Papers by Keyword: Mathematical Simulation

Abstract: The main theoretical aspects of porous and powder materials technological processing is worked out. The proposed material model is based on: - the four-parameter plasticity theory, which reflect the influence of porosity, resistance and the presence of dilatancy of solid phase deformation regime; - the dissipative potential and the load surface expression, that allow to take account such materials elastic - viscous - plastic properties; - the solid phase energy deformation speed with its subsequent over the representative element volume averaging. The peculiarity of this model is that the equilibrium flow concept elastic-viscous-plastic material is an alternative to its elastic-plastic deformation. The proposed equations are suitable for their effective practical using for digital models creation that based on existent software for the of equilibrium processes of compact materials deformation finite–element analysis. The practical use of the proposed methodologies made it possible to determine: - the regularities of the different modules material layers interaction during stamping of bimetallic blanks with an conical working surface; - the porosity distribution over the product volume at the final stage of radial extrusion of the bushings with an internal flange; - the effect of powder material decompression during reverse extrusion of cylindrical products.

Abstract: The stationary thresher machines are widely used worldwide in threshing and separating many crops; they proved to have a high performance, especially in small spaces. The threshing drum is the essential working device of the thresher and plays a fundamental role in threshing efficiency, consumed specific energy, machine productivity, and seeds loss. In this study, a structure of sunflower thresher (open style drum with 45 incline degree loop teeth) was tested, and evaluated for performance under different drum rotational speeds (150, 200, 250, and 300 rpm) and different concave clearances ( 10, 15 and 20 mm). The thresher structure and operating parameters were assessed and optimized concerning damaged and unthreshed seed percentage, threshing efficiency, consumed specific energy, and machine productivity. The obtained results revealed that increasing cylinder rotating speed positively related to threshing efficiency, power requirements, and machine productivity while increasing concave negatively related to threshing efficiency, power requirements, and machine productivity. The highest efficiency of 97.40 %, the maximum productivity of 434.50 kg/h, and the lowest consumed specific energy of 6.85 kW.h/t were obtained at the operational condition of 300 rpm drum rotational speed 10 mm concave clearance. Buckingham's π theorem was followed to find an equation to predict the threshing efficiency theoretically, resulting in an equation with an R2 value of 0.8892. These developments were an excellent choice to uprising the performance of the original thresher drum.

Abstract: Metallurgical processes in Me-O-C systems cannot be studied and controlled using conventional analytical and physicochemical techniques. This is due to the complex physical and chemical interactions occurring in high-temperature metallurgical systems with the formation of various compounds. To study such processes, mathematical (thermodynamic) simulation and other techniques are widely used, among which graphical diagrams illustrating the equilibrium between individual phases or their systems occupy a special place. Diagrams have been proposed that are more common, informative, and herewith universal to study pyrometallurgical processes. The main research objective was to determine the equilibrium composition of the Me-O-C system, i.e., the amount or ratio of its various compounds such as carbides, oxides, pure substances, and, possibly, ternary compounds. The equilibrium compositions of the system were obtained to plot diagrams from not only experimental studies but also the chemical equilibria mathematical simulation results using the Selector software package. The diagrams proposed herein allow establishing a quantitative relationship between the temperature, the ratio of independent components (metal, oxygen, and carbon), on the one hand, and the complete equilibrium composition of the system, which implies data on the amount and type of condensed and gas phases in the system and their ratios, on the other hand. This mechanism is a new tool to study chemical conversions in complex metallurgical processes, which will be very useful for metallurgists, chemists, and technologists.

Abstract: Microbial fuel cell (MFC) is a new technology that uses microorganisms to extract energy from complex organic mixtures. On the basis of aerobic granular sludge we have selected a nitrogen-fixing community of microorganisms that was immobilized on a carbon material (graphite foam, carbon nanotubes). The MFC anode has been developed on the basis of selected biological material. A membraneless glucose / oxygen MFC with bioanode and cathode based on non-platinum group metals or laccase enzyme has been developed. A mathematical model describing the processes in the MFC has been developed, on its base the calculations have been carried out.

Abstract: With the increasing requirements for steel quality, the refining conditions are increasing strict. The high-speed movement of molten steel under mechanical or pneumatic agitation can uniform the temperature and composition, and accelerate the collision of the inclusions to eliminate. However, the electromagnetic field has an important influence on the removal of inclusions in steel and the corrosion of refractory materials. The magnetic phenomenon caused by the movement of molten steel needs to be explored. Considering the complexity of high temperature thermal simulation, this work adopted the physical modeling combined with mathematical simulation method, saturated sodium chloride solution was selected to simulate molten steel as a liquid electrolyte, the magnetic phenomenon caused by solution motion was tested and analyzed, and mathematical model of solution motion magnetization was based on discharge mechanism and magnetic vector potential superposition principle, then the variation law of spatial magnetic field generated by liquid electrolyte flow was discussed. The results show that the simulation results agree with that of the physical modeling, and the mathematical model is promising for prediction of the magnetic field generated by liquid electrolyte flow. Under a constant flow speed of 2000 r/min, a magnetic field with magnetic flux density up to 0.15 Gs was produced, which has a significant effect on the refractory corrosion and removal of impurities in the molten steel.

