Solid State Phenomena Vol. 291

Abstract: This study aimed to determine the influence of fiber volume fraction towards composite toughness and the composite hybrid fracture pattern models reinforced by hemp fiber and fiberglass to find out the ratio of composite toughness from variation of hemp fiber volume fraction and fiberglass A1 (15 : 25), A2 (20 : 20), A3 (25 : 15)%. This research is an experimental method research with the dependent variable is composite toughness and the independent variable is the fiber volume fraction. Based on the test and data analysis, the results for fraction A1 (15 : 25)% have the greatest impact absorption of 10834.6 J/m² compared to A2 (20 :20)% that have absorption of 8470.828 J/m² and A3 (25 : 15)% is 7168.813 J/m². The most prominent one of the three variations of volume fractions on this fracture pattern analysis is the existence of (delamination) or there are fibers which are not perfectly exposed to the matrix. The Delamination usually occurs due to overly tightening of the fibers.

Abstract: Recently, more attention has been paid to the development of gas hydrate deposits, the use of gas-hydrated technologies, suitable for energy-efficient transportation of natural gas, the separation of gas mixtures, production and storage of cold, desalinating of seawater, etc. Hydrate formation is one of the main processes of gas-hydrate technological installations. In the article a model is proposed that describes the kinetics of the formation of hydrate in disperse systems, which are characteristic for real conditions of operation of gas-hydrate installations, on the basis of a stochastic approach using Markov chains. An example of numerical calculations is presented on the basis of the proposed model of the dynamics of the total mass of gas hydrates, and changes in the velocity of their formation and size distribution at different values of the nucleation constants and growth rate of the gas hydrates, and results of these calculations are analyzed. It is shown that the rate of formation of hydrate has a maximum value in half the time period of the whole process. The obtained results of the calculations of the dynamics the total mass of gas hydrates are in good agreement with the results of calculations by the equation of kinetics Kolmogorov-Avrami. The proposed model can be applied to the inverse problem: the determination of the nucleation constants and the rate of growth of gas hydrates by the results of the dynamics of the formation of hydrate and the changes in the fractional composition of the generated gas hydrates.

Abstract: The calculation procedure for determining the plasticity of pre-deformed metals during their processing by pressure has been developed. The calculation procedure is based on a fracture model, which in turn is based on the tensor description of damage accumulation. With known mechanical characteristics, as well as with known plasticity diagrams, the fracture model makes it possible to evaluate the plasticity of pre-deformed bend for any kind of stress state. When manufacturing steeply curved branches using the pipe extrusion method, the procedure was tested. Verification of the mathematical model has shown a high level of its adequacy, and it can be used in assessing the plasticity of pre-deformed billet.

Abstract: It has been demonstrated that vibratory impact mineral loading results in the formation of solid solutions. A technique to determine concentration dependence of inversion degree of solid binary solutions according to the known values of their components activity has been proposed. Values of thermodynamic functions of the solutions mixing in terms of statistic formulas as well as by means of immediate processing of the experiment have been determined.

Abstract: In the shaft metallurgical units (blast furnace, Corex, Finex and Midrex installations) the powder is generated within the process with charge materials as its source or it is introduced into the unit within the process procedure. Accumulation of small particles inside the furnace is diversified and depends on the applied process procedure. Noticeable disruptions of the flow might occur at large degree of dustiness. The article presents the results of model investigation of gas flow resistance and the powder holdup during two-phase flow (gas + powder) through the descending packed bed. The aim of the research was to determine the conditions of the descending bed suspension in the following systems: sinter + coal powder and blast furnace pellets + coal powder. Air was used as a gas. The study results were the basis for defining the conditions in which bed suspension of the model systems occurs. It was found that in case of sinter + coal powder system the most intensive powder holdup in the bed occurs together with the optimal conditions for bed movement distortions.

