The objective of this research was to establish comparatively some relevant features of Turkey oak and sessile oak wood, in order to better understand the drying behavior of these species. The ...analyzed samples were obtained from freshly harvested trees of the same age, originating from the Southern Sub-Carpathians. The microscopic analysis revealed that Turkey oak has larger earlywood pores than sessile oak. In heartwood, they are partly filled with tyloses for both species. The macroscopic analysis showed that Turkey oak wood has a much lower proportion of heartwood (only 50%) compared to sessile oak (90%). The comparative FTIR analysis of the two species showed similar qualitative chemical composition, but also some differences between sapwood and heartwood regarding the relative proportion of the main constituents, and very likely in the structure of lignin. High amounts of extractives were found in Turkey oak sapwood (5.34% in cold water, 7.77% in hot water, and 21.60% in NaOH 1%), close to the values obtained in sessile oak heartwood. The research also revealed that the Turkey oak sapwood and heartwood have statistically similar values of oven-dry density, shrinkage coefficient, fiber saturation point, while in sessile oak, the values are clearly higher in the heartwood.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
This paper presents structures of timber-framed walls designed for passive houses, using natural and waste resources as insulation materials, such as wool, wood fibers, ground paper, reeds ...(Phragmites communis), and Acrylonitrile Butadiene Styrene (ABS) wastes. The insulation systems of stud walls composed of wool–ABS composite boards and five types of fillers (wool, ABS, wood fibers, ground paper, and reeds) were investigated to reach U-value requirements for passive houses. The wall structures were designed at a thickness of 175 mm, including gypsum board for internal wall lining and oriented strand board (OSB) for the exterior one. The testing protocol of thermal insulation properties of wall structures simulated conditions for indoor and outdoor temperatures during the winter and summer seasons using HFM-Lambda laboratory equipment. In situ measurements of U-values were determined for the experimental wall structures during winter time, when the temperature differences between outside and inside exceeded 10 °C. The results recorded for the U-values between 0.20 W/m2K and 0.35 W/m2K indicate that the proposed structures are energy-efficient walls for passive houses placed in the temperate-continental areas. The vapour flow rate calculation does not indicate the presence of condensation in the 175 mm thick wall structures, which proves that the selected thermal insulation materials are not prone to degradation due to condensation. The research is aligned to the international trend in civil engineering, oriented to the design and construction of low-energy buildings on the one hand and the use of environmentally friendly or recycled materials on the other.
The best-possible valorization of each cut log is a priority. The aim of this research was to evaluate the potential of a solution for increasing the conversion efficiency of tapered logs, by ...edge-cutting the narrowest sideboards at 45° and joining them by gluing, in order to obtain usable lumber boards. The modality of obtaining the glued elements was described and the values of the density and bending properties (MOE and MOR) of these elements compared to solid wood elements taken from the same logs and the same position within each log was determined. The envisaged outcome was to determine if the bonded products are suited to be used as cores within laminated products for construction.
Color and chemical changes were investigated in beech wood (Fagus sylvatica L.) following light steaming and further heat treatment for 2.5 h at 200 °C by two techniques (industrial ThermoWood versus ...a laboratory procedure in the presence of air). Colour changes were evaluated in the CIE Lab system, while Fourier transform infrared spectroscopy with attenuated total reflection (FTIR-ATR) investigation was employed to highlight and compare the associated chemical changes. Light steaming caused only minor chemical changes (limited hydrolysis of hemicelluloses) not ready detectable by FTIR. In contrast, heat treatments caused visible changes in the FTIR spectra, especially in the region 1800 to 1500 cm-1, consisting mainly in a clear decrease of the absorption band for conjugated carbonyls at 1643 cm-1 and a slight apparent increase of the absorption bands for lignin at 1506 and 1595 cm-1. A significant variation of the ratios of relevant absorption bands indicated complex chemical changes, including hydrolytic, oxidative, and condensation reactions. FTIR ratios and the mass loss values in the two heat treatments relate, both indicating a more advanced modification in the case of the ThermoWood process.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Turkey oak lumber is difficult to dry, being prone to cracks even at low temperatures. The main objective of the research was to test different drying conditions in order to establish whether ...air-drying or kiln-drying from a green state was more suitable; if the lumber width had an influence on the drying quality; if prior steaming had a positive effect upon the kiln-drying time and quality; if end cracks could be avoided by protecting the board ends; and what the most appropriate kiln-drying conditions were, with conventional drying. The research results recommend kiln-drying as a better alternative than air-drying in terms of both time and quality, but very mild conditions must be applied. Wide lumber parts cracked both when air-dried and when kiln-dried. All defect-free lumber parts dried accurately, with no deterioration. Steaming had a positive effect upon the drying quality; no steamed part cracked. The end protection of the boards was efficient only in the case of kiln-drying.
