Don State Technical University is a modern, rapidly developing research and educational centre of the Southern Russia. It has extensive international links. DSTU graduates technicalists and carries out research in the area of mechanical engineering and metal processing, production machinery and equipment, machine construction and reliability, instrument making and engineering medicine, robotics and mechatronics, standardization and quality management, environmental engineering protection and life safety, vocational education and psychology, economics and management, electronics and system engineering, computer equipment and data systems.

The work objective is to study the formation of orbitally asymptotically stable limit cycles and two-dimensional invariant tori including bifurcations near the attracting sets. The investigators use primarily methods based on the mathematic simulation of the dynamic systems. Some problems of the nonlinear dynamics of the material cutting are considered. A mathematical model of the dynamic system considering the dynamic link formed by the cutting process is offered. Here, the following key features of the dynamic coupling are taken into account: dependence of the cutting forces on the area of a cut-off layer, delay of forces towards the elastic deformation shifts of the tool in relation to the workpiece, restrictions imposed on the tool movements when the back of the instrument is approaching the treated part of the workpiece, forces - cutting velocity relation. The dynamic subsystem of the tool is presented by a linear dynamic system in the plane orthogonal to a cutting surface. Following the research, some guidelines for designing systems with the required stationary manifold in the state space are provided. Importantly, in the neighborhood of equilibrium, various criteria of set causing regular or irregular features of the formed in-cut surface can develop depending on the models interacting under processing.

Exact solutions to two contact problems with unknown contact domains on the elliptic punch penetration in the transversely isotropic elastic half-space are compared. In the first one - a “traditional problem” - the half-space boundary is parallel to the isotropy planes. There can be an axial symmetry case for a circular punch. In the second - a “nontraditional problem” - the half-space boundary is perpendicular to the isotropy planes. Here, the axial symmetry is impossible in principle: even for a circular punch, the contact domain will be elliptical. The contact domains and the forces required for the penetration of the punch at a given value are compared for both problems. The transversely isotropic body model is applicable for describing lots of materials which elastic parameters have been measured in recent decades: composites, ceramics, carbon fiber, graphite-epoxy, glass-epoxy, wood, aged concretes, some metals (titanium, cobalt, zinc), some semiconductors and rocks. They are widely used in the engineering and industry.

The aim is to study the efficiency of numerical models of elastic stress fields in deformed solids. The field point-source method (PSM) designated as the method of fundamental solutions (MFS) in the foreign literature is used when creating these models. The PSM system construction under simulating fields of different physical nature is described. We introduced the concept of a point-source elastic displacement field in the deformed solid. The research is resulted in the developed PSM equations system that can be used for solving various problems in the elasticity theory including the classical first and second boundary value problems solution in the elasticity theory (when either voltage or bias is specified at the boundary), as well as a mixed boundary problem (when displacement is given on one part of the boundary, and voltage - on the other). The properties of PSM in solving standard problems and the Dirichlet problem for a circular domain are studied. The dependences of the numerical solution error on the problem parameters, in particular, on the number of charges that simulate the desired field, on the remoteness of the charges from the boundaries of the solution domain are found. Based on these results, it is concluded that in the numerical solution of the elasticity problems, PSM error decreases with the growth of the number of charges exponentially. This numerical solution property allows in certain cases obtaining the extremely accurate for computing solution with a relative error of the order of 10^-15 that implies the PSM application perspectiveness under the numerical solution of elasticity problems.

The research objective is to study elbow flexion kinematic parameters using the artificial neural networks (ANN). Parameters of the surface electromyogram (sEMG) are used as ANN inputs. The ANN output is kinematic parameters of motion: direction, angular displacement, and angular velocity. The study has involved DSTU students and staff (11 people without pathologies of the musculoskeletal system). The sEMG signals taken from the biceps of each trial subject during no-load elbow bending are registered. During the experiment, shoulder and elbow joints are fixed by the passive exoskeleton. The feature vector for the neural network is formed using methods of the spectral and statistical analysis. The statistical analysis in the time domain includes the determination of the following parameters: dispersion of sEMG amplitude values, arithmetic mean value and mean-square value of sEMG absolute amplitudes, sEMG signal zero crossing rates. In the frequency domain, sEMG signal spectral analysis is performed by Fast Fourier Transform method. The power spectrum and the mean frequency of the power spectrum are determined. Best results of determining the kinematic parameters are obtained when using the mean frequency of the power spectrum and the total integrated sEMG signal power as inputs to the ANN. The ANN is trained by the method of the direct signal propagation and the back propagation of error. The results obtained can be used in the development of the bioelectric control systems for the mechatronic devices.

