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INNO 2/2013 2013

USING THE MORPHOMETRIC CHARACTERISTICS OF WOOD RAW MATERIALS IN THE SAWMILL TECHNOLOGY

Автори: Valentin Shalaev, Stanislav Rykunin

Резюме

The opportunities of use of uneven distribution of knots in wood raw material are considered at cutting lumber on sawn blanks

Ключови думи: morphometric characteristics, wood raw materials, sawmill technology

EN Version

CHALLENGES IN WOOD DENSIFICATION: PROCESSING AND PROPERTIES

Автори: Parviz Navi

Резюме

Wood can be densified and moulded through the combined effects of temperature, humidity and mechanical forces. These processes so called THM treatments. Depending to the processing parameters the physical and mechanical properties of wood can improve considerably. Although, the principles of densification of small wood elements are well known, challenges are faced in scaling-up stage and on the shape memory. The aim of this paper is to explain the origin of the shape memory and the effect of combined Thermo-Hydro-Mechanical on the fixation of compression. The process of densification can be implemented in an open system, a semi-open system or a closed system. In an open system part of the boundary conditions is open to climate and control of moisture content as well temperature of the elements during densification is not possible. But in a closed system all these parameters are under control. Although, densification of wood in an open system improves the mechanical and durability of wood, but the compression-set is not stable. Post-processing THM treatments have shown to constitute an effective means of eliminating the set-recovery. We have shown that hydrolysis of hemicelluloses during THM post treatment plays an important role in the elimination of shape memory through the dissipation of the stresses (relaxation) stored in the microfibrils and the matrix during densification. We have shown that for a total elimination of shape memory it is necessary for the lignin to be in its rubbery state during the THM treatment.

Ключови думи: wood densification, thermo-hydro-mechanical treatments, post-treatments

EN Version

THE SHARE OF BARK IN ENERGY CHIPS FROM SHORT ROTATION COPPICE OF POPLARS AND WILLOWS GROWN ON PLANTATIONS

Автори: Ladislav Dzurenda, Miroslav Dzurenda

Резюме

In this contribution, the results of experimental works assessing the share of bark in energy chips of selected clones of short rotation coppice of Salix viminalis and poplars with 5-year harvesting cycle, grown in the region of Slovakia and Moravia, are shown. Energy chips made of dendromass from fast growing trees grown on plantations is a bio-fuel consisting of juvenile wood and juvenile bark. The share of bark in energy chips influences the environmental properties and ash content of a bio-fuel.

The share of bark in energy chips from clones RAPP, OLM, ULV and Inger of Salix viminalis in bio-fuel is XB = 16,8 ÷ 19,7 % and the share of bark in chips from clones Max5, Oxford, AF2 a Monviso of poplars grown on plantations is XB = 20,97 ÷ 26,67 %.

Ключови думи: bio-fuel, energy chips, share of bark, fast-growing trees, Salix viminalis, Populus

EN Version

QUALITY OF INDOOR AIR IN SMALL CZECH FURNITURE COMPANIES

Автори: Daniela Tesařová, Petr Čech

Резюме

This paper investigates the problematic of emission volatile organic compounds emitted to working, indoor air of the wooden furniture company. The main goal of this research were assessment of quality of indoor air in working environment, which was load of emission VOC emitted from production processes of made furniture. The one part of this research deals of the influence individual technological operations in wooden made furniture in dependence on quality and quantity composition of VOC, which they effects of quality external and internal environment of the furniture company. We analyzed emissions of VOC emitted during the furniture production by the gas chromatograph in conjunction with mass spectrometer and Direct Thermal Desorption. The result of analysis is qualitative and quantitative data in form graph and numerical expression.

Ключови думи: VOC emissions, the furniture company, working environment, gas chromatograph

EN Version

INFLUENCE OF THE NATURAL WOOD VARIABILITY ON THE HEAT TREATMENT PROCESS: EFFECTS OF THE WOOD INITIAL DENSITY ON THE FINAL QUALITY OF THE HEAT TREATED PRODUCT

Автори: Joël Hamada, Anélie Pétrissans, Frédéric Mothe, Meriem Fournier, Mathieu Pétrissans, Philippe Gérardin

