European Journal of Wood and Wood Products最新文献

In this study, the mechanical properties of bonded single-lap joints are analysed by tensile lap shear tests on beech wood. A one-component polyurethane adhesive was used, and three different methods of surface preparation were applied: planing, sanding along the grain, and sanding perpendicular to the grain. Prior to bonding, the wooden lamellae underwent laser scanning to obtain surface profiles, which were then analysed for surface roughness. Scanned surface topographies with their features were integrated into the finite element analysis (FEA) software COMSOL Multiphysics to simulate the lap shear bonding area for different surface profiles and roughness. The FEA model implements linear material models, which represent the adherend and thin adhesive layer, combined with a modified local cohesive zone model for the adhesive bond interfacial forces. The experimental tests were conducted in a dry environment, where a higher surface roughness achieved by sanding correlated with a higher tensile shear strength. This increased surface roughness was attributed to the enhanced mechanical interlocking mechanism. This finding aligns with the FE analysis, which showed that increased surface roughness, micropillars and indentations, led to variations in stress concentration and distribution compared to a smooth surface bond.

Recent studies have identified radial cracks in post and beam supports in timber structures, but there is a lack of systematic studies on the effect of cracks on burning behavior. In this study, the burning behavior of timber specimens with inclination angles of 0°, 15°, 30° and 45° and varying cross-section widths was investigated. The analysis of flame patterns, temperature profiles, the mass loss rate and charring degree showed that cracks had a significant effect on the combustion behavior of wood. The mass loss rate (MLR) was higher for wood with radial cracks compared to wood without cracks. By introducing the concept of charring volume and assessing the effect of cracks based on charring length and depth, it can be seen that cracks have the greatest effect on the area directly exposed to the flame. The effect of cracks increases dramatically when the angle reaches 30°. Cracks affect combustion through two main mechanisms: firstly, external heating accelerates the airflow at the crack, creating an entrainment effect that increases the oxygen content in the combustion zone; secondly, the accelerated airflow enhances thermal convection. This study provides a comprehensive analysis of the effect of cracks on combustion behavior and provides a reference for the restoration of timber-framed buildings.

This study explores the potential for biodegradable machining fluid for wood processing based on common ingredients: water, ethanol, hexane, glycerol, and various ionic liquids, examining its impact on glue properties, Scots pine wood surfaces, and adhesive force. A review of the literature confirms over 60% degradation of all components of the machining fluid within 28 days, except for IL2 and IL3. The research results suggest using water as the main component of the machining fluid due to its highest thermal conductivity and heat capacity values, and ethanol as an equivalent to organic solvents capable of degreasing blade surfaces while rapidly evaporating to cool the blade surfaces, ensuring low viscosity even as one of the main components. Empirical tests confirmed no impact of the studied components of the machining fluid on the solubility of glue and the mechanical properties of the glued joints. Fourier Transform Infrared Spectroscopy analysis with Principal Component Analysis indicated the most significant impact of glycerol on the chemical structure of the wood. However, results confirm the possibility of using this compound as a viscosity regulator for the bio-machining fluid, characterized by a vapor pressure more than 2000 times lower than that of SMF2, indicating the high thermal stability of this component.

The Cura Baglama represents the smallest variant within the traditional Turkish baglama family of stringed instruments. Investigating its structural integrity when subjected to sudden impact loading is essential for advancing efforts in standardisation, development, maintenance, repair, and the preservation of its historically significant design characteristics. This study presents a comprehensive analysis of the dynamic structural response of a cura baglama subjected to controlled drop-test scenarios. A reverse engineering methodology, coupled with three-dimensional explicit dynamic analysis, was employed to examine the instrument’s behaviour under impact loading. The study evaluated the effects of seven distinct impact positions, simulating a drop from a fixed height of 1000 mm. The simulation results provided critical insights into the instrument’s impact response by visualising deformation patterns and equivalent stress distributions across its structure. Regions susceptible to damage were identified by comparing the computed equivalent (von Mises) stress with the material’s yield strength, which served as the threshold for irreversible damage. This approach enabled the determination of the critical drop height corresponding to structural failure in each scenario. The findings indicate that, although all scenarios were simulated at a fixed drop height of 1000 mm, Impact Scenario 5 exhibited the lowest calculated threshold for damage initiation, with a critical drop height estimated at 172 mm based on the material yield criterion. These structural impact response analyses offer valuable guidance for instrument designers, facilitating the development of cura baglama models with enhanced strength. While the findings are specific to the analysed instrument model, the methodological approach can be generalised to similar studies. Furthermore, the findings contribute to the broader preservation efforts of these culturally and historically significant musical instruments.

The use of cross-laminated timber (CLT) and laminated veneer lumber (LVL) in wooden structures including non-residential, tall and large buildings is increasing, even though they might be subjected to important horizontal forces. The asymmetric four-point bending test method, originally used for lumber and glulam, can be used to evaluate the in-plane shear performance of CLT. This test may have led to bending failure in the case of the CLT specimens. In this study, asymmetric four-point bending tests were conducted to evaluate appropriate shear strength and modulus. Span ratio of 0.5–1.0 is recommended for shear failure to occur as the latter is less affected by compression force. The shear strength exhibited a positive correlation with the ratio of the perpendicular layer, suggesting that the shear strength can be easily estimated. The diagonal measurement of shear deformation is a convenient method because it has less effect on deformation due to the direction of the grain.

