scholarly journals Convective hot-air chambers impulse drying of pear wood lumbers

2021 ◽  
Vol 25 (4) ◽  
pp. 107-111
Author(s):  
D.I. Deyanov ◽  
◽  
S.A. Moiseev ◽  
G.N. Kuryshov ◽  
A.A. Kosarin ◽  
...  
Keyword(s):  
Physical And Mechanical Properties ◽  
Internal Stresses ◽  
Structural Elements ◽  
Advantages And Disadvantages ◽  
Hot Air ◽  
Literary Sources ◽  
12 Steps ◽  
Impulse Drying ◽  
Sawn Timber ◽  
Operating Stage

A review of literary sources on the physical and mechanical properties of pearwood and its use as structural elements of furniture is given. The aerodynamic chambers, their advantages and disadvantages, as well as their modernization are considered. The use of impulse modes for drying hardwood is substantiated, including sawn timber from pear wood 50 mm thick, pilot drying of which began in the modernized URAL-72 chamber in 1999 at Intar LLC, Moscow. The moisture content of the wood samples and the value of internal stresses were controlled in accordance with GOST 16588. The process of impulse drying included from 9 to 12 steps, the temperature at the operating stage ranged from 45 °C to 72 °C. It has been proved that the use of pulse modes for drying pear timber saves up to 30% of electricity.

Thermal Decomposition of Vulcanized Structures of Deformed Vulcanizates Containing Various Accelerators

1953 ◽  
Vol 26 (4) ◽  
pp. 759-763 ◽  
Author(s):  
B. Dogadkin ◽  
Z. Tarasova
Keyword(s):  
Stress Relaxation ◽  
Physical And Mechanical Properties ◽  
Heat Stability ◽  
Chemical Bonds ◽  
Structural Elements ◽  
Specific Chemical ◽  
Vulcanized Rubber ◽  
Different Temperatures ◽  
Chemical Groups ◽  
The Given

Abstract According to the hypotheses developed by the authors, vulcanized rubber is a system in which the molecular chains are united by local molecular and chemical bonds of varying intensity. The concentration, distribution, and strength of these bonds determine the principal physical and mechanical properties of the vulcanizates. Consequently the study of the structure of the vulcanizate is of primary practical value. The explanation of the nature of the bonds in a vulcanizate by chemical methods is very difficult, mainly because of the impossibility of distinguishing the specific chemical groups which enter into the composition of the different molecular chains from those bonds between the chains which are responsible for the development of spatial structures. From this view point, the thermo-mechanical method described below, which is based on the study of stress relaxation at different temperatures, is of great significance. As was shown by Dogadkin and Reznikovskii˘, the delayed stress relaxation in a vulcanizate at temperatures up to 70° C is caused by rupture of the local intermolecular bonds and the regrouping of the structural elements of the polymeric chains without destruction of the chemical bonds between them. Accordingly, after some time at these temperatures, a practically balanced stress is established, which depends on the number of the stronger bonds remaining. At temperatures above 70° C, rupture of the chemical bonds between the chains takes place; its speed increases with decrease of the energy activating the rupture of the given type of bond. Particularly in the case of sulfur vulcanizates, we can assume that the following types of bonds exist between the chains of the rubber: (1) —C—C—, which develop as a result of the polymerizationprocesses; (2) —C—S—C— monosulfide; (3) —C—S—S—C— disulfide, and (4) —C—Sn—C— polysulfide, formed as a result of the direct participation of the vulcanizing agent, sulfur, in the process of joining of the molecular chains. The energy of these chains can be estimated as 62.7 kcal, per mole for C—C, 54.5 kcal. per mole for C—S, and 27.5 kcal. per mole for the —S—S bond. Naturally, the heat stability of a vulcanizate will depend on which of the indicated types of bonds predominates.

