Съдържание


INNO 1/2013 2013

AN INNOVATIVE APPROACH IN EDUCATION

Автори: Веселин Брезин, Боянка Желязова, Радослав Милчев, Марина Младенова, Елена Цветкова

Резюме

Strengthening the links between education systems, in order to develop the potential of young people is at the core of European cooperation process. Leading institutions are there to introduce and provide better teaching and learning through use of new information and communication technologies (ICT). One of the priority areas of the Strategic framework for education and training („ET 2020“) is to promote and develop creativity and innovation through new instruments, which use modern ICT and by training teachers to use ICT.

Information and communication technologies provide a variety of methods and tools that open up new opportunities in distance learning students from the University of Forestry. They allow supporting the educational process by organizing it in a way, that takes into account the individual needs of students and allow building up of important digital competencies needed to achieve "knowledge-based" economy.

Ключови думи: distance learning, information and communication technologies, innovation

EN Version

NONDESTRUCTIVE EVALUATION AND PREDICTION OF BENDING BEHAVIOR OF FIBER REINFORCED LAMINATED TIMBER

Автори: Zsigmond Vas, Levente Dénes

Резюме

This paper presents the results of a study conducted to investigate the bending properties of glue laminated timber reinforced with three different materials, jute fiber, glass fiber and carbon fiber respectively. To determine the modulus of elasticity and modulus of rupture both in flatwise and edgewise directions destructive and non-destructive testing methods were used. According to the results the strengthened beams show improved load-carrying capacity and energy absorption capacity by when compared to unstrengthened counterparts. It was further noted that the integrity of the bond depended not only on the adhesive used but also on the FRP type. The predicted MOE values had a good agreement with the static MOE values but the agreement varies in function of FRP type.

Ключови думи: Glue laminated timber, fiber reinforcement, mechanical properties, nondestructive modeling, jute fiber

EN Version

PORE SIZE DIAMETER, SHRINKAGE AND SPECIFIC GRAVITY EVOLUTION DURING THE HEAT TREATMENT OF WOOD

Автори: Mathieu Pétrissans, Anélie Pétrissans, Philippe Gérardin

Резюме

The heat treatment of wood by mild pyrolysis permit to produce a new material called torrefied or retified wood. Heat treated wood possesses new properties like improved decay resistance, higher dimensional stability, hydrophobic character, while strength properties are considerably reduced. The aim of this work was to study the anatomical structure evolution during heat treatment to explain the decreasing of the mechanical properties. The heat treatment has been carried out for a very large temperature range between 180 to 345°C under inert atmosphere on tow European wood species (pine and beech). The anatomical structure has been investigated by Scanning Electron Microscopy before and after heat treatment. On wood block for different treatment temperature mass, volume and shrinkage has been measured. From these results the apparent specific gravity was calculated and the porosity variation estimated. The results of the observations show that they are no evolution of the macroscopic anatomical structure, the vessels and tracheïds diameters remain constant. The volume evolution is probably caused by the diminution of the cellular wall thickness. By combining specific gravity evolution and the microscopic observation it's possible to conclude that the wood porosity increase on a scale lower than the micrometer (meso or nano porosity).

Ключови думи: heat treatment, pore size diameter, porosity, shrinkage, specific gravity, wood

EN Version

THE EFFECTS OF STEM HEIGHT ON THE PHYSICAL PROPERTIES OF EUROPEAN LARCH (Larix decidua Mill.) WOOD

Автори: Nurgül Ay, Elif Topaloglu, Emrah Akpınar

Резюме

The aim of this study was to determine the effect of stem height on the physical properties of European larch (Larix decidua Mill.) wood. The sample trees harvested from Maçka Research Forest in Trabzon. The preparation of small clear specimens and application of test procedures were performed according to Turkish standards. Wood density (oven dry and in 12 % moisture content), basic density, shrinkage and swelling values, were determined for physical properties of wood. Moreover the variation of these properties were determined related to stem height. Consequently, the decreasing trend in the physical properties was observed in direction from bottom to top.

Ключови думи: vertical wood density, stem height, physical properties, European larch

EN Version

SOME PROPERTIES OF FIBERBOARD MANUFACTURED FROM BEECH FIBER AND CHESTNUT SAWDUST

Автори: Derya Ustaömer, Mustafa Usta, Şeyma Bulut

Резюме

In this study, some properties of medium density fiberboard (MDF) manufactured from mixtures of beech (Fagus orientalis) fiber and different ratios of chestnut (Castanea sativa Mill.) sawdust were investigated. The mixture ratios of fiber and sawdust were 85:15 %, 80:20 %, 75:25 %. Urea formaldehyde (UF) and melamine-urea formaldehyde (MUF) were used as resins. Water absorption (WA), thickness swelling (TS), surface roughness parameter (Rz), color change (∆E*) values were determined for MDF panels. Consequently, it was found that the WA, TS, ∆E* and Rz values increased with increasing sawdust ratio.

