Wood-processing industries must be able to estimate the properties of wood to properly manage the wood production chain. For this estimation, changes in certain characteristics over time must be identified so that they can be used to rapidly differentiate a clone or species. Of interest are acoustical, geometrical, physical, and mechanical properties, all measurable in seedlings. Thus, the objective of this research was to analyze the evolution of the ultrasonic wave propagation velocity, diameter, height, basic density, strength, and stiffness starting in nursery seedlings at 3 months of age to trees at 6 years of age, which is the cutting age used by the pulp and paper industry in Brazil. The experiment was conducted in 121 seedlings and 270 trees of three Eucalyptus clones. Within the age range analyzed, the results indicated that all parameters have the potential to be used in a predictive model to estimate the future quality of clones, although the predictive value of these parameters varies. The ultrasonic wave propagation velocity was the only property that maintained the coherent differences among clones from the seedling to the cutting age (6 yr old). The strength, stiffness, diameter, and height maintained coherence from 12 months to the cutting age, whereas the basic density was maintained from the age of 24 months to the cutting age. We hope that these results will contribute to improving the methods to select clones.Abstract
This experiment studied and analyzed termite activities in wooden blocks. The purpose of the study was to develop and test a strategy for isolating termite acoustic emissions (AE) from background noise. This task is not trivial, and therefore the achievement of a clean signal that can be directly associated with termite activities is a good outcome. It is an important step toward achieving an accurate, nondestructive system to detect termite activities in wood. The wooden blocks were immersed in jars that were filled with termites to expose the blocks to termite infestation. The termites' AE, due to their activity in the wood, was recorded using microphones that were fitted in the center of each wooden block. The Cool Edit Pro 2.1 (Syntrillium Software Corporation) sound recording application was used to filter the recorded AE signals. The filtered AE signals were then analyzed using the Matlab application. The wooden blocks experiment showed that termite activities in the wood could be detected using AE recording. Termite activities are clear and detectable in the 4.5- to 5-kHz range of frequencies. Results could also assist in defining the termites' AE signature, to some extent, by analyzing the generated sound due to termite activities in the wood. A clean termite-related AE was successfully extracted from the general AE in the wooden blocks using Matlab R2015a tools.Abstract
A gravity model was formulated to identify the factors related to China's plywood exports and examine whether the impact of factors depended on trade partners using panel data from 2005 to 2015. The data set was divided into three groups based on the income of trade partners. The findings reveal that the factors performed differently in the three groups. For the high income group, gross domestic product (GDP), per capita gross national income (GNI), the ratio of per capita forest area, and Open were related to China's plywood exports. GDP, the ratio of per capita forest area, exchange rate, and Open were correlated to China's plywood export for the middle income group. In the low income group, per capita GNI, the ratio of per capita forest area, Open and Free Trade Agreements were significantly related to China's plywood exports.Abstract
The rapid economic and social growth of China has significantly increased its timber demand, resulting in a heavy reliance on foreign timber supply. Thus, price fluctuation in the international market poses a great risk to domestic timber production and processing enterprises. This study analyzed the dynamic conduction relationship between domestic and international logs and sawn timber markets and how to reduce risks by adjusting the structure of imported products' portfolios. In this article, the multivariate generalized autoregressive conditional heteroskedasticity model is applied to analyze the relationship between domestic and import prices of logs and sawn timber. The study found that among four markets, except one where the short-term spillover effect between domestic logs and sawn timber is large with statistical significance, spillover effects are small. In the long run, there are significant spillover effects between the four markets. Thus, changes in the international log market are very easy to transfer to the domestic log market through trade and then to the downstream domestic and international sawn timber markets. Therefore, in order to ensure timber security in China, this study uses the theory of portfolios to calculate product proportion with minimum risks. The proportion of portfolios indicates that, even though Chinese companies prefer logs, they have to import a great amount of sawn timber due to restrictions on log exports from sourcing countries, which increases the risk of timber supply.Abstract