In recent decades, the proportion of hardwoods in European forests has increased, and this trend is expected to continue in the future. Strength grading of hardwood is an important procedure to produce high-quality glued laminated timber and cross-laminated timber. The existing dataset lacks predefined thresholds and rules governing strength and stiffness indicators for hardwood. This study analyzes several visual and physical strength and stiffness-related parameters, including knot characteristics, density, and dynamic modulus of elasticity, focusing on their influence on the tensile strength and modulus of elasticity in tension parallel to the grain of European hornbeam (Carpinus betulus L.) timber boards. Destructive tensile tests were conducted on boards, and correlations between properties were analyzed. Additionally, the formulas for predicting the tensile strength and stiffness were derived with a coefficient of determination. The research findings can provide valuable insight into the behavior of European hornbeam, contributing to the standardization of strength grading and maximizing its mechanical utilization. Based on the research findings and compared with other tensile properties analysis, European hornbeam boards appear to have potential for use in the production of high-strength glued laminated timber.

Timber colour sorting is an important woodworking process in producing a homogeneously coloured and pleasant looking product. However, for multispecific timber such as light red meranti, LRM (Rubroshorea spp.), which spans a wide gamut of colours, there is an antagonistic compromise between having good separability of colour and the number of bins. This research attempts to solve this by intentionally overclustering the intensity gamut and then automating the selection of ideal colour sorting bins (CSB) for a given batch size to produce high-similarity coloured sorting. 178,327 unique LRM wood samples collected over 8 months of production were used. Machine learning clustering algorithms such as k-means and Otsu multithresholding were tested against percentile and equal spacing methods. Batch sizes of 250 (B250) and 1,000 (B1000) pieces were evaluated. Maximum likelihood estimation was tested against statistical methods to select the CSB, and ideal overcluster setups were determined using the average delta E ((Delta E^*_{00})) assessment. The ‘burn-in rates’ of 3–30 pieces were then evaluated. For the B250 four-bin setup, six overclusters (6C4) performed best, with a recommended ‘burn-in rate’ of 12 pieces. For B1000, 5C4 performed best with a ‘burn-in rate’ of 10 pieces. The 4C3 configuration and the ‘burn-in rate’ of 10 pieces were found to be the best for three-CSB for both B250 and B1000. This study shows the feasibility of using machine learning to automate the bin selection process when the overclustering technique is used to improve colour sorting in situations with a restricted number of bins.

Large parts of banks of canals in the Netherlands are protected by azobé timber sheet piles. Many kilometers of sheet piles in the province of Noord-Holland, are planned to be replaced or to undergo maintenance. Yet, there is insufficient knowledge on the current state of the azobé sheet piles and their residual service life. Based on this, a series of investigations on azobé sheet piles after 57 years of service were performed. Visual inspections showed surface deterioration on the water-exposed side for all boards. Nondestructive testing using micro drilling technique showed no signs of internal deterioration. A maximum reduction in thickness of 17% and an average thickness reduction of 6.7% of original thickness were observed. CT scanning showed that the remaining cross sections of the azobé boards were intact and had comparable density of new azobé boards. An exponential damage accumulation model was used to predict the residuals service life of the timber sheet piles subjected to earth stress. Conservative estimates based on physical measurements and residual bending strength indicate that the sheet piles have an additional service life of 22–43 years from the current state.

Wood fuel pellets are currently one of the ecological alternatives to fossil fuels for heat and power generation. These fuel pellets are produced through the densification/pelletizing process of a preconditioned sawdust material inside huge pellet mill presses, with dies made of multiple small cylindrical channels. While the industrial aspects of the fuel pellets are well understood and controlled, little knowledge was acquired on the flow of wood granular systems (sawdust) through circular dies. In this paper, such a flow was investigated by means of a capillary rheometer, in the case of a pretreated isotropic sawdust. Influences of the feedstock (water content and particle size distribution), extrusion parameters (piston speed, temperature), and die design (entry-cone angle, length of the cylindrical section) on the pellet density and aspect at the die exit were particularly discussed. Water contents were tested uncommonly until 40 wt%. Careful attention was paid to forces applied on the piston as an indication of power requirement in order to determine the best extrusion conditions. Low temperature and high moisture content appear to be the conditions that require lower power, while long capillaries increase density by 20% and give rise to a better aspect.

Permanent fixation of compressive deformation is one critical aspect of wood densification technology. In this study, heated and pressurized nitrogen gas (N₂), steam and their mixture were applied as the heating media to treat surface compressed poplar wood for the compressive deformation fixation. When steam was applied at 0.5 MPa, around 80% of the compressive deformation was permanently fixed. Although heat treatment in N₂ also caused hemicellulose degradation in wood as that caused by heat treatment with steam, yields of acetic acid and aldehyde compounds were significantly lower than that from heat treatment of surface compressed wood (SCW) with steam-N₂ mixture containing more than 50 vol % steam. Heat treatment with steam effectively reduced set recovery of SCW. Set recovery induced from hygroscopicity and water absorption were 2 to 4 times higher than those after treated with steam treatment. Additionally, heat treatment in N₂ resulted in the biggest wood hardness loss. When steam-N₂ volumetric ratio was 1:1, set recovery was over 50% lower than that obtained by heat treatment in N₂, while wood hardness was just slightly decreased. Steam introduction into N₂ for SCW heat treatment significantly reduced the compressive set recovery as well as mass loss. From the perspective of industrial manufacture and application, when the heating medium pressure exceeded 0.3 MPa, steam-N₂ mixture medium with over 50 vol % steam contributed to the permanent fixation of over 50% compressive deformation. Meanwhile, the set recovery of SCW after exposed to high temperature and high humidity was less than 5%, with no excessive hardness loss.