The heat-flow rate and temperature of the heater are measured at various liquid subcooling boiling points. An experimental plant and the obtained results on the heat energy motion in the superficially boiling binary liquid mixtures are described. The experiments have used a quasi-stationary heating method which allows accurate specifying of the critical heat flux ( q_kr ) and the temperature of the heater ( T_h ). An experimental study of the superficial boiling has determined that the critical heat flux density depends significantly on the liquid subcooling. At the liquid nucleus temperature T_L =30⁰С in the mixture of water- n -butanol, 10% critical heat flux reaches a considerable size of 20.68 MW/m², and at T_L =30⁰С - much less q_kr =2.98 MW/m². This is due to the increase in the temperature drop (∆ Т = T_{h kr} + T_L ) at the moment of q_kr .

The grating optical filters are investigated to determine the degree of impact of the geometric grating parameters on the angular characteristics of the light transmission. The filter consists of a plane-parallel transparent substrate with thin-layer gratings on two surfaces. The gratings are formed by alternating transmitting and absorption bands. The relative position of two gratings provides angular selectivity of the light transmission. A graphic-analytical method is developed to determine the angular characteristic of the filter light transmission in the form of the dependence of the light transmission coefficient on the beams incidence angle. The effect of a filter characteristic angle (this angle determines a shift of the gratings on the input and output surfaces), fringe spacing (fringe spacing on each grating is equal to the total width of two adjacent alternating bands), and fringe ratio (relation of the fringe spacing of the input and output gratings) on the angular characteristics of the light transmission. The filter characteristics in the areas of decreasing and increasing transmittance are equidistant, linear, and symmetrical with respect to the characteristic angles of the filters in the range of the incidence angles from 0° up to 60°. At large incidence angles, equidistance, linearity, and symmetry of the characteristics are violated. The obtained regularities should be considered when determining the geometrical parameters of the filters satisfying the required for the specified glazed construction and the preset angular characteristics of the light transmission. It is advisable to apply the filter in the areas where the light transmission control is needed at the change of the beams incidence angle due to the movement of a light source and/or a glazed object relative to each other, especially in architectural glazing.

The subject of this paper is the Ni-P chemical coatings on steels and alloys. The research goal is to determine the capabilities of improving the quality and performance properties of the coatings under the rapid laser processing. Metal physical research methods - optical and electron-probe microscopy, hardness measurement, X-ray and electron microprobe analysis - are used. Anti-friction properties of the irradiated coatings are determined under testing on the tribometer. The study results have shown that the laser irradiation of chemical coatings can increase the hardness of the steel surface layers, advance the adherence strength of the coating to the steel substrate, lower the friction factor, and enhance the wearability of the coated steels.The results obtained allow reasonably choose modes of laser processing for chemical coatings leading to the consolidation and degassing of the steel surface layers, the increase of the coating adhesion to the substrate, the improvement of the surface morphology, the formation of a relatively perfect texture in the steel surface layers, and to the reduction of the burnout of alloying elements from the surface layers of materials.The studies show that the laser treatment of chemical coatings improves the quality of the surface layers of steels and alloys, increases the strength of coating adhesion to the metal substrate, increases the hardness, decreases the friction factor, and increases the wear resistance of steels with chemical coatings.

The work objective is searching new methods of strengthening processing of the cranked shaft. Modern constructive and processing methods of increasing the durability of the engine cranked shaft are considered. Some features of the key processing methods - nitriding, riveting on, steel shot blasting of fillets - are identified. The main task of the constructive methods to increase strength -crankshaft shaping that provides a more uniform stress distribution on shaft volume - both in the stress concentration zones, and outside them is considered. The required design shapes of the shaft are determined experimentally. New installation diagrams for the strengthening and stabilizing vibrowave and shock-vibrating machining of the engine crankshafts are proposed. It is experimentally established that the shock-vibrating machining allows the following: uniform hardening of the surface layer of all part features; sharp edge finishing and rounding; smooth transitions; avoidance of non-rigid shaft distortion that takes place at the local rolling of large part fillets.

