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1.
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   

2.
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   

3.
 The relations among internal temperature, internal pressure, and moisture content distribution in sugi square lumber during high-frequency (HF) heating were determined to clarify the mechanism of water movement during the combination of HF heating and hot air exposure. Green sugi square lumbers were subjected to HF heating under atmospheric pressure. The water movement and pathways in the lumber during HF heating were also investigated. Results showed that internal pressure is the driving force of water movement. HF heating causes a rise in the internal temperature and internal pressure in sugi square lumber. Ordinarily, water in lumber evaporates from the surfaces of lumber during hot air drying. However, with HF heating the internal pressure is generated by the increased temperature, and liquid water is driven not only parallel to the grain but also perpendicular to the grain of the lumber. The ratio of the amount of liquid flow in the parallel and perpendicular directions ranged from 2 : 3 to 1 : 3. When the movement of water in the lumber was traced with a 0.5% aqueous solution of acid fuchsin, water was found to move through the lumber in the longitudinal direction and then flow in a direction perpendicular to the grain or in the radial and tangential directions. Received: June 15, 2001 / Accepted: February 8, 2002 Acknowledgment The authors thank Dr. O.R. Pulido, Institute of Wood Technology, Akita Prefectural University, for discussions and for proofreading this paper. Part of this research was presented at the 51st Annual Meeting of the Japan Wood Research Society, Tokyo, April 2001 Correspondence to:Y. Kawai  相似文献   

4.
Summary This study was to determine the effects of shelling ratio (SR) 0.200, 0.314, and 0.400, relative humidity (RH) 50, 64, 78, and 92 percent, and temperature (T) 10°C, 24°C, and 38°C, on the initial elastic (YE) deformation, irrecoverable creep (YIR) and creep deformations (YC) of sugar maple-veneered-medium-density fiberboard (MDF) composite panels 16 mm thick, 229 by 584 mm in size for the purpose of developing a hardwood composite. This composite would possess creep resistance comparable to conventional softwood plywood and lumber. The YE, YC, and YIR of all composite panels were significantly (at 0.05 level) affected by the SR, RH, and T in this study. However, no differences in creep deformations were found in all specimens between the SR of 0.314 and 0.400, between the RH of 50 and 64 percent, and between the T of 10°C and 24°C conditions. Composite panels with an SR value of 0.314 and 0.400 had YC values approaching that of maple lumber. Panels with SR value of 0.200 displayed lower average YE, YC, and YIR values than those of the Douglas-fir plywood. The effect of T on creep deformation was small when compared to the effects of SR and RH. The YIR accounted for almost 2/3 of the YC for all composite panels. Predicted YE, YC, and YIR values obtained from the multiple regression models predict very well the observed test values. The creep behavior of the composites was explained well by a power-law equation in log-log form for periods of 2 to 10 minutes and 10 to 100 minutes. Reasonable approximations of YC at 2-week intervals were made by extrapolating the short-term creep test results of 10 to 100 minutes log-log regression analysis oor the veneered-MDF composites.  相似文献   

5.
The main purpose of this study was to establish whether sugi lumber with an extremely low Young’s modulus, which is plentifully produced in southern Japan, can be practically used as laminae for glued laminated timber (glulam) from the viewpoint of long-term performance under loading. Bending creep tests were carried out on sugi (Cryptomeria japonica D. Don) glulam with extremely low Young’s modulus laminae (3–4 kN/mm2) for the inner layers, as were tests on hybrid glulam with Douglas-fir (Pseudotsuga menziesii Franco) laminae (14–15 kN/mm2) for the outermost layer and sugi laminae (including those with a Young’s modulus of 3–4 kN/mm2) for the inner layers. The specimens were eight glulam beams with different compositions that were 105 mm wide, 210 mm deep, and 3980 mm long. The term of the creep test was 4 years. The results are summarized as follows. First, there were no significant differences between the Young’s modulus or bending creep of glulam L30 (laminae with Young’s modulus of 3–4 kN/mm2) and that of glulam L50 (laminae with Young’s modulus of 5–6 kN/mm2) for the inner layers. Second, for asymmetric compositions, the behavior of increases and decreases of relative creep due to atmospheric changes showed opposite behavior for glulam loaded from the side of lower Young’s modulus and from the side of higher Young’s modulus. Third, the required experimental term for the creep test to estimate an accurate long-term curve is 1 or 2 years (with data for the first 6 months excluded) when the power law is used for the estimation. Fourth, the values of relative creep in 50 years obtained from the experimental term were much lower than 2, which is the standard value set by Notification No. 1459 of the Ministry of Construction in Japan, and these values were not affected by the composition of the laminae.  相似文献   