Nonchemical high-pressure steam treatments have been intensively researched and commercialized to produce chemical-free wood products with enhanced properties. However, the utilization of high-pressure steam involves vapor-phase reactions using high-temperature steam generated at the expense of high energy input. In this research, influences of reaction media (steam and hot-compressed water) and temperature (100°C and 140°C) during thermal treatment on physical properties and drying behavior of yellow-poplar (Liriodendron tulipifera) heartwood were compared. The length, width, and thickness of the samples were 22.53 mm, 17.18 mm, and 16.72 mm, respectively. After the treatment, the samples were dried under an isothermal temperature condition of 105°C. Data on moisture content and time of drying from drying experiments were fitted with unsteady-state molecular transport equations to calculate overall liquid diffusion coefficients. Dimensions, weight, and true volume of samples were measured for green, thermally treated, and dried samples and the values were used to calculate selected physical characteristics. Additionally, selected mechanical properties were evaluated for samples conditioned to 13 percent moisture content. Results showed that intensified hot-compressed water-treated and control samples had the highest and lowest saturated moisture contents (101% and 44%), respectively, immediately after treatments. Intensified steam-treated and control samples had the highest and lowest total porosity (95% and 82%), respectively. Furthermore, mild hot-compressed water-treated samples showed the greatest compression strength (47.8 MPa) at 13 percent moisture content. Except for steam treatment at 140°C, other treatments significantly decreased the diffusion coefficient. Collectively, samples treated with hot-compressed water at 100°C showed the most improved mechanical properties.Abstract
In this study, triangular specimens of southern pine (Pinus spp.; SP) generated by a star-sawn process were characterized according to knots and deformation. SP specimens were used to understand the differences among glue-line combinations of radial-to-radial, radial-to-tangential, and tangential-to-tangential faces bonded with phenol resorcinol formaldehyde resin. The specimens were tested for shear strength, dimensional stability, wood failure, and delamination rate in accordance with ASTM D1037 and D2559 standards. Among the star-sawn triangular samples studied, bows in tangential-face sections occurred the most. The radial-face sections of SP triangular specimens had more knots but a much lesser degree of deformation than the tangential-face sections. The tangential-to-tangential face glue-line samples showed a lower shear strength, more wood failure, and a greater tendency of delamination and dimensional change, especially when subjected to wet conditions. Confocal microscopic pictures revealed that the tangential-to-tangential glue line showed a greater tendency of deformation in the earlywood part and helped to explain the reason for poor glue-line durability and low shear strength. This article revealed that the star-sawn–process generated wood radial-face samples were more stable than others tested and are perhaps a good alternative for massive panel manufacturing.Abstract
In recent years, a multispot pressure tensioning process appeared in the field of circular saw blade manufacturing. Due to the insufficient understanding about the formation and evolution of the tensioning effect of this process, this study aimed to analyze and optimize the tensioning effect on a circular saw blade tensioned by multispot pressure. It could provide a theoretical basis and key technical parameters for regulating and controlling the tensioning effect of this process. In this article, the natural frequency and the tensioning stress field of a circular saw blade tensioned by multispot pressure were calculated by ABAQUS software. The simulated tensioning stress field was in agreement with the experimental results, which confirmed the accuracy of the simulation model. The influence of process parameters on the natural frequency and tangential tensile stress in the edge of the circular saw blade was examined and compared based on the orthogonal method. Simulation results show that the parameters of the multispot pressure tensioning process have different degrees of influence on the tensioning effect of a circular saw blade. Considering the natural frequency and tangential tensile stress in the edge of a circular saw blade synthetically, optimal process parameters for multispot pressure tensioning were obtained.Abstract
