Съдържание


INNO 2/2016 2016

WANE CUTTING INFLUENCE ON LUMBER VOLUME

Автори: Nadezhda Kulikova

Резюме

When cutting lumber in the sawmill, if there is more left wane, the more voluminous output blanks. Efforts in the sawmill increase, but the increase in volume output blanks pays for effort and makes a profit.

This increase in the volumetric output of lumber due to the cutting board in width in two stages –  in the sawmill and woodworking shop after drying lumber. At the same time, the costs related to that part of the drying lumber, which will be removed in a woodworking shop, will be repaid by increasing the volumetric output of billets produced lumber.

Thus, the timber with a predetermined quantity wane after leaving the drying room may be used in such a form as pieces for a wooden house.

Ключови думи: timber, raw sawn lumber, wane, blanks, voluminous, profit

EN Version

PYROLYSIS OF WASTE WOOD

Автори: Miglena Valyova, Yordanka Ivanova

Резюме

The fast and slow pyrolysis is a both flexible and an attractive method for converting biomass into easy to store and transport products that are used both as an energy source and a feedstock for chemical production. Considerable efforts have been made to convert wood biomass to liquid fuels, energy and chemicals since the oil crisis in the middle of 1970. The aim of the current review is to summarize investigations before 2010 year for understanding of process of pyrolysis. In this review are discussed publications for pyrolysis of waste wood from beech, oak, poplar, pine and other species from 2010 to 2014 years.

Ключови думи: waste wood, pyrolysis

EN Version

STUDY ON THE HARDNESS OF OAK WOOD

Автори: Diyana Mladenova

Резюме

The hardness is among the most important properties of wood. It is closely correlated with the density and mechanical properties. Moreover, it determines the processing of wood. The scope of the stem varies greatly by determination is often very difficult to define.

This work considers the hardness of oak wood, sourced from different habitats in the country and its distribution in the radius of the stem. The influence of age, the width of the annual ring, habitat and altitude are also considered.

Ключови думи: wood, oak, hardness, annual ring

EN Version

ANATOMICAL ANALYSIS OF NATURAL AND THERMALLY MODIFIED WOOD

Автори: Elena Vladimirova, Nikolai Bardarov

Резюме

Thermally modified wood is a unique natural material with special properties, that have been received after heat treatment of natural wood. All these properties are the result of changes in the chemical composition and structure of the wood. The paper aims to identify gaps in the structure of natural and thermally modified wood. The changes in the structure of the wood after its heat treatment were discussed.

We examined the specimens of pine, spruce, summer oak, hornbeam and birch wood. Microscopic preparations were made from the wood specimens before and after heat treatment. The three main sections of wood at different zoom were observed. There have been noticed differences in the construction of anatomical elements.

Ключови думи: thermally modified wood, pine, spruce, oak, birch, hornbeam, microscopic analysis

EN Version

VARIATION OF SOME PROPERTIES OF THE STEM RADIUS AT RESONANT WOOD

Автори: Nikolai Bardarov

Резюме

Many conditions need to be met for producing quality musical instruments. One of them is to have a consistency of structure and properties of wood. It is often difficult, especially for instruments in large dimensions. It is required to be cut large diameter trees.

The article examines variations in the density, compressive strength and flexural strength and modulus of elasticity in the radius of the stem of the spruce. A section for the manufacture of musical instruments is studied in the factory „Kremona AD” – Kazanluk. A section has stayed in dry and heated place more than 12 years. The differences in the properties of the test pieces of juvenile, central and peripheral wood have been established.

Ключови думи: resonant wood, spruce, density, compressive strength, flexural strength, modulus of elasticity

EN Version

BENDING STRENGTH OF T-SHAPE CORNER DETACHABLE JOINTS OF STRUCTURAL ELEMENTS MADE OF PLYWOOD

Автори: Ralitsa Simeonova

Резюме

In this study are given the results from investigation on bending strength of T-shape corner detachable joints of structural elements made of plywood. It has been established the bending moment under compression bending test. The highest bending strength were achieved with screw with cross dowel and Confirmat ∅7 x 70 and ∅7 x 50 mm and lowest bending strength have joints with bolt and nut and two types of eccentric connectors.

