热处理对毛白杨木材物理力学性能的影响

采用蒸汽介质,氧气含量控制在2%以下,在热处理箱内对毛白杨木材进行热处理,研究处理温度(170~230℃)和处理时间(时间1~5 h)对毛白杨木材物理力学性能的影响。结果表明,随着处理温度的提高和处理时间的延长,毛白杨木材的抗胀缩率显著提高,但抗弯强度显著降低;热处理后毛白杨木材的抗弯弹性模量提高。     

热处理温度对圆盘豆木材力学性能的影响

以过热蒸汽为传热介质和保护气体,采用不同温度对圆盘豆木材进行热处理4h,对圆盘豆木材在不同热处理温度下的力学性能变化规律进行研究。结果表明,随着热处理温度升高,圆盘豆热处理材抗弯强度、弹性模量、表面硬度均表现为先升高然后降低的趋势。热处理温度对圆盘豆木材抗弯强度影响最大,对弹性模量的影响次之,对表面硬度的影响最小。     

热处理工艺对落叶松材色及力学性能的影响

对落叶松木材进行热处理,探讨热处理温度和时间对试材颜色指数和力学性能的影响.结果表明:随着处理温度的升高和处理时间的延长,木材的颜色变深,密度和质量降低,各项力学性能亦有下降.     

落叶松锯材目测分级与力学性能相关性的研究

以落叶松锯材为试验对象,依据GBS0005—2003《木结构设计规范》中外观分等的相关规则。对人工林落叶松锯材进行了以节子为检量对象的外观分等试验,并对分等后的锯材进行了弯曲破坏试验,分析比较了外观分等结果与其弯曲破坏检测结果的相关关系。     

弱酸改性对高温热处理杉木结构及性能的影响

为改善高温热处理木材的力学性能,采用亚硫酸钠/亚硫酸浸渍改性杉木,对木质素结构进行磺化修饰,以促进木质素在高温热处理过程中的迁移与重新分布.在高湿高压的环境下对改性杉木进行高温热处理,通过场发射扫描电子显微镜分析热处理前后杉木细胞壁表面微观构造,通过共聚焦激光扫描显微镜确定木质素在细胞壁中的半定量分布,测量了不同热处理...     

红外光谱法研究木材纤维素的结晶度

纤维素的结晶度是基于纤维素超分子结构的两相理论。这个理论认为纤维素由结晶区和无形区(非结晶区)构成,纤维素超分子结构中结晶区重量占纤维素总重量的百分率称为纤维素的结晶度。因此,纤维素的结晶度是说明纤维素内部结构的一个重要指标。它能够体现纤维素材料的某些性质,如:结晶度越高,材料的硬度、比重等也越高,而吸水性,湿胀性及化学反应活性等则     

高温热处理落叶松木材尺寸稳定性及结晶度分析表征

对以热处理介质为空气和N2下落叶松木材(热处理温度180～240 ℃,热处理时问4 h)的抗胀缩率(ASE)、结晶度及红外光谱进行测定和表征.结果表明:相同热处理时间下,随着热处理温度的升高,在180～220℃范围内,无论热处理介质是空气或N2时,落叶松木材的ASE值均达60%以上,介质为N2的木材的ASE值低于空气的;红外吸收光谱表明,3 380 cm-1附近-OH基团的伸缩振动强度随着热处理温度的升高而减少且变化显著,1 730 cm-1附近羰基随温度的升高吸收强度降低,相同条件下N2保护下羟基和羰基吸收峰强度高于空气的;落叶松木材在热处理时间相同的情况下,经过不同超高温度的处理后,木材结晶度的变化趋势是先增加、后减小、再增加,结晶度可达65%以上,同等条件下,N2氛围下木材的结晶度高于空气的.     

