Bulletin PNRPU. Mechanical engineering, materials science

The mechanical properties of the rim of a railway wheel depending on the distance from the tread surface were determined in the article. The results of the experiment, which determines the hard ness of the rim of railway wheel by the method of Vickers, was used as the initial data. This data was converted to hardness according to the Brinell scale and approximated using a monotone curve. Using known empirical equations ultimate strength and yield strength of the wheel rim depending on the distance from the tread surface were determined. It was determined that the ratio of the obtained values of ultimate strength and yield strength of the rim does not correspond to the ratio of the relevant values obtained experimentally. Using experimental data an additional expression relating the ultimate strength and yield strength for steel grade T was obtained. Finite element model of the wheel-rail system, which takes into account elastic-plastic material properties and contact interaction between wheel and rail, was created. The element size in the area of contact interaction is 0.5 mm, for the rest of the model it ranges from 2 to 15 mm. The entire model contains about 0.5 million nodes. The wheel-rail contact interaction problem considering both homogeneous and heterogeneous mechanical properties of the wheel rim was solved. Figures showing the dependence of equivalent stress, plastic, elastic and full deformation in the rim on the distance from the rolling surface are plotted. It is shown that heterogeneous properties are worth considering only in the aim of very accurate determination of the stress-strain state of the system wheel-rail in the contact zone.

The article is devoted to an actual problem associated with the study of the morphology of nonmetallic inclusions (HB) located in the working surface layer at the surface layer of the modification of the plasma jet energy. We investigate the condition of non-metallic inclusions before and after plasma treatment methods of quantitative metallography and fractal parameterization, as well as the redistribution of non-metallic inclusions on the area of the plasma exposure. Quantitative metallographic analysis was performed on an automated complex image analysis and modeling of structures Videotest metal. For the study of phase formation during plasma processing implemented cellular variant of fractal algorithm using Mathcad, MATLAB software. stress distribution model in a metal matrix with inclusions developed in COMSOLMultiphysic program. Fixed a significant difference between the volume fraction of nonmetallic inclusions in the fusion zone and heat zone at the plasma-treated steel 16G2AF. 100% of the investigated samples overheating zone the total amount of non-metallic inclusions is 20-30% higher than the number of inclusions in the melting zone, and this difference increases with increasing heat input. It is found that by changing the polarity of the direct plasma treatment to increase the reverse volume fraction of inclusions observed in the melting zone, and the overheating zone. The use of nitrogen as a protective gas during plasma processing of steel results in the formation of a structure with a uniform distribution of nonmetallic inclusions, welding, obtained using carbon dioxide as the shielding have a structure with a fractal dimension of the inclusions is 20% less in every comparable area, indicating that less a uniform distribution of inclusions. reflow zones for all samples are characterized by small values of the fractal dimension, regardless of the type of shielding gas. Assess the level of stresses near the non-metallic inclusions, which occurs in the metal matrix during deformation. It was found that the non-metallic inclusions larger than 10 microns may yavlyatsya severe stress concentrators - the stress level near an inclusion can exceed the yield strength of steel, and even as high tensile strength.

On the induction high-speed hardening dilatometer various modes of heat treatment of the alloy containing 0,29% of carbon and also chrome, manganese, silicon, molybdenum, vanadium are carried out. As a result of the analysis of dilatometric curves thermokinetic and isothermal diagrams of undercooled austenite decay are constructed. In article the microstructure of sparingly alloyed steel depending on the speed of continuous cooling from temperature of an austenitization and temperature of isothermal holding is analyzed. Comparison of a microstructure of alloy with values of the general microhardness when loading 100 grams on not etched microslice is given. The quantity of various microconstituents at continuous cooling and austempering is counted on dilatometric curves. Critical points of alloy which need to be known for purpose of more exact temperature of heating under quenching for obtaining the required mechanical properties are defined. It is revealed that in the process of three-hour isothermal holding bainitic transformation completely comes to an end, and the remained austenite quantity at further cooling either undergoes martensitic transformation or remains invariable. On the basis of the conducted research some assumptions that for obtaining maximum quantity of bainitic phase (or carbide-free bainite) necessary to apply isothermal holding slightly lower than temperature the beginning of martensitic transformation are made. The maximum strengthening characteristics can be received at a temperature of an isothermal holding, which is closest to temperature of the end of martensitic transformation as hardness of bainite in this case is maximum and the greatest quantity of a lath martensite is formed. Special attention is paid stability of retained austenite. After continuous cooling and austempering the quantity of austenite is insignificant that is confirmed by microstructure pictures.

