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1.
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
2.
Identification of anisotropic vibrational properties of Padauk wood with interlocked grain 总被引:1,自引:0,他引:1
Iris Brémaud Pierre Cabrolier Joseph Gril Bruno Clair Jean Gérard Kazuya Minato Bernard Thibaut 《Wood Science and Technology》2010,44(3):355-367
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
3.
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
4.
Bakary Traoré Loïc Brancheriau Patrick Perré Tatjana Stevanovic Papa Diouf 《Annals of Forest Science》2010,67(8):815-815
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• Vène wood (Pterocarpus erinaceus Poir.) is currently the favorite wood for manufacture of xylophone in Mali. A dynamic analysis method with free boundary
conditions, known as BING, was used to determine the main acoustic properties: specific dynamic modulus (E
L
/ρ), damping coefficient or internal friction (tan δ), sound radiation coefficient (SRC) and peak response (PR). 相似文献
5.
Tian Zhang Shu-Lin Bai Sandrine Bardet Tancrède Alméras Bernard Thibaut Jacques Beauchêne 《Journal of Wood Science》2011,57(5):377-386
The radial trends of vibrational properties, represented by the specific dynamic modulus (E′/ρ) and damping coefficient (tan δ), were investigated for three tropical rainforest hardwood species (Simarouba amara, Carapa procera, and Symphonia globulifera) using free-free flexural vibration tests. The microfibril angle (MFA) was estimated using X-ray diffraction. Consistent
patterns of radial variations were observed for all studied properties. E′/ρ was found to decrease from pith to bark, which was strongly related to the increasing pith-bark trend of MFA. The variation
of tan δ along the radius could be partly explained by MFA and partly by the gradient of extractives due to heartwood formation. The
coupling effect of MFA and extractives could be separated through analysis of the log(tan δ) versus log(E′/ρ) diagram. For the species studied, the extractive content putatively associated with heartwood formation generally tends
to decrease the wood damping coefficient. However, this weakening effect of extractives was not observed for the inner part
of the heartwood, suggesting that the mechanical action of extractives was reduced during their chemical ageing. 相似文献
6.
Daniel Keunecke Walter Sonderegger Karol Pereteanu Thomas Lüthi Peter Niemz 《Wood Science and Technology》2007,41(4):309-327
Despite the exceptional position of yew among the gymnosperms concerning its elastomechanical properties, no reference values
for its elastic constants apart from the longitudinal Young’s modulus have been available from literature so far. Hence, this
study’s objective was to determine the Young’s moduli E
L, E
R and E
T and the shear moduli G
LR, G
LT and G
RT of yew wood. For that purpose, we measured the ultrasound velocities of longitudinal and transversal waves applied to small
cubic specimens and derived the elastic constants from the results. The tests were carried out at varying wood moisture contents
and were applied to spruce specimens as well in order to put the results into perspective. Results indicate that E
L is in the same order of magnitude for both species, which means that a high-density wood species like yew does not inevitably
have to have a high longitudinal Young’s modulus. For the transverse Young’s moduli of yew, however, we obtained 1.5–2 times,
for the shear moduli even 3–6 times higher values compared to spruce. The variation of moisture content primarily revealed
differences between both species concerning the shear modulus of the RT plane. We concluded that anatomical features such
as the microfibril angle, the high ray percentage and presumably the large amount of extractives must fulfil important functions
for the extraordinary elastomechanical behaviour of yew wood which still has to be investigated in subsequent micromechanical
studies. 相似文献
7.
