Introduction. One of the urgent tasks facing the developers of land transport and technological machines is to reduce the vibration effects on the human operator. Vibration impacts are caused mainly by the interaction of the working bodies with the working environment and the running equipment of machines with the microrelief of the supporting surface on which the machine moves. To reduce vibration impacts, vibration protection systems of the cab and operator’s seat are used. The designs of vibration protection systems of seats with the effect of quasizero stiffness are promising. The design of a passive vibration protection system of an operator’s seat based on a parallelogram mechanism, which makes it possible to provide the specified effect of quasi-zero stiffness, is proposed. For practical application of the developed vibration protection system of a seat, it is necessary to solve the problem of assignment and optimization of its main design parameters.

Materials and methods. RMS vertical acceleration of a seat in a stationary coordinate system was taken as the target function for optimizing the design parameters of the vibration protection system of a seat. For the developed calculation scheme of the seat vibration protection system based on a parallelogram mechanism, independent design parameters that influence the mean square vertical acceleration of the seat were identified. To reduce the dimensionality of the problem, some of the parameters were bound by algebraic dependencies, or fixed. The need to reduce the number of independent varying parameters was due to the relatively long simulation time of the individual process of moving the machine along the microrelief of the supporting surface using the developed complex simulation mathematical model of a motor grader with vibration-proof supports of the operator’s cabin and with a vibration-proof mechanism of the operator’s seat. The horizontal length of the parallelogram link, the ductility factor of the damper mechanism, and the horizontal dimension from the rotation axis to the limiting rollers of the mechanism were selected as independent.

Results. A methodology for selecting and optimizing the design parameters of the vibration protection mechanism, presented in the form of a flowchart, which includes the stage of local optimization of the viscosity factor of the damper and the horizontal dimension from the axis to the limiting rollers by the Simplex method, has been developed. Obtaining each individual value of the target function in the local optimization was performed by processing the results of discrete values of seat acceleration obtained by simulating the movement of the machine on a simulation mathematical model. Examples of the application of the developed technique with different sets of initial data are given.

Discussion and conclusions: The application of the developed technique makes it possible to unambiguously determine the values of design parameters of the vibration protection system based on the parallelogram mechanism, including geometric dimensions, the viscosity factor of the damper, as well as, as secondary output parameters, the stiffness and dimensions of the tensile spring of the mechanism.

Introduction. The problem of accelerating and cheapening the construction of roads without reducing their quality can be solved by creating a complex of continuous units. Units, following each other, carry out the whole complex of works aimed at roads construction. One of the elements of the continuous unit that forms the ditch is a straight-flow rotary ripper. It was found that in order to excavate the soil near the axis of rotation of the rotor of a straight-flow rotary ripper, a small rotor with a higher angular velocity should be installed, coaxially with a large rotor. The use of straight-flow rotary rippers for soil development is constrained by insufficient theoretical substantiation of their parameters. Before analysing the interaction of the elements of the working bodies of the straight-flow rotary ripper with the soil, it is necessary to clarify the structural layout of the small rotor.

The method of research. The small rotor should contain two knives connected at the periphery by a disc to give rigidity to the knives; the cross-section of the knives is triangular with a sharpening angle of 20 °, for maximum transformation of the angle of sharpening, the knives must have a saber-shaped shape; two teeth located on the disk to loosen the soil and shift it towards the knives; a shaft tip of the small rotor, the diameter of which must exceed the width of the knife at the point of its connection with the shaft tip; a spiral knife at the end of the shaft tip to loosen the soil and shift it towards the knives. By constructing projections on the transverse-vertical plane of the blade of the knife, the tooth and the disc of the small rotor, when there is a different angle of deviation of the blade in the cutting plane, it is possible to identify the basic geometric parameters of the elements of the small rotor of the straight-flow rotary ripper. Applying the well-known formulas of theoretical mechanics, we will determine the angular velocity of the small rotor and other kinematic parameters.

