共查询到20条相似文献，搜索用时 31 毫秒
1.
Kiyohiko Fujimoto Yasushi Hiramatsu Atsushi Miyatake Kenta Shindo Masahiko Karube Masaki Harada Seiichiro Ukyo 《Journal of Wood Science》2010,56(6):444-451
The object of this study was to investigate the strength properties of edge-glued laminae and to propose a suitable grading
method based on the lamina modulus of elasticity (MOE). Edge-glued laminae composed of lumber with similar MOEs (uniform laminae)
and edge-glued laminae produced by randomly gluing lumber independent of MOE (random laminae) were made from karamatsu (Larix kaempferi) lumber having the same thickness and length, but various widths. For both the uniform and random laminae, there was a strong
correlation between MOE values measured using the longitudinal vibration technique, the static bending test, and a grading
machine. The average values of bending, tensile, and compressive strengths of the uniform laminae were similar to those of
the random laminae. On the other hand, the average strength of laminae without end joints was significantly higher than that
of finger-jointed laminae for both uniform and random laminae. Finger-joints and knots played a significant role in the failure
of specimens, but the edge-gluing and the difference in MOE within an edge-glued lamina did not appear to affect the strength
properties. The bending, tensile, and compressive strengths of edge-glued laminae were strongly correlated to the lamina MOE. 相似文献
2.
LIN Lanying FU Feng Research Institute of Wood Industry Chinese Academy of Forestry Beijing China 《中国林业科技(英文版)》2007,6(3):17-25
Resonance flexural vibration（Fast Fourier Transform, FFT）, ultrasonic wave（Pundit） and stress wave（Metriguard） techniques were examined as means of evaluating the static modulus of elasticity （MOE） and predicting the modulus of rupture （MOR） of finger-jointed lumber specimens made with four kinds of Eucalyptus （Eucalyptus. citriodora, E. exserta, E. grandis x E. urophylla and E. grandis）. Dynamic MOE was calculated from frequency and time obtained from forced vibrations and sounds induced in the four species of finger-jointed specimens. It was found that correlation coefficients between density and static MOE and dynamic MOE were statistically significant at the 0.01 level. And it was also found that the three nondestructive techniques can provide rapid and accurate means to determine the MOE, and the dynamic MOE was more accurate to predict static MOE than density. But the correlation coefficient between dynamic MOE, static MOE and MOR were lower than results reported by other researchers for solid wood, and were not statistically significant. It can be concluded that the three nondestructive techniques are useful for evaluating the MOE, but not suitable for predicting the MOR of finger-jointed. 相似文献
3.
LIN Lanying FU Feng Research Institute of Wood Industry Chinese Academy of Forestry Beijing P.R. China 《中国林业科技(英文版)》2008,(1)
The variation in lumber quality within the supply of eucalypt is large. Effective segregation of the lumber according to "fitness for purpose " is fundamental to enabling the capture of greater value for the finger-jointed. This paper deals with the longitudinal vibration technique as a means of assessing modulus of elasticity (MOE) of solid and finger-jointed specimens made with Eucalyptus grandis × E. urophylla and E. grandis. Dynamic MOE was calculated from resonance frequencies obtained from longitudina... 相似文献
4.
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。 相似文献
5.
间伐小径木指接技术研究 总被引：7，自引：0，他引：7
间伐材指接胶合加工，变短材为长材，弯材为直材，为合理，有效利用间伐材开辟了新路。对间伐材木材含水率，指接端压的大小和时间，指接后养护时间，涂胶量，指榫规格等对指接材抗弯强度的影响进行了研究，并测定了苯酚，间苯二酚，甲醛树脂胶胶合的指接材快速老化性能。 相似文献
6.
以钢琴音板用西加云杉锯材试件为研究对象,依据梁的纵向、横向弯曲原理及其动力学理论,采用振动频率法和声学频率法,测量该批试材在自由支承状态下的基频值,得到杨氏弹性模量值,并对其性能进行评价。 相似文献
7.
采集7种我国具有代表性的云杉属木材及1种作对比用的美国产西加云杉试件,通过纵、横向木材试件在高次振动模式下的试验,测量木材各项声振动参数.研究发现:纵向材与径向材振动参数比之间存在着一定的相关性,据此可以选择各向异性适中,韧性好,纵向、径向振动受剪切影响小的木材制作乐器的音板. 相似文献
8.
