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Reinforced concrete structures play a key role in modern infrastructure, however, corrosion of reinforcement poses a serious threat to their durability and safety. In this study, the sensitivity of a portable X-ray fluorescence analyzer (XRF) to corrosion products on the concrete surface is considered. The experiment was conducted using concrete samples containing varying amounts of iron hydroxide. The results showed that the FRA demonstrates high accuracy and reliability in detecting corrosion, which contributes to the improvement of diagnostic methods and maintenance of reinforced concrete structures.

The article discusses the issue of modernizing the blade root cuff attachment of the main rotor blade of a Mi-8 type transport helicopter. Several geometry options were designed and the stress-strain state of various options in a nonlinear formulation under the influence of operational loads was calculated using numerical methods. Conclusions are provided regarding the strength and mass of the blade root cuff attachment options under consideration. The influence of the tightening value of fasteners and the use of adhesive on the stress distribution along the connection is analyzed. Analytical methods were used to determine the optimal dimensions of fastening elements.

Introduction. Large-scale field studies of the destruction of brickwork carried out by the author in many regions of the world showed that the approach to the research of the durability of building ceramics based on the strength parameter and the frost resistance parameter are not indicative. These parameters do not make it possible to obtain a temporary value of the durability of the material, but are just the basis for an expert assessment.Materials and methods. This paper proves the scientific hypothesis put forward by the author that the destruction of brick material in the brickwork of enclosing structures occurs under the influence of chemical corrosion processes. The process of chemical corrosion is described, the results of thermodynamic calculations of chemical processes are briefly presented. A brief description of the methods of studying the durability of the building ceramics material, which have now received the status of standards, is given.Results. The results of laboratory studies of the process of chemical destruction of the building ceramics material, as well as calculations of the durability of the building ceramics material performed on the basis of the developed method of calculating the durability of the material are presented.Conclusions. Based on the developed theoretical justification and laboratory studies of the process of chemical destruction of the wall ceramics material, it is concluded that the created research methodology and calculation method allow to determine the durability of the material at any stage of its operation.

The possibility of applying the method of multistage loading (Lokati) is considered for the calculation and experimental evaluation of the contact endurance limit. The results of applying the Lokati method to determine the median contact endurance limit of specimens made of aluminum alloy Д16 (D16) and 0.45% carbon steel are analyzed. The tests were carried out according to the scheme “shaft — roller” in rolling conditions without slipping. The criteria for reaching the limit state, the parameters of the multistage loading mode were varied. It is shown that the Lokati method and its basis, the hypothesis of linear accumulation of fatigue damage, make it possible to satisfactorily assess the value of the contact endurance limit of the studied materials.

The work is devoted to the search for new materials with high functional characteristics using the Avinit vacuum-plasma technologies developed by us, based on the complex use of coating methods (plasma-chemical CVD, vacuum-plasma PVD (vacuum-arc, magnetron), processes of ion saturation and ion surface treatment), stimulated by non-equilibrium low-temperature plasma. Processes of controlled plasma-chemical synthesis of the formation of multicomponent coatings in "metal-carbon" systems – Avinit coating (TiC, MoC) using vacuum-arc sources of ionized atomic fluxes of titanium and molybdenum in an argon-benzene plasma environment were developed and their characteristics were studied depending on their conditions formation. Metallographic studies confirm the possibility of low-temperature application of high-quality wear-resistant high-hard "metal-carbon" coatings with a hardness of 18,000-30,000 MPa, while ensuring good adhesion to the substrate materials (steel DIN 1.2379) without reducing strength and without deteriorating the cleanliness class of the original surface. The conducted tribological tests using the "cube-roller" scheme reveal high tribological characteristics of steel DIN 1.2379 tribopairs with developed coatings and testify to the promisingness of the developed multi-component multilayer coatings Avinit (Ti-C, MoS) for increasing wear resistance and reducing the coefficient of sliding friction in friction nodes. The developed plasma-chemical vacuum-plasma coatings are applied to mock-up samples of the working compressor blades of the GTE of aircraft engines. Proven modes allow to get high-quality, uniform coatings with high adhesion. This gives reason to consider the developed process as an alternative for expanding the range of new Avinit vacuum-plasma erosion-resistant coatings and developing structures of anti-friction wear-resistant coatings to increase the performance of friction pairs in "coating-steel" and "coating-coating" systems.