6.
One of the most important quality aspects of a laminated veneer product is its shape stability under changing relative humidity (RH). This study aimed to establish an understanding of how the orientation of individual veneers in the laminate, i.e., orientation according to fibre orientation and orientation of the loose (the side with ‘lathe checks’) or tight side of the veneer, affects the shape stability. Three-ply laminates from peeled veneers of beech (Fagus sylvatica L.) were studied. The four types of laminate were the following: loose sides of all veneers in the same direction (cross and parallel centre ply) and loose sides of the outer veneers facing inward (cross and parallel centre ply). Four replicates of each type yielded 16 samples. The samples were exposed to RH cycling at 20% and 85% RH at 20°C, and the shapes of the samples were determined. The shape stability was influenced by the veneer orientation. Laminations with the middle veneer perpendicular to the top and bottom veneer (cross-laminated) showed the best shape stability, especially when the loose sides of the veneers were oriented the same direction. In parallel-laminated veneers, the laminates with opposite directions of the loose sides in the two outermost veneers showed the best shape stability. The major explanation of the behaviour of the laminates is that the loose side expanded more than the tight side from the dry to the humid climate, which was shown by optical 3D deformation analysis (ARAMISTM). After RH cycling, the laminates with cross plies showed visible surface checks only when the tight side was facing outwards.  相似文献   

7.
Penetration rates of laser pulses transmitted from a small-footprint airborne light detection and ranging (LiDAR) system in closed-canopy, middle-aged (40–50 years old) hinoki cypress (Chamaecyparis obtusa Sieb. et Zucc.) and sugi (Cryptomeria japonica D. Don) plantations that had similar levels of canopy openness were studied. The number of transmitted pulses was 107 427 points/ha for the hinoki cypress stand and 122 883 points/ha for the sugi stand. The penetration rates of the first (Pf) and second pulses (Ps) that reached the ground were 0.1% and 1.0% in the hinoki cypress stand, and 2.6% and 5.5% in the sugi stand, respectively. Penetration rates for the total number of pulses (Pf+s) that reached the ground within each stand were 1.1% and 8.1%, respectively, and values for Pf+s, Pf, and Ps for sugi and hinoki cypress stands were significantly different (P < 0.001). The results of this study indicated that the generation of accurate digital terrain models in dense hinoki cypress stands with complex topographies using only the data from laser pulses with poor laser penetration rates is likely to be difficult.  相似文献   

8.
Sawdusts of sugi (Cryptomeria japonica) wood prepared before and after steam drying at 120°C in a kiln were extracted with n-hexane and ethyl acetate to give n-hexane extracts and ethyl acetate extracts. From gas chromatography-mass spectrometry analysis of the ethyl acetate extracts from woods before and after steam drying, the components of 4-epi-cubebol, cubebol, and 2,7(14),10-bis-abolatrien-1-ol-4-one, which existed in the raw sugi wood, were proved to disappear in the steam-dried wood. These components were also absent in the ethyl acetate extract of the steam-condensed solution of waste steam from the kiln outlet. When these three components were treated with 0.2% (v/v) acetic acid solution at 120°C, δ-cadinene was produced as a major product from both 4-epi-cubebol and cubebol by dehydration and cleavage of the cyclopropane ring, and cryptomerone from 2,7(14),10-bisabolatrien-1-ol-4-one by hydration. The chemical changes of the three components presumably occur during steam drying of the sugi wood. This study was presented in part at the 85th Spring Meeting of the Chemical Society of Japan, Kanagawa, Japan, March 26–29, 2005  相似文献   

