Wood and Fiber Science (E-Journal)
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MASS ESTIMATION OF PILED ROUND BARS THROUGH VIBRATION TESTS
No full textA simple method was developed to estimate the mass of each piled round bar using a vibration test. Specimens used in the tests were Japanese cedar (Cryptomeria japonica D. Don) round bars (diameter = 180 mm, length = 2000 mm) with a pith and a back split. Vibration tests were conducted, and the effect of sticker positions on the vibration test was investigated. The vibration tests were conducted for each piled round bar and the estimation accuracy of the vibration method with additional mass (VAM) was examined. By placing the round bar on the stickers, the resonance frequency of the longitudinal vibration was stable while that of the bending vibration decreased with the increase in the distance between the sticker and the specimen end and stabilized when this distance was greater than or equal to 0.2l (l:specimen length). When the round bars were piled with no stickers, the bending resonance frequency could not be identified and the VAM estimation accuracy of the longitudinal vibration depended on the specimens. The estimation accuracy of VAM for the longitudinal vibration of the piled round bars while using stickers made of wood and rubber was superior to that without stickers. The estimation accuracy of VAM for the bending vibration was sufficiently high. These results were attributed to the reduction of the vibration restraint by the stickers and the contact between adjacent round bars.
FITTING STATISTICAL DISTRIBUTION MODELS TO MOE AND MOR IN MILL-RUN SPRUCE AND RED PINE LUMBER POPULATIONS
No full textIt has been mathematically demonstrated that the distribution of modulus of rupture (MOR) in a graded lumber subpopulation does not have the same theoretical form as the distribution of the mill-run population from which the subpopulation is drawn. However, the distributional form of the graded lumber subpopulation does depend heavily on the distributional form of the full mill-run population, and thus it is important to characterize the distributions of full mill-run lumber populations. Previous studies presented evidence suggesting that commonly-used distributions such as normal, lognormal, and Weibull distributions might not be suitable for modeling mill-run modulus of elasticity (MOE) and MOR; rather, nontraditional distributions such as skew-normal and mixed normal seem to be more appropriate models for the MOE and MOR of mill-run populations across mills and time. Previous studies of this kind have been carried out using only southern pine (Pinus spp.) lumber. In this study, we extend this work by investigating whether the distributional forms found to adequately fit southern pine mill-run lumber populations also adequately fit other species (or species groups). The objective of this study is to identify statistical models that fit MOE and MOR distributions in mill-run spruce (Picea spp.) and red pine (Pinus resinosa) lumber populations. Mill-run samples of 200 spruce 2 × 4 specimens and 200 red pine 2 × 4 specimens (for a total of 400 test pieces) were collected, and the MOE and MOR for each specimen were assessed. Various distributions were fit to the MOE and MOR mill-run data and evaluated for goodness-of-fit. In addition to further demonstrating that traditional distributions such as normal, lognormal, and Weibull may not be adequate to model mill run MOE and MOR populations, the results suggested that mixed normal and skew normal distributions might perform well across species
EVALUATING DESIGN OF MORTISE AND TENON FURNITURE JOINTS UNDER BENDING LOADS BY LOWER TOLERANCE LIMITS
No full textThis study aimed to estimate the design value for mortise and tenon joints. In this respect, the design value for static load tests was determined using lower tolerance limit methods. A lower tolerance limit value at 0.99/0.99 confidence/proportional level was chosen as a design value (199.05 N.m) to secure higher joint reliability in a furniture frame. A side frame of a simple wooden chair was theoretically analyzed to obtain internal forces acting on joints, whereas the load of 1000 N was applied in the vertical direction on the top of the front leg. A full-frame chair with mortise and tenon joints would not be overstressed when a chair is under static load while not exceeding 2000 N. By applying this method, all chairs should survive static load up to 2000 N. While performing cyclic front-to-back load test, all tested chairs met the American Library Association requirements for light-duty service load, specified for household chairs. This study demonstrates that a joint failure could be prevented under expected loads specified by the standard if the joint design value is known
MANUFACTURING AND INTERFACIAL BONDING BEHAVIOR OF EVA FILM REINFORCED FLEXIBLE DECORATIVE VENEER
No full textPolyethylene film reinforced flexible decorative veneer has attracted wide attention. However, its curling deformation has not been well solved due to the high processing temperature. Ethylene-vinyl acetate copolymer (EVA) has lower melting temperature and better flexibility than polyethylene. In this work, EVA film was selected to enhance Manchurian ash (Fraxinus mandshurica) aimed at preparing flexible decorative veneer with high strength and low curling degree. Box-Behnken experimental design method was applied to determine the optimum processing parameters. The secondary overlaying performance of the flexible veneer was evaluated. Under optimum conditions the EVA reinforced veneer obtained a maximum transverse tensile strength of 2.42 MPa. EVA can form a continuous interface with the veneer, which was helpful to improve the flexibility of the veneer. Curling degree of the EVA film reinforced veneer was far less than that of the polyethylene reinforced veneer even at the same processing temperature. EVA reinforced flexible veneer was good to be used to decorate wood-based panels without additional adhesives. Both immersion peel strength and surface bonding strength of the prepared decorative panel can meet the requirements of GB/T 15104-2006.