The interrelation between physical and mechanical properties of the polymeric composite and fractal dimension of structural elements its surface

2021 ◽  
pp. 54-60
Author(s):  
Val.I. Surikov ◽  
◽  
E.A. Rogachev ◽  
A.M. Lasitsa ◽  
◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Physical And Mechanical Properties ◽  
Polymeric Composite ◽  
Polymeric Composite Material ◽  
Structural Elements ◽  
Qualitative And Quantitative Analysis ◽  
Force Microscopy ◽  
Qualitative And Quantitative ◽  
Atomic Force ◽  
Dimension Parameter

The paper shows the promising use of the "fractal dimension" parameter for qualitative and quantitative analysis of the surface structure of samples based of micrographs obtained by scanning electron microscopy and atomic force microscopy. The interrelation of this parameter with some mechanical characteristics of polymeric composite material PTFE-3%tu121 is investigated.

scholarly journals ANALYSIS OF EXTERNAL ENGINEERING NETWORK METHODS

2020 ◽  
Vol 4 (157) ◽  
pp. 7-11
Author(s):  
V. Zhvan ◽  
V. Donenko ◽  
S. Kulish ◽  
A. Taran
Keyword(s):  
Physical And Mechanical Properties ◽  
Directional Drilling ◽  
Horizontal Directional Drilling ◽  
Technological Parameters ◽  
Optimal Method ◽  
Advantages And Disadvantages ◽  
Analytical Review ◽  
Conducting Research ◽  
The Cost ◽  
Selection Of

The article is devoted to the effective analysis of trench and trenchless pipeline laying technologies. In the course of the work, an analytical review of pipeline assembly was performed, the main technological parameters, the scope of each method, and their advantages and disadvantages were determined. List of considered pipeline laying methods: trenching, horizontal directional drilling, mechanical puncture, hydraulic puncture, microtunneling and punching. The article analyzes the classical trench method and the most widely used trenchless ones: horizontal directional drilling; mechanical puncture; hydraulic puncture; microtunneling; punching. Each of these methods has several advantages and disadvantages. The choice of the optimal method of laying the pipeline depends on many factors: the physical and mechanical properties of soils and hydrogeological conditions, the length and diameter of the pipeline, the presence of other communications, buildings and structures, as well as the budget that customers have. Work time is the last deciding factor. Based on the results of the analysis of pipeline laying technologies and expert survey of construction industry experts, the cost table of each method was compiled, outlining the main characteristics of the technology: length of pipeline, speed of work, scope, cost, and the advantages and disadvantages of each of the considered methods. The conclusions about the use of each of the pipeline laying methods were made. Each of the methods has its advantages and disadvantages, so to choose the method of work it is necessary to conduct a comprehensive assessment of technological parameters, cost, scope and timing of work. The cost of lay-ing the pipeline consists of the following factors: conducting research; selection of diameter and determination of pipeline length; choice of laying method and equipment necessary for the works; selection of equipment, shut-off and control equipment and other materials arranged on the pipeline; terms of performance of works. Taking into account these factors, an estimate is made, which determines the cost of installation of a particular pipeline. After the analysis, we can conclude that among the methods of trenchless laying of pipelines can be identi-fied horizontally directional drilling, it is this method of laying the pipeline will be appropriate to use for our region. The drilling technique allows to carry out pipelines under obstacles, to pull long segments of networks, to repair site damage. This method is universal and can be used in almost any environment. Keywords: trenches, horizontal directional drilling, mechanical puncture, hydraulic piercing, microtunnelling, punching, pipeline.

scholarly journals MECHANICAL STRENGTH OF COAL: METHODS OF DETERMINATION AND FACTORS OF INFLUENCE (REVIEW)

2021 ◽  
Vol 6 ◽  
pp. 4-17
Author(s):  
V.V Koval ◽  
D.V. Miroshnichenko ◽  
O.V. Bogoyavlenska
Keyword(s):  
Mechanical Strength ◽  
Physical Properties ◽  
Physical And Mechanical Properties ◽  
Mechanical Tests ◽  
Point Of View ◽  
Statistical Characteristics ◽  
Measuring Instruments ◽  
Industrial Processing ◽  
Average Value ◽  
Advantages And Disadvantages