The work objective is to study the effect of the temperature lime burning conditions in a rotary kiln on the quality indices of the industrial lime used in the steelmaking. The methodology for studying the heat transfer conditions and the temperature behavior of the bulk material under the heat passage and temperature-waves propagation in the semibounded space of a rotary kiln is offered. It is shown that a system of equations describing boundary conditions of the limestone heating by the radiant heat flux becomes increasingly complicated in the case of the parallel convective heat transfer. To simplify the calculations, it is suggested to reduce the combined radiant and convective heat transfer to the convective one (in form) using the known criterial dependences. The investigation results of the heat transfer in the ‘flame - limestone’ system with testing apparent and optimum temperatures in the burning zone are presented. The thermal effect in the rotary kiln on the lime quality indices is specified experimentally under the laboratory and plant conditions. Conditioning of the slag adjustment by the lime consumption during the steel electrosmelting in an arc furnace is defined. Conclusions on the effect of the furnace thermal performance on the principle processes of the carbonate raw materials kilning in the industrial lime manufacturing are formulated. The optimal furnace temperature conditions for manufacturing quality lime with more than 90% CaO are specified.

The research objective is to study tribological properties of the lubricating compositions based on the Castrol oil and ZIATIM -201 plastic lubricant modified by the ferromagnetic nanosuspension. A qualitative X-ray phase analysis by the diffractometry method is conducted on the ARL X´TRA computerized system to specify the compound of the synthesized ferromagnetic nanoparticles. An aqueous suspension of ferromagnetic nanoparticles is studied on CPS Disk Centrifuge Model DC24000 to determine the particle sizes. The investigation has been conducted by determining the tribological characteristics using four-ball machine. The preparation of lubricating compositions based on a number of sequence operations - ferromagnetic particles synthesis, their stabilization, and paste concentrate preparation - is described. On the basis of the X-ray data, it is found that the ferromagnetic particles composition corresponds to FeFe₂ O₄ magnetite. The sedimentation analytical data processing has shown the polydisperse nature of the derived magnetite nanoparticles. Based on the tribological studies, the antiwear properties are evaluated in wear scar diameter, the load wear index value is calculated, and the bearing capacity of the lubricant according to the welding load and critical load for the lubricants under study is identified. Thus, it is found that the lubricant compositions with magnetite additives based on ZIATIM -201 plastic lubricant and Castrol oil with magnetite content of 0.1% wt. offer high antiwelding and antiwear properties. Increase in the magnetite content in lubricants leads to the degradation of their antiwear properties.

The research subject is a design process of gas-air system (GAS) of multi-purpose, transport, and high-altitude (including stratospheric) airships. This research objectives are a methodological design support of the new-generation airship GAS; the development of practical recommendations for selecting geometrical and physical parameters of the basic GAS elements. The functionality of the new-type airship GAS is analyzed. The design technique of the multi-purpose, transport, and high-altitude (including stratospheric) airship basic GAS parameters as applied to the adiabatic process of heat exchange of the buoyant gas and air in the airframe with the environment is developed. The algorithm corresponding to the offered technique has been implemented and introduced in the «Aerostatics» block of the updated conceptual software for various types of airships. The algorithm is written in the object-oriented C++ programming. The basic airship GAS parameters depending on their volume, flight altitude, climbing rate, and gas type (air, helium, phlegmatized hydrogen) are studied. The presented table and graphic interpretations of the GAS calculated parameters of the airships of different purpose in a wide range of their dimensions allow develop some practical recommendations for selecting the geometrical and physical parameters of the basic GAS elements. These findings can be used by the aircraft community in developing advanced models of the aeronautic equipment.