It is recommended that the comparative data of bending strength is taken into consideration when the designers and engineers have to choose the type of joints in the furniture constructions.

Ключови думи: furniture construction, plywood, joint, bending strength, bending moment

EN Version

COMPARATIVE RESEARCH ON THE DESTRUCTIVE BENDING MOMENTS OF SOME CORNER JOINTS OF FRAME STRUCTURAL ELEMENTS MADE OF SOLID SPRUCE WOOD WITH A CROSS SECTION OF 50 X 30 MM PART III: END CORNER MORTISE AND TENON JOINTS

Автори: Georgi Kyuchukov, Borislav Kyuchukov, Vassil Jivkov, Assia Marinova, G. Gruevski, Z. Kalapotliev

Резюме

The results from the research on the destructive bending moments of the end corner mortise and tenon joints of structural elements made of solid spruce wood with a cross section of 50 x 30 mm are given whereas these joints are used mainly in the construction of sitting furniture, tables and beds.

It was established that the type of joints has significant influence on the destructive bending moment. This is defined by the type and size of joint elements and the area of the contact surfaces of the joints.

The following joints are destroyed at a considerably big bending moment:

  • Haunched blind mortise and tenon joint;
  • Blind twin mortise and tenon joint;
  • Blind mortise and tenon joint
  • Haunched through twin mortise and tenon joint;
  • Haunched through mortise and tenon joint;
  • Haunched blind twin mortise and tenon joint;
  • Twin through mortise and tenon joint;
  • Through mortise and tenon joint.

It is recommended that the research results are taken into consideration in strength design of furniture.

Ключови думи: corner joints, frame structural elements, destructive bending moments, solid spruce wood

EN Version

COMPUTATION OF THE HEAT FLUX NEEDED FOR UNILATERAL WARMING UP OF FLAT SPRUCE DETAILS BEFORE THEIR BENDING

Автори: Nencho Deliiski, Neno Trichkov, Dimitar Angelski, Zhivko Gochev

Резюме

An approach for the computation of the heat flux, which is needed for warming up of flat wood details during unilateral heating aimed at their plasticizing in the production of curved outside parts for corpses of stringed music instruments, has been suggested. The approach is based on the numerical integration and differentiation of the solutions of a linear model for the calculation of the non-stationary 1D temperature distribution along the thickness of subjected to unilateral heating flat wood details. The paper presents solutions of the model concerning the non-stationary change in the specific heat flux needed for warming up of flat spruce details with thicknesses of 6, 8 and 10 mm during their unilateral heating at temperatures of the electrically heated metal band equal to 100, 120, and 140 oC.

Ключови думи: unilateral heating, flat wood details, heat flux, plasticizing, bending

EN Version

MATHEMATICAL DESCRIPTION OF THE SPECIFIC HEAT CAPACITY OF THE WOOD ABOVE THE HYGROSCOPIC RANGE DURING WOOD FREEZING

Автори: Nencho Deliiski, Natalia Tumbarkova, Rayko Stanev

Резюме

A mathematical description of the specific heat capacity c of wood above the hygroscopic range during wood freezing has been suggested. The description takes into account the physics of the freezing process of both the free and the hygroscopically bound water in the wood. It reflects also the influence of the fiber saturation point of wood species on the value of their c during wood freezing and the influence of the temperature on the fiber saturation point of the wood during its freezing. A software program has been prepared for the computation of c according to the suggested mathematical description. With the help of the program, computations have been done for the determination of c of often used in veneer and plywood production beech and poplar wood with moisture content 0.4 kg∙kg-1u≤1.2 kg∙kg-1 at the temperature range between 0 oC and –60 oC during freezing of the wood.

Ключови думи: wood, freezing, specific heat capacity, mathematical description, bound water, free water, computatio

EN Version