Wood and Fiber Science (E-Journal)
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LOWER TOLERANCE LIMIT APPROACH TO EQUATION-BASED RATIONAL DESIGN VALUES FOR T-SHAPED MORTISE AND TENON JOINTS
Get PDFA nonlinear regression expression was fitted to the test data obtained from a study of the bending moment capacity of 320 rectangular T-shaped mortise and tenon furniture joints consisting of 64 configurations of five specimens each. A statistical lower tolerance limit approach was then used to explore the degree to which these values should be reduced when used for design purposes and the confidence that a user might have in these reductions. The procedure followed was to apply statistical lower tolerance limit techniques to the ratios obtained by dividing each test value by its corresponding estimated value. To gain insight into the relationship of a specific confidence–proportion level and its corresponding reduction factor on the percentage of an estimated value that could be used for design purposes, lower tolerance limits were computed for four confidence–proportion levels. The results illustrate a statistical technique that can be used to determine reduction factors and the impact of the selection of any of the given confidence–proportion levels on design values.
IDENTIFICATION OF THE LENGTH DISTRIBUTION OF LUMBER DEFECT-FREE AREAS
Get PDFPresented here are the results of statistical analysis of length distribution of defect-free areas (DFA) of pine, beech and oak blanks. The investigated empirical distributions of the lengths of defect-free areas nearly always exhibit right-side asymmetry and “heavy tails”, with high coefficients of variation (30% c 110%). Therefore, the arithmetic mean of these lengths is not an appropriate measure for description of any of the investigated samples, and to describe the dimensional and qualitative characteristics of blanks, not only characteristics of location must be used, but also the relative characteristics of the dispersion. It is proposed that rather than use estimates of variability, to apply an assessment of stability – the value inverse to the squared coefficient of variation, which allows, with minimal computational cost, to correctly compare the lengths of DFA obtained from different lumber and in different operating conditions. It is shown that the distribution of lengths of DFA for pine, oak and beech blanks can be only described entirely by two theoretical distributions – the Burr and log-logistic, with different parameters for different wood species and various sizes of defect-free areas
CRADLE-TO-GRAVE LIFE CYCLE ASSESSMENT OF SYNGAS ELECTRICITY FROM WOODY BIOMASS RESIDUES
Get PDFForest restoration and fire suppression activities in the western United States have resulted in large volumes of low-to-no-value residues. An environmental assessment would enable greater use while maintaining environmental sustainability of these residues for energy products. One internationally accepted sustainable metric tool that can assess environmental impacts of new bioenergy conversion systems is the life cycle assessment (LCA). Using the LCA method, this study evaluated the synthesis gas (syngas) electricity produced via a distributed-scale biomass thermochemical conversion system called the Tucker renewable natural gas (RNG) system. This system converts woody biomass in a high-temperature and extremely low-oxygen environment to a medium-energy syngas that is burned to generate electricity. The system also produced biochar as a by-product and tar as a waste. Results from the life cycle impact assessment included an estimate of the global warming (GW) impact from the cradle-to-grave production of syngas for electricity. When the carbon sequestration effect from the biochar by-product was included, GW impact value (0.330 kg CO2-eq/kWh) was notably lower compared with electricity generated from bituminous coal (1.079 kg CO2-eq/kWh) and conventional natural gas (0.720 kg CO2-eq/kWh). Other environmental impacts showed that syngas electricity ranged between the direct-biomass-burned electricity and fossil-fuel-combusted electricity for different impact categories. This occurred because, although the woody biomass feedstock was from a renewable resource with less environmental impact, propane was consumed during the thermochemical conversion. Specifically, the evaluation showed that the highest greenhouse gas (GHG) emissions contribution came from burning propane that was used to maintain the endothermic reaction in the Tucker RNG unit. If the tar waste from the system were converted into a low-energy syngas and used to supplement propane consumption, a further decrease of 41% in GHG emissions (ie fossil CO2) could be achieved in this cradle-to-grave assessment.
Predicting of cutting force during gypsum fiber composite milling process using response surface methodology
Get PDFGypsum fiber composite (GFC) is a kind of building material widely used in interior decoration. Milling is the most commonly used machining process for GFC. Cutting force as an important cutting characteristic parameter has significant influence on the quality of machined surface, power consumption, and tools wear. The tangential force (Fx) and normal force (Fy) were measured and analyzed to find out the effects of milling parameters on these cutting forces. Milling parameters considered were spindle speed, feed rate, and depth of cut. The response surface methodology (RSM) was selected to develop mathematical models and optimize milling parameters. The results showed that with the increase of feed rate and depth of cut, the Fx and Fy increased. But the cutting forces decreased with the increase of spindle speed. The optimization results indicated that high spindle speed, low feed rate, and small depth of cut are preferable for milling of GFC to obtain the best result.