五种白桦木材的抗弯强度和抗弯弹性模量的研究

本研究主要对五种新培养的速生白桦木材的物理力学性质进行了测试，并根据测试结 果进行了变异分析及方差分析，分析结果表明，白桦木材的力学性质较好，物理力学性质差 异不显著，适宜作家具材。此结果表明，可根据木材物理力学性质因子选取优良树种。     

火炬松种源建筑材抗弯性质的变异及与树龄、晚材率、木材密度的关系

福建南屿15年生火炬松31个种源间木材抗弯弹性模量(MOE)的群体平均值为6 702.6 MPa,变化范围为5 042.5～8 610.2 MPa;抗弯强度(MOR)群体平均数为99.11MPa,变化幅度为77.32～119.79 MPa.种源间木材抗弯弹性模量(MOE)、抗弯强度(MOR)存在显著差异,二者广义遗传力大于0.441、0.422,方差分析中遗传方差分量在43.07%～60.79%范围内,环境方差分量范围为39.21%～56.93%,说明MOE、MOR除在遗传上受中等程度控制外,还显著受到环境条件影响.种源内MOE、MOR变异系数远大于种源间变异,说明火炬松材质改良在种源选择的基础上进行个体改良效果较好.树龄、晚材率和木材密度与MOE、MOR在0.01水平上呈显著正相关,木材基本密度估测MOE、MOR优于晚材率.火炬松种源木材MOE、MOR值与引种栽培地点有关.南屿靠近海岸线,并且纬度低于所有种源原产地纬度.火炬松种源原产地地理气象因子中,纬度对木材抗弯性能没有影响,经度与MOE、MOR呈较大的负相关,经度对抗弯性能的影响最大,6-9月降水/年降水次之,其他因素影响不显著.     

基于横向振动法对樟子松木材进行应力分等的研究

以樟子松木材为试验对象,分别运用横向振动法和静态弯曲法得出其动态弹性模量和静态抗弯弹性模量,重点对二者的关系以及尺寸、节子等因素对动态弹性模量的影响进行了研究.其结论是：动态弹性模量与静态抗弯弹性模量以及抗弯强度都有很好的相关关系;尺寸对动态弹性模量没有显著性的影响;节子的个数对木材动态弹性模量有显著性影响.     

Prediction of mechanical properties of Chinese fir wood by near infrared spectroscopy

Mechanical properties and the visible and near infrared (NIR) (350–2500 nm) spectra obtained from longitudinal and transverse face of 155 small clear wood samples of Chinese fir (Cunninghamia lanceolata) were measured, and 103 of them were used to establish calibration models. Calibrations were tested on an independent set (52 samples). Differences between calibrations developed by using the longitudinal and transverse face were small. The calibrations developed by using NIR spectra (350–2500 nm) collected from transverse face were slightly inferior to those developed by using NIR spectra collected from longitudinal face. When reducing the spectral range to between 780 and 1050 nm, the calibrations developed by using NIR spectra collected from longitudinal face were slightly inferior to those developed by using NIR spectra collected from transverse face, and reducing the spectral range causes no decrease in the quality of the models developed using NIR spectra collected from transverse face. Partial lease square (PLS) modeling and test showed that calibrations developed using the visible and NIR spectra from transverse and longitudinal faces and calibrations developed by using the reducing spectral range (780–1050 nm) from the transverse face were moderate, and have a RPD range from 1.51 to 1.90. It is concluded that NIR spectroscopy can be used as an initial screening. __________ Translated from Journal of Northwest Forestry University, 2007, 22(5): 149–154 [译自: 西北林学院学报]     

Effect of intermittent heat treatment on crystallinity in wood cellulose

The effect of intermittent heat treatment on cellulose crystallites in wood was studied to evaluate quantitatively the changes of crystallinity induced by intermittent and continuous heating. The changes in crystallinity were found to be strongly affected by the intermittent heat treatment. The increased crystallinity, the width of the crystals, and the piezoelectric properties were the same for the first intermittent heating as for continuous heating. Further intermittent heating for the same time duration and temperature had no effect on the above properties, probably due to the stopping of the thermal reaction during the interval. Our results suggested that intermittent heat treatment has certain critical cooling temperatures that stop the thermal reaction and are closely related to the duration of the interval. Samples once exposed to a certain duration of heat treatment and then cooled need more time, about twice that of the first duration of intermittent heating compared with continuous heating, to reach maximum crystallinity in wood cellulose.     

