Search

The subject of this paper is the analysis of the influence of laser cutting of oak wood on its drying process. The subject of the research was the comparison of the drying process and the quality of the dried wood in samples cut by classical technology (sawing) and samples cut with the use of laser. The research was carried out on two sets of samples which were subjected to an identical drying process. Continuous moisture loss and final moisture attained, moisture gradients before and after drying, and internal tensions before and after drying were monitored by means of the fork test and the cut-test. The final moisture content at the end of drying was 8.09% for the saw-cut samples and 8.22% for the laser-cut samples, a difference of only 0.13%. The analysis of the individual characteristics observed showed that the influence of the cutting technology did not have a significant effect on the drying process or the quality of the dried oak sawn timber.

In this work, we focus on the prediction of the influence of CO2 laser parameters on the kerf properties of cut spruce wood. Laser kerf cutting is mainly characterized by the width of kerf and the width of the heat-affected zone, which depend on the laser power, cutting speed, and structure of the cut wood, represented by the number of cut annual rings. According to the measurement results and ANN prediction results, for lower values of the laser power (P) and cutting speed (v), the effect of annual rings (ARs) is non-negligible. The results of the sensitivity analysis show that the effect of v increases at higher energy density (E) values. With P in the range between 100 and 500 W, v values between 3 and 50 mm·s−1, and AR numbers between 3 and 11, the combination of P = 200 W and v = 50 mm·s−1, regardless of the AR value, leads to the best cut quality for spruce wood. In this paper, the main goal is to show how changes in the input parameters affect the characteristics of the cutting kerf and heat-affected zones for all possible input parameter values. [ABSTRACT FROM AUTHOR]

The present paper deals with the analysis of cross-section surface irregularities after CO2 laser cutting. The surface irregularities of beech (Fagus sylvatica L.), oak (Quercus petraea), and spruce (Picea abies L.) wood were quantified by primary profile parameters using a digital microscope. The arithmetic mean height (Pa), used as the basic parameter, was supplemented by amplitude parameters (Pv, Pp, Pz) and the Psm parameter, through which the shape of the irregularity was specified in more detail. A statistically significant change was demonstrated when changing the values of the feed speed and the power of the CO2 laser. The results of this article confirm that the surface irregularities increased with an increasing laser power and decreasing feed rate. The scanned topographic images also provide a more detailed explanation of the measured P-parameters and point out the risks associated with the evaluation of the cross-section with the primary profile. [ABSTRACT FROM AUTHOR]

The paper deals with the fire technical characteristics of insulation panels made of recycled technical textiles from the automotive industry. The introductory part focuse an of the use of recycled textiles, a description and division of technical textiles, a description of the examined material and its composition, combustion processes, and the method of handling waste textiles. The monitored characteristics were the determination of the ignitability of the material, the gross calorific value as well as the radiant heat resistance. The measurements were carried out on samples from recycled technical textiles before and after their treatment with flame retardants (Isonem Anti-fire Solution, Ecogard B45, HR Prof, woven carbon foil, non-woven carbon foil). The best results in the ignitability test after treatment with liquid flame retardants were obtained after treatment with Ecogard B45. The results show that when flame retardants are used, the released heat during the combustion of the monitored materials treated through the dipping method is significantly lower from 13.7 MJ/kg to 23.7 MJ/kg. The lowest gross calorific values were achieved when using liquid flame retardant HR Prof when applied by dipping. The proportion of material that did not burn was very low (4.61 to 5.63%). After exposure to radiant heat for 10 min, the highest mass loss was 13.6% (dipping in Ecogard B45) and the smallest 1.8% (non-woven carbon foil). Based on results, it shows that flame retardant ECOGARD® B45 for the insulation material Senizol AT XX2 TL60 made from recycled technical textiles is the most suitable fire protection. [ABSTRACT FROM AUTHOR]

In addition to traditional chip methods, performance lasers are often used in the field of wood processing. When cutting wood with CO2 lasers, it is primarily the area of optimization of parameters that is important, which include mainly laser performance and cutting speed. They have a significant impact on the production efficiency and cut quality. The article deals with the use of an artificial neural network (ANN) to predict spruce wood cut characteristics using CO2 lasers under several conditions. The mutual impact of the laser performance (P) and the number of annual circles (AR) for prediction of the characteristics of the cutting kerf and the heat affected zone (HAZ) were examined. For this purpose, the artificial neural network in Statistica 12 software was used. The predicted parameters can be used to qualitatively characterize the cutting kerf properties of the spruce wood cut by CO2 lasers. All the predictions are in good agreement with the results from the available literary sources. The laser power P = 200 W provides a good cutting quality in terms of cutting kerf widths ratio defined as the ratio of cutting kerf width at the lower board to the cutting kerf width at upper board and, therefore, they are optimal for cutting spruce wood at 1.2·10−2 m·s−1. [ABSTRACT FROM AUTHOR]

This research work aims to investigate the effects of thermal modification and wood cutting direction (transverse, radial and tangential) on the content of extractives, lignin, cellulose, and hemicelluloses, and on the thermal conductivity of Norway spruce (Picea abies L.) wood. Samples were thermally modified for 3, 6, and 9 h at temperatures of 160°C, 180°C, and 200°C in the oxidizing atmosphere with natural convection. The extractives, lignin, cellulose, and holocellulose contents were determined by wet chemistry methods, the structural changes were evaluated by using Fourier-transform infrared spectroscopy (FTIR). The highest relative content of extractives was determined at the temperature of 200°C and a thermal modification duration of 9 h. The lignin content decreased at the temperature of 160°C and increased at higher temperatures due to the formation of pseudo-lignin. The cellulose content increased, and hemicellulose content decreased with the increased temperature and thermal modification duration. FTIR analyses revealed changes mainly at the temperature of 200°C, primarily a decrease in the intensities of the characteristic absorption bands of lignin due to degradation reactions. Markedly, density and thermal conductivity decreased mostly due to depolymerization of hemicelluloses. Regarding the thermal conductivity, a slightly higher decrease in transversal and tangential sections was determined. [ABSTRACT FROM AUTHOR]