Takaaki Fujimoto Hisashi Akutsu Miki Nei Kazuhito Kita Makoto Kuromaru Kazuyuki Oda 《Journal of Forest Research》2006,11(5):343-349
Genetic parameters for wood stiffness and strength properties were estimated in a 29-year-old hybrid larch stand (Larix gmelinii var. japonica × Larix kaempferi). The study included 19 full-sib larch families from Hokkaido, northern Japan. Implications of these genetic parameters in
wood quality improvement are subsequently discussed. Traits included in the analyses were the dynamic modulus of elasticity
of green logs (E
log), the modulus of elasticity (MOE), the modulus of rupture (MOR), compression strength parallel to the grain (CS) in small
clear specimens, wood density (DEN), and diameter at breast height (DBH). DEN had the lowest coefficients of variation and
MOE the highest. The narrow-sense heritability estimates of E
log, MOE, MOR, and CS were 0.61, 0.44, 0.60, and 0.43, respectively, and those of DEN and all mechanical properties increased
from an inner to outer position within the stem. E
log and DEN had high positive phenotypic (0.52–0.83) and genetic (0.70–0.92) correlations with MOE, MOR, and CS. The mechanical
properties of the inner position of the stem had rather high phenotypic and genetic correlations with those of the outer position
and overall mean. The predicted gains in wood stiffness (E
log and MOE) were higher than those of the strength properties (MOR and CS). The predicted correlated responses in MOE, MOR,
and CS when selecting for E
log and DEN were 72.6%–97.8% of a gain achievable from direct selection of these traits. DBH showed an insignificant correlation
with all mechanical properties, although selection of this trait had a slightly negative effect on the mechanical properties. 相似文献
8.
Anisotropy of wood vibrational properties: dependence on grain angle and review of literature data 总被引:1,自引:1,他引:0
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
9.
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
10.
The influence of moisture content (MC) on the dynamic modulus of elasticity of structural lumber was investigated using transverse
vibration testing methods. The flexural rigidity (EI) of a transversely vibrating beam was calculated as the modulus of elasticity (E) multiplied by the moment of inertia (I). The increase in E of lumber due to reduction in moisture content was computed by assuming that the flexural rigidity remains constant with
changes in moisture content. Reductions in I due to shrinkage were compensated by the increases in E which led to a proposal for a species-dependent MC adjustment model for modulus of elasticity. The model was validated using
38 mm × 89 mm × 4,290 mm western Canadian Spruce–Pine–Fir dimension lumber evaluated in the “as-received” and “dry” conditions.
Results obtained from the species-dependent model agreed closely with those from the E adjustment equation for dimension lumber given in ASTM D 1990. The results show that the ASTM moisture adjustment procedures
can be used to adjust dynamic E values for changes in moisture content also. 相似文献
11.
Aida Se Golpayegani Iris Brémaud Joseph Gril Marie-France Thevenon Olivier Arnould Kambiz Pourtahmasi 《Journal of Wood Science》2012,58(2):153-162
Vibrational properties of wood are affected by several parameters, of which extractives can be one of the most important ones.
Wood for European musical instruments has been often studied, but traditional Middle Eastern ones had been left unnoticed.
In this study white mulberry (Morus alba L.), the main material for long-necked lutes in Iran, was extracted by five solvents of various polarities (water included).
Free-free bar forced vibrations were used to measure longitudinal (L) loss tangent (tanδ), storage (elastic) modulus (E′) and specific modulus (E′/γ) in the acoustic range. Their anisotropy between the 3 axes of orthotropy was determined by dynamic mechanical analysis.
Native wood had a quite low E
L′/γ but its tanδ was smaller than expected, and the anisotropy of tanδ and E′/γ was very low. Removal of extractives caused tanδ to increase and moduli to decrease. Acetone, the most effective solvent on damping despite a moderate extraction yield, increased
tanδ
L by at least 20% but did not modify E′/γ as much. When used successively, its effects masked those of solvents used afterwards. Anisotropy of E′/γ was nearly unchanged after extraction in methanol or hot water, while tanδ was much more increased in R than in T direction. Results suggest that in white mulberry, damping is governed more by nature
and localization of extractives rather than by their crud abundance. 相似文献
12.