Ключови думи: Fiberboard, physical properties, sawdust, surface roughness

EN Version

3D VISUALIZATION OF THE DEFROSTING PROCESS OF BEECH PRISMS IN THE VENEER PRODUCTION

Автори: Ненчо Делйски, Радослав Милчев, Веселин Брезин, Иван Христов

Резюме

The paper presents a new approach for the 3D colour visualization of the obtained with the help of own mathematical model calculated results about the non-stationary temperature distribution in the volume of frozen wood materials with prismatic shape during their defrosting. An example for the application of the approach for visualization of the temperature distribution in frozen beech prisms 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 (wood with ice from the bounded water in it) and 0,6 kg.kg-1 (wood with ice from both the bounded and the free water in it) during their defrosting at temperature of the processing medium 80 оC has been given. The results from the studies can be used for the creation of an optimal energy saved thermal treatment of prismatic wood materials during their defrosting with an aim of following plasticizing in the veneer production.

Ключови думи: frozen wood, beech prisms, defrosting, 3D visualization, temperature distribution

EN Version

INVESTIGATION OF INTERACTION OF BASIC COMPONENTS OF THE WOOD WITH UREA FORMALDEHYDE RESIN

Автори: Иван Генов, Йорданка Иванова, Миглена Вальова

Резюме

The quantity of the wood components (cellulose, lignin, holocellulose) before and after interaction with urea formaldehyde resin (UFR), their nitrogen content and IR spectra were investigated. Increasing of the quantity of these components and of their nitrogen content was established. New bands, belonging to UFR were registered in IR spectra.

Ключови думи: wood, UFR, cellulose, holocellulose, lignin, WPB

EN Version

MANUFACTURE AND TRADE OF WOOD PRODUCTS IN BULGARIA IN THE IN THE CONTEXT OF STABILITY, GROWTH AND GOVERNMENT POLICY

Автори: Николай Нейков, Нено Тричков, Владислав Тодоров, Ангел Петков

Резюме

Over the years before and after the transition of Bulgarian economy from governmentally planned to market economy the wooden products played important role in many regions of the country. During the past few years and especially in the time of crisis many of the enterprises suffered of low revenues and some went bankrupt. It is important to prescreen the past and the present of wood working sector in Bulgaria to reveal its stability and growth.

Ключови думи: woodworking, sector analysis, crisis, Bulgaria

EN Version

IMPLEMENTATION OF THE „BUSINESS ADVISOR“ INFORMATION SYSTEM FOR OPTIMIZING THE ECONOMIC RELATIONSHIPS BETWEEN SUBJECTS IN WOOD CUTTING ACTIVITY

Автори: Николай Стоенчев, Анна Розева, Павел Дичев

Резюме

The sustainable develpoment of forestry is closely related to the rational distribution of the income obtained from the wood use, the main part of it being cutting. For the successful and foresight regulation of the relationships between economic subjects that maintain and perform cutting activity both reliable legal base and intime operarational information are required. Current investigation aims to support the right management decision making by implementing the “Business advisor” information system for the precise definition of the production expenses when determining the initial prices in auction procedures for cutting assignment in the state forests.

Ключови думи: information system, cutting auction, production expenses

EN Version

REDUCTION OF THE LOAD ON THE MAIN DRIVE SHAFT OF BAND SAWS

Автори: Славчо Соколовски, Ненчо Делйски

Резюме

Analysis of the load on the main drive shaft of band saw is provided in three cases:

Bending couples resulting from the strain forces of the saw band and the belt transmission are absorbed by the shaft.

The bending couple resulting from the force of strain of the saw bend is absorbed by the shell of the bearing unit and the bending couple caused by the strain force of the belt transmission is received by the shaft.

Bending couples from the strain forces of the saw band and the belt transmission are received by the shell of the bearing unit.

Strain forces of the saw band and the belt transmission loading the main drive shaft are determined. Validating test strength calculations of the main band saw shaft are made.

Constructive solutions to reduce the bending in the console parts of the main drive shaft which will improve the work of the saw band and the V-belt transmission are proposed.

