落叶松结构集成材承载性能足尺检测与特性评价

针对我国尚无结构集成材足尺检测基础数据的现状,重点开展足尺材料测试和评价研究。研究以普遍应用的落叶松集成材为对象,按GB/T26899-2011《结构用集成材》国家标准对3种国际通用规格的结构集成材进行足尺承载特性测试。依据检测结果,按美国ASTM D2915-10《结构用木材和木质产品抽样和数据分析标准》规定的非参数法和参数法统计分析方式,确立了落叶松集成材抗弯弹性模量(MOE)和抗弯强度(MOR)的特征值数据及正态分布、对数分布和威布尔分布下的拟合优度;确定了各规格结构集成材MOE、MOR的变化趋势。针对不同组别之间MOE及MOR的尺寸效应,利用回归分析方法确立了MOE和MOR的关系;初步确定了结构用集成材的特征值和承载特性的评价方式,为国产树种结构集成材的设计和应用提供了重要的理论支撑。     

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.     

声－超声技术评价兴安落叶松规格材的抗弯性质

测量落叶松规格材的波速、峰值电压、时间形心和频率形心等声－超声参数,以及气干密度、抗弯弹性模量和抗弯强度等物理力学性质,研究声－超声参数、气干密度、动态弹性模量等与抗弯性质之间的相关性。为了探索利用声－超声技术预测落叶松抗弯性质的可行性,分别以动态弹性模量和声－超声参数及气干密度为自变量,建立预测其规格材抗弯性质的回归模型。结果表明：所有的声－超声参数、气干密度与抗弯弹性模量均在0.01水平显著相关,峰值电压、频率形心、气干密度与抗弯强度在0.01水平显著相关。利用气干密度、峰值电压和波速3个参数为自变量建立的抗弯弹性模量和抗弯强度的预测模型的相关性(决定系数 r2分别为0.83和0.66)与传统的超声波方法(以动态弹性模量为自变量建立的抗弯弹性模量和抗弯强度预测模型,r2分别为0.80和0.34)相比,模型的预测能力显著提高。利用声－超声技术能够较好地预测落叶松规格材的抗弯力学性质,特别是抗弯强度。     

杉木人工林规格材的足尺弯曲、压缩分级测试

利用人工林杉木制成尺寸为45 mm×90 mm×2 600 mm规格材,根据GB/T 50329、ASTM D4761分别进行足尺弯曲、压缩分级测试.结果表明,规格材的弯曲弹性模量(MOE)、弯曲强度(MOR)、顺纹压缩强度(UCS)平均值均表现出相似趋势:SS>No.2>No.1.SS等级、No.1等级和No.2等级规格材的MOE特征值分别是10.34、9.87和10.17 GPa;MOR特征值分别是26.93、20.25和20.74 MPa;UCS特征值分别是21.59、20.64和20.33 MPa;随着MOR增加,UCS/MOR降低;与无疵小试样测试相比,足尺规格材的SS等级、No.1等级和No.2等级的MOE平均值分别是无疵小试样的1.13、1.08和1.12倍;MOR平均值分别是无疵小试样的84.8%、70.8%和78.7%;UCS平均值分别是无疵小试样的81.1%、74.3%和75.9%.     

落叶松规格材抗弯性能特征值研究

以国产兴安落叶松规格材为例,根据美国标准ASTM D4761-96对规格材进行抗弯弹性模量和抗弯强度测试,并参照ASTM D1990-97,利用非参数法和参数法估计,初步得出兴安落叶松规格材抗弯弹性模量和抗弯强度特征值.为完善我国结构用规格材强度测试方法与强度特征值确定方法标准提供参考.     

温度对意杨木材弯曲性能的影响

本文讨论了在60～180℃的温度范围内，老杨素材、防火材和他水材的抗育强度（MOR）、抗弯弹性模量（MOE）、静曲破坏功和韧性系数（Zb）随温度的变化规律。结果表明，三种试材的抗弯曲性能均是MOE素材＞MOE防火材＞MOE饱水材；MOR素材＞MOR防火材＞MOR饱水材。素材的静曲破坏功随温度的增加呈明显下降趋势。她水材的Zb值变化较大。     

