Wood and Fiber Science (E-Journal)
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Assessment of White Spruce and Jack Pine Stem Curvature from a Nelder Spacing Experiment
Get PDFThis study presents a method for calculating stem curvature for trees with multiple deviations. Generally, tree curvature is assessed using the maximum deflection method. It consists of measuring the farthest point from a straight line drawn between the large and small ends of a stem. It works fairly well for a single deviation but gives poorer results for stems with several deviations. The stems used for developing this method were harvested from a 32-yr-old Nelder spacing experiment established near Woodstock, New Brunswick, Canada. A total of 96 trees were selected for this study from the white spruce (Picea glauca [Moench] Voss) and jack pine (Pinus banksiana Lamb.) that were planted on the same Nelder circle. This particular plantation design offered a gradient of initial spacings ranging from 640 to 12,000 stems/ha. Results of analysis revealed that initial spacing had an impact on tree curvature. Stem curvature increased with wider initial spacing. However, this influence varied between species and differed according to the method used to calculate curvature. The vector length calculation method showed that stem curvature in jack pine was more pronounced and more often encountered at lower densities than in white spruce. It was also observed that tree shape was influenced by the cardinal points with white spruce growing more in westerly and southerly directions
Effects of Cutting Direction, Rake Angle, and Depth of Cut on Cutting Forces and Surface Quality during Machining of Balsam Fir
No full textEffects of cutting direction with respect to grain angle, rake angle, and depth of cut on cutting forces and surface quality during machining of balsam fir were evaluated. These factors were analyzed within a perspective of their application to a chipper-canter machining process. Balsam fir is one of the most important boreal species in Canada and is widely used in the pulp and paper industry and construction applications. Wood samples prepared at four cutting directions (0-90°, 15-75°, 30-60°, and 45-45°) were machined using four rake angles (35, 45, 55, and 65°) and three cutting depths (1, 2, and 3 mm). Results showed that rake angle was the most important factor affecting cutting forces and surface quality. Furthermore, as rake angle increased, the effect of cutting direction and depth of cut on cutting forces and surface quality became less important. At 65° rake angle, cutting forces decreased and surface quality increased as depth of cut passed from 3 to 1 mm. Surface quality also improved as cutting action changed from the 0-90° to 45-45° direction. The results gave useful information for improving the performance of the chipper-canter in terms of surface quality and energy consumption
Variation of Internal Checks Related to Anatomical Structure and Density in Eucalyptus Nitens Wood
No full textThe occurrence of internal checks and their relationship with anatomical structure and basic density in three clones of Eucalyptus nitens plantation trees grown in the eighth region of Chile were studied. Two trees per clone were sampled. The number, radial location, and length of internal checks were determined in samples oven-dried at temperatures increasing from 50 to 100°C. Wood anatomical features including vessel frequency and diameter and annual growth ring width were measured by image analysis. Results show that internal checks were greater for clones with lower basic density. Internal check frequency decreased with height in the tree and increased from pith to bark. A low wood basic density was related to greater ring width and vessel frequency, which contributed to the development of internal checks
Wood Modification Using a Urea-Formaldehyde Prepolymer
No full textUrea-formaldehyde prepolymer and heat treatment were used to improve the properties of fast-growing wood. Results showed that the chemical modification not only decreased moisture absorption, but also increased bending strength and compressive strength parallel to grain. Fourier transform infrared spectroscopy analysis showed that the intensity of the hydroxyl and carbonyl absorption peak decreased, which indicated that the NH-CH2-OH of urea-formaldehyde prepolymer reacted with the wood carboxyl (C=O) and hydroxyl (—OH). The position of the X-ray diffraction peaks of modified wood did not change, indicating that the structure of cellulose did not change. The thermogravimetric analysis showed that the thermostability of fast-growing wood was improved. Scanning electron microscopy revealed that the cell wall and vessels were filled with impregnated chemicals
Effect of Latewood Proportion on Mechanical Properties of Finnish Pine Wood Modified with Compression Drying
Get PDFMechanical and structural changes caused by compression drying of Finnish pine wood (Pinus sylvestris L.) were studied. Elastic modulus, yield stress, Brinell hardness, and latewood proportion were determined for eight boards. Radial compression during the drying process was found to increase latewood proportion by approximately 18% as a result of earlywood deformation. Elastic modulus and yield stress were higher in the radial direction (128 and 2.25 MPa) than in the tangential direction (99 and 2.09 MPa) for green samples, whereas they were higher in the tangential (288 and 4.74 MPa) compared with the radial direction (201 and 3.59 MPa) for dried specimens. Elastic modulus, yield stress, and Brinell hardness correlated significantly (R2 = 0.65, p < 0.05; R2 = 0.73, p < 0.01; R2 = 0.69, p < 0.01, respectively) with latewood proportion. Compression drying enhanced the tangential mechanical properties and surface hardness of Finnish pine wood as a result of increased latewood-to-earlywood ratio
Property Modeling of Changbai Larch (Larix Olgensis Henry) Veneers in Relation to Stand and Tree Variables
No full textThe key objective of this work was to investigate properties of Changbai larch (Larix olgensis Henry) veneers in relation to stand and tree variables using both linear regression (LR) and linear mixed effects (LME) models. A veneer data set was formed with 36 sample trees from four stands in China. Each tree was cross-cut into six segments along the vertical stem. The results showed that tree diameter at breast height (DBH), tree height, and branch height exhibited certain degrees of association with either veneer modulus of elasticity (MOE) or ultrasonic propagation time (UPT) but not with veneer density. Both veneer MOE and UPT exhibited a polynomial pattern along the tree stem. Stem position was found to be the only significant variable affecting veneer density. The highest veneer MOE appeared to be situated between the second and third stems from the butt. LME and LR models were clearly similar with regard to parameter estimates. However, the overall standard error and p value from the LME model were smaller than those from the LR model, indicating that the LME model was more effective for stem-specific analysis. After adjusting confounders including the stem position, tree height exhibited no association with veneer MOE. This result did not occur with standard LR analysis
State of the Art Paper: Effects of Fire-Retardant Treatments on Chemistry and Engineering Properties of Wood
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Microstructure and Mechanical Properties of Silvergrass Fiber Cell Walls Evaluated by Nanoindentation
Get PDFSilvergrass is a natural biological material with high mechanical strength and toughness and has potential as a raw material in wood-based composites. Structure and mechanical properties of fiber cell walls of silvergrass stalk in nanoscale were measured by nanoindentation. Silvergrass fiber cells have multilayered structure and diameter between 5 and 20 μm. Nanoscale mechanical tests showed that fibers of the upper stalk of silvergrass had better mechanical properties than those of the lower stalk and silvergrass fibers had better mechanical properties than wood fibers at the cell wall level. Macrohardness of the silvergrass stalk was 0.330 GPa evaluated from nanoindentation tests. Results found by nanoindentation were also verified by longitudinal tensile strength testing and particleboard manufacture