Several previous studies have investigated the effects of heat treatment on the chemical composition, along with the physical and mechanical properties, of wood from various species. However, the ...effects of these property changes upon the machining properties and surface quality of machined wood have been studied much less. The main goal of this work was to investigate the comparative cutting power consumption during milling and the resulting surface roughness of heat-treated and untreated beech wood (Fagus sylvatica L.). Several cutting regimes were tested by combining different values of rotation speed, feed speed, and cutting depth. The cutting power and the processing roughness were assessed and compared. The results clearly showed that the cutting power involved in the milling of heat-treated beech wood was up to 50% lower than that of untreated wood, but the processing roughness was slightly higher.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The comparative behavior of heat-treated and untreated beech wood (Fagus sylvatica L.) were studied in response to planing. Beech wood samples were heat-treated in an electric oven without air ...circulation, at atmospheric pressure, at 200 °C for 1, 2, 3, 4, 5, or 6 h. After conditioning, both the heat-treated samples and the untreated controls were planed at a rotation speed (n) of 4567 rpm and a feed speed (u) of 10 m/min via a “silent power” cylindrical cutter. The cutting power was measured during machining by a Vellemann DAQ board. After processing, the surface quality was measured along and across the cutting direction with a stylus MarSurf XT20 instrument, and the processing roughness was assessed by the roughness parameter Rk. The influence of the heat-treating duration upon the cutting power and the processing roughness were analyzed and correlated to the mass loss after the heat treatment. Linear regression functions were generated for both of the correlations.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
This paper presents the results of an experimental study performed on seven violins obtained from a top plate made of resonance spruce and a back plate made of curly maple. Each pair of plates had a ...different modification to its thickness profile. Some were thickened and others were thinned compared to the classical thickness profile. Then, a soloist played a musical sequence on each violin and the acoustic signals were recorded. The sound quality of the signals was evaluated with a psycho-acoustic evaluation based on a blind questionnaire completed by listeners. It turned out that: (1) respondents with more musical experience (especially those with over 26 years of experience) were more demanding in assessing sound clarity and offered the widest range of scores in assessing this quality; (2) the musical experience of the respondents influenced to the highest degree the appreciation of the warm sound quality; (3) the scores for the violins with thinned plates were weaker, especially according to the psycho-acoustic analysis; and (4) the highest score was obtained by the violin with the thickest plates, which can be correlated with the two dominant frequencies extracted from the FFT analysis, whose values coincide with the frequencies of the B1− and B1+ modes.
Small-diameter wood resulting from thinning operations is an important secondary wood resource. Compared to wood originating from mature trees of the same species, it is less stable in shape and ...dimension when exposed to environmental humidity changes. To reduce its hygroscopicity and valorize this secondary wood resource in solid wood panels for outdoor use, wood samples cut from mature and small-diameter spruce, black pine, lime, and beech logs were heat-treated at 180 and 200 °C for 1 to 6 h in air at atmospheric pressure. Mass loss, swelling coefficients, and anti-swelling efficiency (ASE) were established for each wood type for a comparison between species. Mature and small-diameter wood was also compared under the influence of different temperature/time combinations. The heat treatment conditions that led to a mass loss of maximum 5% in each case were: 200 °C/3.5 h (mature spruce), 200 °C/5 h (thin spruce), 200 °C/3 h (mature pine), 200°C/3.7 h (thin pine), 200 °C/3.2 h (mature lime), 200 °C/2h (thin lime), 200°C/3 h (mature beech), and 200 °C/2.7 h (thin beech). Small-diameter spruce, pine, and lime (the soft species) recorded better dimensional stabilization than the mature wood of each species (ASEvol=49.7% compared to 39.3% for spruce, 38.6% compared to 38% for pine, 52.3% compared to 44.4% for lime), while small-diameter beech behaved differently (with ASEvol=43.5% compared to 48.5 for the mature wood).
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
This paper introduces a numerical methodology based on a 3D turbulent flow computation developed to assess the aerodynamic performances of lumber drying kilns. The numerical results are validated ...against experimental data obtained by applying five different fan speeds and reversible air flow. The distributions of the energy loss coefficient and of the non-uniformity flow coefficient were plotted along the flow path in both normal and reverse directions and the regions with larger air loss values were identified. The numerical computation revealed that three quarters of the airfl ow delivered by the fans bypasses the wood stacks through different gaps, consequently leading to a low aerodynamic effi ciency (of 24-25 %) of the kiln.
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