THE EFFECT OF VARIABLES ON LABORATORY TERMITE TESTING: PART 3 - TEST BLOCK DENSITY AND MOISTURE CONTENT.
No full textThe objective of this study was to determine the impact on termite feeding of wood ring count and MC in standard tests. Introduced species (Coptotermes formosanus) were tested in an American Wood Protection Association (AWPA) E1-97 standard laboratory test. Samples with a ring count in the range of 6 – 10 rings per inch (RPI) had a higher, but not significantly different, weight loss than the 4 – 6 RPI specified by E1-97. With respect to the MC, it was determined that a lower level of moisture than that currently specified by AWPA E1 would be preferred over the higher MC achieved in ASTM D3345. Sample placement on top of the sand was recommended over the burial procedure in ASTM D3345
VARIATION IN WOOD PROPERTIES OF HYBRID POPLAR LUMBER BY RADIAL AND VERTICAL POSITION IN STEM; A CASE STUDY FROM BOARDMAN, OR
No full textUnderstanding of wood quality of hybrid poplar is critically important for manufacturers who want to know the suitability of the wood for specific products. To this end, lumber was milled from the merchantable stem of four hybrid poplar clones ages 10-11 yr., grown at single site near Boardman, OR. The vertical and radial position in the stem were recorded for each board and the boards were kiln dried, surfaced, and samples from each board tested to determine specific gravity (SG), dimensional stability, hardness, screw withdrawal, and bending strength and stiffness (modulus of rupture [MOR] and modulus of elasticity [MOE], respectively) from small clear specimens. Results show differences in wood properties relative to vertical and radial position in the stem. SG, hardness, screw withdrawal, and bending properties of lumber samples generally increased with height in tree. Tangential hardness, SG, and MOR varied significantly between different sides of the trees corresponding to predominant wind in the area. Boards milled from the center of the stem had lower MOE and MOR than boards milled from nearer the bark. The results of this study may be used to target specific stem locations for different end uses.