Moisture intrusion can be significantly higher along specimen edges, particularly at edges where longitudinal grain is exposed, which is referred to as the edge effect. The influence of edge effects on moisture durability are assumed to decrease as the edge area to total-surface-area ratio decreases. Moisture durability assessment of laminated veneer lumber (LVL) is commonly evaluated using accelerated weathering (AW) and outdoor exposure methods, where small specimens are analyzed. The influence of specimen size (i.e., edge effect) on moisture durability evaluation of LVL was investigated in this study. To vary specimen size, three widths with constant length and thickness were evaluated. In addition, three AW methods were used to characterize how the method of inflicting degradation influenced edge effects. No consistent trends in mechanical property loss were found across AW methods, indicating that the influence of specimen size varied with AW method. The greatest influence of specimen size occurred when cyclic vacuum-soak-dry was included, where water absorption decreased significantly with increasing width, and three of four mechanical properties evaluated displayed an influence of specimen size. The smallest influence of specimen size occurred when a single soak-dry procedure was included, where only one of four mechanical properties evaluated displayed an influence of specimen size. Results from this study provide evidence that edge effects may occur during LVL moisture durability assessment but that the severity is dependent on AW conditions.Abstract
Cross-laminated timber (CLT) technology has the potential for utilization of lower grades and underused species of lumber, because the core layers perpendicular to the principal loading direction transfer loads through shear, which is not correlated to the grade of lumber. Currently the product standard specifies the minimum grade requirements for all lumber to be used as CLT laminations. In this study, the effect of the presence of knots in the transverse core layer of CLT billets was examined in matched CLT samples where the heavy presence of knots and the related grain disturbance in the transverse core layer were the only variables compared with knot-free reference. All samples were tested as short beams in three-point bending and all failed in rolling shear in the transverse core layer. The presence of knots had no measurable effect on the shear capacity or stiffness of the tested CLT beam samples.Abstract
Methyl bromide (MB) fumigation of oak (Quercus sp.) logs destined for export is required to mitigate risks associated with movement of the oak wilt fungus, Bretziella fagacearum. Alternative fumigants with efficacy against B. fagacearum are needed because of MB's ozone-depleting properties. Fumigation with sulfuryl fluoride (SF) is considered a promising substitute. Logs (1.8 m long) were obtained from Quercus trees (18.3 to 29.2 cm diameter at breast height) that were naturally infested (NI) or artificially inoculated (AI) with B. fagacearum to compare pathogen colonization and survival following fumigation with SF and MB. The logs were fumigated with SF for 72 hours with 240, 280, and 320 g/m3 or 96 hours with 128 and 240 g/m3. MB fumigations were conducted using the current treatment schedule for oak logs destined for export (240 g/m3 for 72 h). Frequencies of successful pathogen isolation before treatment were higher for AI logs than for NI logs based on isolation rates from sapwood chips. Treatments greatly reduced frequencies of viable pathogen presence, but no treatment was successful in eradicating the pathogen. Experiments were conducted on blocks (10.2 by 10.2 by 11.4 cm3) obtained from Quercus trees to investigate simulated penetration and diffusion of SF and MB into oak logs. Slow, variable fumigant diffusion never reached concentration–time products lethal to B. fagacearum. Based on these results, reliance on SF alone as a quarantine measure may require higher concentration × time products to achieve quarantine level control of the oak wilt fungus in logs.Abstract
The potential for using a low molecular weight polyethylene (PE) polymer to improve the properties of creosote-treated wood was evaluated on samples of six different wood species. Samples were impregnated with creosote alone or amended with the PE additive and then tested to failure in third-point loading to determine modulus of elasticity and modulus of rupture. Samples were then subjected to three soak–dry cycles to assess the impact of moisture uptake on fastener performance or water repellency. The presence of the PE was associated with lower preservative retentions, but had no significant effect on modulus of elasticity, modulus of rupture, water repellency, or fastener withdrawal resistance. The results suggest that the additive limited preservative uptake, but did not improve any of the wood properties evaluated.Abstract