Ключови думи: band saw, main drive shaft, belt transmission, strength calculations, construction

EN Version

RESEARCH ON THE QUALITY OF PROCESSED SURFACES WHEN CUTTING SPRUCE LOGS WITH NARROW BAND SAW BLADES

Автори: Валентин Атанасов

Резюме

Research on the quality of the processed surfaces was performed with narrow band saw blades in winter conditions. For experiments was used horizontal band saw „Wood – Mizer“ WM 3000. Research was conducted in „Chil Tepe – 97“ Ltd. manufacturing facility in the town of Laki. The cutting tools are with normal and hardened teeth. The results after modification of some technological factors such as feed speed, cutting height and cutting tool operation time are analyzed. Practical recommendations are proposed.

Ключови думи: horizontal band saw, narrow band saw blades, processed surfaces

EN Version

STUDY OF STATIC STRENGTH OF A MILLING WOODWORKING MACHINE SPINDLE BY FEM

Автори: Нели Станева, Васил Власев

Резюме

A static analysis of a milling spindle with two bearing supports from five-operating woodworking machine KP400 with lower position and console V-belt pulley is carried out by the method of finite elements (FEM) with program Cosmos WorksÒ. The milling spindle 3D model is generated with Solid WorksÒ with all elements of the real spindle – key-slot, grooves for clip ring, tread for fixing of the cutter, segments, chamfers, filets, etc. Von Mises stresses, equivalent strains, resultant displacements, stress intensities (P1 – P3) and factor of safety distribution is obtained and visualized. A decrease of the spindle inter-support distance is offered which brings about to reduction of stresses, strains, displacements, as well as to increase of the minimum factor of safety and will give opportunity to increase the vertical motion at spindle adjustment for this type of construction of the cutting mechanism.

Ключови думи: spindle, milling woodworking machine, static analysis, FEM, Cosmos Works

EN Version

INCREASING THE WORK PRODUCTIVITY BY CREATING WORK PROGRAMMES FOR CNC WOODWORKING CENTRE USING MACROS

Автори: Марина Младенова, Богомил Брезин

Резюме

This article presents the results of a research carried out by the authors of three different approaches of creating work programmes for universal woodworking machine center with computer control (CNC woodworking centre) on work productivity – input of operations by the CNC software, import from CAD software and using created macros. 

The analysis of the results proves that the programming and the use of macros greatly increases work effectiveness when creating work programmes for CNC woodworking centres which leads to increased productivity and competitive advantage.

Ключови думи: CNC woodworking centre, work programme, CAD/CAM, macros

EN Version

INFLUENCE OF THE VENEER QUALITY AND LOAD DIRECTION ON THE STRENGTH PROPERTIES OF BEECH PLYWOOD AS STRUCTURAL MATERIAL FOR FURNITURE

Автори: Васил Живков, Ралица Симеонова, Ася Маринова

Резюме

Plywood is a widely used material in the construction of different furniture types. The production of seating furniture – chairs, armchairs, etc., has the highest share. Knowing plywood’s properties is a prerequisite for its efficient use in the industrial production and improvement of the quality of consumer products. The objective of this study is to evaluate the influence of the veneer quality on the density, bending strength and modulus of elasticity of 20-21 mm thick plywood made of beech veneer.

The results showed that the veneer quality does not have an impact on the density, bending strength, and modulus of elasticity. Load direction under bending has a significant influence on the strength and deformation properties.

The results of this study will provide an opportunity for optimization of furniture construction made of beech plywood.

Ключови думи: beech plywood, furniture construction, bending strength, modulus of elasticity, load direction in bending

EN Version

COMPARATIVE ANALYSIS BETWEEN THE DESTRUCTIVE BENDING MOMENTS OF END AND T-SHAPE CORNER JOINTS OF FRAME STRUCTURAL ELEMENTS MADE OF SOLID CHESTNUT WOOD WITH A CROSS SECTION OF 50 X 25 MM

Автори: Георги Кючуков, Georgi Gruevski, Борислав Кючуков

Резюме

A comparative analysis between the destructive bending moments of end and T-shape corner joints of details from solid chestnut wood (Castanea sativa Mill.) with cross section of 50 x 25 mm has been done.

In this study has been found that the types of joints and the area of their contact surface have considerably influence on their strength characteristics. The T-shape corner joints have in average about 20 % higher destructive bending moment compare to the end corner joints. The non-dismountable mortise and tenon joints are destroyed by average of 80 % higher bending moment compare to the dismountable joints. Dowel joints have two times lower bending moment compare to the mortise and tenon joints and from 3 to 24 % higher bending moment compare to the dismountable joints. 