9.
In this report, we undertook studies of the viscoelastic properties of wood from the viewpoint of the fine structure and properties of the constituent materials in the wood cell wall. To measure the mechanical properties of the wood as the behavior of the cell wall, it is required to perform the longitudinal tensile test using a homogeneous specimen. In this study, microtomed specimens of sugi (Cryptomeria japonica D.Don) earlywood were used for the creep test, which were conducted at the fiber saturation point. The substantial creep compliance of the cell wall was simulated using a simplified viscoelastic model consisting of a Voigt element and an independent spring in series. Based on the experimental results, the values of the parameters were optimized. The results were as follows: (1) the longitudinal tensile creep deformation tends to increase with the elapsed time, similar to the bending creep behavior; (2) the magnitude of the longitudinal creep function increases with MFA; and (3) each parameter in the simplified viscoelastic model is markedly affected by the MFA. Based on these results, the mechanism of the longitudinal tensile creep deformation of wood is discussed.  相似文献   

10.
Binderless particleboards were manufactured from sugi (Cryptomeria japonica D. Don) heartwood and sapwood by hot-pressing (pressure: 5 MPa; temperatures: 180°, 200°, and 220°C; times: 10, 20, and 30 min), and the board properties [internal bonding (IB), thickness swelling (TS), water absorption (WA)] were investigated to evaluate the self-bonding ability. The IB, TS, and WA of the boards from sugi heartwood were better than those of the boards from sugi sapwood at any hot-pressing condition. Therefore, it was suggested that the self-bonding ability of sugi heartwood was superior to that of sugi sapwood. Then, sugi heartwood and sapwood powder with grain size 10 βm were used as a binder for plywoods. Four kinds of plywood were manufactured from the combination of powder and veneer, both of which were prepared from sugi heartwood and sapwood under the same hot-pressing conditions as the binderless particleboard, and the adhesive shear strength and wood failure of the plywood were investigated. As a result, the plywood composed of sugi heartwood veneer met the second grade of JAS for plywood, when either powder was used as a binder, when they were pressed at 200°C for 20–30 min and 220°C for 10 min.  相似文献   

11.
Grain deviations and high extractives content are common features of many tropical woods. This study aimed at clarifying their respective impact on vibrational properties, referring to African Padauk (Pterocarpus soyauxii Taub.), a species selected for its interlocked grain, high extractives content and uses in xylophones. Specimens were cut parallel to the trunk axis (L), and local variations in grain angle (GA), microfibril angle (MFA), specific Young’s modulus (E′ L /ρ, where ρ stands for the density) and damping coefficient (tanδL) were measured. GA dependence was analysed by a mechanical model which allowed to identify the specific Young’s modulus (E′3/ρ) and shear modulus (G′/ρ) along the grain (3) as well as their corresponding damping coefficients (tanδ3, tanδG). This analysis was done for native and then for extracted wood. Interlocked grain resulted in 0–25° GA and in variations of a factor 2 in E′L/ρ and tanδL. Along the grain, Padauk wood was characterized, when compared to typical hardwoods, by a somewhat lower E′3/ρ and elastic anisotropy (E′/G′), due to a wide microfibril angle plus a small weight effect of extracts, and a very low tanδ3 and moderate damping anisotropy (tanδG/tanδ3). Extraction affected mechanical parameters in the order: tanδ3 ≈ tanδG > G′/ρ > > E′3/ρ. That is, extractives’ effects were nearly isotropic on damping but clearly anisotropic on storage moduli.  相似文献   

12.
Effects of side chain hydroxyl groups on pyrolytic β-ether cleavage of phenolic model dimers were studied with various deoxygenated dimers under pyrolysis conditions of N2/400°C/1 min. Although phenolic dimer with hydroxyl groups at the C α − and C γ −positions was much more reactive than the corresponding nonphenolic type, deoxygenation at the C γ -position substantially reduced the reactivity up to the level of the nonphenolic type. These results are discussed with the cleavage mechanism via quinone methide intermediate formation, which is activated through intramolecular hydrogen bonds between C α − and C γ − hydroxyl groups.  相似文献   