Резюме

This study aims at making a link between the investigations of the wood industry on the control of the quality in forest (production of wood adapted to the industrial requirements) and the studies on the wood heat treatment to improve the wood durability and dimensional stability. Heat treatment was carried out under nitrogen at 220 °C. A set of 14 samples (250x110x25 mm) from 7 European oak (Quercus petraea) trees of various French origins were scanned at dry state by X-ray tomography before and after heat treatment for analyzing the effects of treatment on the variation of wood density within and between the samples. The moisture uptake test also was performed and the equilibrium moisture content rates were calculated. The results showed to the naked eye the evident dark color of samples with differences between samples treated at 230 °C and 220 °C; no color differences within samples of heartwood, but differences between heartwood and sapwood. The density values of all samples decreased after the treatment. Mass loss (ML) ranged from 11,27 % to 13,28 % and was major when density was initially high. The treatment had no significant modification on the homogeneity of the density, but the near portion of sapwood was affected. The effects of wood density on the results of heat treatment were the same within samples of same tree but when comparing different trees the trend was highly variable. In conclusion, studying the effects of wood initial density variability on the heat treatment process needs further analysis such as chemical and biological analysis along with X-ray tomography and needs to be carried out on several species.

Ключови думи: characterisation, control, heat treatment, CT scanning, variability, wood density

EN Version

HEAT RESISTANCE OF FURNITURE PARTS COVERED BY PLASMA TREATED FOILS

Автори: Ján Sedliačik, Tomasz Krystofiak, Pavol Antal, Mária Šmidriaková, Lis Barbara

Резюме

Surface finish of furniture parts with foils is very popular way of decorative 3D–finish of furniture. As the foil is a thermoplastic material, for furniture parts used in interiors of bathroom or kitchen it is important to be water resistant and heat resistant. We tested polyethylene (PET) and polyvinylchloride (PVC) foils with 9 various colourations and gloss, 4 types of polyurethane based dispersions and two press settings. MDF was used as the base board. Surface of selected foil types was modified by electric discharge plasma. Measurement of the contact angle Θ of the surface of foils was done with distilled water as wetting liquid, according to EN 828. Estimation of the adherence of foils to the substrate with the pull-off method was done according to the procedure EN ISO 4624. Heat resistance of glued joint was tested by heating the samples in a chamber at temperatures from 50 °C to heat destruction. The appearance and damage of all tested samples were assessed visually. The results have shown that the type of adhesive, type of foil and vacuum pressing process are significant for joint quality. Heat resistance can be increased up to 20 or 30 °C by proper setting of the pressing process. Appearance was improved on plasma treated samples.

Ключови думи: heat resistance, foil, polyurethane dispersion, vacuum pressing, surface finish

EN Version

RESEARCH ON THE CUTTING OF SPRUCE LOGS IN WINTER CONDITIONS WITH NARROW BAND SAW BLADES

Автори: Живко Гочев, Валентин Атанасов

Резюме

Experimental researches were performed in winter conditions with a horizontal band saw „Wood-Mizer“ WM 3000. The tests were conducted in manufacturing conditions of the „Chil Tepe – 97“ Ltd. facility in town of Laki by processing spruce logs. Two types of cutting tools were used: with normal and hardened teeth. The results are analyzed and some recommendations are proposed for more efficient use of this machine types

Ключови думи: horizontal band saw, narrow band saw blades, frozen wood

EN Version

INFLUENCE OF SOME ANATOMICAL FEATURES ON THE DENSITY OF WOOD

Автори: Николай Бърдаров, Катерина Новоселец

Резюме

The wood of coniferous trees is characterized by simple and orderly structure. Within the annual ring the traheids are sealed and thickened. The work examines the relationships between anatomical characteristics of wood and its density.

The traheids have been examined in the wood of the spruce. Traces in the dimensional change in the annual ring have been measured successively from the earliest to the latest. The studied wood is divided into groups with narrow and wide rings. A comparison is made between the values for individual groups to seek relationships between anatomical structure and the density of wood.

Ключови думи: conifers, annual rings, traheids, spruce

EN Version

STRUCTURAL MECHANICAL CHARACTERISTICS OF ORIENTED STRAND BOARDS

Автори: Николай Йосифов, Стефан Делин

Резюме

The oriented strand board (OSB) is a relatively modern type of engineered wood product used broadly in construction industry and the furniture production. An essential structural parameter of the OSB plate is the orientation of the layering strands (flakes) in the 3-D space XYZ, which pre-determines significant diversity in the directional strength of the final material. A structural model of a 3-layered OSB is presented and the parameters of the morphological structure are analyzed. Optimal limits of the principal morphology criteria ratios are established and optimized dimensions of the flakes are recommended. An empirical equation for calculating the bending strength of the manufactured composite plates is derived. In conclusion, an average value of the principal ratio RE = Eb׀׀ / Eb⊥= σb׀׀ / σ0⊥= 2,25 is suggested, that could be used in the OSB production.

