Plasma spraying is one of the most effective methods allowing both to restore worn surfaces of parts and create wearresistant coatings on new parts aiming the increase of their service life. Properties of the produced coatings depend on number of parameters, such as a plasma temperature, a chemical and fractional composition of the sprayed mixture, a distance from a plasma torch to the surface of a part, etc. Mathematical modeling of the process can significantly reduce the cost of processing of technological modes and is widely used at present for a calculation of technological parameters. The paper is devoted to mathematical simulation aiming to determine an effect of the injected ceramics content on the change in a temperature of a particles flow, as well as finding the modes in which the particles of high-temperature ceramics will be in the liquid state when they are deposited on the surface of a product. A mathematical model of particles heating in plasma has been formulated and a system of equations has been compiled. The system of equations has been solved numerically in Mathcad by a standard procedure using the Rkadapt function. Calculations have been carried out for a volume concentration of Al2O3 ceramics in a mixture from 5 to 50 % and for a plasma temperature at the exit from the plasma torch in the range from 6000 to 10000 K. Calculations have shown that the concentration of ceramics does not significantly affect the temperature of a mixture. The temperature of the particles depends to a large extent on the temperature of the plasma and the diameter of particles. It has been determined that for the entire range of calculated values the temperature of the self-fluxing powder in contact with the substrate exceeds a melting point. Fractional particle size has a strong effect on the temperature of particles at the moment of contact with the substrate. The dependences of a temperature of the ceramic phase on the particle size at different concentrations and plasma temperature have been determined. Analysis of the coatings microstructures has shown a good correlation with the results of the calculation.

The paper presents investigations on studying the influence of plasma jet parameters (current, sputtering distance, consumption of nitrogen plasma forming gas), fractional composition of an initial powder on characteristics of plasma powder coatings from ceramics with a non-equilibrium structure. Optimization of APS parameters (plasma spraying in air) has been carried out for the following materials: NiAl, Al₂O₃–Cr₂O–TiO₂ – 15 % (CaF₂–Ni) and FeCr30Mo3 – 12 % CaF₂ – 50 % TiC. The optimization of sputtering parameters has been made on the basis of obtaining maximum coefficient of the material use. Structure of coatings, their chemical and phase compositions have a determining effect on physical and mechanical properties of the coatings, in particular, on porosity, adhesion strength and wear resistance. In its turn, a structure and a composition of the coating formed on the substrate depend on energy characteristics of the plasma sputtering process, an efficiency of heat exchange processes between dispersed and gas phases of high-temperature plasma jet, and also on a composition, a structure, and properties of the used materials. Thus, a stable distribution of a solid oxide phase has been observed in the volumes of sputtered materials and there are no surface zones with a deficiency of such inclusions that positively affects operability of the investigated wear-resistant coatings. While carrying out plasma deposition of Al₂O₃–Cr₂O–TiO₂ – 15 % (CaF₂-Ni) powders, a coating with a higher micro-hardness has been formed in comparison with Al₂O₃–Cr₂O–TiO₂ – 15 % (MoS₂–Ni) powders that is due to a decrease in porosity and an increase in uniformity of coatings. Graininess of the coatings exerts a significant influence on density of coatings, nature of phase distribution and strength characteristics (wear resistance and adhesion strength).