The results of the study of non-isothermal mass-exchange processes occurring during liquid corrosion of iron-concrete are presented. The degree of development of this direction of research is shown: the classification of liquid corrosion of concrete is given, the effect of “free calcium hydroxide” on the stability of cement stone minerals is described, the relative change in the strength of concrete depending on the dimensionless concentration of calcium hydroxide is shown. For concrete and reinforced concrete structures subjected to liquid corrosion, the boundary value problem of non-isothermal mass transfer in the “cement concrete - liquid” system is formulated on the basis of a nonlinear differential equation of mass conductivity of a parabolic type with an arbitrary form of the initial concentration distribution function and combined boundary conditions of the first, second and third kind. A combined approach to solving the problem of non-isothermal unsteady mass transfer is proposed, based on the division of the life cycle of a building structure into “micro-processes”, followed by the separation of the thickness of the structure within the considered small time interval into concentration zones. Analytical solutions to the problem of unsteady mass transfer in the processes of liquid corrosion of concrete for each selected concentration zone have been obtained, allowing to calculate the concentrations of the target component in the solid phase, thereby predicting the dynamics and kinetics of destructive processes of cement concretes. Extensive numerical experiments have been carried out showing the effect of process parameters on the dynamics and kinetics of liquid corrosion of reinforced concrete.

Objective. To assess durability of antiretroviral therapy in first line in HIV-infected patients in real clinical practice in the Russian Federation and determine association between basic clinical and demographic characteristics and durability of treatment.Materials and methods. A non-interventional retrospective study was conducted collecting data from primary medical records of HIV-infected patients who signed informed consent form and had started antiretroviral therapy in first line. Patients were enrolled if the third component was a non-nucleoside reverse transcriptase inhibitor (NNRTI) or ritonavir boosted protease inhibitor (PI/r) plus two nucleoside reverse transcriptase inhibitors (NRTIs). Also, patients must have been followed up for at least 96 since start of treatment. Durability of therapy was retrospectively assessed at 48±8 and 96±8.Results. 536 patients were enrolled. Percentage of patients without change of therapy was approximately 76% and 60%, and the mean duration of therapy without changes was approximately 47 and 79 weeks at 48±8 and 96±8 weeks, correspondingly. Durability of treatment was not different for NNRTI+2NRTIs and PI/r+2NRTIs. Only age ≥ 40 years as a basic characteristic was associated with ART change prior to 96 weeks: OR=1.391, 95% CI 1.005-1.925.Conclusions. In real clinical practice in Russia, durability of first-line antiretroviral therapy corresponds published scientific data (in terms of percentage of patients without change of treatment and its duration without change). Durability of treatment and factors associated with its early switch or stop should be investigated in prospective studies further.

The article deals with the issues of increasing the durability of machines and mechanisms at various stages of the product life cycle. The components on which the durability of equipment. The requirements for the anode materials, the composition of the working fluid, the test results for the implementation of the reparation technology are given. The results of the developed and patented technology for increasing the durability of tribosystem parts are presented, new compositions of working fluids are obtained to implement the method of repair and processing of parts at the manufacturing stage, new devices are developed, manufactured and tested under operating conditions that increase the life of parts at various stages of the product life cycle, new stands for testing of developed technologies. The developed methods, arrangements of machine and mechanism units, which allow to implement wear compensation during operation, provide a significant (1,5–3 times) increase in the resource.

An increase in the rate of coal mining and a reduction of its prime cost can be ensured by comprehensive mechanization and automation of the system of mine auxiliary transport through the widespread introduction of overhead monorail tracks. The potential use of mine monorail tracks are conditioned by the following factors: low payload ratio of the train; reduction of the mine workings cross-section area due to transfer of auxiliary transport to the upper part of the workings; high operational safety; as well as the possibility of dismantling the track in the unused sections and subsequently installing it in new mine workings. The use of rubberized rollers in the drives of mine monorail locomotives enables the coefficient of adhesion of the wheel with the monorail to be increased. It also reduces dynamic loads and the noise level during operation. The purpose of this research is to assess the durability of polymeric rims of drive wheels for mine monorail locomotives, taking into account their operating conditions. Stress distribution over the contact area of the wheel rim with the monorail was determined, enabling the development of measures to increase the service life of drive wheels of mine monorail locomotives to be developed. It was established that the effect of the monorail track deformation has no significant impact on the durability of drive wheel rims of mine monorail locomotives. A mathematical model was obtained to determine the durability of drive wheel polymeric rims, taking into account the maximum dynamic forces arising during the contact of drive wheels with the monorail. The durability of wheel polymeric rims of mine monorail locomotives was assessed in accordance with the Bailey criterion with regard to the maximum values of dynamic contact loads arising during the monorail train movement. It was also established that an increase in the carriage mass from 20 to 47 kN leads to 32 % less durability of a monorail locomotive drive wheel rim (from 8700 to 5900 hours).

