杉木和I-72杨人工林木材干缩性质的研究

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。     

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).     

Pilot Study to Examine Radial Variation in Annual Ring Width, Density and Shrinkage

The annual ring width, density and shrinkage variation from pith to bark in Chinese fir (Cunninghamia lanceolata) and Boka sugi (Cryptomeria japonicd) were studied and compared. The results show that the ring width decreased sharply from pith to bark for Chinese fir. However, the ring width variation pattern for Boka sugi followed a different way, i.e., the ring width decreased to the fifth ring, increased to the tenth ring, decreased again to the fifteenth, and then increased to the twentieth, where it became constant. The large variations of Boka sugi appeared to show the maintenance of fast growth for many years. The annual ring mean density of Chinese fir increased gradually from pith to bark. However, the density changes for Boka sugi indicated the opposite trend, i.e., the mean density decreased gradually from pith to bark. The former showed a pattern as the same as a pine and a larch, and the latter was often found in a cedar and a cypress. The longitudinal shrinkage in juvenile wood was much hig     

Propagation behavior of acoustic wave in wood

We used acoustic tests on a quarter-sawn poplar timbers to study the effects of wood anisotropy and cavity defects on acoustic wave velocity and travel path, and we investigated acoustic wave propagation behavior in wood. The timber specimens were first tested in unmodified condition and then tested after introduction of cavity defects of varying sizes to quantify the transmitting time of acoustic waves in laboratory conditions. Two-dimensional acoustic wave contour maps on the radial section of specimens were then simulated and analyzed based on the experimental data. We tested the relationship between wood grain and acoustic wave velocity as waves passed in various directions through wood. Wood anisotropy has significant effects on both velocity and travel path of acoustic waves, and the velocity of waves passing longitudinally through timbers exceeded the radial velocity. Moreover, cavity defects altered acoustic wave time contours on radial sections of timbers. Acous-tic wave transits from an excitation point to the region behind a cavity in defective wood more slowly than in intact wood.     

人工林杉木和杨树木材物理力学性质的株内变异研究

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.     

Radial variation in partial compression properties perpendicular to the grain of Japanese larch (Larix kaempferi)

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.     

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。     

杨树与落叶松原木中应力波的不同传播速度

通过应力波测试仪对健康的杨树和落叶松原木试件进行检测试验,研究应力波在这2种原木试件中径向、弦向和纵向(原木心材和边材)传播速度之间的关系以及径向传播速度和直径、弦向传播速度和检测角之间的相关关系.结果表明:在这2种树种中,应力波径向传播速度和原木直径呈正相关,原木纵向边材传播速度比相应心材中的要大,弦向传播速度与检测角呈现二次函数关系.通过试验分析得出应力波在原木纵向心材和边材传播速度与径向传播速度比的域值.     

Prediction of wood stiffness, strength, and shrinkage in juvenile wood of radiata pine

Development of optimal ways to predict juvenile wood stiffness, strength, and stability using wood properties that can be measured with relative ease and low cost is a priority for tree breeding and silviculture. Wood static modulus of elasticity (MOE), modulus of rupture (MOR), radial, tangential, and longitudinal shrinkage (RS, TS, LS), wood density (DEN), sound wave velocity (SWV), spiral grain (SLG), and microfibril angle (MFA) were measured on juvenile wood samples from lower stem sections in two radiata pine test plantations. Variation between inner (rings 1–2 from pith) and outer (rings 3–6 from pith) rings was generally larger than that among trees. MOE and MOR were lower (50%) in inner-rings than in outer-rings. RS and TS were higher (30–50%) for outer-rings than inner-rings, but LS decreased rapidly (>200%) from inner-rings to outer-rings. DEN had a higher correlation with MOR than with MOE, while MFA had a higher correlation with dry wood MOE than with MOR. SLG had higher significant correlation with MOE than with MOR. DEN and MOE had a weak, significant linear relationship with RS and TS, while MOE had a strong negative non-linear relationship with LS. Multiple regressions had a good potential as a method for predicting billet stiffness (R ² > 0.42), but had only a weak potential to predict wood strength and shrinkage (R ² < 0.22). For wood stiffness acoustic velocity measurements seemed to be the most practical, and for wood strength and stability acoustic velocity plus core density seemed to be the most practical measurements for predicting lower stem average in young trees.     

