Съдържание


Vol. 7, Issue 2, 2018

COMPUTATION OF THE ENERGY CONSUMPTION FOR WARMING UP OF FLAT OAK DETAILS BEFORE THEIR BENDING

Автори: Nencho Deliiski, Neno Trichkov, Dimitar Angelski, Ladislav Dzurenda, Zhivko Gochev, Natalia Tumbarkova

Резюме

A software program has been prepared in the calculation environment of Visual Fortran for solving of own 1D non-linear model of the one sided heating process of flat wood details. With the help of the program, the 1D non-stationary temperature field in flat oak details with initial temperature of 20 oC, moisture content of 0.15 kg.kg-1, thickness of 12 mm, 16 mm, and 20 mm during their 30 min one sided heating at temperature of 80 oC of the heating metal body has been calculated. After integration of the temperature field, the energy consumption for warming up of the details before their bending in the production of curved back parts of chairs has been calculated. The obtained results are graphically presented and analyzed.

Ключови думи: oak details, one sided heating, bending, energy consumption

EN Version

WOOD COLOUR MODIFICATION OF FRAXINUS EXCELSIOR L. DURING THE PROCESS OF THERMAL TREATMENT WITH SATURATED WATER STEAM

Автори: Ladislav Dzurenda, Adrián Banski

Резюме

The aim of the paper is to determine the colour of European ash wood (Fraxinus excelsiorL.) in the CIE-L*a*b* colour space during the thermal treatment with saturated water steam at the temperature of t = 137.5 ± 2.5 °C for the time of τ = 7.5 hours. The colour of European ash wood changes from white with a yellow hue to brown during the process of colour modification. Mentioned hue of thermally modified wood is described with the coordinates of CIE-L*a*b*colour space:  L* 65.6 ± 1.4; a* = 10.8 ± 0.5; b* = 21.7 ± 0.9. Irreversible colour change of the European ash wood resulting from the process of thermal modification with saturated water steam widen the possibility for its use in the field of construction and carpentry, design as well as in the field of art.

Ключови думи: wood, European ash (Fraxinus excelsiorL.), the CIE-L*a*b*colour space, thermaltreatment, saturated water steam

EN Version

MODELING OF THE FREE SPATIAL VIBRATIONS OF WOOD SHAPER AND ITS SPINDLE

Автори: Georgi Vukov, Zhivko Gochev

Резюме

The proposed study deals with the modeling of the free spatial vibrations of a woodworking shaper and its spindle. An original mechanical - mathematical model of woodworking shaper and its spindle, developed by the authors, is presented in this work. The model provides the opportunity to explore the free undamped space vibrations of this type of machinery. In this model the woodworking shaper and its spindle are regarded as rigid bodies, which are connected by elastic elements with each other and with the motionless floor. A system of matrix differential equations is compiled and analytical solutions are presented. The natural frequencies and mode shapes for a specific machine can be obtained with their help. The model is supplemented in order to investigate the free damped space vibrations of the considerate system. The new model takes into account the damping properties of machine's elements. A new system of matrix differential equations is developed and the relevant analytical solutions are presented. They allow various numerical solutions for specific machines. The models take into account the characteristics in the construction of woodworking shapers. They include all necessary geometric parameters of this system. Numerical solutions and graphs can be obtained with the help of the developed models. These solutions and graphs are necessary for analyzing the free undamped and the free damped space vibrations of a particular considerate machine.

Ключови думи: wood shapers, free vibrations, modeling

EN Version

NON FORMAL EDUCATION IN DESIGN FIELD

Автори: Alin M. Olărescu, Thomas Gronegger, Biborka Bartha, Marina Cionca, Ioan Muscu

Резюме

In this paper several guidelines and methodological approaches for non-formal education in the field of design are presented. The research is based on eight years experiences of the authors in organizing and guiding one week of international (Romanian and Austrian students and teachers) design workshops in Romania.

Ключови думи: non-formal education, design, workshop

EN Version

EXOTICISM IN FURNITURE DESIGN

Автори: Regina Raycheva

Резюме

This paper deals with research on different manifestations of exoticism as a strategy for innovation in design and form-building of furniture. The interest in exotic and distant cultures and their art gives rise to a tendency: the emergence of culture mix. Decorative design elements from the East are being integrated with existing furniture types in Europe, or are used to create new ones. The study is done by selecting examples and commenting the phenomena of exoticism in interior and furniture, observed in the works of architects and cabinet-makers from the past. The art of Asia influenced both royal persons and common people long before the development of modern transportation and media widened the horizon.

Ключови думи: furniture design, culture mix, history of furniture, 20th C design

EN Version

KNITWEAR: FROM CLOTHING TO FURNITURE

Автори: Regina Raycheva, Desislava Angelova

Резюме

The paper is focused on a tendency, clearly defined these last years, of the application of knitting technique in furniture design. Traditions and contemporary knitting techniques are researched, as well as materials used. Analysis is made of their implementation in furniture. A number of examples are researched in an attempt to classify the application of knitwear in different furniture types, their function, as well as the most often used techniques and materials. By means of selection, classification, visual identification and comparative morphologic analysis, the potential of this technique is revealed.