Background. The XX century has led mankind to solve many new problems, which are characterized by the appearance of structurally and functionally complex systems (SFSS), which required the emergence of tasks to ensure their high reliability and reliability. From the experience of using SFSS for its intended purpose throughout the entire life cycle, by the beginning of the XXI century, a number of important shortcomings were identified: the difference between the actual level of reliability of structural elements and regulatory requirements; calculating the cost of work performed on the SFSS during their operation to ensure resource and reliability; insufficient efficiency of the work performed at the SFSS to ensure resource and reliability; the inability in many cases to correctly diagnose equipment damage during operation; the absence of a single logically sound system of regulatory documents; the lack of a unified scientific methodology for ensuring the strength, resource, reliability and safety of SFSS; the lack of a centralized management system for the quality assurance of SFSS, the negative impact of the human factor. The whole family of factors under study required the application of the fundamentals of the system concept of ensuring high quality of SFSS. This article is devoted to solving a number of the above tasks. Materials and methods. To solve many problems, the authors of the article propose the use of the following approaches and theoretical methods: the integrated use of thermodynamics methods, the operator theory of functional analysis and statistical modeling, the theory of internal time asymmetry of critical SPSS with long periods of active existence. Results and conclusions. New results of the application of modern functional analysis and evaluation of the asymmetry of internal time are obtained.

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ABSTRACT: Introduction. Mineral wool is one of the widely used materials in the construction industry. A wide range of technologies and structures with integrated mineral wool is also connected with the following: ventilated facades of buildings, facades made using FICS (facade insulation composite system) technology, insulation of roofs and attics, and much more. Methods and materials. Under different conditions, the nanostructure durability for mineral wool fibers will vary significantly. Currently, there are no scientifically based methods for assessing the durability of the nanostructure. Results. The article proposes to evaluate the nanostructure durability for the of mineral wool fibers based on the developed method of chemical destruction of building ceramics. The methods of laboratory analysis of the building ceramics material and their modernization for the nanostructure of mineral wool fibers are given. Discussion. According to the results of experimental studies, it was found that the corrosion process in the mineral wool material occurs by the mechanism of reaction of alkali metal hydroxides with silicon and aluminum oxides in the mineral wool material, removing them into solution and leading to chemical destruction of the material, which is generally similar to the studied process of destruction of the wall ceramics material. The results obtained allow us to conclude that the process of chemical destruction of mineral wool has a greater dependence on temperature and less dependence on the concentration of hydroxides than the process of destruction of brick material. Conclusions. The results of the conducted studies allow us to calculate the temperature coefficient of the destruction process rate in the Van't-Hoff formula, the coefficients in the Arrhenius equation and the value of the activation energy of the destruction process. Examples of field studies are given.

ABSTRACT: Introduction. To create concrete with a set of physical and mechanical characteristics, a rational selection of the components of the concrete mix is required, including the use of finely dispersed fillers, including those based on recyclable materials, and a highly effective chemical additive of a certain nature and reactive action, which has a complex effect on concrete system. Methods and materials. The effectiveness of the components in used additive was assessed by changing the indicators of compressive strength, tensile strength in bending, the assessment of which was carried out according to GOST 10180-2012 “Concrete. Methods for determining the strength of control samples. For carrying out scientific and experimental studies, the following materials were used: Portland cement CEM I 42.5N; natural sand; fine microsilica; complex chemical additive with increased plasticizing and reactive effects. Results. The combination of polycarboxylate polymers and nanodispersions of silicon hydroxide enhances the effectiveness of each component, which is reflected in a significant increase in the coefficient of crack resistance of concrete at high compressive strength. It has been established that when using a complex nanopolymer chemical additive, the increase in tensile strength in bending is 67% and it exceeds the increase in compressive strength by more than 30%. Discussion. An increase in hydration activity in the presence of a nanopolymer additive has a positive effect on the compaction of the emerging concrete structure. Confirmation of the formation of a dense and strong structure during the hardening of nanomodified concrete is an increase in the water resistance of concrete by 2.5 times and its frost resistance by more than 2.5 times. Conclusion. The advantage of nanomodified concrete is its increased chemical resistance to carbon dioxide and magnesia corrosion and, in accordance with the index of chemical resistance coefficient, CCSт> 0.8, and GOST R 58895-2020, the developed nanomodified concrete belongs to chemically highly resistant concretes. It is advisable to recommend nanopolymer concrete with high physical and mechanical properties for the manufacture of structures for overhead power transmission lines (OPL).