Effect of coupling media on velocity and attenuation of ultrasonic waves in Brazilian wood

Coupling media are necessary to ensure that transducers bond to wood specimens to minimize coupling losses and improve the accuracy of ultrasonic measurements. There are several types of coupling media available, and the optimal choice is not known. In this work, we analyzed the results of ultrasonic wave attenuation for 0.1-MHz longitudinal and transverse transducers with six different materials as coupling media in nine species of Brazilian wood with densities in the range 700–1170 kg/m³. Tests were performed using constant pressure on the transducer and with wave propagation in the longitudinal direction. For transverse transducers, the polarization was in the radial and tangential directions. The results were analyzed statistically and showed that, for attenuation in both longitudinal and transverse waves, the material used for coupling had significant effects, whereas the wood species had no effect. For longitudinal waves, the statistical evaluation showed that the coupling material performance was strongly dependent on the species of wood, but it was not possible to observe any tendency of behavior associated with specific anatomical properties.     

Radial variations of wood properties in <Emphasis Type="Italic">Casuarina equisetifolia</Emphasis> growing in Bangladesh

Radial variations of wood properties (basic density, fiber length, vessel element length, and compression strength) in plantation-grown Casuarina equisetifolia in Bangladesh were investigated for effective utilization of the wood. Samples disks at breast height were randomly collected from trees in a 10-year-old plantation in Cox’s Bazar Forest Division, Bangladesh. The basic density showed a near-constant value up to 30 mm from the pith and then rapidly increased up to 60 mm from the pith. The fiber length and vessel element length gradually increased from the pith to bark. When radial variation of wood properties was determined according to relative distance from the pith, similar radial patterns were observed among the sample trees, indicating that the wood properties in C. equisetifolia may be related to the growth rate. The compression strength parallel to the grain (CS) increased from the pith to bark. A significant positive correlation was found between the air-dried density and the CS. The results obtained indicated that wood around the pith has a relatively low density, and wood outside the pith area has a relatively high density, suggesting that it could be used as structural lumber. Part of this report was presented at the 58th Annual Meeting of Japan Wood Research Society, Tsukuba, March 2008     

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.     

Prediction of transverse shrinkages of young-growth Sitka spruce (Picea sitchensis) and western hemlock (Tsuga heterophylla) with ultrasonic measurements

Abstract

The objective of this study was to examine the potential of acoustic measurement as a rapid and nondestructive method to predict the dimensional stability of young-growth Sitka spruce and western hemlock. Ultrasonic velocity, peak energy, specific gravity, and radial and tangential shrinkages were measured on twenty-four 25-×102-×y 25-mm specimens obtained from a 58-year-old stand in Southeast Alaska. We found that specific gravity and peak energy of ultrasonic signals were not good predictors of transverse shrinkage, as indicated by poor correlations. Ultrasonic velocity, on the other hand, was found to be a significant predictor of transverse shrinkage and therefore has good potential to be used as a field method to evaluate dimensional stability. The single-parameter prediction model explained 86% of transverse shrinkages in western hemlock and 71% of transverse shrinkages in Sitka spruce. Further study is needed to test the capability and feasibility of using acoustic velocity to predict both longitudinal and transverse shrinkages of wood in standing trees.     

Wood properties of <Emphasis Type="Italic">Pericopsis mooniana</Emphasis> grown in a plantation in Indonesia

The relationships between growth characteristics and wood properties were investigated for a threatened species, Pericopsis mooniana, to promote the establishment of plantations of this species in the tropics. Growth characteristics (diameter and height) and stress-wave velocity (SWV) of trees were measured for 22-year-old P. mooniana trees planted in Indonesia. The trees were categorized into three groups, fast-growing, middle-growing, and slow-growing trees, to investigate the effect of growth rate on the wood properties. In addition, radial variation of anatomical characteristics and wood properties were determined. No significant correlation was found between growth characteristics and SWV. The values for the vessel diameter, cell wall thickness of wood fibers, wood fiber length, basic density, modulus of elasticity, and modulus of rupture from wood at the bark side were higher than those at the pith side. On the other hand, vessel frequency gradually decreased from pith to bark. These results suggested that low-quality wood, such as juvenile wood, existed near the pith area.     

Transverse shrinkage variations within tree stems of <Emphasis Type="Italic">Melia azedarach</Emphasis> planted in northern Vietnam

This study quantified variations within tree stems in tangential shrinkage (α_T), radial shrinkage (α_R), and tangential/radial shrinkage ratio (α_T/α_R) of Melia azedarach grown in two different sites in northern Vietnam. The overall values of α_T, α_R, and α_T/α_R were 7.05%, 4.38%, and 1.64, respectively. The variation pattern in α_T and α_R was found to increase gradually from pith to bark and this trend was similar on both sites. In radial direction, the α_T/α_R decreased significantly from 10 to 50% of the radial length from pith before approaching a constant value toward the outside. The transverse shrinkage variation with height was very small and without statistical significance. There were strong positive relationships between transverse shrinkage and basic density (BD). This implies that the selection for high wood density may lead to increase wood transverse shrinkage. In addition, the α_T and α_R had significant positive linear relationships with both acoustic wave velocity (V_L) and dynamic modulus of elasticity of log (DMOE_log). This result suggests that it might be possible to sort lumber with large transverse shrinkage by stress wave method for M. azedarach planted in northern Vietnam.     