杉木人工林3个目测等级规格材的力学性质

对596根横截面尺寸为45mm×90mm的杉木人工林3种规格材(目测等级SS,No.1,No.2)抗弯、抗拉、抗压力学性质进行测试。结果表明:3个等级的弹性模量(MOE)、抗弯强度(MOR)、抗拉强度(UTS)及抗压强度(UCS)平均值从SS等级到No.2等级的变化呈V形,No.1等级的各项力学指标平均值略低于No.2等级;5%分位值(除MOE值外)从SS等级到No.2等级都呈下降趋势;不同目测等级的MOR,UTS,UCS值在0.01水平差异极显著,弹性模量与强度及各强度之间都存在较好的相关性。此外,当试件数量较少时,选择相同弹性模量范围内的强度平均值能较好地反映人工林杉木规格材弯曲强度、拉伸强度及压缩强度间的定量关系。     

微波处理对圆竹软化效果的影响

为改善圆竹家具弯曲构件软化工艺,推进圆竹家具工业化生产,以红竹竹筒为研究对象,采用微波加热进行软化处理,分析微波功率、处理时间和初含水率（10.6%、45.3%）对红竹圆竹软化效果的影响,并以弹性模量（MOE）和抗弯强度（MOR）为指标对软化效果进行评价。结果表明：随着微波功率提高,红竹MOE先下降后上升,500 W时达到最小值,较未处理材下降65.23%;MOR总体随功率提高而下降,在700 W时小幅上升,800 W时红竹出现严重内裂,强度较对照材下降47.21%。红竹MOE随微波处理时间的延长下降,在360 s时达到最小值,较未处理材下降75.44%。含水率45.3%红竹的MOE和MOR较气干红竹（含水率10.6%）大幅下降,分别下降了81.75%和65.13%。适当提高微波功率、处理时间及初含水率可降低红竹的MOE和MOR,提高红竹软化效果,但功率过高、时间过长会使MOE回升、红竹强度大幅下降。     

应力波法评价结构用指接材的抗弯性能

采用应力波无损检测方法测试落叶松、樟子松结构用指接规格材的动态弹性模量,并建立了动态弹性模量与抗弯强度的线性关系。研究结果表明,动态弹性模量与静态弹性模量和抗弯强度之间存在线性相关性。     

落叶松指接规格材弹性模量的研究

研究指接、锯材等级对兴安落叶松结构用指接材弹性模量的影响,分析不同检测方法评估落叶松指接规格材弹性模量的可靠性。以落叶松锯材为原料,根据纵向基频振动(FFT)测试结果将其分为M_E12、M_E14、M_E16、M_E18四组,制备截面为40 mm×90 mm的规格材和指接规格材;分别利用纵向基频振动(FFT)、横向振动(TV)、机械应力分等级(MSR)测试评估指接材的静态弹性模量。结果表明:落叶松规格材和指接规格材是一种高弹性模量的锯材,其平均弹性模量大于SPF目测二级规格材的弹性模量;分级后,不同等级指接材弹性模量差异显著;指接加工降低中低等级锯材的弹性模量,但不影响高等级锯材的弹性模量;利用MSR测试结果评估指接材的弹性模量效果最佳,但其设备复杂,结合FFT设备的优点,推荐工厂使用FFT在线检测落叶松指接规格材的弹性模量。     

Dynamic modulus of elasticity and bending properties of young Taiwania trees grown with different thinning and pruning treatments

The effects of different thinning and pruning methods on the bending strength and dynamic modulus of elasticity (DMOE) of young Taiwania (Taiwania cryptomerioides Hay) were investigated. The average DMOE, modulus of elasticity (MOE), and modulus of rupture (MOR) in the thinning treatments showed the following trend: no thinning > medium thinning > heavy thinning. This indicates that thinning reduces average bending properties. The average DMOE, MOE, and MOR in the pruning treatments showed the following trend: medium pruning > no pruning > heavy pruning. According to this tendency, better average qualities of lumber and specimens were from wood subjected to no-thinning and medium-pruning treatments according to an ultrasonic wave technique and static bending tests. However, most results showed no statistically significant differences among thinning, pruning, and thinning and pruning treatments. The average values of DMOE, MOE, and MOR of visually graded construction-grade lumber were significantly greater than those of below-grade lumber. Moreover, there were very significant positive relationships between density, ultrasonic velocity, DMOE, MOE, and MOR, although the determination coefficients were small.     