Ключови думи: wood composite plates, oriented strand board (OSB), load capacity, principal criteria ratios, morphological structure

EN Version

MODELING OF THE DEFROSTING PROCESS OF PRISMATIC BEECH MATERIALS

Автори: Ненчо Делйски, Ladislav Dzurenda, Славчо Соколовски, Камен Пецов

Резюме

By the first co-author earlier a 3-dimensional mathematical model has been created, solved, and verified for the transient non-linear heat conduction in frozen prismatic wood materials during their heating. Now in the model the dependence of the fiber saturation point of the separate wood species from the temperature has been incorporated.

The paper presents graphically solutions of the updated model of the obtained calculated results about the temperature distribution in the volume of beech frozen materials with prismatic shape with thickness 0,4 m, width 0,4 m, length 0,8 m, initial temperature -40 оC, and moisture content 0,3 kg.kg-1 and 0,6 kg.kg-1 during their defrosting at temperature of the processing medium of 80 оC.

Ключови думи: frozen wood, beech prisms, defrosting, modeling, temperature distribution

EN Version

NUMERICAL INVESTIGATIONS OF THE NATURAL FREQUENCIES AND MODE SHAPES OF THE TORSIONAL VIBRATIONS IN THE SAW UNIT OF A KIND OF WOOD SHAPERS, USED IN THE WOOD PRODUCTION

Автори: Георги Вуков, Валентин Славов, Георги Ковачев, Васил Власев

Резюме

Some numerical investigations of the natural frequencies and mode shapes of the wood shaper’s saw unit are presented in this study. These researches are done on the base of a concrete mechanic-mathematical model for investigation of free torsional vibrations of a wood shaper’s saw developed by the authors. The main features in the construction of these kind wood shapers are rendered an account of this model. The two most commonly used driving mechanisms are modeled – with a wedge belt and with a ribbed belt. The studies allow a comparison of the vibration behavior of the mechanism for both drives. The results of this study allow the determination of the resonant work regimes. The exactly determination of these regimes is important for introduction of adequate measures which can guarantee their using. The investigation`s results can be used as a base for making some recommendations concerning the increase of reliability of the wood shapers as well as the accuracy and quality of their production.

Ключови думи: wood shapers, modeling, torsional vibrations

EN Version

DETERMINATION OF WEIGHT FACTORS OF QUALITY INDICES OF PARTICLEBOARDS

Автори: Юлия Михайлова, Нено Тричков, Цветелин Евстатиев

Резюме

The quality of each product is a set of a great number of indices and characteristics that define its ability to meet the consumers’ requirements.

By means of survey of specialists, the more important indices determining the quality of particleboards were ranked and weight factors for each index were calculated. With these weight factors, the determination of composite quality index of PBs will be possible. The results also give guidelines for improvement of the quality of this type of material.

Ключови думи: quality, indices, expert assessment, ranking, concordance, weight factor, PBs

EN Version

METHODOLOGY FOR EVALUATION OF SOUND POWER LEVELS IN WOODWORKING MILLING MACHINES

Автори: Павлин Вичев

Резюме

Woodworking machines belong to the noisiest working machinery that requires study and analysis of noise characteristics in order to reduce the levels of noise emissions.

Noise generation is a complex process that depends on the design features and technical characteristics of the machine and its cutting tools, on one hand and the cutting process and the type of material to cut, on the other.

Generated noise can be categorized as idling noise and cutting noise, depending on the working process and each one of them has to be assessed and analyzed independently. 

The objective of the current study is to present a methodology for evaluation of sound power levels, generated by woodworking milling machines, assessed by measuring the sound pressure levels.

Ключови думи: sound power, sound pressure level, milling machines

EN Version

POSSIBILITIES FOR THE CONSERVATION OF TIMBER, USED IN RESIDENTIAL AND PUBLIC BUILDINGS

Автори: Борислав Кючуков, Ралица Симеонова

Резюме

The results for the defining of the quantity of the intake substance (intake – P), swelling -  shrinkage – the volume anti-swelling effect – ASEv, coefficient of effectivity – Kasev of the treated with conservative means beech timber (Fagus silvatica L.) and Macedonia pine (Pinus peuce Gris.) have been given. The processing of the sample bodies has been carried out in concordance with requirements of the active standards. As conservative means are used impregnator and finish – impregnator, offered by the Italian firm „Atria“.

The results from the research could be used as recommendations in the furniture production, wood assembled houses and constructions in the special productions, as well as from laboratories for testing timber and timber materials, and for preventive control of the quality of the produced timber products.