Radial and between-family variations of the microfibril angle and the relationships with bending properties in Picea jezoensis families

With emphasis on tree breeding for wood quality in Picea jezoensis, we aimed to evaluate radial and between-family variations in the microfibril angle (MFA) of the S₂ layer in the latewood tracheids in 10 open-pollinated families of 43-year-old P. jezoensis trees. In addition, the relationships between MFA/wood density with the modulus of elasticity (MOE) or modulus of rupture (MOR) were investigated. Significant differences in MFA between families were found from the pith toward the bark. MFA showed higher values around the pith area, although some families showed relatively lower values than others around this area. In addition, due to a larger coefficient of variations of MFA near the pith, the potential for juvenile wood MFA improvement may be greater compared with mature wood. MOE was correlated with MFA in juvenile wood and with wood density in mature wood, whereas MOR was mainly correlated with wood density at radial positions in both woods. Therefore, to improve the MOE and MOR of P. jezoensis wood, both MFA and wood density would be factors to consider in both juvenile and mature woods. On the other hand, there are indications that, only wood density would be an important criterion for improving mature wood properties.     

Determination of fiber length and juvenile and mature wood zones in Acer velutinum Boiss. trees grown in Iran

In our investigation we studied fiber lengths and the transition age from juvenile to mature wood in Acer velutinum Boiss. For this purpose, samples from three normal maple trees at a Noshahr site in northern Iran were selected. Disks were cut at breast height. Test samples were taken along a radial direction from the pith to the bark, accounting for every ring during a 48-year period. We used the Franklin method to distinguish between fibers of juvenile and mature wood. The results show that the fiber length increased along the radial direction from the pith to the bark. The transition age between juvenile and mature wood was determined at the 14th annual ring from the pith.     

Possibility of improvement in fundamental properties of wood of acacia hybrids by artificial hybridization

Growth, specific gravity, and wood fiber length of Acacia mangium, Acacia auriculiformis, artificial acacia hybrid clones, and combinations, which were planted in a trial forest in Bavi, Vietnam, in July 2001, were examined. The radial variations from pith to bark were investigated to clarify the effect of genetic factors on these traits. Superiority of hybrids over their parents ranged from 36.3% to 41.6% for diameter, from 20.0% to 25.3% for height, from 6.9% to 20.7% for specific gravity, and from 6.1% to 12.8% for wood fiber length. The hybrid possessed heterosis in diameter, height, specific gravity, and wood fiber length regardless of whether the female parent was A. mangium or A. auriculiformis. The profiles of wood fiber length and specific gravity in the radial direction were similar for all the trees investigated. Wood fiber length was initially 0.5–0.6 mm near the pith and then increased slowly, finally reaching 1.0–1.2 mm near the bark. The specific gravity of acacia increased from 0.49–0.58 near the pith to 0.63–0.74 near the bark. From a relative distance of 30% from the pith, the specific gravity increased slightly and seemed to be stable. The relations among tree diameter, specific gravity, and wood fiber length were fair and could be represented by positive linear regression formulas. Hybrids for which A. auriculiformis was the female parent and A. mangium was the male parent had a faster growth rate and longer wood fibers than the inverse hybrids. Part of this report was presented at the 6th Pacific Regional Wood Anatomy Conference, Kyoto, Japan, December 2005     

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。     

Radial modulus of rupture in radiata pine measured by individual rings

New equipment was developed to measure the strength of individual annual rings in green wood under predominantly tensile stress. This equipment was then used to assess the variation of the radial modulus of rupture (rMOR) in thirty-six 25-year-old radiata pine trees taken from three sites in New Zealand. The rMOR for individual rings ranged from 4.2 to 12.7 MPa and was calculated on the assumption that during bending of the specimens fracture was caused by the tensile force in the radial direction (i.e., perpendicular to the tangential-longitudinal plane). No consistent trends were observed in rMOR from pith to bark; nor was there any evidence of differences between the three sites. However, there was substantial between-tree variability that manifested mainly in different average rMOR values for the trees rather than in variations from pith to bark. These results indicate that there are no concerns with respect to splitting resistance for the juvenile wood of radiata pine. It will be of interest to investigate whether splitting resistance is under genetic control.