Friction properties of antifriction polymeric materials were obtained through a series of experiments, which were carried out in Institute of Continuous Media Mechanics of the Ural Branch of Russian Academy of Sciences Professor A.A. Adamov. Numerical experiment program was based on the results of experiments to study the effect of frictional properties on the parameters of contact spherical bearing with a layer of modified PTFE. Two variants contact interaction of spherical bearing elements with an anti-friction layer are considered: without lubricant and with lubricant. The mathematical problem statement of contact interaction of elastic bodies through antifriction layertaking into account the friction on mating surfaces have been made through the work. The friction coefficient depends on load and decreases as the load increases, based on the results of experiments. The influence of the friction coefficient on the contact parameters spherical bearing with a antifriction interlayer of modified PTFE in axisymmetric investigated. Two variants of contact interaction is considered: without lubricant and with lubricant. The seven of options relations load- friction coefficient is considered for each contact options. The distribution of the relative contact pressure and the relative contact tangential stress is analyzed and the influence the frictional properties of the modified PTFE for all contact options investigated in the framework of a numerical experiment. The qualitative and quantitative changes in patterns the contact parameters identified. Dependence of the maximal values of parameters the contact zone on load quantity and friction coefficient were obtained. The trend of reducing adhesion area contact surface has been registered with increasing load and decreasing the friction coefficient.

In case of development of mathematical models of the flow and heat exchange polymeric materials in the various channels, including the channel forming tool it is necessary to set the rheological characteristics of the polymers investigated. However, in some cases it is difficult to determine the properties, since the material properties are not determined, for example, graft polyethylene, because grafting takes place directly in the channel of the extruder. The paper has been considered the problem of numerical and experimental determination of rheological properties of polymeric materials. The experiments have been performed for the three extruders used for the simultaneous creation of three-layered cable insulation. As a result of the experiment were obtained by the value of the pressure in the channels, temperature, time and mass of the materials, used the last to determine the flow rate of materials for the three extruders. In this investigation was used a properties of three materials for creation insulations of cable. The Polyethylene Borealis LE 0592 was used for shield 1 (channel 1), Borealis LE 4205 for insulation (channel 2) and Borealis LE 0505 for shield 2 (Channel 3). The experimental results were taken as input for mathematical modeling processes of flow and heat transfer in the channels investigated extruders. A developed three-dimensional mathematical model of heat and mass transfer has been realized by using the finite element method in ANSYS software package. During the numerical research have been defined rheological characteristics that are included in the power law, and the temperature coefficient. The effect of each of the parameters on the material consumption for each of extruders was estimated. The conclusion about the significant influence of parameter anomalies and the initial viscosity for flow rate, and the small effect of the temperature coefficient for the considered flow regimes was made. The consumables-pressure characteristics of the cable heads on the basis of numerical and experimental investigations have been built, the comparison of which was showed a good consistency of the results.

The paper presents recommendations for the implementation of final qualifying work towards a Master 22.04.01 “Materials Science and Technology of Materials”. It substantiates the importance of the student's ability to work independently. Modern approach to the work is that it is carried out on the basis of a systematic analysis of the set of research topics. And it must be done comprehensively, taking into account technological, economic and environmental factors. The role of the scientific director is in education a student abilities, based on the formed competences. These are: to conduct independent scientific research, formulate and solve professional problems, professionally express the specific information, to argue and defend their science point of view. The work addresses the following learning objectives: a) forming the skills of planning and carrying out scientific research; b) forming the skills of scientific information processing, analysis, interpretation and argumentation of the results of the study; c) develop the ability to apply the acquired knowledge in solving of tasks in the direction of the preparation; d) develop the ability to develop scientific recommendations and suggestions. The scientific director of the student is assigned from the department and oversees the work were done in time. To students are assigned counselors, who supervise the work on individual parts of the project (research, technology development, design, feasibility study for construction, heat treatment technology, etc.). The consultants are teachers of other departments, specialists of different enterprises and research institutes, post-graduate students. Final work is done in factories, research institutes or laboratories of the department. And he must comply with safety regulations and internal regulations of the organization, where does the job.