The paper is devoted to a physical modeling of the process pertaining to interaction of the machined material with metal deposits along a hole edge which are obtained on a smooth tool surface due to its electro-erosion modification. A technique for obtaining single holes on a cutting tool (strip) is given in the paper. The paper describes main geometric elements which have obtained due to the action of a single electric discharge. Geometric parameters of a single hole initiated on a working strip surface in the course of this effect have been given in the paper. The paper provides a justification and description of a tape tool prototype used in the investigations brass band strips, on which a washer with different rounding radius of an outer edge is fixed. The prototype makes it possible to simulate metal deposits on the modified working surface of the strips. The paper presents methodology for carrying out experiments on investigations for interaction of the created strip prototype with a processed material, including a description of a device for studying the process of washer interaction with the samples from paraffin and gypsum. Photographs are given that allow to visualize a destruction process of samples which is caused by a washer (model of metal deposits). The paper shows stages of sample fracture when using washers with different rounding radius and describes nature of the destruction for various sample materials. The results of the conducted studies reflecting an influence of the shape of an outer washer edge, in particular a radius of its rounding, on the course of characteristic stages in the process of destruction of samples from paraffin and gypsum are presented and discussed in the paper. It has been experimentally confirmed that metal deposits which are formed at the hole edge and extend beyond an initial surface contour, represent cutting-deforming elements with a capability to destroy material which ranks below in hardness to metal of the deposits.

Milling picks for road milling machine are considered as equipment which must meet the most stringent requirements associated with fatigue and static strength. Therefore, majority of modern milling picks are manufactured while using high-quality steels alloyed with manganese and chromium. In order to extend service life of the picks for the road milling machine they are supplemented with carbide inserts soldered to the head. In this connection, an application of high-speed hot extrusion technology which has already proved itself in a number of investigations as a highly efficient technology for obtaining precise billets for tools with increased mechanical properties, manufacture of road milling picks, is a very promising direction of the research. The aim of the research is to create a computer model for high-speed hot extrusion in order to intensify a process pertaining to development of technology for manufacturing bimetal picks for road milling machines and to compare the obtained results of modeling and experimental studies. A comparative analysis of the plastic flow in real and model samples has shown that the obtained models provide a qualitative and reliable picture of the plastic flow in the process of highspeed hot extrusion. Modeling in DEFORM-3D eliminates complicated calculations and significantly reduces a number of experimental studies while developing new technological processes.

A mathematical modeling of geometric and kinematic relations has been made in respect of an operational zone for one of the standard machine tool sections which is used for simultaneous double-sided abrasive processing of highly-accurate lenses with a small rigidity (with a thin centre) under free lapping conditions. An analytical expression has been obtained for calculation of a sliding velocity in an arbitrarily selected point either on a surface to be processed or on a processing surface. As the proposed technology for simultaneous double-sided processing presupposes oscillatory motion of only processing tools then in order to eliminate a joint opening (a local contact fault between lapping surfaces of a tool and a work-piece) length of a drive piece must be not less than a specified value. In this case a convex tool is rigidly connected with a drive piece and it makes a reversing rotary motion (an oscillatory motion) around a centre of the processed spherical surface and a hinged joint of the centre with an output element of the technological equipment actuation mechanism is realized by transition of the drive piece ball end with a spherical seat in the output unit. In order to reveal analytical dependence of tool drive piece length on radius value of the processed spherical lens surface and friction coefficient in the contact zone of the tool and a work-piece the paper has considered a flow pattern of force while processing concave surfaces of lenses having small radius of curvature in case when the tool is positioned at the top. The friction coefficient included in the obtained expression has been determined for grinding while using suspensions of М40, М28, М10 micro-powders in a cast-iron grinding instrument and polishing while using polyrhythm suspension in a pitch and urethane-foam polisher. A method of the inclined plane has been used in this case and following the method a work-piece of optical glass has been initially lapped to the tool with the help of the appropriate abrasive suspension and the required angle has been determined at the moment when the work-piece started its sliding movement along the tool surface.

