Съдържание


Vol. VIII, Issue 2 2019

NORMS FOR DESTRUCTIVE BENDING MOMENTS OF T-SHAPE CORNER JOINTS OF FRAME STRUCTURAL ELEMENTS MADE OF SOLID SPRUCE WOOD WITH A CROSS-SECTION OF 50 Х 30 MM

Автори: Georgi Kyuchukov, Borislav Kyuchukov, Vassil Jivkov, Assia Marinova

Резюме

In the presented research are established the normative values for the destructive bending moments of the most common used T-shape corner joints of frame structural elements made of solid spruce wood with a cross-section of 50 х 30 mm in arm compression bending load.

The established normative values can be used for the needs of the preventive quality control of furniture production as well as for the strength design of the sitting furniture, tables, and beds. For that purpose, it is recommended to draw up these normative values as a normative document which to use in the inner factory control of furniture quality.

Ключови думи: corner joints of frame structural elements, destructive bending moments, solid spruce wood, norms for destruc-tive bending moments of T-shape corner joints

EN Version

HISTORY OF CHILDREN’S FURNITURE AND INTERIOR

Автори: Pavlina Vodenova

Резюме

The importance of the development of a particular society has always been the focus it has on the weaker and the more vulnerable, some of whom are children. Often the banal phrase "Children is our Future" can be heard, but there is a huge amount of truth in it. That is why everything related to their proper development – physiological, mental, physical, etc. has been and will continue to be of the utmost importance since only a harmoniously developed child could be realized as a full-grown adult.

This article will look at the historical development of children's furniture and interior in connection with this type of changes in society.

Ключови думи: furniture for kids, kid’s interior, history

EN Version

STIFFNESS COEFFICIENTS IN JOINTS BY STAPLES OF SKELETON UPHOLSTERED FURNITURE

Автори: Desislava Hristodorova

Резюме

The presented study is the result of a laboratory testing under bending stress by collecting arms by corner butt joints with 2 staples type М1/40 of Scots pine (Pinus sylvestris L.) members and boards (OSB, PB, PW) to determine the deformation behaviour of the joints.

The aim of the study is to establish the stiffness coefficients by examining the influence of the material, the reinforcement by means of a triangular wood member and the type of joints on the deformation behaviour of butt joints by staples.

The results obtained could be used as a basis for future research to predict the deformation behaviour of furniture constructions as well as to find their application in the design of skeletons of upholstered furniture.

Ключови думи: upholstered furniture, end corner joints, staple joints, stiffness coefficients

EN Version

PAULOWNIA, CHARACTERISTICS AND PERSPECTIVES OF ITS EXPLOITATION

Автори: Zoran Janjić, M. Janjić

Резюме

The dynamic development of industry and technology and the increased need in the field of wood industry have led to a reduction in the forest fund. The depleted forest fund can not meet the market's needs because it takes a lot more time to reach full maturity, so there is a reason for commercial timber, which includes paulownia.

Paulownia is a wood that has exceptional growth rates and for a short period of time give a large amount of wood. Everything is used from wood. It is used as heating material, erosive protection, industrial wood, honey plant, ecological wood, decorative wood, in animal feed, pharmaceutical industry, etc. Biomass from paulownia is suitable both for silage and for alternative renewable energy sources. One of the most promising applications is bioethanol derived from cellulose. The cultivation and use of paulowane contributes to the maintenance of ecological balance and conservation of nature on our planet.

Because of the wide range of applications, the need for paulownia is constantly increasing.

Ключови думи: paulownia, characteristics, exploitation

EN Version

SELECTED PHYSICAL AND MECHANICAL PROPERTIES OF COMBINED WOOD BASED PANELS FROM WOOD FIBERS AND SAWDUST

Автори: Viktor Savov, Julia Mihajlova, Rosen Grigorov

Резюме

The production of wood fiber mass is a very energy-intensive process This is also one of the reasons for the higher cost of this material in comparison of that at particleboards. One possibility to partially solving this problem is the inclusion of industrial wastes, which has not undergone a refining process, in MDF composition.

There is a significant amount of industrial wastes resulting from logging – these are mainly the sawdust resulting from the processing of solid wood with a band saw. It should be pointed out that this method of obtaining solid wood materials is widespread, both globally and in Bulgaria.

This report presents a study on the influence of the content of coniferous sawdust on the properties of combined panels from wood fiber and sawdust. Produced panels were with variation of sawdust content from 0 to 50% and respectively the fiber content was from 100 to 50%. The increase in sawdust content was with a step of 10%. The main physical and mechanical properties of panels were determined and experimentally-statistical equations for the influence of coniferous sawdust content on the properties of the panels were derived. It was determined at what percentage of sawdust the panels have properties that meet the requirements of the relevant standards for MDF.

Ключови думи: MDF, refining, combined wood based panels, coniferous sawdust

EN Version

SUSTAINABLE APPLICATION OF WOOD IN CHILDREN’S DESIGN

Автори: Ivanka Dobreva-Dragostinova

Резюме

After a period of massive use into the industrial production of plastic and synthetic materials, the trends are once again directed to natural materials and wood holds the championship in this respect. The variety of timber applications in design for children is large. There are huge series of products as well as limited series and unique ones. In the most of the designer developments is clearly visible the desire to focus on sustainable design searches. The report is an attempt to explore the possibilities for sustainable use of wood in the context of the increased criteria for harmlessness and safety as well as to address the extent to which these two aspects are complementary or opposing.

