国产油松、马尾松原木品质应力波法试验及其缺陷研究

为了探讨振动法测量木材动态弹性模量时应力波波速的差异性,本实验选取含有不同节子及内部孔洞的国产油松、马尾松原木为试验材料,采用纵向敲击法测量原木试材的动态弹性模量。建立原木缺陷的数学模型,模拟计算和分析表明,木材节子及孔洞对应力波波速及弹性模量均有影响,而且降低了木材品质。     

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。     

落叶松铁路货车材应力分等的研究

1　试验目的与试验材料所谓应力分等 ,就是用一种机械设备来测试木材的强度及抗弯弹性模量 ,再根据强度或抗弯弹性模量确定木材的等级。我国对木材等级的确定 ,不论是何种用材 ,都是采用人工检测的方法 ,从外观上按木材的自然缺陷如节子、斜纹、虫眼等来划分。而往往有些表面缺     

实木板材的动态弹性模量检测

以市场上购买的气干核桃楸、水曲柳和红松板材为试材,采用基于打击音的快速傅里叶变换(FFT)频谱分析方法,检测试材的动态抗弯弹性模量,并与力学实验机测定的试材静态抗弯弹性模量作比较。结果表明:用声共振FFT快速自动检测实木板材的弹性模量具有普遍性意义,且比简单根据木材密度估计的方法提高了木材静弹性模量推测的准确度和精度。     

温度及水分状态对美国红松弯曲弹性模量的影响

应用温度控制系统,对美国红松小试样规格材进行测试,检验木材温度及水分状态对木材弯曲弹性模量的影响.结果表明:温度对木材的抗弯性能具有显著影响,随着温度的升高,木材的抗弯性能逐渐减弱;相同承载条件下,含水率越高,冻结木材的抗弯曲性能越强.对于纤维饱和材,冰点以下其弹性模量随着温度的降低而迅速增加,在冰点以上则增加缓慢;对于非纤维饱和材,其弹性模量受温度影响变化幅度在冰点两侧区别不明显.冻结木材弹性模量相对于常温(20℃)情况下(相对弹性模量)受温度和含水率变化的影响十分显著,而非冻结木材的相对弹性模量对温度变化均表现不敏感.通过建立的相对弹性模量-温度试验模型,能较好地预测不同温度及含水率下的木材弯曲弹性模量相对于常温的变化幅度.该研究为不同温度条件下尤其是低温时的木材弹性模量测量结果修正提供了试验依据.     

基于纵向共振法测试杨树原木应力波波速及弹性模量的研究

在介绍纵向共振法检测木材应力波波速及弹性模量的方法原理的基础上,利用应力波测试仪DirectorHM-200TM对杨树原木的应力波波速及弹性模量进行了测试.检测发现杨树原木的动态弹性模量与三点弯曲法测试的烘干后杨树锯材的静态弹性模量间具有较好相关性;当将杨树原木的密度视为常数时,其应力波波速的平方与烘干后杨树锯材静态弹性模量间仍具有很好的相关性,从而增加了进一步利用该应力波测试仪对木材进行应力分等的可行性,并为下一步自行研制基于该原理的测试仪器提供了依据.     

节子对木材胶合性能的影响

研究樟子松的节子类型、尺寸和组坯方式对其胶合性能的影响.结果表明:胶合面上节子的存在会降低木材的胶合性能,以节子尺寸的影响较显著,而节子类型的影响不显著 ;随着两胶合面节子相对面积的增加,木材的胶合性能降 低.在集成材的生产过程中,建议去除直径25 mm以上的节子,或避免两胶合面上直径＞25 mm节子的对接,可避免节子对木材胶合性能的影响.     

林产工业专业文摘

<正>节子对木材胶合性能的影响文章研究樟子松的节子类型、尺寸和组坯方式对其胶合性能的影响。结果表明:胶合面上节子的存在会降低木材的胶合性能,以节子尺寸的影响较显著,而节子类型的影响不显著;随着两胶合面节子相对面积的增加,木材的胶合性能降低。在集成材的生产过程中,建议去除直径25mm以上的节子,或避免两胶合面上直径25mm节子的对接,可避免节子对木材胶合性能     

超声波预测落叶松规格材的抗弯性能

用超声波法测量落叶松规格材的动态弹性模量(DMOE),用弯曲试验测量其静态抗弯弹性模量(MOE)和抗弯强度(MOR),分析DMOE与MOE和MOR的相关性。研究结果表明:落叶松规格材的DMOE值比MOE高;DMOE与MOE和MOR的相关性均在0.01水平显著,DMOE与MOE的相关性高于DMOE与MOR的相关性。     

人工林杉木结构用集成材层板抗弯性能研究

以人工林杉木（Cunninghamia lanceolata）层板为研究对象,分析3种指榫长度和4种嵌合度对杉木指接层板抗弯性能的影响,比较不同等级杉木指接层板和非指接层板的抗弯性能,建立抗弯性能之间的相关性方程。结果表明,指榫长度与嵌合度对指接层板的抗弯强度和抗弯弹性模量有显著影响,人工林杉木层板较优指接工艺参数为：指榫长度15 mm、宽距比0.18、嵌合度0.1 mm;分等对指接层板和非指接层板的抗弯性能亦有显著影响,I等、II等指接层板的抗弯强度特征值分别为28.7、26.6 MPa,与未分等杉木指接层板抗弯强度特征值相比分别提高了17.14%和8.57%。基于应力波法获得的杉木层板动态抗弯弹性模量与静态抗弯弹性模量、静态抗弯弹性模量与抗弯强度之间均呈显著性正相关,相关系数r分别为0.838和0.691。     

纤维板的静曲弹性模量及静曲强度的动态检测

利用振动无损检测法测得纤维板的动态静曲弹性模量,并用一元和二元回归分析了纤维板的密度、静态静曲弹性模量、动态静曲弹性模量、静曲强度之间的相关性。结果表明:纤维板的静态静曲弹性模量与动态静曲弹性模量之间,或动态静曲弹性模量与静曲强度之间均密切线性相关;以纤维板的动态静曲弹性模量和密度为自变量与静曲强度建立的二元回归方程,其相关程度较一元回归更为密切。密度及长度与横截面面积比值较大的纤维板,其动态静曲弹性模量与静态值较为接近。     

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.     

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。     

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。     

小波分析在中密度纤维板无损检测中的应用

以中密度纤维板为试件,通过纵向共振和弯曲振动试验讨论小波分析方法用于无损检测的可行性.结果表明:小波分析得到的中密度纤维板试件动弹性模量与常规弯曲静弹性模量在0.01水平下相关性非常显著,可以用小波分析方法测得的动弹性模量来表征常规弯曲静弹性模量;可以用小波分析的方法判断出试件是否有缺陷,小波分析在试件缺陷无损检测方面具有优越性.     

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）.     

Applications of wavelet transformation in the nondestructive test of medium density fiberboard

Taking medium density fiberboards (MDF) as samples, the feasibility of the applications of wavelet analysis in a nondestructive test is discussed in this paper. The main results are as follows: the modulus of elasticity of longitudinal resonance, measured by wavelet analysis, can replace the conventional static modulus of elasticity. Their correlation coefficient is significant (p < 0.01). The defect of samples can be judged by wavelet analysis, which is superior because it is a nondestructive test. __________ Translated from Scientia Silvae Sinicae, 2006, 42(10): 91–94 [译自: 林业科学]     

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