Eiichi Obataya Sakae Shibutani Kensuke Hanata Shuichi Doi 《Journal of Wood Science》2006,52(2):111-114
Japanese cedar wood specimens were steamed at 80°, 100°, and 120°C over 14 days, and their equilibrium moisture content (M)
at 20°C and 60% relative humidity, longitudinal dynamic Young’s modulus (E), bending strength (σ
max), and breaking strain (ε
max) were compared with those of unheated specimens. Steaming for a longer duration at a higher temperature resulted in a greater
reduction in M, σ
max, and ε
max. The E of wood was slightly enhanced by steaming at 100°C for 1–4 days and 120°C for 1–2 days, and thereafter it decreased. The
slight increase in the E of sapwood was attributable to the reduction in hygroscopicity, while sufficient explanation was not given for a greater
increase in the heartwood stiffness. Irrespective of the steaming temperature, the correlations between M and the mechanical properties of steamed wood were expressed in terms of simple curves. M values above 8% indicated a slight reduction in E and s max, whereas M values below 8% indicated a marked decrease in the mechanical performances. In addition, the e max decreased almost linearly
with a decrease in the value of M. These results suggest that hygroscopicity measurement enables the evaluation of degradation in the mechanical performances
of wood caused by steaming at high temperatures. 相似文献
13.
Takaaki Fujimoto Yohei Kurata Kazushige Matsumoto Satoru Tsuchikawa 《Journal of Wood Science》2010,56(6):452-459
Near-infrared (NIR) spectroscopy coupled with multivariate analysis was applied to estimate multiple traits of sawn lumber.
The effects of the lumber conveying speed (LCS) and measurement resolution of spectra (MRS) on the calibrations were examined.
NIR spectra ranging from 1300 to 2300 nm were acquired at LCSs of 10, 20, and 30 m/min and at MRSs of 2, 4, and 16 nm. Prediction
models of bending strength (F
b), modulus of elasticity in bending tests (E
b), dynamic modulus of elasticity (E
fr), and wood density (DEN) were developed using partial least-squares (PLS) analysis. LCS and MRS did not significantly influence
the calibration performance for any wood property. The regression coefficients also showed no clear differences for any of
the conditions. This indicates that the important explanatory variables included in the models are not greatly influenced
by these measurement conditions. PLS2 analysis results, when presented graphically, allowed easy interpretation of the relationships
between wood mechanical properties and chemical components, e.g., bending strength and stiffness were mainly related to polysaccharides
cellulose and hemicellulose. NIR spectroscopy has considerable potential for online grading of sawn lumber, despite the harsh
measurement conditions. 相似文献
14.
J. Ilic 《Wood Science and Technology》2001,35(1-2):157-166
Dynamic elastic modulus (EL) and wave velocity (V) were determined using resonance vibrations from initially green, 100 × 50 mm sample boards of Eucalyptus regnans F. Muell., and after several stages of drying to oven dry. EL and V were determined from impact induced vibrations and spectral analysis. EL and V from green wood were positively related to basic density and normal shrinkage, only V was negatively related to green
density, and both EL and V were negatively related to green moisture content and the number of internal checks after drying. The latter relationship
has the potential to provide a simple method of segregating highly check prone material. No significant relationships were
obtained with collapse. Outside the hygroscopic range, in low shrinkage material, EL increased little or gradually, while in high shrinkage, collapse prone material, it increased more rapidly, but no clear
breakpoint was evident. In the hygroscopic range, EL increased rapidly in all samples. V increased curvilinearly throughout the entire moisture range, but no difference between
collapse prone and non-collapse prone material was observed.
Received 16 February 1998 相似文献
15.
Properties of the cell wall constituents in relation to the longitudinal elasticity of wood 总被引:2,自引:0,他引:2
This study examined the origin of the moisture dependency of the longitudinal Youngs modulus of wood (E
L
) in relation to the microfibril angle (MFA) of the S2 layer of the secondary wall. Microtomed early wood specimen of sugi (Cryptomeria japonica D.Don) were used for the experiment. The following was revealed:
16.
To investigate the influence of heating and drying history on the microstructure of dry wood, in addition to the dynamic viscoelastic
properties, CO2 adsorption onto dry wood at ice.water temperature (273 K) was measured, and the micropore size distribution was obtained
using the Horvath-Kawazoe (HK) method. Micropores smaller than 0.6 nm exist in the microstructures of dry wood, and they decreased
with elevating out-gassing temperature and increased again after rewetting and drying. Dry wood subjected to higher temperatures
showed larger dynamic elastic modulus (E′) and smaller loss modulus (E″). This is interpreted as the result of the modification at higher temperature of the instability caused by drying. Drying
history influenced the number of micropores smaller than 0.6 nm in dry wood not subjected to high temperature, although the
difference in the number of micropores resulting from the drying history decreased with increasing out-gassing temperature.