Ключови думи: End and T-shape corner joints of frame structural elements; Destructive bending moments of corner joints; Sweet chestnut solid wood

EN Version

COMPARATIVE STUDY ON THE DESTRUCTIVE BENDING MOMENTS OF SOME END CORNER JOINTS OF STRUCTURAL ELEMENTS OF SOLID BEECH WOOD WITH CROSS SECTION OF 50 X 25 MM

Автори: Борислав Кючуков, Георги Кючуков, Васил Живков

Резюме

The paper shows the results of the studies on the strength characteristics of the end corner joints of the structural elements of solid beech wood with a cross section of 50 x 25 mm used in the construction of seating furniture.

It has been found out that, on the basis of the values of the destructive bending moment, the non-dismountable end corner joints are arranged in the following descending order: half-open mortise and tenon joint; blind stub mortise and tenon joint with dowel and cross dowel; blind stub mortise and tenon joint and dowel joints.

It has been found out that, on the basis of the values of the destructive bending moment, the dismountable end corner joints are arranged in the following descending order: joints with two one-piece connectors “Confirmat” following by joint with two universal connectors with bolt and cross dowel.

It is recommended to use the studies’ results in calculating the dimensions of seating furniture.

Ключови думи: corner joint of details; destructive bending moments; beech solid wood

EN Version

MODELING AND ANALYSIS OF THE ELEMENTS AND STRUCTURE OF THE ARMCHAIR FOR A REST

Автори: Янчо Генчев, Георги Вуков, Валентин Славов

Резюме

Upholstered furniture consists of supporting structure (skeleton) and upholstery. The proposed work presents modeling and analysis of the elements and structure of an armchair for a rest. The study is done on the base of modern software products, using traditional research of this type of sizes and load schemes According to the study, some necessary recommendations for the design optimizing concerning its practical implementation with specific parameters are given.

Ключови думи: Armchair for a rest, modeling, the design optimizing

EN Version

METHODS OF FORMING COATS WITH ANTIQUE EFFECT

Автори: Панайот Панайотов, Живко Георгиев, Диана Николова

Резюме

Methods of finishing for creating antique effects were analyzed. It was established that to create these finishes - chemical stains, patina powder, sealer and top-coats are used. It is easy and quick to achieve these effects, when they are formed on tannin-containing wood. It is established that antique effects can be coated on wood which doesn’t contain tannin (Spruce, Scots Pine), if the effects are made by suitable stains, paints and top-coats. It was made technologies for making „multicolored chestnut“, „antique paint“ and „crackle“ effects on chestnut and ash wood. These special effects are in use in modern fluency in furniture with antique effects. The most important qualities were explored.

Ключови думи: wood, chemical stains, old finishes, furniture with antique effect

EN Version

EARTHQUAKE RESISTANCE OF TIMBER STRUCRUTRES

Автори: Панайот Панайотов, Силвана Петкова

Резюме

The prime objective of this paper is to describe the basics of the seismic design of the timber constructions. The experience from North America and Japan shows that when designed properly wooden structures can resist extreme conditions like earthquakes. The ability of structures to develop plastic deformations without drastic reduction of strength and resistance is called ductility. The purpose of this paper is to present the ductile behavior of the timber structures in tree directions – material; element/joints; structure as a whole. Timber has orthotropic properties and although it behaves in ductile manner when loaded under compression, especially perpendicular to the grain, it is brittle under tension perpendicular to the grain. The connections in timber structures introduce a foundational aspect in terms of the seismic behavior of the construction, since they act as ductile valves and enable dissipation of energy. Due to its global ductility, the structure posses the ability to withstand deformations without developing high stress concentrations. Seismic resistance of timber structures is based on their advantages – a low-self load; ductile joints; in general very regular building layouts. The paper was done as a specialized literature survey and is based on the conceptions of the capacity seismic design and the system of structural Eurocode standards (EN 1995-1-2:2004 and EN 1998-1:2004).

