共查询到20条相似文献,搜索用时 31 毫秒
1.
Yutaka Ishimaru Kazutoshi Arai Masato Mizutani Katsuhito Oshima Ikuho Iida 《Journal of Wood Science》2001,47(3):185-191
Some properties of wood (hinoki:Chamaecyparis obtusa) moisture-conditioned by an adsorption process from a dry state and by two desorption processes (from a water-saturated state and from a state with a moisture content slightly below the fiber saturation point) were investigated. The moisture contents of wood conditioned by the adsorption process and by the desorption process continued to approach to one another for the moisture-conditioning period of over 50 weeks. Accordingly, sorption hysteresis should be regarded as a transitional phenomenon that occurs during the process of approaching the true equilibrium, which requires a long time. The wood conditioned by the desorption process beginning from a water-saturated state showed slightly smaller dimensions than those conditioned by the adsorption process with the same moisture content; however, the wood conditioned by the desorption process from a moisture content below the fiber saturation point showed slightly larger dimensions than those conditioned by the adsorption process. The wood conditioned by the adsorption process from a dry state showed a higher modulus of elasticity and modulus of rupture than did the wood conditioned from a water-saturated state with the same moisture content. The mechanical properties of the wood also varied based on the states at which the desorption process was started. This is a notable characteristic of the relation between the drying condition and the mechanical properties of wood. 相似文献
2.
Sudijono Dwianto Wahyu Yusuf Sulaeman Iida Ikuho Furuta Yuzo Minato Kazuya 《Journal of Wood Science》2004,50(4):371-374
Mechanical property changes due to the moisture content (MC) and/or temperature changes were examined for 15 Indonesian wood species. A static bending test was carried out at 20°C, 65% relative humidity (air-dry), and water-saturated at 20°C (wet-20) and 80°C (wet-80). For individual test conditions, modulus of elasticity (MOE) and modulus of rupture (MOR) increased linearly with specific gravity regardless of wood species; however, maximum deflection did not correlate with specific gravity for any MC or temperature conditions. The relative values of MOE and MOR measured in wet-20 to air-dry conditions were variously affected from slightly to strongly depending on the wood species. However, the relative values always decreased markedly when saturated in water at 80°C, regardless of wood species. The relative MOE, MOR, and maximum deflection values due to the change in MC or MC and temperature combined were independent of specific gravity but may be dependent on wood type: softwood or hardwood. 相似文献
3.
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 相似文献
4.
Compression of wood under saturated steam, superheated steam, and transient conditions at 150°C, 160°C, and 170°C 总被引:1,自引:1,他引:0
In this paper, the compressive deformation of hybrid poplar wood (Populus deltoides?×?Populus trichocarpa) at high temperature (150, 160, and 170°C) and under various conditions of steam pressure was studied. Temperature and conditions of steam environment affected the relative density change and creep deformation during compression, as well as properties of the resulting densified material. While the temperature significantly affected the compression deformation of specimens compressed under transient and superheated steam conditions, temperature within the range studied had little effect on the compressive deformation in saturated steam. In all tested conditions, compression deformation was achieved without cell wall fractures. Higher temperature of compression, regardless of steam condition, resulted in lower equilibrium moisture content. In specimens compressed under saturated steam, the modulus of rupture (MOR) and modulus of elasticity (MOE) were increased proportionally to the increase in density, while the compression under superheated steam produced lower increase in the MOE and MOR than expected based on the increase in density. Compression in transient steam conditions at 170°C produced densified wood with higher MOE and MOR than expected based on the increase in density. 相似文献
5.
Arne Steffenrem Pekka Saranpää Sven-Olof Lundqvist Tore Skrøppa 《Annals of Forest Science》2007,64(8):799-806
Genetic- and environmental variation and correlation patterns were characterized for modulus of elasticity (MOE), modulus of rupture (MOR) and related wood traits: latewood proportion, wood density, spiral grain, microfibril angle and lignin content in five full-sib families of Norway spruce. The families were evaluated on the basis of clearwood specimens from the juvenile -mature wood transition zone of 93 sampled trees at age 30 year from seed. Family-means varied significantly (p < 0.05) for all wood traits studied except lignin content. MOE varied between 7.9–14.1 GPa among trees and 9.4–11.0 GPa among families. MOR varied between 47–87 MPa among trees and 61–71 MPa among families. Families remained significantly different in an analysis of specific MOE (MOE/density) and MOR (MOR/density). Hence, solely relying on wood density as a wood quality trait in tree breeding would not fully yield the potential genetic gain for MOE and MOR. Correlations between wood structural traits and specific MOE and MOR are presented and discussed. 相似文献
6.