三种典型竹质工程材料纵向弹性模量评价 总被引：1，自引：1，他引：0
以重组竹、竹束单板层积材（BLVL）、竹集成材为代表的竹质工程材料受到越来越多的关注和应用。文中采用超声波法、自由横向振动法和力学法分别对上述3种典型竹质工程材料的纵向动态弹性模量（MOE）进行评价比较,结果表明,横向自由振动法能较为快速、准确和无损地评价出竹质工程材料的MOE,MOE的变异系数与其自身铺装结构有关;重组竹、BLVL和竹集成材的一阶共振频率分别为455.73、380.41和487.62 Hz;超声波在竹集成材的纵向上传播速度最快,重组竹其次,BLVL最慢;三点弯曲力学测试发现3种竹质工程材料的断裂模式不同,全顺向的重组竹为竹纤维拉断和界面剪切破坏,纵横组坯的BLVL为横向竹束拉断以及竹/木复合界面分层,而更多体现实竹性能的竹集成材为底层竹材维管束拉断和拔出破坏,其断裂载荷为重组竹> BLVL >竹集成材,而断裂位移为竹集成材> BLVL >重组竹。 相似文献
9.
四种方法测木质材料动弹性模量的对比研究 总被引：1，自引：0，他引：1
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。 相似文献
10.
Comparative study on three dynamic modulus of elasticity and static modulus of elasticity for Lodgepole pine lumber 总被引：2，自引：0，他引：2
LIANG Shan-qing FU feng 《林业研究》2007,18(4):309-312
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. 相似文献
11.
Song-Yung Wang Cheng-Jung Lin Chih-Ming Chiu Jin-Hau Chen Te-Hsin Yung 《Journal of Wood Science》2005,51(1):1-6
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. 相似文献
12.
Raquel Gonçalves Cinthya Bertoldo Pedroso Marcus Vinicius Massak 《Journal of Wood Science》2013,59(2):127-132
In contrast to wood from native forests, the lumber harvested from planted forests is primarily composed of boards from younger trees. Given the possibility of using wave propagation methods to classify wood for structural purposes, it is important to evaluate if the ultrasonic parameters tend to vary with the age of the tree in a similar manner as static bending parameters. Experiments were conducted using structural beams taken from Pinus elliottii trees that were 8, 9, 13, 15, 22 and 23 years old. The beams were tested by ultrasound in the longitudinal direction and by static bending. The results showed that age of the tree influences the wave propagation velocity, stiffness constant and modulus of elasticity. The results were sorted into two groups based on the variation of these parameters: wood pieces from trees up to 15 years old and wood pieces from trees older than 15 years of age. Statistically, the flexural strength did not change with age due to the significant influence of knots on this parameter, which overcomes the influence of age. The data obtained by ultrasound follow the same trends with age as the elastic modulus in static bending. 相似文献
13.
The objectives of this study were to establish the method of evaluating wood mechanical properties by acoustic nondestructive
testing at standing trees and at logs of a Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) plantation, and to compare three acoustic nondestructive methods for evaluating the static bending modulus
of elasticity (MOE), modulus of rupture (MOR), and compressive strength parallel-to-grain (σc) of plantation wood as well. Fifteen Chinese fir plantation trees at 36 years of age were selected. Each tree was cut into
four logs, for which three values of dynamic modulus of elasticity, i.e., E
sw, of the north and south face based on stress waves to assume the measuring state of the standing tree, E
fr, longitudinal vibration, and E
us, ultrasonic wave, were measured in the green condition. After log measurements, small specimens were cut and air-dried to
12% moisture content (MC). Static bending tests were then performed to determine the bending MOE and MOR, and compressive
tests parallel-to-grain were made to determine σc. The bending MOE of small clear specimens was about 7.1% and 15.4% less than E
sw and E
us, respectively, and 11.3% greater than E
fr. The differences between the bending MOE and dynamic MOE of logs as determined by the three acoustic methods were statistically
significant (P < 0.001). Good correlation (R = 0.77, 0.57, and 0.45) between E
sw, E
fr, and E
us and static MOE, respectively, were obtained (P < 0.001). It can be concluded that longitudinal vibration may be the most precise and reliable technique to evaluate the
mechanical properties of logs among these three acoustic nondestructive methods. Moreover, the results indicate that stress
wave technology would be effective to evaluate wood mechanical properties both from logs and from the standing tree. 相似文献
14.
There have been many attempts to predict the performance of glulam beams. Several approaches have been taken, from early empirical techniques to more sophisticated stochastic methods. In recent years, more emphasis has been placed on the modeling of material properties. Generally, the modulus of elasticity (MOE) has been used as a criterion of laminar strength for the prediction of glulam performance in the traditional models. Most of the current models are based on MOE that was measured using the long span test; that is, they account only for variability between pieces of lumber. Therefore, these models do not account for the variation of material properties within a given piece of lumber. Five methods were considered to choose the appropriate one that could effectively predict the performance of glulam in this study. Prediction of glulam performance was done by the transformed section method. MOEs measured with the five methods were applied to a strength prediction program to compare the actual test results and the predicted results. MOEs used as input variables are as follows: long span MOE of the static bending test, localized MOE of the static bending test, long span MOE of the stress wave test, localized MOE of the stress wave test, and MOE of the machine stress rating (MSR) test. Results of the localized test showed excellent signification compared to those of the long span test. The MSR method, when used as input variable, obtained the most approximate result, so it is considered adequate for predicting the strength of glulam.An outline of this paper was presented at the 48th annual meeting of the Japan Wood Research Society, Shizuoka, April 1998 相似文献
15.