Abstract: Nowadays various light concrete types have many advantages as compared to heavyweight concrete (total structures mass decrease, increased thermophysical properties, less material consumption). Various industrial wastes use such as fly ashes, slag and bottom ash was suggested to enhance the light concretes effectiveness. This is greatly important for a green light concrete production since it is very important to obtain new types of environmentally friendly materials using wastes. The article substantiates the light concrete use and creation with organo-mineral additives based on industrial waste, analysis of the second-order mathematical model describing the bottom ash (BA) amount effect of Vung Ang TPP and expandable polystyrene spheres (EPS) on the light concrete density and compressive strength at the age of 28 days of normal hardening is done. In this work, the BA and EPS amounts varied from 14.5 to 45.5%, respectively, of the cement weight and from 24.5 to 55.5% of the concrete mix volume. The effect of expanded polystyrene spheres (EPS) and bottom ash (BA) TPP "Vung Ang" amounts as the input parameters on the polystyrene concrete properties (PCP) were investigated in this study. On the one hand, various proportions of BA (14.5, 20, 30, 40 and 45.5%) were blended in concrete mixes as partial weight replacement for Portland cement. On the other hand, EPS amount was replaced by the fresh concrete volume in the range from 24.5% to 55.5%. Additionally, the central composite design method of Box-Wilson for second order factors was used to predict the EPS and BA effects on the polystyrene concrete properties. The results showed that the proposed regression equations of this mathematical model achieved an adequate prediction accuracy. Hence, the effects of both bottom ash contents and expanded polystyrene spheres on the dry density and 28-day compressive strength of the PSC-specimens were significant. In the future, further investigations have to be carried out to study the quality prediction of green light concrete containing various wastes.

Abstract: Investigations of the rheological properties and the formation of the structure of stainless steel were performed. A computer model of the process of hammer forging of the turbine blades made of stainless steel 1.3 m long in the package Deform-3D was developed , with the help of which the necessary coefficients and parameters are determined to ensure maximum convergence of the calculated and experimental process data. The obtained data were used to create a mathematical model for stamping a large-sized turbine blade made of stainless steel with a length of 2.1 m. Mathematical modeling of the processes of stamping and distorting of a large-sized blade in the software package Deform-3D has been performed. The influence of process parameters on the stress-strain state (SSS), forming, temperature field in the forging at various stages of stamping. Determined temperature and deformation modes of stamping, the need for additional heating and optimal forgings geometry by stamping.

Abstract: The paper presents the results of the analysis of thermal state of continuous cast bloom on the stage of incomplete crystallization in the area of possible places of application of technology of Mechanical Soft Reduction (MSR), received during simulation on mathematical model, which was implemented in the software package using the finite element method. For the conditions of continuous cast bloom with a cross section of 360-400 mm, we studied the characteristics of temperature change over the cross section of the bloom, the growth dynamics of the solid shell, the number of the solidified component, and the end point position of solidification depending on the technological parameters for continuous casting of A516, 5140 1070 and AISI steel brands. The obtained data on the thickness of the crystallized shell of continuous cast bloom and the amount of solid phase depending on the casting speed and steel grade allowed us to conclude about the possible place of installation of the MSR unit. The results of mathematical simulation can be transferred in a digital form to the strength model of deformation of continuous cast bloom at the stage of incomplete crystallization.

Abstract: A mathematical modeling approach as well as experimental data analysis have made it possible to establish significant factors affecting the relative diameter of the axial porosity zone. The minimal values of this parameter determine if the ingot can be used for the fabrication of rolled steel rods over 300 mm in diameter, because chill extensive axial defects prevent from producing high quality bars of a large diameter. Commercial information analysis and experimental results have enabled to develop a model relating the axial porosity zone dimension, ingot geometry and process parameters of teeming 6.61 ton and 7.0 ton ingots. The improvement of the model obtained has enabled to establish that the axial porosity zone is primarily affected by the following factors: hot top size, slenderness ratio, the H/D ratio and insulation heat capacity. When these parameters are controlled to reduce the relative diameter of the axial porosity zone, the number of shrinkage defects decreases and the quality of large diameter rolled steel becomes better. The proposed ingot geometry improves the direction of the advance of the metal solidification front to the ingot thermal center, located in the hot top. Besides, the solidifying metal is better fed with the hot top melt.

Abstract: The mathematical model for heat transfer during solidification of steel in the mould of slab caster was established in this paper. The temperature distribution of slab surface was described. Based on the work which was described above, the model of flux film state was developed in present paper. Lubrication function of mould flux and the effects of main factors on lubrication had been discussed. The simulation results provided theory foundation for appraising lubrication function of flux and optimizing casting production.