Abstract: The authors of the paper consider the concept of further prospective development of mining enterprises. The basis of this concept are scientific results obtained during the study of physical and chemical processes of solids conversion into the gaseous state: coal → gaseous fuels. It was established that the main base of development of mining regions is a mining power-chemical complex. The basic segment of which is a well underground coal gasification station. It is established that increase of indicators of efficient operation of the station from gasification is possible by synthesis of technical and technological decisions on the use of coal seam energy. When coal gasification is over, the gasifier passes into a mode of thermal generator with the use of alothermal technique to remove heat and thermic decomposition products from the degassed space of the gasifier. Generator gas at its initial temperature (1100 – 1300oС) around an underground gasifier creates a powerful heat boiler with a temperature regime of 200 – 300oС. It was established that at work of six gasifiers on a coal seam with thickness of 1.0 m with geometrical parameters each at a width of 30 m and at the length of 450 m energy-thermal power will be 237.8 MW. At the same time, additional energy resources can be obtained by involving segments of alternative forms of energy supply to the life cycle of the mining enterprise.

Abstract: This study aims to find material steel for animal feed chopper machine which is not easily corroded with method of hot dip galvanizing (HDG). Steel as machinery components or construction often gets broken before the predicted time because of corrosion. The HDG method was begun by pre-treatment process which were polishing, degreasing, rinsing I, pickling, rinsing II, fluxing, and drying. The main process of galvanizing was done by dipping in 98% of zinc solution with temperature variation of 430, 450, 470, and 490°C. The coating thickness measurement was run with Coating thickness NOVOTEST TP-1M. The corrosion was tested with electrochemical method of potentiodynamic polarization with AUTOLAB PGSTAT 128. The highest value of coating thickness was at galvanized temperature of 490°C which was 88.9 ± 3.24%. The value of standard deviation was indicated by how much the coating homogeneity formed. This was in line with the amount of corrosion rate at galvanized temperature of 490°C. The highest corrosion rate values in H₂SO₄ and NaCl environment were 1.18 and 0.21 mm/year. The highest hardness value of Zn layer is galvanizing temperature of 490°C which rises 41.71% of the base metal. The coating thickness, corrosion and surface hardness test have thee good agreement.

Abstract: This article is focused on solving the problem of power supply for the mining and industrial regions of Ukraine. This problem is caused by a significant import dependence on natural gas, the lack of efficient technologies in the integrated development of the energy resources of gas-coal deposits and the deterioration of social and economic, as well as environmental conditions in mining regions. As a promising direction for solving the problem of rational use of methane from coal mines and reducing the hazardous gas emissions into the atmosphere, the implementation of gas hydrate technologies into the technological complex of a coal mine has been proposed. The Clausius-Clapeyron equation has been improved for the conditions of gas hydrates formation, which considers the presence of an excess in non-equilibrium defects and is supplemented, taking into account the thermal effect of phase transformations, with all the time positive thermal effect of the defects relaxation. It has been revealed that one can intentionally control the relaxation energy of defects by the thermodynamic stimulus of phase transformations in the process of hydrate formation. The experimental dependences have been determined of the change in hydrate accumulation on the time of hydrate formation, with the methane hydrates production and taking into account the parameters of pressure and temperature. It has been revealed that the maximum fast time of hydrate formation at T = 1°C and P = 10 MPa is the time which amounts to 2.5 hours. The experimental dependences have been determined of the gas hydrates formation out of a methane-air mixture of degassing holes, on the methane concentration, on pressure and temperature parameters. It has been determined that the greater the methane concentration in the mixture, the greater must be the pressure in the system for the gas hydrates formation.

Abstract: For the first time in this article, a mathematical model has been developed for calculating the temperature fields in arbitrary areas in electron-beam welding; this model was created in the form of a boundary value problem of mathematical physics for a parabolic equation of heat conductivity with Dirichlet boundary conditions. A new integral transformation was constructed for a two-dimensional finite space, with the use of which, as well as the finite element method and Galerkin's method, a temperature field has been determined in the form of a convergent series.

Abstract: The method and unit for experimental research of membrane formation from titanium alloys under conditions of superplastic is developed, which allows to determine necessary parameters of deformation. The unit is designed to deform titanium sheets in isothermal conditions by applying a uniform distributed load. When membrane is formed by a gas medium, a biaxial tension is realized. This type of test is used to assess the plastic properties of metals. In this work, the limiting deformations of the sheet titanium alloy OT4-0 have been evaluated in the formation of the membrane. Installed during the process of superplastic deformation the connection between the external parameters of deformation (force, temperature) with the depth of formation of the membrane in time and strain distribution along its generatrix.