Results. Based on the method of constructing a projection on the transverse-vertical plane of the blade of a knife, a tooth and a disc of a small rotor, when there is a different angle of deviation of the blade in the cutting plane, the main geometric parameters of the elements of the small rotor of a straight-flow rotary ripper are revealed. According to the formulas of theoretical mechanics, the following are determined: the circumferential velocity of the point on the surface of the shaft, the angular velocity of the small rotor, the time of one revolution of the small rotor, the path of the unit for one revolution of the small rotor. The dependence of the radius of the point on the blade of the knife of the small rotor on the angle of rotation of the beam is constructed and approximated.

Conclusion. By constructing projections on the transverse-vertical plane of the knife blade at different angles  of deflection of the blade in the cutting plane the optimal shape of the knife blade has been determined, the transformation of the angle of sharpening of the blade depending on the angle of deviation of the cutting plane from the plane perpendicular to the blade, the front, back corner of the knife blade, the profile of the blade of the small rotor knife in space was revealed, a structural layout of the small rotor was made, the circumferential velocity of the point on the surface of the shaft, the angular velocity of the small rotor, the time of one revolution of the small rotor, the path of the unit for one revolution of the small rotor are calculated.

Introduction. This article presents the results of a study of the wear out effect the carbide tip for the cutting element of a milling machine on the resulting cutting strength when milling asphalt concrete. The relevance of the work is due to insufficient information about the wear out effect on the strength of cutting resistance, and, consequently, it is not possible to predict changes in loads on the working body of milling machines during its operation with worn cutting elements.

Materials and methods. The experimental studies to determine the cutting resistance force that occurs during the milling of asphalt concrete with a maximum mineral aggregate size of 16 mm. used for the top layer of the coating and for roads with normal traffic conditions (A16vn), depending on the thickness of the chip being cut and the degree (percentage) of wear of the cutting element were carried out. To conduct the study, a pendulum stand, which is most suitable for studying the interaction of a single cutting element of a road milling cutter with asphalt concrete, was used.

Results. As a result of experimental studies, it was possible to obtain the data allowing a reasonable approach to the choice of the interval of replacement of cutting elements during the operation of milling equipment, which, in future, will lead to an increase in the productivity of equipment and its service life. The achieved results make it possible to adjust previously obtained mathematical models and calculation methods of milling machines, taking into account the degree (percentage) of wear of cutting elements.

Discussion and conclusions. The conducted studies make possible to determine the dependence of the cutting strength on the percentage of wear of the cutting element and the thickness of the chip being cut. At the same time, it can be concluded that in practice it is necessary to set additional safety margins when designing elements of a milling machine, taking into account the wear of the cutting element.

Introduction. The formation of a ‘cargo frame’ around large cities leads to a change in the composition of the traffic flow on bypass roads, and an increase in the total traffic flow of trucks of various categories. In addition, the active development of suburban areas with residential complexes contributes to an increase in traffic. The totality of the reflected phenomena leads to the emergence of a certain kind of transport problems, primarily associated with a decrease in throughput. Quite often, such problems are observed at regulated intersections, which requires a prompt change in the control mode; for this, the necessary measure is the mandatory consideration of the technical and dynamic parameters of trucks, which are not fully taken into account in the existing reduction factors. In order to establish the degree of influence of these parameters on the change in the main characteristics of the traffic flow, such as the average travel time and average speed, this study was carried out.

Methods and materials. When performing the study, the methods of natural observation, statistical analysis and modelling were applied. The necessary materials for the study were devices for automatic collection of traffic flow characteristics, such as video cameras and traffic detectors, Any Logic version 8.0 for modelling, and a package of descriptive statistics in MS Excel.