The technique of calculating the radial sliding bearings of infinite and finite length running on a double-layer stratified lubricant is presented. The technique is based on the use of the self-simulated variable that allows obtaining the exact self-similar problem solution both in polar and in cylindrical coordinates, as well as the parameter value characterizing the interface of the stratified layers. These tasks are complicated by the simultaneous consideration of the lubricant viscosity-pressure relation, the presence of the friction-adapted supporting profile of the bearing bush, and the effect of the axial lubricant feed in the finite-length bearing. As a result, computational models are obtained for two-layer stratified lubricants the numerical analysis of which allows establishing the impact of variables on the basic bearings performance - components of the bearing capacity vector, friction forces, as well as optimal values of the reference profile parameter, the lubricant supply, and its viscous ratio in the stratified layers.

The process of improving the surface layer quality and service properties of the machine parts in response to the treatment of the surface plastic deformation (SPD) using the dynamic methods is studied. The aim of the work is to improve the efficiency and reliability of the surface layer processing through the use of the adequate theoretical models at the technological design stage. The study results of the effect of the dynamic pressure maintenance methods (PMM) on the part performance properties are analyzed. The dependencies for the determination of the surface roughness and the hardened layer depth are proposed. The flow analysis of the dynamic PMM has shown that despite a large number of the theoretical and experimental studies, the prediction of the residual stresses in the surface layer is quite a challenge. The application of the universal program system ANSYS which is based on the finite element method (FEM) allows to accurately calculate the stress-strain state parameters of the part surface layer after processing. According to the computer simulation results, the residual stress distribution graphs are presented, and the validity of the offered theoretical models is established. The research results can be used to predict the surface layer quality and the part service properties after processing by the dynamic PMM at the technological design stage.

The research objective is to study the correcting capacity of a new soft decoder of Reed-Muller codes. The technique of achieving the goal is an experimental study of the decoder using a specially built simulation model of the antinoise data transfer channel. The model message source and receiver handle the numeric data identified in F₃ field. The communication line of the constructed model produces digital or continuous signals depending on the settings. In the case of continuous signals, two variants of the basic signal distortion and their combinations are considered. Noise immunity of the simulated communication link is provided by using Reed-Muller second-order codes identified over F₃ field, and the new soft-decision decoder for these codes. The results of the simulation experiments show that the decoder under study in both digital and semicontinuous channel allows correcting more errors than it is guaranteed by the minimum code distance. The decoder has proved the most effective in the semicontinuous communication channels. The decoder’s correcting capacity depends heavily on the communication line type and on the signal distortion mode; it is not sensitive to the error location within the codeword. Conclusions are made on the use of the new decoder in the low-rated communication channels to provide noise immunity, and in a number of the cryptographic applications.

The research objective is to develop the technique of assessing a human factor risk in the ‘staff - hoists - production environment’ system. The proposed method allows evaluating the degree of staff training and of the appropriate managerial solutions at the machine-building enterprises operating hoists. Three groups of hazards associated, respectively, with the false staff operation, the hoist state, and the production environment of the machine builder, are considered. An interpretation of the potential adverse event instance (misfortune, incident, accident) is presented. Based on the analysis of the accident investigation reports at the machine-building enterprises operating hoists and on the conducted questionnaire surveys, the specific dangerous actions of the staff and executive officers (managers and expert personnel) are identified and classified. As a result, the matrix is constructed to determine the probability of potential accidents, incidents or misfortunes depending on the frequency of the false staff actions. The study allows drawing the following conclusion. At the machine-building enterprises of the 4th hazard class, it is considered expedient to apply the expert analysis method to assess the organizational human error causes when running the plants with hoists. Under these conditions, the method of risk assessment appears quite simple and effective in terms of the engineering safety analysis.

The aim of this work is to determine strengths and weaknesses of the current management system of a large university as in the case of the Federal State-Funded Educational Institution of Higher Vocational Education “Don State Technical University” (DSTU). The analysis of the appropriate scientific literature, field studies, and the consolidation of the available relevant information on the development of the DSTU management system are used as the research methods. The work undertaken allows getting the full picture of the information campaign features aimed at the engineering education promotion. Its strengths and weaknesses, risks and opportunities are identified. Tools of influence on the target audience are shown. The results of the diagnostics allow describing the problem field of the initial communication situation. At the same time, an important condition for improving information processes is revealed: the communication should not just show the choice advantages, but also raise the subjective safety level under decision making. The performed work leads to the following conclusion. Under current circumstances, the central focus of the management system of the technical university should be the development of new competitive educational services.