Problem. The T-156B hinge frame of the loader, which is an upgraded frame of an agricultural tractor, creates loads during work operations for which it was not designed. Such loads lead to breakdowns and further shorten the life of the entire machine. The frame is the basic element around which the machine is built. The loader that had just been removed from the conveyor did not have builtin durability and reliability. While designing a road construction machine, an account of the features, nature, and conditions of its operation should be taken. Goal. The goal is to develop a hinge frame design technique that takes into account the loads experienced by the frame with a virtual simulation of real-world situations during the loader process. Methodology. The adopted approach is based on the use of a Solidworks computer program with three-dimensional modeling and an Ansys motion program for calculating the dynamics of multicomponent bodies taking into account the hinge and contact interaction. Results. In the work three cases of technological operations of the loader were considered. 1. Lifting a full bucket. 2. Collision with an obstacle that is difficult to overcome 3. Movement over an uneven surface with the raised loader arm. The results of the calculations provided forces and torques in the hinge of the half-frames, as well as the effort of the frame. Based on the results obtained, the endurance of the frame in the Ansys motion software package was calculated. Originality. The analysis of load-bearing systems with a virtual simulation of the machine’s actual behavior with the help of Ansys motion software allows to obtain more accurate results, significantly reducing the time for the design and cost of field testing. Practical value. This approach to the analysis of the carrier system behavior can be recommended for designing and determining the technological capabilities of wheeled, tracked, and special machines.

Currently, there are various methods of testing vehicles and its components used by different car manufacturing companies. Also, these methods are given in the UNECE regulatory documents in the field of transport, but these documents do not take into account the separate operating conditions of cars in different regions. In this regard, the paper presents the road and climatic conditions of Central Asia characterized by peculiar characteristics. Based on the climatic features of the operation in a hot region, technical requirements have been developed for electromechanical sensors of cars for operation in hot climatic conditions, which should ensure the reliability of these components when the car runs at least 250,000 km. The method of testing electromechanical sensors of cars has been presented. It is established that in order to ensure the normal operability of sensors operating in hot climates, it is necessary to conduct tests at a nominal ambient temperature 45 ± 5 °C. The test procedure is built based on this parameter. All developed test methods are consistent with current standards in the field of electromagnetic, electromechanical and other electrical parameters of the automotive industry. Schematic diagrams of stands for testing have been given. The paper reflects the methodology of accelerated reliability tests, in which the temperature is set as the accelerating factor. The tests fully reflect the operational characteristics of the movement of cars in a sharply continental climate with a hot slope of ambient temperature with sharp temperature changes. After each test, it is determined that the nominal parameters of the sensors are checked for compliance with the established requirements. Conclusions reflecting the results of the work carried out have been made.

Energy saving, operational reliability of buildings and structures for various purposes is determined by the durability of building materials and products used in their construction. To date, frame building composites have been developed on the basis of polystructural theory. The frame technology for the manufacture of building products consists in the preliminary manufacture of frames from coarse-pored mixtures, followed by filling voids in the hardened frame with a matrix-plasticized binder, fine-dispersed or fine-grained composition, while the frames and matrix can be formed on various binders. This technology makes it possible to obtain building materials and products with a combination of the most diverse and even incompatible binders with a predetermined set of properties, i.e. opens the way to directional materials science. The paper presents the results of theoretical research and calculation of the technological physical and mechanical properties of frame composite building materials. The regularities of the structure formation of frame composites at the level of the formation of frames and matrices, as well as when they are combined, are revealed. It is established that the process of impregnating the frame with a matrix obeys the laws of motion of freely dispersed or connected dispersed systems. Formulas for calculating structural stresses in hardening frame composites are derived. Analytical dependences for calculating the thermal conductivity coefficient of products are obtained from phenomenological positions. Expressions for the calculation of the modulus of elasticity are obtained for models of ordered aggregates and the kinetics of the processes of destruction of frame composites under their loading is shown. Theoretical dependences for calculating the diffusion coefficient in frame composites on the main structure-forming factors are established.