Okan Wood Mechanical Strength＇s Response to Heat Treatment Condition Changes

以过热蒸汽为传热介质和保护性气体,在热处理温度为160℃、180℃、200℃、220℃,热处理时间为2h、4h、6h、8h的条件下对圆盘豆木材进行高温热处理,研究圆盘豆木材在不同热处理条件下的力学性能变化规律。结果表明,随着热处理温度升高和热处理时间延长,圆盘豆热处理材抗弯强度降低;弹性模量在160℃时最高,然后降低;硬度的变化趋势不明显。红外光谱分析表明,热处理使木材中的半纤维素、纤维素、木素发生降解反应,导致木材力学强度降低。     

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。     

圆盘豆木材力学强度对高温热处理条件变化的响应

以过热蒸汽为传热介质和保护性气体,在热处理温度为160℃、180℃、200℃、220℃,热处理时间为2h、4h、6h、8h的条件下对圆盘豆木材进行高温热处理,研究圆盘豆木材在不同热处理条件下的力学性能变化规律。结果表明,随着热处理温度升高和热处理时间延长,圆盘豆热处理材抗弯强度降低;弹性模量在160℃时最高,然后降低;硬度的变化趋势不明显。红外光谱分析表明,热处理使木材中的半纤维素、纤维素、木素发生降解反应,导致木材力学强度降低。     

Models for predicting lumber bending MOR and MOE based on tree and stand characteristics in black spruce

In this study, a stepwise method was introduced to identify the best variables for predicting lumber static bending modulus of elasticity (MOE) and modulus of rupture (MOR) based on stand and tree characteristics in black spruce (Picea mariana). In the initial development of the technique, the two equations were fitted independently using ordinary least squares (OLS). A test for cross-equation correlation using black spruce data showed highly significant correlation between the two equations. Since the cross-equation correlation exists between the two equations, more efficient parameter estimation can be achieved through joint-generalized least squares, better known as seemingly unrelated regression (SUR). A simultaneous system of two equations was derived for black spruce. The two methods were evaluated and compared for some statistical parameters. The results indicated that there is a small difference between the two methods, but parameter estimates from seemingly unrelated regression estimation had smaller standard errors in all cases as compared to those from ordinary least squares estimates. Therefore, the system estimation methods theoretically perform better for simultaneously interdependent systems of equations and the appropriate system estimation approaches are recommended for estimating coefficients in simultaneously interdependent systems of forestry equations.     

潮湿与真菌腐朽对室外用铁杉胶合板力学性能影响的研究

Hem-fir plywood were exposed to two brown rot fungi, Gloeophyllum trabeum and Postia placenta, and one white rot fungus, Trametes versicolor, to investigate the effect of fungal decay on mechanical properties of plywood. Results showed that modulus of rupture （MOR） and modulus of elasticity （MOE） of hem-fir plywood declined significantly by inoculating fungi, and weight loss of sample had a modest decrease. The fungi also made a greater effect on MOR than on MOE. Of three fungi, Postia placenta caused a most significant weight loss, and Gloeophyllum trabeum resulted in a largest flexural properties loss. Substantial declines in MOR and MOE of hem-fir plywood were also observed when the plywood samples were stored under wet conditions over 15 weeks, even in the absence of fungal attack.     

热处理对慈竹重组材性能的影响

以丛生竹类的慈竹竹篾为原料,运用不同的热处理温度对其进行高温热处理并压制慈竹重组材,对热处理前后慈竹的化学组分进行分析,并对慈竹重组材的物理力学性能进行测定。研究结果表明,当热处理温度从190℃上升至210℃后,慈竹化学组分和慈竹重组材力学性质出现急剧的变化,保证力学强度的前提下,考虑户外用材的尺寸稳定性及生物耐久性的要求,可选用热处理温度190℃,热处理时间2 h的热处理工艺。     

疏水改性对杉木微观力学性能的影响

为提高木材尺寸稳定性,利用烷基烯酮二聚体对杉木进行疏水改性处理,同时运用纳米压痕技术分析评价疏水处理对木材纳米力学性能的影响.结果表明,当处理剂的质量分数为5％、处理时间为30 min时,疏水效果最好,同时最节约成本;疏水处理会降低杉木S2层细胞壁的弹性模量,当处理剂质量分数为5％时影响较小;杉木S2层细胞壁蠕变值会随处理剂质量分数和处理时间的增加呈现上升的趋势.