PARABOLIC BEHAVIOR OF THE YOUNG’S MODULI RATIO OF WOOD OBTAINED BY VIBRATION TESTS WITH TIME DURING DRYING
Get PDFA method to estimate the water distribution within wood lumber was developed using bending and longitudinal vibration tests. Sitka spruce and Japanese cedar green wood were left inside a controlled environment of 20°C and 65% relative humidity. The bending and longitudinal vibration tests were performed and the Young’s modulus was obtained by each testing method. And then, the temporal changes in the ratio of Young’s modulus based on the bending vibration to that based on the longitudinal vibration were investigated during drying. The ratio of Young’s modulus increased and then decreased with time during drying due to the difference between the Young’s modulus of the outer portion of wood and that of the inner portion. The temporal change in the ratio of Young’s modulus was similar to the estimate using a simple cross-sectional model developed in this study. The bending Young’s modulus calculated using Euler-Bernoulli’s elementary theory could be used instead of that using the Goens-Hearmon regression method based on the Timoshenko theory of bending.
Schedule Modification of drying rate to Decrease The drying time of juvenile Tectona grandis L. wood
Get PDFThe authors investigated modifying schedules to increase the drying rate (DR) and reduce the total drying time for Tectona grandis L. wood from juvenile plantations. The initial MC ranged from 92 to 115%. A conventional teak schedule was used as the basis for developing two faster drying schedules and for comparison. The modifications resulted in a reduction in drying time from 125 to 105 hours, a 16% energy savings and less than 1% MC variation in dried lumber; however, this change caused a slight decrease in wood quality. The relationship between the DR, the lumber's MC, and drying time was modeled. As expected, the dry-bulb temperature and wet-bulb depression had the greatest influence on DR; however, an inflexion point was found in the relationship between DR and MC at a 40% MC for all three drying schedules. The inflection point indicates when diffusion becomes the primary driving force of moisture movement, therby llimiting the DR, and indicating when the kiln conditions should be accelerated to minimize the total drying time. DRhour should remain over 0.5%/hour (high value for tropical species) for the first 72 hours (3 days), until the lumber reaches 40% MC and then be lowered to 0.5%/hour until drying is completed
LATERAL LOAD RESISTANCE BEHAVIOR OF WOOD-PLASTIC-TO METAL SINGLE-BOLT CONNECTIONS IN OUTDOOR FURNITURE
Get PDFThe lateral load resistance behavior of an unconstrained, two-member, single-bolt connection in outdoor furniture applications was investigated. The unconstrained connection consisted of a wood-plastic composite (WPC) main member fastened to a metal plate as a side member through a 6.35-mm-diameter bolt without a nut or washer used. Experimental results indicated that unconstrained WPC-to-metal single-bolt connections had a significantly higher lateral resistance load if the WPC main member is loaded in the direction perpendicular to the WPC material extrusion direction than the parallel direction. Tested connections failed with bolts having one plastic hinge bent, which occurred at the interface between the metal plate and WPC main member, accompanied by the WPC main members having a compressive yield fracture at their sides close to the metal plate, but no obvious compressive mark was observed at the opposite sides. Proposed linear and yield mechanical models were verified experimentally as a valid means for deriving estimation equations of lateral resistance loads of unconstrained WPC-to-metal single-bolt connections
INVESTIGATING CHEMICAL PROPERTIES AND COMBUSTION CHARACTERISTICS OF TORREFIED MASSON PINE
Get PDFTo investigate chemical properties and combustion characteristics, masson pine was torrefied using GSL 1600X tube furnance in the argon atmosphere. The properties of torrefied masson pine were respectively determined through thermogravimetry (TGA), fourier transform infrared spectrometer (FTIR) and X-ray diffraction (XRD). Results showed that thermal decomposition of hemicelluloses, cellulose and lignin occurred during torrefaction process. Crystalline region of cellulose was destroyed when temperature was up to 250℃. The effect of torrefaction temperature was more significant than that of residence time. Torrefaction improved combustion characteristics of masson pine. The optimum process was 300℃ of torrefaction temperature and 2.0h of residence time. Combustion process of torrefied masson pine included drying, oxidative pyrolysis and char combustion. Torrefied masson pine had a lower H/C and O/C ratios, peak temperature of oxidative pyrolysis and char combustion and burnout temperature. It had a higher energy density, ignition temperature and activation energy. This data will be significant to understand the torrefied masson pine for energy product to directly combustion