The paper considers a method for justifying the choice of a corrosion-resistant material for the manufacture of a blowout preventer body based on computer simulation of an elastic-plastic task in the ANSYS Mechanical APDL software. To describe the material properties, a multilinear deformation model is used, the reference points of which are calculated as a result of working out the macro developed by the authors based on two models: RambergOsgood and the “method of sequential corrections” proposed by TSAGI specialists. The paper presents the results of computer simulation on the loading of the PShKM-ASMT-114x21 preventer body by working and double starting pressure for four variants of body materials. The calculations confirmed the high safety factor of the body for the currently used 40X steel showed sufficient working capacity of corrosion-resistant steels 20X13 and 30XMA. However, a computer experiment detected very extensive zones and the level of plastic strains as a result of loading the body made of 12X18H10T steel with double starting pressure. The obtained results indicate that the investigated preventer can be manufactured in corrosionresistant versions K1 and K2, but for the execution of K3 it is necessary to develop a fundamentally different geometry of the body.

Introduction. Pressure-operated thick-walled hull structures are the most common type of high-duty welded structures. When these structures are loaded with internal pressure, a complex biaxial stress field arises in them, which is summed up with the fields of residual welding stresses. Therefore, when selecting a technology for manufacturing critical welded structures, the results obtained during conventional uniaxial tests of samples are insufficient. The variety of factors affecting the performance of structures, and the difficulties of separate assessment of their influence, caused the need to maximize the approximation of experimental conditions to the real working conditions of the structure.Materials and Methods. Testing of full-scale structures has a number of advantages, but they are extremely expensive, and, as a rule, only one, the weakest link, is identified, the bearing capacity of the other structural elements remains unclear. For testing, UDI radiometric installations designed for different sample sizes were used. The presented installations allow testing samples of various shapes, types of welded joints (butt, T-bar), changing the position of welded parts.Results. Without rejecting the results obtained during the testing of full-scale structures in the works of the Bauman Moscow State Technical University, DSTU, NRC «Kurchatov Institute» – CRISM «Prometey», and the authors proposed to conduct the basic scope of the research on individual structural elements that would reflect the characteristic features of loading, manufacturing technology, and operating conditions. The design of the «fitting-sheet» connections was applied, which made it possible to increase the indicators of the failure initiation and propagation to the level of the base metal.Discussion and Conclusions. Schemes of structures for obtaining a biaxial tension or bending field in samples were presented. Samples tested according to the proposed schemes allowed us to draw conclusions about the performance of welded joints under conditions close to the actual operation of the structures under study. The proposed test scheme is used by research laboratories in our country and around the world.

The constitutive relations for fiberglass were obtained. New methods were developed to analyze its behavior as microdamage accumulates and under the exposure to an aggressive alkaline environment. A finite element model was built to assess the stress-strain state of a fiberglass panel for predicting its durability in response to stresses and an alkaline environment. The convergence of the solutions was studied depending on the number of finite elements and the time step. The behavior of a fiberglass panel was analyzed with and without considering its deformations. The results show that the damage accumulated in a fiberglass panel must be taken into account to improve its durability.

The calculation scheme of the reel of the combine harvester “Lida-1300” is given. The operating time of the bearing of reel support for service life of the combine, the frictional loads of the bearing and the bending stresses of the shaft are determined. Loading blocks are formed with increasing, decreasing and arbitrarily changing load. The influence of values of the softening parameters α and hardening parameters β, the duration of the loading stage on the calculated wear value and durability is analyzed. It has been established that for unchanged or insignificantly changing values of the parameters α and β, the calculated wear values coincide at the end of the loading block, regardless of the order of loads (increasing, decreasing or arbitrarily changing) and the duration of the loading stage. While with a significant difference between the parameters α and β, the coincidence of the calculated wear values at the end of the loading block appears only for a short duration of the loading stage (approximately two orders of magnitude less than the estimated lifetime). A comparison of the calculated wear kinetic curves is made under regular and irregular loading with an operating time of 2.0·107 cycles.

FEA of stress state for Pisa Tower is accomplished. Imaginary vertical orientation of the tower is simulated as well as its actual leaning position too. Moderate deformational incompatibility between “column drum” and “stem” load-bearing systems is revealed. Twofold overstressing of lower colonnade is found comparatively to the stem surface. Tower’s compressive stress concentrators are described. The inner helical passage into stem causes a periodical stress concentration about 1.5 – 2 times in the passage vicinity. Arch compression concentrator tied to stem – basis transition is revealed. Places for priority monitoring of marble masonry are pointed out.Some methodic experience is gained due to lively and successful student participation in all phases of the Pisa Tower FEM simulation.