扭叶松实木板材三种动态弹性模量和静态弹性模量比较研究(英文)

采用Pundit、Metriguard、FFT等三种无损检测方法和常规弯曲法对加拿大扭叶松(lodgepole pine)蓝变与非蓝变实木板材的动态及静态弹性模量进行检测和比较研究。结果表明,蓝变材三种动态弹性模量及静态弹性模量均高于非蓝变材;对比分析表明,蓝变材和非蓝变材的动态及静态弹性模量存在差异,其中动态弹性模量差异均达到0.01显著性水平,静态弹性模量差异达到0.05显著性水平,并且心、边材及密度值不同是导致以上差异的主要原因。相关性分析表明,动态与静态弹性模量间相关性达到0.01显著性水平;尽管三种无损检测方法测量结果存在差异,但它们之间仍存在密切相关性,FFT 技术测量的准确性高于Pundit和Metriguard;板材中结子数影响木材动态和静态弹性模量,随着板材结子数增加弹性模量相应地降低。     

Impregnation and mechanical properties of three softwoods treated with a new fire retardant chemical

Three softwoods, Sugi (Cryptomeria japonica), Korean Pine (Pinus koraiensis) and Hinoki (Chamaecyparis obtusa), were vacuum–pressure impregnated with a fire retardant chemical consisting of ammonium phosphate polymer (APP), guanyl urea phosphate (GUP), phosphonic acid and a minor amount of additives. The variation in impregnation between and within wood species was investigated. A significant relationship and similar trends were found between fire retardant chemical (FR) uptake and specific gravity (SG), as well as void volume filled (VVF) and SG. Moreover, the effects of fire retardant treatment on mechanical properties, including modulus of rupture (MOR), static modulus of elasticity (MOE) and dynamic modulus of elasticity (DMOE), were evaluated. The results indicated that the trend of impregnation and regression function varied between species and positions within the same species. However, the relationship of SG and chemical uptake and that of VVF and chemical uptake could be represented by a positive linear regression, and the trends were similar between wood species. Both of SG and VVF increased with increasing FR uptake. After fire retardant treatment, the MOR and static MOE were reduced compared with before treatment. Conversely, the DMOE increased after treatment.     

Comparative study on three dynamic modulus of elasticity and static modulus of elasticity for Lodgepole pine lumber

The dynamic and static modulus of elasticity （MOE） between bluestained and non-bluestained lumber of Lodgepole pine were tested and analyzed by using three methods of Non-destructive testing （NDT）, Portable Ultrasonic Non-destructive Digital Indicating Testing （Pundit）, Metriguard and Fast Fourier Transform （FFT） and the normal bending method. Results showed that the dynamic and static MOE of bluestained wood were higher than those of non-bluestained wood. The significant differences in dynamic MOE and static MOE were found between bulestained and non-bluestained wood, of which, the difference in each of three dynamic MOE （Ep. the ultrasonic wave modulus of elasticity, Ems, the stress wave modulus of elasticity and El, the longitudinal wave modulus of elasticity） between bulestained and non-bluestained wood arrived at the 0.01 significance level, whereas that in the static MOE at the 0.05 significance level. The differences in MOE between bulestained and non-bluestained wood were induced by the variation between sapwood and heartwood and the different densities of bulestained and non-bluestained wood. The correlation between dynamic MOE and static MOE was statistically significant at the 0.01 significance level. Although the dynamic MOE values of Ep, Em, Er were significantly different, there exists a close relationship between them （arriving at the 0.01 correlation level）. Comparative analysis among the three techniques indicated that the accurateness of FFT was higher than that of Pundit and Metriguard. Effect of tree knots on MOE was also investigated. Result showed that the dynamic and static MOE gradually decreased with the increase of knot number, indicating that knot number had significant effect on MOE value.     

利用超声波检测杉木抗弯弹性模量

以大尺寸杉木板材为研究对象，通过超声波测试仪对其动态弹性模量进行无损检测及用微机控制电子式木材万能试验机测试其静曲弹性模量，并分析了两种试验方法测定结果之间的关系。结果表明：（1）杉木板材的静曲弹性模量E1和动态弹性模量E2之间呈线性相关，不同厚度的试样无论是作为独立样本还是合并成总体样本空间，其相关性都非常显著，相关系数为0．75～0．95；（2）各种规格的杉木静曲弹性模量平均值E1与动态弹性模量平均值E2的比值E1／E2受杉木板材的厚度影响较小，其值为0．768～0．837。     