Titanium and niobium alloys are widely used at present in aircraft, nuclear energy, microwave technology, space and ultrasonic technology, as well as in manufacture of medical products. In most cases production technology of such products involves an implementation of a quality polishing surface. Mechanical and electrochemical methods are conventionally used for polishing products made of titanium and niobium alloys. Disadvantages of mechanical methods are low productivity, susceptibility to introduction of foreign particles, difficulties in processing complex geometric shapes. These materials are hard-to-machine for electrochemical technologies and processes of their polishing require the use of toxic electrolytes. Traditionally, electrochemical polishing of titanium and niobium alloys is carried out in acid electrolytes consisting of toxic hydrofluoric (20–25 %), sulfuric nitric and perchloric acids. The disadvantage of such solutions is their high aggressiveness and harmful effects for production personnel and environment. This paper proposes to use fundamentally new developed modes of electrolytic-plasma treatment for electrolyte-plasma polishing and cleaning products of titanium and niobium alloys while using simple electrolyte composition based on an aqueous ammonium fluoride solution providing a significant increase in surface quality that ensures high reflectivity. Due to the use of aqueous electrolyte the technology has a high ecological safety in comparison with traditional electrochemical polishing. The paper presents results of the study pertaining to the effect of titanium and niobium electrolytic-plasma polishing characteristics using the developed mode for productivity, processing efficiency, surface quality, and structure and properties of the surface to be treated. Based on the obtained results, processes of electrolytic-plasma polishing of a number of products made of titanium alloys BT6 (Grade 5), used in medicine and aircraft construction, have been worked out in the paper.

The paper provides substantiation on application of elastic annular concentrators of ultrasonic systems which allows to increase an intensity of tool vibrations. It has been shown that elastic elements are used as resonators and tools in a number of ultrasonic technological systems. However an application of the elastic elements as concentrators of ultrasonic vibrations has been insufficiently studied and requires research and development of recommendations for usage. For this purpose theoretical studies have been carried out and they have helped to perform modal and harmonic analysis of several variants for a computer model of a ring with outer diameter D = 50 mm. Models of rings with various hole sizes from 20 to 40 mm have been analyzed while changing hole axis position relative to ring axis. The paper shows modes of ring flexural vibrations which can be either flat or three-dimensional depending on frequency of forced oscillations. It has been pointed out that an increase in a ring internal diameter is accompanied by higher amplitude of bending oscillations in the thinnest ring section. The same effect is achieved by increasing eccentricity of a hole axis. The paper contains recommendations for determination of rational geometric parameters which allows to increase an oscillation amplitude gain ratio and it is determined as ratio of ring section thickness. It has been established that decrease in section thickness is accompanied by higher number of frequencies for ring resonance oscillations. So, if a concentric ring and a ring with small hole diameter have only one resonance frequency, then thin-walled rings with a variable cross-section have not less than three natural resonance frequencies of oscillations that makes it possible to increase a range of vibration frequencies and technological capabilities of the ultrasonic system. It has been also found that an intensity in fluctuations of the ultrasonic system is increased even more if at the same time a cross-section of a ring with variable stiffness is decreased as along thickness so across the width.

One of the reasons constraining use of a continuously adjustable gear train with compound poly-sector gear wheels in general and its most perspective version that is a planetary continuously adjustable gear train in particular is its design complexity. For example, a complex design of the mechanism for regulation of transmission gear ratio is specified by the use of involute gearing that requires a presence of backlash and bottom clearances for normal functioning and, therefore, autonomous but synchronous movement of a planet gear, as well as sectors of a central gear. In order to simplify the design of especially this mechanism for continuously adjustable gear train the paper justifies a transition to a backlash-free gearing and during this process either a planet gear or sectors of central gear are forcibly moving for regulation of the transmission ratio without losing contact with the mating element. Contact constancy of interacting elements under load is ensured by their force closure which is meant to overcome an action of gearing forces. The paper describes options for implementation of backlash-free gearing as a result of planet gear and central gear force closure, each variant is characterized by selection of active (controlled) and passive (execution of force closure) gear element. In the case of gear transmission with planet pinion coaxial tooth rims it is appropriate to implement a version with involute gearing, passive planet gear and active gear sectors of central gears. In the case of gear transmission with planet pinion opposite tooth rims the most acceptable option is with the cycloidal pin wheel gear, active planet gear and passive gear sectors of central gears. The paper proposes to carry out the force closure for teeth of gear components by means of an elastic element (a spring). A method for determination of parameters for an elastic element has been described depending on a planet gear design and the paper also shows simplification level in the gear design.