Mohammad Derikvand Nathan Kotlarewski Michael Lee Hui Jiao Gregory Nolan 《Wood material science & engineering》2020,15(3):172-181
ABSTRACTThe main goal of this study was to investigate the visual characteristics, recovery rate, and flexural properties of sawn boards from a fibre-managed plantation Eucalyptus globulus resource as a potential raw material for structural building applications. The impacts of the visual characteristics, strength-reducing features, and variation in basic density and moisture content on the bending modulus of elasticity (MOE) and modulus of rupture (MOR) of the boards were investigated. The reliabilities of different non-destructive methods in predicting MOE and MOR of the boards were evaluated, including log acoustic wave velocity measurement and numerical modellings. The MOE and MOR of the boards were significantly affected by the slope of grain, percentage of clear wood, and total number of knots in the loading zone of the boards. The normal variation in basic density significantly influenced the MOE of the boards while its effect on the MOR was insignificant. The numerical models developed using the artificial neural network (ANN) showed better accuracies in predicting the MOE and MOR of the boards than traditional multi-regression modelling and log acoustic wave velocity measurement. The ANN models developed in this study showed more than 78.5% and 79.9% success in predicting the adjusted MOE and MOR of the boards, respectively. 相似文献
7.
Influence of temperature and steam environment on set recovery of compressive deformation of wood 总被引:3,自引:2,他引:1
Low-density hybrid poplar wood (Populus deltoides?×?Populus trichocarpa) was densified by mechanical compression under saturated steam, superheated steam, and transient conditions at temperature levels of 150, 160, and 170°C. Furthermore, compression of wood under saturated steam conditions at 170°C, followed by post-heat-treatment at 200°C for 1, 2, and 3?min, was performed. To determine the influence of compression treatment on the set recovery, specimens were subjected to five cycles of water soaking and drying. Modulus of rupture (MOR) and modulus of elasticity (MOE) of specimens compressed under saturated steam conditions at 170°C and post-heat-treated at 200°C were determined in the dry condition and after five soak/dry cycles. Higher temperature of the compression treatment resulted in lower equilibrium moisture content, while the steam conditions during the treatment and the post-heat-treatment did not have significant effect. Furthermore, the highest degree of densification was obtained in specimens compressed under saturated steam conditions at 170°C and post-heat-treated at 200°C. The steam condition and temperature influenced the set recovery of compressive deformation. Reduced hygroscopicity does not necessarily imply reduced set recovery. The results established that considerable fixation of compressive deformation can be obtained by compressing the wood in a saturated steam environment and by post-heat-treatment at 200°C. The short heat-treatment had no influence on MOR or MOE, but soaking/drying treatments caused a decrease in the MOR and MOE. 相似文献
8.
Thibaud Surini Fatima Charrier Jér?me Malvestio Bertrand Charrier Amine Moubarik Patrick Castéra Stéphane Grelier 《Wood Science and Technology》2012,46(1-3):487-501
An original heat treatment performed under vacuum pressure was investigated. Maritime pine samples were treated at six different temperatures: 140, 160, 180, 200, 230 and 260°C. The physical and mechanical consequences, i.e. bending strength (MOR), modulus of elasticity (MOE), hygroscopic behaviour, equilibrium moisture contents and anti-swelling efficiency (ASE) were studied. A no-choice feeding test according to the NF EN 117 standard was achieved. Temperatures up to 200°C had no significant effect on wood properties. However, at 230 and 260°C, the decrease in MOR was severe, reaching 42.5 and 62.5%, respectively. Whatever the treatment conditions, wood samples were still highly degraded by termites, revealing no increase in their durability. 相似文献
9.