13.
The anisotropy of vibrational properties influences the acoustic behaviour of wooden pieces and their dependence on grain angle (GA). As most pieces of wood include some GA, either for technological reasons or due to grain deviations inside trunks, predicting its repercussions would be useful. This paper aims at evaluating the variability in the anisotropy of wood vibrational properties and analysing resulting trends as a function of orientation. GA dependence is described by a model based on transformation formulas applied to complex compliances, and literature data on anisotropic vibrational properties are reviewed. Ranges of variability, as well as representative sets of viscoelastic anisotropic parameters, are defined for mean hardwoods and softwoods and for contrasted wood types. GA-dependence calculations are in close agreement with published experimental results and allow comparing the sensitivity of different woods to GA. Calculated trends in damping coefficient (tanδ) and in specific modulus of elasticity (E′/ρ) allow reconstructing the general tanδ-E′/ρ statistical relationships previously reported. Trends for woods with different mechanical parameters merge into a single curve if anisotropic ratios (both elastic and of damping) are correlated between them, and with axial properties, as is indicated by the collected data. On the other hand, varying damping coefficient independently results in parallel curves, which coincide with observations on chemically modified woods, either “artificially”, or by natural extractives.  相似文献   

14.
Glued laminated timbers (glulam) or planks 50mm thick were added to structural steel columns and beams as covering materials. The wood used in the glulam was sugi (Cryptomeria japonica D. Don) laminated with resorcinol resin adhesive between woods and epoxy resin adhesive between wood and steel. The 50mm thick planks of sugi around the steel were fixed with spirally threaded nails (screws), and 25mm long wood plugs were used to cover the tops of the nails. The 50mm thick glulam showed 1h of fire resistance. The temperatures of the flanges and webs of steel were 100°C at 1h and 200°C after 4h. The epoxy resin used to bond the wood and steel was an appropriate adhesive from a recycling perspective because it is easy to separate or peel from the steel.  相似文献   

15.
In our previous report, we investigated the effect of the microfibril angle (MFA) in the middle layer of the secondary wall (S2) on the longitudinal creep behavior of a thin homogeneous earlywood specimen sugi. In the present study, we investigated the role of moisture on the tensile creep behavior of wood. We discuss the creep behavior of the wood cell wall from the viewpoint of the composite structure of the cell wall and the properties of the constituent materials. A microtomed thin specimen of earlywood of sugi (Cryptomeria japonica D.Don) was used for the longitudinal tensile creep test. Creep tests were conducted at three moisture stages (oven-dry, air-dry, fiber saturation point) over a broad range of MFA. Results showed that the longitudinal tensile creep behavior was highly dependent on both the moisture content and the MFA. With a small MFA, the variation in the creep function among the three moisture states was very small. For a large MFA, the variation in the creep function was larger. At low moisture contents, the magnitude of the creep function was very small, while at high moisture content, it was very large except for the case of specimens with very small MFA. Those results show that the longitudinal tensile creep behavior was directly affected by the fine composite structure and the internal properties of the cell wall constituents.  相似文献   

16.
The conversion of silvopasture to different land use systems cause effective changes in soil carbon distribution, due to disturbances in soil aggregation promoted by soil management and changes in crop residues inputs and decomposability. We evaluate the C and N stocks, and organic C fractions in soils under continuous arable land (AR) and silvopasture with apple trees and grass (SP); and after 4 years of conversion from silvopasture to arable land (SP-AR) and grassland (SP-GL). Total N (TN) and organic C (TOC), as well as microbial biomass carbon (CMB), light fraction (CLF) and heavy fraction (CHF) were evaluated at two different depths (0–10 and 10–20 cm). After 4 years of conversion, SP-AR and SP-GL presented C and N stocks similar to the observed for SP when the 0–20 cm depth was considered. However, AR presented TOC and TN stocks around 21 and 10% lower than SP, respectively. SP-AR tended to present the lowest CMB stocks and was positively correlated with salt extractable organic C (r 2 = 0.60, P < 0.001). CLF values declined by 62% from 0–10 to the 10–20 cm at SP and SP-GL, however there was no variation with increasing depth for AR and SP-AR. CHF represented the highest C fraction in soil, corresponding to 82% of TOC. Except for AR, δ13C values of the light fraction increased with increasing depth. In general, heavy fraction tended to be more enriched in δ13C than light fraction. In a long-term, conventional tillage can significantly contribute to reduce TOC and TN stocks when compared to the silvopastoral system.  相似文献   