四种方法测木质材料动弹性模量的对比研究

为寻找比较准确的估计木质材料静弹性模量的方法,以色木方材为例,采用纵向应力波、超声波、纵向共振和弯曲共振等4种方法检测41个无瑕疵试件的动弹性模量,采用静态载荷法测量其静弹性模量,并分析二者的相关性,采用配对t检验比较不同方法的差异。研究结果表明：四种方法测得的木质材料动弹性模量均高于其静弹性模量,但静、动弹性模量之间均呈显著的线性相关性,R2都大于0.7,因而四种方法都可以用来估计其静弹性模量。其中,弯曲共振法得到的样本试件动弹性模量与静弹性模量的差值均值最小,且相关性最高,因而运用弯曲共振法对木质材料静弹性模量进行估计最为准确,检测值也最接近静弹性模量值。     

Dynamic modulus of elasticity and bending properties of large beams of Taiwan-grown Japanese cedar from different plantation spacing sites

The effect of plantation spacings (types A-E) on the bending strength and dynamic modulus of elasticity of 41-year-old Taiwan-grown cedar (Cryptomeria japonica D. Don) was investigated. The results indicate that the highest values for the static bending modulus of elasticity (MOE), modulus of rupture (MOR), and dynamic modulus of elasticity (E_D, E _Dt) occurred in trees obtained from those most densely planted (type A); there was a significant difference between type A and the other four spacing types (B, C, D, and E), but there were no significant differences among those four types. Interrelations among MOE, MOR, E _D, and E _Dt could be represented by positive linear regression formulas, which revealed highly significant differences. The relations among the square value of stress-wave transmission velocity (V_t ² and V_t ²⁾ and MOE, MOR, E _Dl, and E _Dt, respectively, could be represented by positive linear regression formulas. The differences were highly significant.Part of this report was presented at the International Wood Engineering Conference '96, New Orleans, LA, USA, October 1996     

Static bending strength performances of cross-laminated woods made with five species

Thirty types of three-ply parallel- and cross-laminated woods were prepared from five species, and their static bending strength performance were investigated. The modulus of elasticity (MOE), proportional limit stress, and modulus of rupture (MOR) perpendicular to the grain were increased by cross-laminating, and the extent of the increase increased with decreasing density of the species. The measured values of MOE parallel and perpendi-cular to the grain of parallel-laminated woods and perpendicular to the grain of face laminae of cross-laminated woods were approximately equal to those calculated from true MOEs of individual laminae. However, the MOE parallel to the grain of face laminae of cross-laminated woods was much lower than the calculated MOE owing to the effect of the deflection caused by shear force on the MOE. The percentage of deflection caused by shear force versus total deflection (Y _s) showed high values, from 16.1% (buna) to 40.5% (sugi), and it decreased linearly with increasing shear modulus in the cross section of the core. In addition, there was an extremely high positive correlation between the MOR and the measured MOE parallel to the grain of face laminae of cross-laminated woods. The MOR was also highly dependent on the shear modulus in cross section of the core.Part of this paper was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, April 2000     

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.     

Assessment of flexural properties of different grade dimension lumber by ultrasonic technique

The dimension lumber （45mm×90mm×3700mm） of plantation Chinese fir （Cunninghamia lanceolata （Lamb.） Hook.） was graded to four different classes as SS, No. 1, No.2 and No.3, according to national lumber grades authority （NLGA） for structure light framing and structure joists and planks. The properties of apparent density was determined at 15% moisture content, bending strength and stiffness were tested according to American Society for Testing and Materials （ASTM） D198-99, and dynamic modulus of elasticity （Eusw） was measured by ultrasonic technique, for predicting the flexural properties of different grade lumbers. The results showed that Eosw was larger than the static MOE. The relationship between Eusw and static MOE was significant at 0.01 level, and the determination coefficients （R2） of the four grade lumbers followed the sequence as R^2No.2 （0.616）〉 R^2ss （0.567）〉 R^2No1 （0.366）〉 R^2No.3 （0.137）. The R^2 of Fusw and MOR were lower than that of the Etru and MOR for each grade. The Eusw of all the grade lumbers, except No.3-grade, had significant correlation with the static MOE and MOR, thus the bending strengthof those grade lumbers can be estimated by the E The Etru valuesof four grade lumbers followed a sequence as No.2-grade （10.701 GPa） 〉 SS-grade （10.359 GPa） 〉 No.l-grade （9.840 GPa） 〉 No.3-grade （9.554 GPa）. For the same grade dimension lumber, its Eusw value was larger than static MOE. Mean values of MOR for four grade lumbers follow a sequence as No.2-grade （48.67 MPa） 〉 SS-grade （48.16 MPa） 〉 No.3-grade （46.55 MPa） 〉 No. 1-grade （43.39MPa）.