The paper provides an analysis for production of four-wheel drive dump trucks with an articulated frame and it also describes a practical experience pertaining to operation of dump trucks as mining automotive transport. Technical characteristics for some models of articulated dump trucks manufactured in Russia and Belarus are presented in the paper. The paper gives examples for transportation of run-of-mine ore at enterprises of Russia and abroad. The attention has been focused on specific features concerning organizational, technological and design decision making while introducing and promoting articulated dump trucks. It has been established that articulated dump trucks make it possible to improve an efficiency of mine development during construction period and when ore mining and processing enterprises are put into operation especially in geographically remote and inaccessible areas. The paper proposes technological solutions allowing to expand the scope of articulated dump truck application at mining enterprises while using them for quarry development excavating deep deposits of solid minerals. It has been revealed that reduction in overburden volume can be achieved by transition from a certain depth to lower capacity dump trucks or special dump trucks operating on elevated slopes of roads. The paper shows that one of perspective directions for development of mining technology on kimberlite deposits is an opening of lower quarry horizons by peripheral road tunnels of spiral shape while using articulated dump trucks. The presented technological solutions require further research and design consideration and study and they will allow to ensure resource efficiency and safety of surface mining while extracting minerals at previously uneconomic ore deposits. In order to realize an import substitution program for four-wheel drive dump trucks with an articulated frame it is necessary to carry out marketing research on potential market for machines of this class required for open-pit mining in order to justify prospects for provision of the Russian production market.

The paper introduces a new notion that is a graph of crossroad transport flows. It has been shown that the given graph serves as a unification of conflict graphs. The paper provides numerical characteristics of graphs on conflict interaction of transport flows in the process of their merging and intersection at crossroads of various configuration. The following construction of the graph has been carried out: merging graphs where their nodes correspond to conflicting flows and their edges indicate what flows enter into a merging conflict between themselves; intersection graphs where graph nodes correspond to conflicting flows and their edges indicate what flows enter into an intersection conflict between themselves. Taking into account the conflict interaction between traffic and pedestrian flows, traffic conditions and traffic trajectories before possible physical interaction the traffic flow graph takes such form which contains complete information about existing conflicts for the required intersection. As a result of the construction in accordance with theoretical aspects of a graph theory and actual interaction of transport and pedestrian flows at intersections, some regularities have been revealed that allow to estimate a danger of any particular intersection within the urban street-road network. The proposals can be identified as hazard markers of an object and that is especially topical with due account of available actual data on driving regimes, traffic light regulation, flow intensity and driving speed (especially single vehicles exceeding permissible driving speed for urban traffic or taking into account local restrictions on certain sections of street-road network) which form a vehicle or pedestrian graph. The proposed approaches can be used to assess quality of road traffic in conflict areas of the street-road network in cities and settlements and public roads as well.

The paper is devoted to a challenging problem of ensuring traffic safety on the sections of a highway vertical curve and it provides an analysis for works concerning design, lay-out and organization of a project roadway. A change in vehicle speed has been analyzed depending on the length of a curve and a maximum longitudinal slope of a project roadway. The paper presents statistical data about accidents in the Republic of Belarus for several years on the sections of curves pertaining to project roadways. Comparative analysis of difference between point marks on a parabola is given in the paper and the parabola is inscribed in the fracture of the project roadway while using two methods. The paper presents the following errors: geodetic measurements in excesses while laying out pavement, elevation points along pavement axis while making road pavement. Emergence of centrifugal force causes a change in shearing and holding forces. Excess of the shearing force on the holding one leads to spontaneous sliding in the direction of a shearing force vector. Technical solutions have been developped on the basis of systematic functional and active deterministic method. The solutions are protected by invention patents of the Republic of Belarus and they ensure safety passages of highway sections with this type of curves in a longitudinal profile. While constructing and accepting a road for operation it is necessary to control references of curve elements in the longitudinal profile according to the results of executive surveys and in case of operation it is necessary to inform a driver about a safety speed for a passage through such sections