Results. In the course of the study and the experiment, a difference in the main characteristics of the traffic flow when using standard reduction factors and without using them, taking into account the dynamic and technical parameters of trucks was established. At the object of the study, the difference in the value of the average travel time () for various methods of accounting for trucks, observed in the range [-51.5%; 16.8%] and average speed () in the range [20%; 34%] was determined. As a result of mathematical research, functional relationships between the average speed and traffic intensity are determined, taking into account the presence of trucks of various categories, their technical and dynamic parameters. The ways of further research are determined.

Introduction. Malfunctions of the elements of the fuel injection system lead to a deterioration in the performance of diesel engines. The largest proportion of faults that occur during the operation of battery injection systems are electro-hydraulic injectors. For the timely detection of malfunctions, the injectors are diagnosed. The most accurate determination of the technical condition of the injectors can be made using specialized diagnostic stands with their removal from the engine. As a rule, the diagnosis is a conclusion about the general technical condition of the injector. To ensure high quality and reduce the complexity of repairs, it is necessary to use new methods and tools that allow for in-depth diagnostics of injectors with the identification of specific defects. The purpose of the presented work is to identify possible differences in the change in the set of diagnostic parameters when changing individual structural parameters in order to be able to determine specific defects in injectors during their diagnosis.

Materials and methods. The hydrodynamic processes occurring in the electro-hydraulic injector during its operation were described by a system of differential equations of the first order. Numerical experiments were carried out to study the influence of changes in structural parameters on diagnostic parameters. The calculations using the software environment for mathematical calculations Mathcad were carried out. The calculations at different combinations of pressures in the fuel accumulator and the duration of the control pulse corresponding to certain engine operating modes were carried out.

Results. The paper presents the graphs of the dependences of the cyclic supply, the average fuel consumption in the drain line, the delay in the start of the needle lift, the duration of the needle lift and landing, the duration of the injection and the sensitivity of these diagnostic parameters on the gaps in the interfaces ‘needle guide spray body’, ‘plunger multiplier – sleeve’, from the magnitude of the leakage of the control valve.

Discussion and conclusion. As a result of numerical experiments, differences in the change in the set of diagnostic parameters with a change in individual structural parameters were found.

Introduction. During the combustion of diesel fuel in a diesel engine with an increased fuel supply, as a result of its incomplete combustion, soot particles are formed, which are either released into the atmosphere or inevitably enter the engine oil. Soot, polluting the engine oil, causes a change in its quality indicators. Soot is very small particles formed by a complex reaction mechanism in the flame of a fuel-rich region during the combustion of hydrocarbons in the absence of air, mainly consisting of a mixture of amorphous carbon and organic matter.

Materials and methods. This paper presents the results of a literary review aimed at studying the ways of soot occurrence during the operation of diesel engines, its effect. The mechanical properties of diesel soot are also discussed on the surfaces of friction pairs and engine components.

Conclusions. The soot content in engine oil will increase sharply in engines with exhaust gas recirculation, which leads to an increase in temperature in the friction zones and viscosity of the lubricant, as well as to the formation of deposits on hot parts. These processes occur due to the discharge in the crankcase space and the intensification of the intake of gases from the combustion chamber. Oil change intervals should be monitored at an increased rate of soot entering the engine oil.

Scope of the study / opportunity. This type of study will help determine the causes of soot in a diesel engine, understand the consequences of using engine oil contaminated with soot particles.

Originality / value. The conducted research can be the basis for the development of recommendations for improving the maintenance of internal combustion engines for enterprises that have cars with diesel engines at their disposal in order to increase the resource of power units and reduce operating costs.

Introduction. The technological process of restoring a part should provide more than 80% of the resource and no more than 50% of the cost of a new part. The wear resistance of the applied coating determines the resource of the restored part operating under waterjet and boundary friction. The microhardness of an iron-based electrolytic coating is one of the key indicators of wear resistance. The study of the results of statistical processing and the factors most affecting the increase in the microhardness of the iron-based coating will make it possible to recommend and optimize the deposition conditions for obtaining the most wear-resistant coatings.