ACOUSTIC WAVE PROPAGATION IN STANDING TREES —PART II. EFFECTS OF TREE DIAMETER AND JUVENILE WOOD
No full textThe objective of this study was to investigate the effects of tree diameter and juvenile wood on acoustic wave propagation in standing trees. Two-layer tree models with various diameters and proportions of juvenile wood were constructed to examine the effects of these two factors on propagation patterns and velocity of acoustic waves. The simulation results and analysis indicated that acoustic wave propagation in trees is dependent on both tree diameter and propagation distance. In the context of time-of-flight (TOF) acoustic measurement on standing trees with a test span of 1.2 m, when tree diameter is 10 cm or less, or slenderness is twelve or greater, wave propagates as quasi-plane waves in tree trunk, and the tree velocity determined using the TOF method is then comparable to the log velocity measured using the acoustic resonance method. When tree diameter is 40 cm or larger, or slenderness is three or less, wave propagates as dilatational waves in the tree trunk; thus, the three-dimensional wave equation should be considered for wood property prediction. When tree diameter falls between 10 and 40 cm or slenderness falls between 3 and 12, wave propagation is in a transitional phase. Mathematical models were developed to convert the tree velocity in the transition mode to the resonance velocity. It was found that juvenile wood content resulted in a 113-m/s reduction in acoustic velocity. In addition, our analysis indicated that wave propagation in standing trees is controlled by the wood properties of entire cross section, not just the outerwood. Therefore, the wave velocity measured on standing trees reflects the global properties of the wood between the two measuring points
ANALYSIS OF HYGRO-MECHANICAL BEHAVIOR OF WOOD IN BENDING
No full textThe empirical test developed as validation for a new beam element model that can account for both mechanical and environmental load action in finite element analysis is presented. The testing protocol allows for the identification and analysis of contributing deflection components in bending under varying MC conditions, including mechano-sorption. The components of deflection in the shear-free span of a four-point bending test and their responses to varying moisture are evaluated with an analytical procedure. The experiment was conducted on clear-straight-grained sapwood and heartwood specimens of Norway spruce (Picea Abies)(30 x 15 x 640 mm3). The program consisted of three phases: (1.) long term (LT) experiments under constant temperature of 60oC and relative humidity (RH) cycles between 40% and 80%, (2.) a short term static experiment to determine the variation in the sample set and the load-level of the LT experiment on end-matched specimens, and (3) creep tests at 60o and constant humidity at either 40% or 80% to determine the effect of moisture on the viscoelastic creep. Mass changes and hygro-expansion measured on matched specimens were used in the analytical method. Constitutive models used for describing the material-level response to loads and moisture changes were applied to the shear-free segment of the specimens disregarding actual moisture gradients and fiber orientation inside the test specimens. A successful identification of each deflection component and isolation of mechano-sorption component was accomplished. In the 90 da of testing, the dominant component of the total deflection was the elastic component, followed by the mechano-sorptive component. Creep was found to be nonnegligible and important in the correct description of mechano-sorption. The effect of moisture on the viscoelastic behavior showed most important during loading and first stages of decreasing deflection rate phase
REVIEW OF BOOK, THE BASEBALL BAT: FROM TREES TO THE MAJOR LEAGUES, 19th CENTURY TO TODAY
No full textBook about the baseball bat and the wood used in the bat
Exploration of membrane-based dehumidification system to improve the energy efficiency of kiln drying processes: Part I Factors that affect moisture removal efficiency
Full text linkGreen wood drying through a steam kiln-drying technology is an energy-demanding process. This process consumes a large amount of energy to evaporate water from wood and discharge it to the atmosphere through venting. The thermal energy loss from the venting of dry kilns takes up to 20% of total energy consumed by the whole wood-drying operation because a considerably large amount of thermal energy is stored in the exhaust air. Harvesting and reusing such waster thermal energy wood improve the energy efficiency of kiln-drying process. Advanced moisture-selective membranes have been used to dehydrate humid air or gas steam because of the advantages of low energy requirements, simplicity of operation, and high specificity. However, the application of the membrane in wood-drying processes has not been addressed. Therefore, this study aimed to investigate the feasibility of using a moisture-selective membrane system to dehydrate the warm moist exhaust air to achieve an energy-saving purpose. The membrane material was polydimethylsiloxane (PDMS) with high water vapor permeability. A small membrane-based dehumidification system was constructed to evaluate the effects of four factors (temperature, airflow rate, initial RH, and vacuum pressure) on the efficiency of moisture vapor removal. Statistical analysis in terms of response surface methodology was carried out. The major findings include 1) an increase in the temperature and vacuum pressure caused a significant increase in the efficiency of moisture vapor removal, 2) the initial RH had little influence on the efficiency of moisture vapor removal, 3) increasing the airflow rate had a negative impact on the efficiency of moisture vapor removal, and 4) the regression model can be used to predict the efficiency of moisture vapor removal. This PDMS membrane would be a possible solution for a pre-drying process at relatively low operation temperatures (<45oC), that is dehumidification process.