The article substantiates the importance and problems of determining of such an indicator of the quality of solid fossil fuels, as mechanical strength. The strength of coal depends on a large number of factors (viscosity, brittleness, properties of structural bonds, etc.), the change of which is impossible to take into account. Therefore, the strength of coal in the sample, piece, pack and formation must be represented by some integral index, which inevitably fluctuates around a certain average value and can be determined only approximately. The evaluation of the strength properties of coal should be carried out on the basis of mass tests using statistical methods that allow to calculate the average value and coefficient of variation. Since the strength dispersion is mainly due to the natural inhomogeneity of the coal, the excessive accuracy of the measuring instruments has almost no effect on the statistical characteristics. Laboratory methods of mechanical tests of mine samples, in comparison with full-scale, as a rule, are very accessible and, at qualitative performance of tests, are highly reliable. The properties of coal as an object of enrichment and use are largely related to its physical properties. The physical properties of coal and mineral impurities significantly affect the formation of the main parameters that characterize the particle size distribution and fractional composition, it`s changes during the mining, transportation and enrichment processes. The basic physical and mechanical properties of solid fuels from the point of view of their industrial processing have been listed, the review has been made of the most widespread methods of study of coals mechanical durability and the equipment used for these purposes. The main advantages and disadvantages have been summarized of these methods, as well as their relationship. The factors have been Indicated tinfluencing the mechanical strength of coal. The expediency of using existing methods from the point of view of informativeness for thesphere of its application has been estimated. The methods common in the coal processing industry are considered in more detail. Keywords: coal, solid fuel mining, mechanical strength, determination methods, influencing factors, grinding strength, crushing index. Corresponding author V.V. Koval, e-mail: [email protected]

On the Microstructure of HPT Processed Cu under Variation of Deformation Parameters

2006 ◽  
Vol 503-504 ◽  
pp. 51-56 ◽  
Author(s):  
Erhard Schafler ◽  
Anna Dubravina ◽  
Bernhard Mingler ◽  
Hans Peter Karnthaler ◽  
Michael Zehetbauer
Keyword(s):  
Hydrostatic Pressure ◽  
High Pressure Torsion ◽  
Profile Analysis ◽  
Domain Size ◽  
Internal Stresses ◽  
Stress And Strain ◽  
Structural Elements ◽  
Microstructural Parameters ◽  
Deformation Parameters ◽  
Deformation Stages

The evolution of strength characteristics and the microstructure of copper subjected to high pressure torsion (HPT) are studied under variation of strain and hydrostatic pressure. Measurements of Multiple X-ray Bragg Profile Analysis (MXPA) yield microstructural parameters like dislocation density and arrangement, as well as crystallite (domain) size and distribution, and long-range internal stresses. TEM investigations are carried out to analyse the structural elements and to compare them with the results of MXPA. The strength behaviour is studied by microhardness measurements. The investigations are performed within wide ranges of resolved shear strains 􀁊 = 1 to 400 and of applied pressures p = 0.8 to 8 GPa. The onset of the deformation stages IV and V is strongly affected by the hydrostatic pressure i.e. shifted to higher values of stress and strain with increasing pressure. The experimental results indicate the occurrence of recovery effects, which seem to be of static as well as of dynamic nature, and to be responsible for extended ductility in SPD materials.

scholarly journals Calculation of accuracy with the coordinate-positional method of basing

2021 ◽  
Vol 2131 (3) ◽  
pp. 032005
Author(s):  
M Kovalevich ◽  
T Neypert ◽  
P Davydov
Keyword(s):  
Technology Development ◽  
Rapid Development ◽  
Point Of View ◽  
Industrial Robots ◽  
Structural Elements ◽  
Advantages And Disadvantages ◽  
Assembly Accuracy ◽  
Industrial Manipulators ◽  
Current Experience ◽  
Large Aircraft