Ключови думи: Intake, Swelling, Shrinkage, Volume anti-swelling effect, Coefficient of effectivity, Conservative means, Beech timber (Fagus silvatica L.) and Macedonia pine (Pinus peuce Gris.)

EN Version

INVESTIGATION OF THE OPERATING CONDITIONS BY CUTTING OF POPLAR AND PINE LOGS THROUGH WIDE BAND SAW BLADES WITH PART-SET AND SWAGE-SET TEETH

Автори: Живко Гочев

Резюме

The paper presents some experimental results concerning cutting process of poplar and pine logs through wide band saw blades with part-set and swage-set teeth. The researches were carried out in a production process of company „Fagus Ltd“, town Pernik. The influence of the feed speed and height of cutting on the productivity of the process and energy consumption were analyzed. The results are suitable to have a better knowledge and work out of the production and operating indexes and its optimization by using of wide band saw blades.

Ключови думи: width band saw blade, part- set, swag-set, teeth, cut-out, process, pine, poplar, logs

EN Version

DETERMINATION OF TREE SPECIES IN QUANTITATIVE INDICATORS OF THEIR VASCULAR CELLS

Автори: Николай Бърдаров, Дияна Младенова

Резюме

The wood of deciduous species are characterized by complex structure and greater specialization of cells. Besides the different diameter and density for each type trachea may be more or less similar in size. The work examines the differences of the trachea in several mestnorastyashti several tropical tree species.

Measured are the dimensions of cells and their variation within the annual ring. Certain cells are area variances and their diameter. Comparison is made between anatomical characteristics of individual species.

Ключови думи: wood, deciduous trees, tracheas

EN Version

DEVELOPMENT OF A MODEL FOR THE VARIABLE TENSILE STRESS IN BAND-SAW BLADE

Автори: Стефан Стефанов

Резюме

As a continuation from a previous paper, an original model is proposed for the variable tensile stress in the blade (the saw band) which girdles the two wheels of a band-saw. The case of a spring mechanisms for tensioning the saw band is treated. The internally statically indeterminate problem of the closed band’s contour is solved in a way as required by the course of Strength of Materials. At an instant position of the blade, the tensile stress in all the cross-sections along the band is searched for, taking into account: the assembly pre-tension; the cutting force; the bending of the saw band at the wheel periphery; the heating; the centrifugal inertial forces due to the curvilinear blade’s motion as a new point in the development of the model proposed now. Another new, basic point is that the spring is not ideally stiff but “normal” now. An equation for the tensile internal force at an „opening“ in the band is deduced by involving differential and integral analysis. The equation is solvable by iteration. In case of zero cutting force, the L'Hôpital's rule is applied.

Ключови думи: band-saw blade, statically indeterminate closed contour, tensile force and stress along a saw band, centrifugal inertial forces

EN Version

EFFECT OF PRESSING PRESSURE ON INDICES OF FIBREBOARDS MANUFACTURED FROM WOOD OF HARD BROAD-LEAVED SPECIES

Автори: Юлия Михайлова, Виктор Савов

Резюме

The main factor defining the performance of the hard thin FBs is the pressure applied in the process of piezothermal treatment. In order to manufacture a product designed by engineering, the pressing pressure should be with a specific value determined in advance. The latter is in correlation dependence on the tree species, the characteristics of the wood-fibre mass and of the wood-fibre carpet. Determining, out of these factors, is the resistance that the carpet shows under the applied external load, with it depending mainly on the characteristics of the mass and, to a determining degree, on the tree species used for the manufacture of the boards.

In this paper, an investigation on the effect of pressure during manufacture of thin FBs on the basis of beech and cerris oak wood is presented. Derived are the main dependences of the performance of FBs on the factors examined in case of application of the methods of regression analysis, with use of the least squares method. Established are the optimum values of pressure depending on the thickness of the boards and the design thickness set.

Ключови думи: FBs, hard wood-based raw material, piezothermal treatment, thickness, density

EN Version

TRENDS FOR APPLICATION OF THE WEDGE AND RIBBED BELTS IN MODERN WOODWORKING MACHINЕRY

Автори: Георги Ковачев

Резюме

The current paper makes an overview of trends in the use of V-belts and ribbed belts in modern woodworking machines. Driving of different types of mechanisms in machines is most often accomplished by using belt drives. They have many advantages and some of the most important are: simple construction, quiet operation, large towing capacity, the possibility of simultaneous operation of several belts and further more. Widely spreads are both the V-belts and ribbed belts. Improved construction and use of high quality materials for their production leads to betterment their performance.

