WOOD RESEARCH Volume 61, Number 6, 2016
Olena Pinchevska, Andriy Spirochkin, Ján Sedliačik, and Rostislav Oliynyk

Quality assessment of lumber after low temperature drying from the view of stochastic process characteristics

The quality of lumber drying is traditionally evaluated after the process. This paper proposes the algorithm of quality assessment of low-temperature convection lumber drying in accordance with the target values of the average final moisture content and its dispersion in the stack. The stochastic model of the process with random initial and boundary conditions, which allows calculating the dispersion of the final moisture content (MC) was proposed. To describe the kinetics of the wood drying process in the low-temperature chamber in view of the thermodynamic characteristics, 34 processes of drying of oak and pine lumber with the thickness of 30, 40 and 50 mm were made at the wood-processing enterprises in Ukraine. The theoretical equations of lumber low-temperature drying and the values of the coefficients that characterize the influence of material thickness, temperature and moisture fields’ distribution in the material during the drying process were obtained. The check of the proposed models on the uniformity of the average values and dispersion of the current moisture content showed a slight difference between the experimental and calculated values. These models allow predicting the quality of the low-temperature drying on the spread of target moisture content, which enables selection of rational drying schedules.

WOOD RESEARCH Volume 65, Number 6, 2020
Igor Novák, Angela Kleinová, Ivica Janigová, Matej Mičušík, Ján Sedliačik, Miroslav Šlouf, Pavlo Bekhta, Ján Matyašovský, and Peter Jurkovič

Properties of water steam-treated maple wood (Acer pseudoplatanus L.)

The hydrothermal treatment of maple (Acer pseudoplatanus L.) wood by steam represents the modification method with the effective heat transfer, which can improve industrially significant properties of wood, i.e. its color, hydrophobicity and subsequently dimensional stability. The maple wood was modified by steam at 125°C during 8 hours, and at pressure of 0.18 MPa. The water contact angle of steam-treated maple wood increased from 44.9° (for untreated maple wood) to 55.3° (for steam-treated maple wood), and the stability of water drop on steam-treated maple wood surface increased. FTIR spectra show an increase in C=O and glycoside bonds concentration on the surface of steam-treated maple wood, but the concentration of C-O-C groups decreased. SEM micro photos confirmed the deformation and shrinking of maple wood cells due to steam treatment. XPS measurements confirmed, that the concentration of oxygen as well as C=O and C-O-O groups on the surface of steam-treated maple wood showed a slight decrease in comparison with pristine wood sample.

WOOD RESEARCH Volume 64, Number 3, 2019
Sergiy Kulman, Liudmyla Boiko, Diana Hamáry Gurová, and Ján Sedliačik

Prediction the fatigue life of wood-based panels

This work presents the results of an experimental investigation of the vibration response of cyclically loaded wood-based panels. The maximum temperature of the stationary state of the activation zone of samples of wood-based panels in the form of a rigid cantilever with their cyclic load at loading frequencies from 0 to 50 Hz and maximum internal stresses from 0.98 to 5.36 MPa was investigated. The purpose of this study is to determine the temperature of selfheating and to determine the dependence of the temperature on the loading conditions. The mathematical model is proposed in the form of system nonlinear ordinary differential equations, where stress, strain and temperature were used as the essential variables. The behaviour of the system is completely determined by the ratio of the introduced external energy and the value of the order parameter. The critical value of the order parameter depends on the thermo-physical properties of the material and is equal to the ratio of the value of the heat transfer coefficient multiplied by the area of thermal dispersion to the coefficient of linear thermal expansion.