mm。由此可知,发展闽楠人工林可以得到质量与闽楠天然林相近的板材。     

Investigation on transversal variation of poplar tension wood quality using ultrasound wave parameters

Transversal variations of some ultrasound wave parameters (phase velocity, group velocity, attenuation coefficient and acoustic radiation) were measured from the pith to the bark of poplar tension wood discs in different orthotropic directions. Over 80 cubic specimens of 2 × 2 × 10 cm³ (radial, tangential and longitudinal, respectively) were prepared and tested acoustically. Samples containing tension woods were separated from normal ones using anatomical experiments. Results showed acoustical behaviour of normal and tension wood improved in longitudinal direction while the distance between pith and bark increased; also, wave parameter variations were less important in radial and tangential directions. In addition, phase velocity and acoustic radiation – which significantly varied – were the best parameters for quality assessment of poplar wood compared with group velocity and attenuation coefficients. Since samples near the bark were acoustically better than counterparts near the pith, they could be used in products requiring more strength, like lumber. Finally, acoustic radiation and phase velocity were correlated more strongly with density than group velocity and attenuation.