Ключови думи: woodworking machines, V-belts, ribbed belts

EN Version

WOOD-PARTICLE BOARDS OF INTENSE WATER RESISTANCE BASED ON HYDROPHOBIC UREA-FORMALDEHYDE RESIN

Автори: Лиляна Вълчева

Резюме

Research work has been carried out in view of establishing the possibilities of obtaining particle boards with intensified water- resistance on the bases of urea-formaldehyde resin and hydrophobic composition of hideglue-paraffin emulsion. The results of the research prove that the hydrophobic emulsion used is compatible with the urea resin and that it guarantees a high degree of hydrophobization  of the particle boards /water- sorption  below 25 %, thickness of swelling below 4 %/ under relatively high strength indicators /bending strength above 18 N/mm², internal bond strength above 0,45 N/mm²/. On the basis of a planned experiment the impact of the following technological factors has been established: content and concentration of the hydrophobic solution, pressing temperature and pressing time on the properties of particle boards based on hydrophobic urea-formaldehyde resin. The following values have been defined as optimal: content 2 %, concentration 30 %, pressing temperature 177,5 oC and pressing time 0,5 min/mm.

Ключови думи: particle boards; intensified water- resistance; urea-formaldehyde resin; hydrophobic emulsion; technological factors

EN Version

INFLUENCE OF WATER-THERMAL CYCLIC TREATED ON THE ADHESION OF PROTECTIVE COATS, FORMED ON WOOD

Автори: Панайот Панайотов, Живко Георгиев, Невена Баташева

Резюме

Wood outdoor exposed in normal atmospheric condition affect the colour and texture due to the impact of UV spectrum of light. Although UV rays penetrate into the wood to a depth of not more than 75–100 µm, they are main cause for initiation of weathering it, due to the conduct of complex and physical- chemical processes. As a result of the combined effects of climatic factors, significant structural changes occur in the surface layer (surface erosion). These changes are denoted by the term weathering. This is impact on the aesthetic appearance of the product and the quality of protective coatings. The water plays an important role for wood destruction. The weathering could be minimizing with surface treatment. These treatments can be performed both with soaking up funds forming protective and decorative coatings. The function of these coatings is to receive and minimize external impact and thus extended to life of articles, therefore increase their durability. It is perform an analysis of adhesion of protective and decorative coatings, formed on building wooden products, water-thermal cyclic treated. It is established that the adhesion decrease after water-thermal treating. It is establish that the water penetrates through to the coats distort its adhesion to wood surfaces. It is made recommendation about the conduct of appropriate activities for coating refresh.

Ключови думи: wood elements, protective coats, building products; water-thermal treatment

EN Version

ANALOGY AS A BASIC TECHNIQUE IN THE PROCESS OF CREATING NEW PRODUCTS

Автори: Десислава Ангелова

Резюме

The analogy as a basic technique used in a number of design methods as a result of the application of close and distant similarities from other areas, has been studied in the present report. It is based on a very common and recommended technique of creative thinking.

Analogy is the basic means of the subjective logic of people, based on the systematic approach to the comparison of objects. Making analogies develops intuition and imagination, as in fact it is a result of the qualitative synthesis of the appearance of the technical system by a distant similarity. The professional development of designers is connected with the gradual acquisition and development of the capacity of synectic techniques.

The analogies are very widely used in the design of industrial products. The creation of new products and services can be significantly enhanced by applying this technique, compared with the use of random ideas.

The aim of this report is to show the effectiveness of this technique for improving the creative process and present the working mechanisms of the most frequently used design methods using the technique of analogy.

Ключови думи: analogy, types of analogies, action principles, creative process

EN Version

OPPORTUNITIES FOR SUSTAINABLE DEVELOPMENT OF LOGGING THROUGH OPTIMIZATION OF BUSINESS RELATIONS BETWEEN ECONOMIC SUBJECTS

Автори: Николай Стоенчев

Резюме

Wood has so far remained a major source of revenue that fund forest-cultural activities. It creates livelihood of populations in forest areas and improvement of its organization is in the interest of the state as a major forest owner and private timber companies and local communities.

The present study has attempted comparative characteristic of economic results obtained by private logging companies. Different options has been discussed for improving relations between state and private forestry companies to achieve a lasting balance of interests in the allocation of income from logging under regulations established by the legislation, practical experience and advanced theoretical concepts in this area.

Ключови думи: forestry, competitiveness, efficiency

EN Version