A larger number of micropores smaller than 0.6 nm exist in the microstructure of dry wood in more unstable states, corresponding
to smaller E′ and larger E″ than in the stable state. Consequently, unstable states are considered to result from the existence of temporary micropores
in the microstructures of dry wood, probably in lignin.
Part of this report was presented at the 55th Annual Meeting of the Japan Wood Research Society, Kyoto, March 2005, and at
the 56th Annual Meeting of the Japan Wood Research Society, Akita, August 2006 相似文献
17.
The radial compression behaviors of acetylated cedar wood were measured in various liquids. The compressive Young’s modulus
(E) of acetylated wood was reduced by soaking in water, toluene, and acetone, but it was always greater than that of water-swollen
unmodified wood at the same swelling level. The behaviors of acetone-swollen unmodified wood were similar to those of acetylated
wood rather than those of water-swollen unmodified wood. These results indicated that the swelling of hydrophobic wood components
had a lesser influence on the E of wood than the water-swelling of unmodified hydrophilic components. After large compression (ε > 45%), a part of the strain
remained unrecovered because of irreversible mechanical deformation. Since the remaining strain was smaller in the wood specimens
indicating greater stress relaxation, it was assumed that the viscoelastic deformation of amorphous matrix components is important
for lesser irreversible deformation and effective shape recovery of wood. In contrast with water-swollen unmodified wood,
the acetylated wood and acetone-swollen unmodified wood exhibited greater shape recovery despite their relatively higher E. This suggested that the swelling of hydrophobic wood components reduced the viscosity of the matrix rather than its elasticity,
resulting in more effective shape recovery with lesser softening. 相似文献
18.
Jun Tanabe Akira Tamura Mika Hamanaka Futoshi Ishiguri Yuya Takashima Jyunichi Ohshima Kazuya Iizuka Shinso Yokota 《Journal of Wood Science》2014,60(5):297-304
This study aimed to evaluate radial and among-family variations of wood properties in Picea jezoensis. A total of 174 trees were randomly selected from 10 open-pollinated families in a progeny trial for measuring stem diameter, dynamic Young’s modulus of log (DMOElog), annual ring width (ARW), air-dry density (AD), modulus of elasticity (MOE), and modulus of rupture (MOR). Mean values of DMOElog, AD, MOE, and MOR were 9.60 GPa, 0.41 g/cm3, 9.44 GPa, and 76.6 MPa, respectively. Significant differences among families were observed in all properties. F values obtained by analyzing variance in wood properties were higher than those generally observed in growth traits. In addition, F values in wood properties remained relatively higher from the 1st to 25th annual ring from the pith, although F value in ARW rapidly decreased with each increase in annual ring number. These results indicate that genetic factors largely contributed to the variance in wood properties compared with the growth traits. 相似文献
19.
The use of calibrated near-infrared (NIR) spectroscopy for predicting of a range of solid wood properties is described. The methods developed are applicable to large-scale nondestructive forest resource assessment and to tree breeding and silviculture programs. A series ofPinus radiata D. Don (radiata pine) samples were characterized in terms of density, longitudinal modulus of elasticity (E
L), and microfibril angle (MFA). NIR spectra were obtained from the radial/longitudinal face of each sample and used to generate calibrations for the measured physical properties. The relations between laboratory-determined data and NIR fitted data were good in all cases, with coefficients of determination (R
2) ranging from 0.68 for 100/MFA to 0.94 for densitystrip. A good relation (R
2 = 0.83) was also obtained forE
L estimated using data collected by SilviScan-2. The finding suggests that an NIR instrument could be calibrated to estimate theE
L of increment cores based on SilviScan data. In view of the rapidly expanding range of applications for this technique, it is concluded that appropriately calibrated NIR spectroscopy could form the basis of a testing instrument capable of predicting a range of properties from a single spectrum obtained from the product or from the raw material. 相似文献
20.
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 (ED, 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 (Vt
2 and Vt
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 相似文献
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