Ключови думи: furniture design, knitingr, knitted techniques

EN Version

WOOD-BASED PANELS WITH LOW FORMALDEHYDE EMISSION BY COLLAGEN AND KERATIN BIOPOLYMERS

Автори: Ján Sedliačik, Ján Matyašovský, Peter Jurkovič, Mária Šmidriaková

Резюме

Urea formaldehyde (UF) adhesives are the most commonly used for wood-based panels, but their main disadvantage is an intensive formaldehyde emission. The aim of the investigation was to reduce the release of formaldehyde from UF bonded wood materials by developing and testing new and more efficient modifiers that bind formaldehyde and form more stable methylene bonds resistant to hydrolysis of the adhesive. Methylol pre-condensate additives with varying ratios of glutaraldehyde and urea modified by fibril proteins based on collagen and keratin were tested. The measurements confirmed the decrease of formaldehyde at all concentrations of methylol pre-condensate compared to the reference sample. Formaldehyde emissions were evaluated from five-layer plywood according to JIS A 1460 (2001): "Building boards. Determination of formaldehyde emission. Desiccator method". The most significant decrease of formaldehyde emission up to 37% was achieved with the application of 5% methylol pre-condensate into UF adhesive standard. The gluing quality has been assessed according to standards EN 314-1 and EN 314-2 and the tested plywood meet the requirements of the standard for Class 1 – suitable for application in the interior.

Ключови думи: wood-based panels, urea-formaldehyde resin, collagen, keratin, plywood

EN Version

INVESTIGATION OF PLASTIC/WOOD COMPOSITES

Автори: Igor Novák, Igor Krupa, Ján Sedliačik, Zuzana Nógellová, Ján Matyašovský

Резюме

Polyolefin (linear low-density polyethylene, LLDPE) was blended with date palm wood (DPW) powder to prepare composites with concentrations of filler ranging from 10 to 70 wt.%. The Young´s modulus of the composites significantly increased with an increase in the filler content in the entire concentration range. The presence of the filler improved the flexural strength, which was represented by the flexural stress at peak. The water absorption test revealed that the composites had a strong tendency to absorb water, which was dependent on the filler content. The experimental data were compared with several theoretical models.

Ключови думи: LLDPE, date palm wood, composites, mechanical properties, water absorption, adhesion

EN Version

QUANTITATIVE YIELD IN SAWING THIN LOGS OF SCOTS PINE (PINUS SYLVESTRIS L.) FOR PRODUCTION OF DIMENSIONAL LUMBER WITHOUT DEFECTS

Автори: Neno Trichkov, Daniel Koynov

Резюме

This paper presents experimental work results on establishing the quantitative yield of sawing thin round Scots pine (Pinus sylvestris L.) logs for production of dimensional lumber without defects. The experimental work was performed on thin logs obtained from the top part of tree stems. These were examined for the presence of the wood defects, their size and number. Following the normal production sequence, the thin logs were sawn into lengths of 500, 800, 1000 and 1200 mm. These, in turn, were plain sawn into boards and after that into dimensional lumber with widths of 3, 6 and 9 mm. The obtained pieces were analysed and conclusions were drawn on the quantitative wood yield depending on pieces’ thickness and length. The data allow to evaluate more accurately and objectively the technology and machinery in order to ensure more efficient processing of thin roundwood.

Ключови думи: Scots pine (Pinus sylvestris L.), stems, dimensional quality characteristics, materials of solid wood

EN Version

STATIC ANALYSIS OF A UPHOLSTERED FURNITURE FRAME MADE OF SCOTS PINE AND PB WITH STAPLE CORNER JOINTS BY FEM

Автори: Nelly Staneva, Yancho Genchev, Desislava Hristodorova

Резюме

3D geometric model of one-seat frame for upholstered furniture was created by the CAD system Autodesk Inventor Pro®. A linear static analysis was carried out with CAE system Autodesk Simulation Mechanicalâ by the method of finite elements (FEM) simulating light-service loading of the frame.

The orthotropic material characteristics of pine solid wood (Pinus Sylvestris L.) for the rails and particleboard (PB) for the side plates are considered in the analysis. Corner joints in the framewith staples and PVA glue were considered. FEA was performed with regard to laboratory establishedcoefficients of rotational stiffness of used staple corner joints in the frame – case butt joints and end to face butt joints.

As a result, the most loading construction part of the frame with staple corner joints is established – the rear upper rail of the seat where the maximum values for linear displacements,nodal rotationsand stresses are received due to the nature of the applied loading.

Ключови думи: upholstered furniture frame, staple joints, PB, static analysis, CAE, FEM

EN Version