17.
Under fixed cutting conditions, the surface finish roughness is correlated to the grain angle. However, the means of determining the grain angle automatically and accurately is still a challenge for on-line control of the router. It is therefore necessary to develop a new technology to determine the grain angle accurately and automatically. In this research, a laser light scattering pattern was used to accurately determine the grain angle. The light scattering pattern image was a quasi-ellipse caused by the grain direction and tracheid effect. A new modified Hough transform ellipse analysis technology was adopted to determine the ellipse parameters that could be used to determine the grain angle. The results indicated that the measured grain angle using the method proposed here was accurate and effective. The measured grain angle coincided with the real grain angle. There was an insignificant difference between the measured grain angle of Japanese beech (Fagus crenata blume) and that of sugi (Cryptomeria japonica D.Don) under two machining conditions that gave planed or sawn finishes. However, the accuracy of the measured grain angle of sugi was better than that of Japanese beech for the planed finish, the accuracy of the measured grain angle of Japanese beech was better than that of sugi for the sawn finish, and the accuracy of the measured grain angle for planed samples was better than that for sawn samples of both sugi and Japanese beech.  相似文献   

18.
To understand the viscoelasticity of wood three dimensionally, a longitudinal tensile creep test for 12 species was conducted to examine the changes with time in the lateral strain and the viscoelastic, i.e., apparent Poisson’s ratio. The changes in the lateral strain (ɛ T and ɛ R) were similar to those in the longitudinal strain (ɛ L). That is, during creep, the absolute value of lateral strain continued to increase with the gradual reduction in the increase rate; immediately after the removal of the load, it recovered abruptly; then, it recovered slowly and finally reached a certain value. The rate of increase in the longitudinal strain during creep was smaller than that in the absolute value of lateral strains. The apparent Poisson’s ratio became large during creep because the lateral strain increased more than the longitudinal strain. The analysis of lateral strain by decomposition into three components, that is, instantaneous strain, delayed elastic strain, and permanent strain, has revealed that the lateral permanent strain in the transverse direction contributes most to the increase in the apparent Poisson’s ratio during creep.  相似文献   

19.
The radical coupling reaction leading to the β-0′ quinonemethide intermediate of p-coumaryl alcohol was analyzed by semi-empirical molecular orbital calculation with MOPAC2002. By analyzing the radical monomer in a one-electron oxidation, the spin density of the unpaired electron at the 4-oxygen was less than half of the values at the C1, C3, C5, and Cβ positions. By analyzing the transition state during the radical coupling reaction, the activation enthalpy was evaluated as 9.76 kcal/mol, which corresponds to the activation energies for the propagation of common vinyl polymers. From the analysis of atomic interactions in the transition state, it was found that the activation enthalpy was largely composed of a high coulombic repulsion between Cβ of the first monomer and the phenolic oxygen of the second monomer. After passing the transition state, the two radical monomers formed a metastable quinone-methide intermediate. The optimum conformation of the quinonemethide intermediate was formed from the meta-stable conformation through a second transition state with a small energy barrier. Part of this article was presented at the 46th Lignin Symposium, held in Fukuoka, October 31-November 1, 2002  相似文献   

20.
We seek the minimum harvest age and threshold price for sustaining forest management by constructing a stochastic dynamic programming model using a geometric mean-reverting process for log price dynamics. Three decisions—“Wait for harvest”, “Harvest & Plant”, and “Harvest & Abandon”—are assumed. The applied growth simulator is deterministic. Using the monthly time series data of sugi (Cryptomeria japonica) log price from 1975 to 2006, our analyses show that when the reverted mean is lower than the cost, the minimum harvest age increases as the current price approaches the threshold price, then declines. In other cases with a higher reverted mean, the minimum harvest age increases as the current or initial log price decreases. When the initial log price approaches the threshold price, the minimum harvest age tends to increase. These phenomena can be used to evaluate the possibility of management abandonment under a stochastic situation of log price dynamics.  相似文献   

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