Abstract The article is devoted to the assessment of assembly accuracy when positioning with the use of industrial manipulators (robots). Classic assembly technologies are outdated and have many disadvantages that can be solved by the automation of industrial processes, which became possible due to the rapid development of robotization. In the material there are investigation the possibility of using industrial robots for positioning structural elements of aircraft from the point of view of achieving the required assembly accuracy. For the analysis, foreign literature sources and the current experience of introducing similar technologies by large aircraft manufacturers were used. To assess the assembly accuracy, the formulas for the functional size error were used. An enlarged technological assembly process is presented, graphic materials with basing schemes are presented. Based on the data obtained, the advantages and disadvantages of basing with the help of industrial robots at this stage of technology development are formulated, taking into account the existing production experience.

scholarly journals Tactics of Primary Emergency Radiation Diagnosis of Politrauma

2021 ◽  
Vol 102 (1) ◽  
pp. 57-65
Author(s):  
Yu. G. Shapkin ◽  
P. A. Seliverstov ◽  
N. Yu. Stekolnikov
Keyword(s):  
Computed Tomography ◽  
Radiation Risk ◽  
Whole Body ◽  
Economic Losses ◽  
Care Organization ◽  
Advantages And Disadvantages ◽  
Whole Body Computed Tomography ◽  
Literary Sources ◽  
X Ray Computed ◽  
High Level

The review considers the problem of choosing the optimal tactical approach to primary emergency radiation diagnosis of injuries during polytrauma based on data on indications for use, advantages and disadvantages of modern methods and protocols of radiation imaging. Literary sources were searched in the MedLine/ PubMed and eLibrary databases published from 2009 to 2019.The tactics of selective radiation diagnosis of polytrauma involves performing sequential studies (sonography, X-ray, computed tomography) of body areas in which damage is suspected by the mechanism of injury and clinical data, which limits the accuracy of the diagnosis and increases the duration of the examination. Primary multi-helical “whole-body”computed tomography including head, neck, chest, abdomen and pelvis examination, reduces the percentage of missed injuries, the duration of the examination and the time before emergency surgery, which can significantly reduce mortality in polytrauma. Its use is justified in patients with severe combined trauma if a high level of emergency hospital care organization is provided. Using “whole-body” computed tomography significantly increases the dose and economic costs, but the benefits of it for the survival of patients with polytrauma can outweigh the radiation risk and economic losses. Further development of technologies and protocols for multispiral computed tomography can significantly reduce the dose of radiation and the duration of the study. Clear and well-founded criteria for the selection of patients are needed for whom the use of “whole-body” computed tomography will be an effective strategy for radiation diagnosis.

scholarly journals Analysis factors affecting formation on the clutch durability between asphalt-concrete layers of road clothing

2021 ◽  
pp. 26-31
Author(s):  
Liydmyla Levkivska ◽  
◽  
Jafar Musa Elallak
Keyword(s):  
Asphalt Concrete ◽  
Complex Analysis ◽  
Physical And Mechanical Properties ◽  
Difficult Situation ◽  
Factors Affecting ◽  
Operational Conditions ◽  
The Road ◽  
Number Of Factors ◽  
Literary Sources ◽  
On The Road

This article reflects the importance of the road network for the social development of society and the development of the economy of the country as a whole. On the basis of literary sources provides complex analysis of roads in Ukraine, their current functional state and tendencies of development. It is established that the road industry is in a rather difficult situation due to unsatisfactory transport and operational conditions of the vast majority of Ukrainian roads. Construction of new roads is extremely rare because of lack of financial resources. Road works are usually carried out to preserve the network of already existing roads and to ensure their necessary transport and operational status. According to the results of the analysis, one of the main reasons for the premature destruction of newly constructed or repaired non-rigid pavements is the low strength of interlayer adhesion in the contact area of the newly covered material with the layer below. The effect of clutch durability between asphalt layers on the road strength has been studied in detail. A number of factors that affect the quality of clutch durability between layers are analyzed. It is established that in order to ensure the strength of grafting between asphalt concrete layers of road clothing, it is necessary to strictly observe the technological regimes of their laying, above all temperature; to take into account the physical and mechanical properties of materials at the construction stage and the influence of climatic and mechanical factors, or most often their complex effect on the operation of the highway.

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