Nebojsa Todorovic

Drying of beech (Fagus sylvatica L.) timber in oscillation climates: drying time and quality

Abstract The influence of oscillating climate conditions during the conventional drying of beech timber on drying time and drying quality has been analyzed. Three conventional drying cycles were carried out as well as nine cycles, in which the oscillations of equilibrium moisture content (EMC), temperature, and their combination were applied. The combinations of two amplitudes (10% or 20%) and two frequencies (3 or 6 h) were used in different test runs. Higher drying quality regarding casehardening was achieved both in runs with oscillations of EMC (gap values 2.2–2.4 mm) and in runs with temperature oscillations (gap values 2.3–2.4 mm) compared with conventional runs (gap values 2.5–2.9 mm). The oscillations of both temperature and EMC did not improve any of the observed parameters.

Influence of wood properties and technological parameters of processing on cutting power in milling of thermally modified beechwood

The paper presents results of influence of thermal modification on cutting power required for milling wood processing. The experiment was conducted for the different treatment temperatures (170°C, 190°C and 210°C) and different technological parameters of processing (feed and cutting depth). Cutting powers during milling were measured on four groups of beech wood samples, dimensions 35×16×400 mm, separately for heartwood and sapwood. The following mechanical and physical properties of the processed samples were tested: bending properties (modulus of rupture and modulus of elasticity), cross-sectional and tangential hardness, and air-dry density. The measuring device used for measuring, monitoring and displaying cutting power was developed at the Wood Machining Centre at the Faculty of Forestry in Belgrade. The results point out the differences in the powers required for processing heat-treated wood compared to untreated wood. The analysis shows that with the increase in treatment temperature, the required cutting powers decrease.

Basic physical properties of spruce wood (Picea abies Karst) from plantations

The basic physical properties of spruce wood from plantations in the surroundings of Banja Luka were researched. The dependence of growth ring diameter and wood density, density, volume porosity, shrinkage, fibre saturation point and absorption of moisture were analysed on three trees average age about 16 years. The data for breast height and for all specimens from breast height to 9.3 m were statistically processed. The research and analysis of the basic physical properties of plantation-grown spruce wood shows that the effect of growth ring diameter on the density is negative and that the dependence is logarithmic, which confirms the previous results. Average value of wood density is lower than the usual value reported in references. Average value of radial shrinkage is 3.90%, and tangential 8.10%. This research confirms the linear dependence between the nominal density and volumetric shrinkage of spruce wood and that density has a negative effect on the coefficient of surface anisotropy. At breast height, average value of the coefficient of surface anisotropy is 2.16, volume porosity 72%, and fibre saturation point 32.6%. Average rate of absorption is 3.42% per day, for the first 7 days, and 0.12% per day for the last 30 days. The study results were compared to the results reported by other authors.