Ikuho IIDA 《中国林学(英文版)》2012,14(2):107-111
Elastic and strength properties(proportional-limit stress(σ prop ),Young's modulus(E),breaking stress(σ max )in static bending parallel to grain in a longitudinal direction),as well as stress relaxation in air-dried condition and water-saturated conditions at seven different constant temperatures and increasing and decreasing temperatures were investigated for wood from Chinese-fir and poplar plantations.The results show that hygrothermal conditions considerably affect these mechanical properties.The higher the moisture content(MC)or temperature,the lower the strength of wood.Further investigation of the effects of constant temperature on stress relaxation indicates that high temperature specimens have low relaxation moduli and high fluidity.In the case of increasing temperature the range of the modulus of relaxation is larger than in the case of a reduction in temperature,while the residual moduli do not show large differences.This is because the modulus at high temperatures decreases more than that at low temperatures.The fluidity of specimens in a state of water desorption increases slowly at the beginning,increases quickly until the MC reaches an equilibrium moisture content(EMC)and then becomes stable,which is quite different from that in a water-saturated state.Fluidity in a desorption state is much higher than in a water-saturated state.This is probably due to the fact that the former is in an unstable state which can be interpreted as a state with internal strain and has therefore a greater potential to release strain. 相似文献
10.
In a detailed study of the relation between the deflection caused by shear force and the constitution of a laminated material
beam, we derived an equation for calculating the shear modulus of a laminated material beam from the shear moduli of individual
laminae. The validity of the derived equation was investigated using crosslaminated wood beams made with five species. The
calculated shear moduli parallel to the grain of face laminae ranged from 48.3 MPa to 351 MPa, while those perpendicular to
the grain of face laminae ranged from 58.0 MPa to 350 MPa. The calculated shear moduli increased markedly with increasing
shear modulus in a cross section of perpendicular-direction lamina of a cross-laminated wood beam. The calculated apparent
modulus of elasticity (MOE) of cross-laminated wood beams agreed fairly well with the measured apparent MOE values. This fact
indicated that the apparent MOE of cross-laminated wood beam was able to be calculated from the true MOE values and shear
moduli of individual laminae. The percentage of deflection caused by shear force obtained from the calculated apparent MOE
(Y
sc) was close to that obtained from the measured apparent MOE (Y
s) and there was a high correlation between both values. From the above results, it was concluded that the derived equation
had high validity in calculation of shear modulus of a cross-laminated wood beam. 相似文献
11.
Jinghui Jiang Jianxiong Lu Yongdong Zhou Rongfeng Huang Youke Zhao Jiali Jiang 《Wood Science and Technology》2014,48(2):253-267
The properties of oak heat treated at temperatures of 160–220 °C, oxygen concentrations of 2–10 %, steam pressures of 0.1–0.4 MPa and treatment time of 2–4 h were investigated. Although modulus of elasticity (MOE), modulus of rupture (MOR) and equilibrium moisture content (EMC) of the heat-treated wood (HTW) were reduced, the value of $ \Updelta E^{*} $ was increased, and the dimensional stability [anti-swelling efficiency in radial (ASE-R), anti-humidity efficiency (AHE)] was improved considerably. Six regression equations (temperature, oxygen concentration, steam pressure and time as functions of MOE, MOR, ASE-R, AHE, EMC and $ \Updelta E^{*} $ ) were developed for the estimation and a nonlinear programming model was derived with operation research theory to obtain the most desirable HTW properties under some production constraints. 相似文献
12.
木/塑纤维复合材料力学性能平衡性初探 总被引:4,自引:1,他引:3
《木材工业》1998,12(3):19-20,24
用于轿车内衬件的木/塑纤维复合材料,既要求有一定的力学强度又要求有一定的弹性和韧性,本文就木/塑纤维复合材料力学性能的平衡性(主要指静曲强度与弹性模量的平衡)进行了研究。试验表明:不同的胶粘剂对木/塑纤维复合材料的力学性能的平衡性具有很显著的影响。 相似文献
13.
Jun Tanabe Akira Tamura Jyunichi Ohshima Kazuya Iizuka Shinso Yokota 《Scandinavian Journal of Forest Research》2017,32(1):39-44
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. 相似文献
14.
15.
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
16.