采用机械应力分等法对天然林落叶松锯材进行动态弹性模量EMSR测定，依据美国标准ASTM D 4761-05测量其四点平弯与侧弯的弹性模量E4f、E4s和抗弯强度（MOR），并分析EMSR与E4f、E4s、MOR的相关性。结果显示，EMSR与E4f、E4s相关性存在较大差异，且后者高于前者。相关系数分别为0.555、0.681。 E4f、E4s与MOR相关性高于EMSR与MOR的相关性，E4s与MOR的相关性高于E4f与MOR的相关性。实验表明，采用机械应力分等法提高木材分等准确性还需进一步研究。 相似文献
16.
Jun Shen 《Frontiers of Forestry in China》2006,1(4):431-437
Longitudinal sawn wood are usually selected as samples in the study of sound properties of a musical instrument board. But
in real production, radial sawn timber are cut and are also widely used as vibration component. Therefore, it is very important
to evaluate the vibration properties of the board in the round, especially for the sound radiation characteristic of radial
sawn timber and its relationship to longitudinal sawn timber. However, for the national and international experts, researches
on radial sawn timber and its role and function in sound emission have not yet been developed. This paper describes a study
of seven important spruces that grow up in the Sichuan and Heilongjiang provinces of China, and one Picea sitchensis specimen from North America. Under the high bending vibration mode, resonance frequency and other parameters of longitudinal
and radial wood were tested. Analysis result disclosed the relationship between longitudinal and radial wood vibration property.
An important conclusion of wood for musical instruments with proper anisotropy, fine toughness, and weak shear of longitudinal
and radial vibration was inducted.
__________
Translated from Scientia Silvae Sinicae, 2006, 42(3): 21–24 [译自: 林业科学, 2006, 42(3): 21–24] 相似文献
17.
18.
Existing log grading procedures in the United States make only visual assessments of log quality. These procedures do not incorporate estimates of the modulus of elasticity (MOE) of logs. It is questionable whether the visual grading procedures currently used for logs adequately assess the potential quality of structural products manufactured from them, especially those for which MOE is of primary concern. The purpose of this study was to investigate the use of stress wave nondestructive evaluation techniques to sort red maple logs for the potential quality of lumber obtained from them. Ninety-five red maple logs were nondestructively evaluated using longitudinal stress wave techniques and sorted into four stress wave grades. The logs were then sawn into cants and lumber. The same procedure was used to obtain stress wave times in the cants and lumber. The lumber specimens were then dried and graded using a transverse vibration technique. The results of this study showed that good relationships existed between stress wave times measured in logs, cants, and the lumber produced from the logs. It was found that log stress wave grades have positive relationships with the lumber grades. Logs with high stress wave grades produced high-grade lumber. These findings indicate that the longitudinal stress wave technique has potential in sorting logs and cants for the production of high MOE products.The Forest Products Laboratory is maintained in cooperation with the University of Wisconsin. This article was written and prepared by U.S. Government employees on official time, and it is therefore in the public domain and not subject to copyright. 相似文献
19.
Reduction in the rotation ages of softwood saw-log plantations in South Africa is causing increased proportions of low stiffness sawn lumber at final harvest. It has been shown for some species that the microfibril angle (MFA) of the S2 layer of tracheids is strongly related to the modulus of elasticity (MOE) of wood, even more so than wood density, especially in wood formed during juvenile growth. The objectives of this study were to describe the variation in MFA in young Pinus patula trees and to determine the relationship between MFA and the dynamic MOE of sawn P. patula lumber. Thirty 16- to 20-year-old trees from six compartments from the Mpumalanga escarpment were processed into discs and lumber. The MFA, density and ring width were measured at two height levels using Silviscan 3. The average annual ring MFA varied between 7° and 29°; the pattern of variation depended mainly on height level and the ring number from the pith. The MFA in P. patula followed the same within-tree variation trends as in New Zealand-grown Pinus radiata but the average MFA was lower in absolute terms and differences between height levels were less pronounced. The MFA and density exhibited highly significant Pearson correlations of 0.73 and 0.70, respectively, with board dynamic MOE. A multiple regression model, which included MFA, density and ring width, explained 71% of the variation in the dynamic MOE of boards. A sensitivity analysis on the model showed that MFA and density had approximately similar influences on predicting the dynamic MOE of Pinus patula boards. 相似文献
20.
This study assesses the changes in elastic behaviour (i.e. modulus of elasticity – MOE) and mass loss of different hardwood
and softwood species exposed to decay in laboratory soil-bed tests. Elasticity moduli were determined using conventional static
methods as well as a dynamic method based on flexural vibration. The results obtained show a high correlation between dynamic
and static bending measurements for all the timber species tested at different stages of fungal decay. Furthermore, the non-destructive
MOE assessment proved to be a good tool for the early detection of wood decay.
Received 5 January 1999 相似文献