Ключови думи: seismic design, timber constructions, earthquakes

EN Version

TESTING THE LEARNING OUTCOMES OF WOOD TECHNOLOGY COURSE

Автори: Mehmet Acar, Yusuf Ziya Erdil, Ali Kasal, Selcuk Demirci

Резюме

In this study, realization level of learning outcomes is examined within the context of a pilot course. Purpose of this study is to test learning outcomes of the pilot course which are determined by instructor. For this purpose, “Wood Technology” course, which has been taught at Department of Wood Science and Furniture Design and Department of Woodworking Industrial Engineering, is chosen as a pilot course. The course consists of 12 units. Learning outcomes of each unit are prepared by the instructor. To test realization level of learning outcomes, two different questionnaire were prepared and applied to students who had taken the course in the period when study was conducted. One of the questionnaire was to determine „students’ expectation“ from each course unit before teaching. The other questionnaire was to determine „achieved level“ at the end of each course unit. To check the validity of achieved level, a quiz was given at the end of each course unit. In addition, another questionnaire was applied to determine level of „achieved learning outcomes“ of graduated students. All data were analyzed statistically and results were compared by t tests. As a result of statistical analyses, it was determined that students underestimated their learning outcomes by 105 %; i.e.; they learned two times more than their expectation. In general, it can be concluded that determination and testing learning outcomes in a course is necessary in order to achieve a better learning-teaching balance.

Ключови думи: Learning outcomes, National Qualification Framework For Higher Education, Wood Technology Course

EN Version

FURNITURE IN THE RENAISSANCE - BULGARIAN DESIGN OR NOT?

Автори: Александра Първанова

Резюме

Renaissance is a turbulent period of change, both economically and socially. Interior and furniture plays a big role socio-cultural environment. The design and taste of the Bulgarians are formed on the basis of already occurred European styles. Chair schools that have been appearing are trying to adjust our own culture to that which is modern in Europe during this dynamic period. Despite the difficulties faced with Bulgarian designer, he found a back door to national development in this area.

Ключови думи: furniture, design, Renaissance, Bulgarian design

EN Version

CONTEMPORARY DWELLING PLANNING SCHEMES ANALYSIS

Автори: Мария Маринова

Резюме

In the years of rapid construction the building's large scale comes to the fore, shifting the importance from the individual dwelling as a building component unit. The stress is laid on the quantitative rather than on the qualitative aspect of the project, thus neglecting the floor plans; the planning schemes optimization is often at the expense of the individual dwelling size and functionality. The purpose of this work is to analyze the specific dwelling planning schemes in modern residential buildings and to trace the trends in their development.

Ключови думи: planning schemes, trends, dwellings

TECHNOLOGICAL OPPORTUNITIES SURVEY OF FOREST SHORT ROTATION PLANTATIONS IN BULGARIA FOR ENERGY BIOMASS PRODUCTION* PART 1: ANALYSIS OF THE PRODUCTION OF ENERGY FROM BIOMASS IN BULGARIA AND PERSPECTIVES FOR CREATING ENERGY PLANTATIONS FROM SHORT ROTATION WOOD CROPS

Автори: Константин Маринов, Живко Гочев, Станимир Стоилов

Резюме

This report presents some problems on the state and future use of biomass as a renewable source for production of heat and electricity in Bulgaria and Europe. The report covers the potential opportunities of the agricultural lands in Bulgaria for production of energy plantations (SRP) and in particular from forest tree species such as poplar, willow and black locust. A review of their main advantages and disadvantages is made and recommendations for their future development in Bulgaria are presented.

Ключови думи: renewable, wood biomass, short rotation coppice

EN Version

TECHNOLOGICAL OPPORTUNITIES SURVEY OF FOREST SHORT ROTATION PLANTATIONS IN BULGARIA FOR ENERGY BIOMASS PRODUCTION* PART 2: TECHNOLOGY STAGES OF CREATION AND CULTIVATION OF WOOD BIOMASS PLANTATIONS

Автори: Константин Маринов, Живко Гочев, Станимир Стоилов

Резюме

A study on the technologies for creating and growing SRC plantations for the production of biomass for energy purposes has been conducted in the present report. An analysis of the main steps in the technological process has been made. Recommendations are made to the Bulgarian farmers on the necessary techniques for incorporating the crops and the use of appropriate machinery for site preparation, planting and growing of crops.

Ключови думи: short rotation crops, mechanized technologies

EN Version

TECHNOLOGICAL OPPORTUNITIES SURVEY OF FOREST SHORT ROTATION PLANTATIONS IN BULGARIA FOR ENERGY BIOMASS PRODUCTION* PART 3: ANALYSIS OF THE TECHNOLOGIES AND MACHINES FORWOOD BIOMASS PLANTATION HARVESTING

Автори: Константин Маринов, Живко Гочев, Станимир Стоилов

Резюме

The present survey analyzes the key technologies for harvesting SRC plantation for production of biomass and the typical harvesters, suitable for willow, poplar and black locust harvesting in Bulgaria. The advantages and disadvantages of the various technological schemes are highlighted and some recommendations to the Bulgarian producers on their application are made.

Ключови думи: SRP crops, biomass, harvesters, mechanized harvesting

EN Version