Christoph Buksnowitz Robert Evans Ulrich Müller Alfred Teischinger 《Wood Science and Technology》2012,46(6):1239-1246
This study presents three-point bending test results of Norway spruce clear wood specimens loaded on the radial-longitudinal plane in two different load cases. The tested samples were graded as resonance wood for instrument making and were characterised by narrow annual rings and relatively low density. The modulus of elasticity (MOE) and the corresponding modulus of rupture (MOR) are illustrated separately for the samples with straight grain and the group showing the specific growth pattern of indented rings (‘hazel growth’). With the longitudinal wood anatomical direction parallel to span width, the fibre deviation caused by the indents reduces MOE and MOR values, whereas a ‘reinforcing’ effect of the indents could be observed for the load case with span width parallel to the radial direction. Both aspects lead to a reduction in anisotropy for hazel-growth Norway spruce (anisotropy MOE: indented rings 11.6, straight grain 14.7, anisotropy MOR: indented rings 6.9, straight grain 8.9), which partly explains the exceptional position of this growth pattern for the construction of high-class musical instruments with outstanding mechanical and acoustical performance. 相似文献
17.
Hamid Reza Taghiyari 《Wood Science and Technology》2011,45(2):399-404
The present study is aimed at investigating the effect of heat treatment of nano-silver-impregnated Populus nigra on weight loss, modulus of rupture (MOR), modulus of elasticity (MOE), and compression parallel to grain. Specimens were
impregnated with 200 PPM water-based solution of nano-silver particles at 2.5 bar in a pressure vessel. For heat treatment,
both nano-silver-impregnated and simple specimens were kept for 24 h at 45°C and then further for 24 h at 145°C and finally
for 4 h at 185°C. MOR decreased from 529 to 461 kg/cm2 in heat-treated specimens; MOE and compression parallel to grain were though improved. Also, comparison between heat-treated
and nano-silver-impregnated heat-treated specimens showed that there was a decrease in MOR and MOE in nano-silver-impregnated
heat-treated specimens. This shows that nano-silver impregnation facilitates transfer of heat in wood and it may increase
the process of degradation and pyrolysis of wood structures in deeper parts of specimens. 相似文献
18.
19.
Ikuho Iida Michiyasu Kudo Jyunji Onizuka Yutaka Ishimaru Yuzo Furuta 《Journal of Wood Science》2002,48(2):119-125
Previously we showed that the relaxation modulusEt of water-saturated wood during temperature reduction maintained its initial value despite the decrease in temperature, although during temperature elevationEt showed a marked decrease. In the present study, to clarify the mechanism of relaxation during temperature elevation and reduction, Young's modulus was measured in stress relaxation experiments with changes in temperature, and relaxation behavior was simulated using a Maxwell model consisting of five elements. Furthermore, the dynamic Young's modulus and dynamic loss modulus were measured during both temperature elevation and reduction. The results obtained suggested that the unique relaxation behavior during temperature reduction was caused by decreases in Young's modulus and coefficient of viscosity (i.e., an increase in fluidity) compared with those during elevation of temperature. The decrease in Young's modulus and increase in fluidity were considered to be due to an unstable structure in wood that occurred during temperature reduction. This unstable structure probably develops in the nonequilibrium state of temperature toward a true equilibrium state. Wood should be more unstable during temperature reduction than during temperature elevation because of the decrease in molecular motion when the temperature is lowered.Part of this report was presented at the 49th annual meeting of the Japan Wood Research Society, Tokyo, April 1999 相似文献
20.
H. Heräjärvi 《Wood Science and Technology》2004,37(6):523-530
The purpose of this study was to determine the modulus of elasticity (MOE) and the modulus of rupture (MOR) in the radial bending test for small, clear specimens of Finnish birch (Betula pendula Roth and B. pubescens Ehrh) wood originating from mature trees. The dependency of MOE and MOR on the specific gravity of birch wood was studied, and the relationship between MOE and MOR was modelled at the different heights and at the different distances from the pith of the tree. For B. pendula, the mean values for MOE and MOR were 14.5 GPa and 114 MPa, whereas B. pubescens had means of 13.2 GPa and 104 MPa, respectively. At the corresponding specific gravity, the bending stiffness and strength values did not differ between the two species. The results indicated a linear relationship between the MOE and MOR, irrespective of the birch species or the within-stem location. Both MOE and MOR increased clearly from the pith towards the surface of the tree and decreased slightly from the base to the top of the tree. It seems that if products with as high stiffness and bending strength as possible are wanted, sorting of raw materials into different grades according to their within-tree origin can be of value. 相似文献