Materials and methods. The studies on equipment that let to obtain the necessary data with the required accuracy were carried out. The mathematical processing using modern statistical data processing tools that excluded possible errors, let to obtain the dependence of factors with the necessary accuracy was carried out.

Results. During the study of the developed sulfate-chloride electrolyte for the deposition of an iron–chromium coating, it became necessary to determine the effect of deposition conditions – ‘factors’ (temperature, acidity of the electrolyte, cathode current density) on the microhardness of the coating – ‘response’. It was found that the combination of the factors ‘temperature’ and ‘cathode current density’ in the coded values of 1.5. 2.0 and -2 are the most significant. The deposition conditions in order to obtain a coating with maximum microhardness are optimized.

Discussion and conclusions. As a result of the conducted studies for the effect of the deposition conditions  of the Fe-Cr alloy from the sulfate-chloride electrolyte on the microhardness of the coating, it was found that in order to obtain high-quality coatings of the iron-chromium alloy with high microhardness, it is necessary to strictly comply with the requirements of the deposition conditions and acidity to a greater extent. As the current density and temperature of the electrolyte, compared with the acidity of the electrolyte, iron baths are installed and regulated by equipment.

Introduction. This article discusses the technology of designing asphalt concrete pavements, using the Superpave method. The Superpave (SUperior PERforming Asphalt PAVEments) system was developed by the Strategic Highway Research Program (SHRP) in the USA. The aim of the program was to find new ways of designing asphalt concrete pavements that will work better at extreme temperatures and heavy traffic loads.

Currently, the system of volumetric design of asphalt concrete mixtures is being actively implemented in Russian road construction industry. This is an adaptation of the American Superpave method and is being implemented in our country in the form of a series of new standards. The Superpave volumetric and functional design system in particular addresses several pavement-related problems: permanent deformation, which results from poor asphalt mix shear strength at high temperatures, and low temperature damage, which occurs when the asphalt pavement is subjected to stress exceeding the compressive and tensile strength. The elimination of the above problems is carried out due to the most reasonable selection of the components of the asphalt concrete mixture.

Materials and methods. Studies of bitumen binders were carried out according to the methods laid down in the technical requirements: GOST R 58400.1-2019 Public roads. Materials binding petroleum bitumen. Technical requirements taking into account the temperature ranges of operation.

The selection of the PG brand of bitumen binder using Superpave technology was carried out using the example of a polymer-bitumen binder that meets the requirements of GOST 52056-2003 PBB 90 (sample 4) and a bitumen binder obtained from tar with the addition of thermoplastic elastomer (hereinafter referred to as TEP) of the SBS type that meets the requirements of GOST 52056-2003 PBB 90 (sample 3).

Results. The article provides a review of technical documentation in order to familiarize with the methodology for selecting the brand of bituminous binder for asphalt mix. In the course of the research, the technological features of the system of volumetric functional design of the asphalt concrete mixture according to the Superpave method, as well as the determination of the brand of bituminous binder, were considered. The introduction of foreign experience in road construction can contribute to the improvement and improvement of the quality of Russian roads.

Discussion and conclusions. Based on the experimental data carried out in the work, it can be concluded that the goal has been achieved, namely, the brands of bitumen binder have been selected using Superpave technology that meet the requirements of GOST R 58400.1–2019 and GOST R 58400.2-2019, namely for polymer-bitumen binder (PBB 90 according to GOST 52056-2003) – PG 58-28, and on the basis of tar with the addition of SBS – PG 64-28 grade TEP, respectively.

Having studied the physical and chemical characteristics of the initial reagents, as well as the results of numerous chemical experiments, brands of PG bitumen binders were selected using Superpave technology and depending on climatic conditions and transport loads GOST R 58400.1-2019 Public roads. Materials binding petroleum bitumen. Technical requirements taking into account the temperature ranges of operation and GOST R 58400.22019 Public roads. Materials binding petroleum bitumen. Technical requirements taking into account the levels of operational transport loads.