Ключови думи: sustainable design, eco-friendly design, design of children’s environment

EN Version

STUDY ON THE SOUND ABSORPTION CHARACTERISTICS OF WOOD FROM SCOTS PINE

Автори: Pavlin Vitchev, Yonka Ivanova, Desislava Hristodorova

Резюме

In this paper, the absorption properties of wood materials from Scots pine (Pinus Silvestrys L.), which are widely used in flooring and wall linings, have been experimentally studied. The frequency-dependent sound absorption coefficient (αp) was determined in octagonal frequency bands with an average geometric frequency of 100 Hz to 2000 Hz. The tests were carried out using an impedance tube, according to the requirements of BDS EN ISO 10534-1:2006. The obtained results are of a particular interest from both scientific and practical point of view, given that the sound absorption coefficient has a decisive impact on the reverberation time. The latter is the main acoustic parameter of a room depending on its intended purpose.

Ключови думи: sound absorption, Pinus silvestrys, reverberation time

EN Version

INFLUENCE OF THE CUTTING MODE ON THE SURFACE QUALITY DURING LONGITUDINAL PLANE MILLING OF ARTICLES FROM SCOTS PINE S

Автори: Pavlin Vitchev, Zhivko Gochev

Резюме

The current study investigates the changes in the surface quality of experimental samples of Scots pine (Pinus sylvestris L.) wood during a milling process, performed with different rotation speed of the cutting tool (n), feed rates (U) and different thicknesses of the removed layer (h). On the basis of the performed experiments, graphical dependencies, representing the relationship between the different factors have been derived. In order to achieve a higher quality of the milled (processed) surfaces, practical recommendations for the optimal values of the evaluated factors have been suggested. The surface roughness of the material (surface) was measured with a roughness tester, type „SurftestSJ-210“ (Mitutoyo, Japan).

Ключови думи: milling, surface quality, cutting mode, Scots pine (Pinus sylvestris)

EN Version

RESEARCH OF THE INFLUENCE OF ADDING ROTTEN WOOD ON THE MECHANICAL QUALITY OF PELLETS

Автори: Branimir Šafran, Matija Jug, Kristijan Radmanović, Lučić Ružica Beljo, Marin Hasan, Igor Vicković, Stjepan Risović

Резюме

This paper analyzes the effect of adding wood attacked by brown rot fungi to basic wood raw material with the aim of increasing the mechanical strength of wood pellets. Wood attacked by brown rot fungi has an increased share of lignin which is natural glue and can contribute to better mechanical properties of wood pellets. Wood pellets were produced on a single pellet press and pressed with adjusted production parameters at two different temperatures. Produced pellets were tested on some mechanical and physical properties. The analysis of experimental results has shown the statistical significant improvement of the mechanical properties of pellets by adding brown rot fungi wood.

Ключови думи: wood pellets, brown rot fungi wood, single pellet press, mechanical properties

EN Version

METHOD (ALGORITHM) FOR A NUMERICAL AND GRAPHIC DETERMINATION OF STIFFNESS IN BENDING OF STRUCTURAL PARTICLEBOARDS

Автори: Nikolay Yosifov, Stefan Delin

Резюме

The algorithm refers to a nomogram for numerical and graphic determination of stiffness in bending of structural particleboards (SPBs). SPBs are technologically formed composite wood-based products with standardised designation P6 with wide application in construction, furniture manufacturing and interior. As evaluation criterion for the load-carrying capacity of the boards, i.e. for their fitness for use in various structural solutions, serves their strain-strength index stiffness in bending St, defined in technical literature as a product of the inertia moment of the cross-section Jy and the modulus of elasticity in bending Em. For the time being, in engineering calculations, only indirect estimates for this index on the basis of the values for the modulus of elasticity in bending are used.

The algorithm for numerical and graphic determination of stiffness in bending of SPBs is based on:

-   the physical nature of the composite as technologically formed layered material and the simulation modelling of its cross-section as a “double T beam”;

-   the experimentally established empirical dependences of the modulus of elasticity in bending on the bulk densities of the composite board and the wood raw material.

Ключови думи: algorithm, stiffness in bending, modulus of elastisity in bending, bulk density, composite, inertia moment

EN Version

POTENTIAL FOR DEVELOPMENT OF RURAL TOURISM IN DOLNA PRESPA

Автори: Vladimir Karanakov, Vladimir Koljozov, Zoran Trposki

Резюме

The motive for such a study was the valorization and categorization of architectural heritage in some rural areas in Macedonia that are located close to larger urban areas and the possibility of sustainable spatial development as well as the promotion of rural areas through action in areas such as architecture, urbanism, spatial planning, environmental protection, development of the civil sector and development of rural tourism.

For this purpose, we analyzed three rural entities and villages in the Prespa region. We selected the locations because they are located close to larger town centers such as Resen and Bitola and the border with R. Greece and this is the potential for development of rural tourism.

Ключови думи: rural tourism, rural architecture, Dolna Prespa

EN Version