Background. The paper discloses sources of the aero engine failures that caused aero accidents or crashes. Also are highlighted the data on sources of the most frequent failures. Materials and methods. On the base of published materials the work disclosed the main sources of failure occurred in operation. The conclusions evaluate and explain specific groups of failures. Results and conclusions. The most usual aero engine failures in operation are human factor and malfunction. The work results may be applied to analysis of specific failures within a set of malfunctions, development of new products and creation of the reliability ensuring programs.

Further improvement of the methodology of maintenance and repair of aviation equipment is possible only if modern non-deformational technologies are widely used to increase and restore the durability of their structural elements, for example, such as processing with pulsating subsonic air flows – gas pulse processing. This article presents the results of the methodology development for using the technologies to increase the durability of the aircraft engine and landing gear system components subject to fatigue destruction, having a significant impact on flight safety, by using a promising technology to enhance the reliability of the parts based on processing by non-stationary subsonic air flows, the results of the development of methods, aimed at improving the efficiency and safety of air transportation by increasing the reliability and service life of structural elements of aircraft, equipment and mechanisms, optimizing the timing of inspections and repairs using the technology to increase and restore the durability by processing with pulsating subsonic gas flows. The results of the research aimed at optimizing the maintenance and repair of aircraft through the use of gas-pulse processing of their structural elements, as well as algorithms for processing cracks in the aircraft structural element in order to prevent its further spread, restoring the mechanical properties of the aircraft structural element that decreased as a result of the impact of non-stationary air flows during operation and processing areas with increased location density in order to prevent the formation of cracks. The results of the development of a methodology for the use of non-deformational strengthening technologies, especially based on pulsating subsonic air flows (gas pulse treatment) in the process of aircraft maintenance and optimization of diagnostics of aviation equipment, considering the influence of media, including non-stationary air flows on the material properties of structural elements.

The article considers a number of new directions in the development of methods and means of experimental mechanics. They are: the unification of test and calculation methods; the development of equipment and test methods in extreme conditions; the widespread use of acoustic emission methods and video recording during testing; the creation and development of equipment and methods for complex testing (for example, wear-fatigue) of materials and products. The achievements of Belarusian scientists are also noted in the field of experimental mechanics of contact interaction, including: an adhesiometer for measuring the molecular interaction of technical surfaces; a millitribometer for measuring friction forces under loads which are characteristic of a precision contact; an onboard tribometer for testing materials for friction and wear in extreme conditions of the action of space factors.

The paper presents the main hypotheses of frost destruction of cement concrete. The influence of cyclic temperature changes and the effect of static and dynamic (shock) loads on concrete on changes in the structure and strength of concreteis considered. The paper provides results of comparative tests of frost resistance of concrete containing a porous additive and a plasticizer, which contribute to an increase in the density and impermeability of its structure. It has been shown experimentally that the introduction of air-entraining additives with an additional effect of hydrophobization is productive from the standpoint of ensuring frost resistance of concrete of relatively low classes (up to C30/37), compressive strength up to 50 MPa and water absorption by mass more than 4.0 %. It is advisable to increase the frost resistance of concrete with greater impermeability and strength by increasing these indicators, in particular, due to the maximum decrease in the initial water content and high-quality compaction. This conclusion is experimentally confirmed by the data presented in the paper, since the “mechanism” of frost destruction of cement concrete is multifactorial, and the growth of its density (impermeability) and strength provide a higher ability to resist “force” effects associated with repeated alternating deformations of concrete, as well as the action of external loads, accumulation of fatigue phenomena, hydrodynamics of liquid filtration under the influence of changing temperature fields, etc. A comparative assessment of concrete frost resistance has been carried out using standardized and patented techniques containing a porous (air-entraining) additive, as well as plasticizing and mineral additives of amorphous micro-silica, introduced into concrete in order to increase its density, impermeability and strength and on this basis – increasing frost resistance. Experimental data are presented, reflecting the relationship and patterns of decrease in frost resistance of concrete subjected to the simultaneous action of static (for compression – different levels from the corresponding indicator of concrete strength) and shock, concentratedly applied dynamic loads. The regularity of the relationship between the accelerated frost destruction of concrete and the action of mechanical loads that cause cracking in its structure has been confirmed.

The article considers the main provisions and equations of the applied theory of inelasticity, which belongs to the class of flow theories under combined hardening. The material functions that close the applied theory of inelasticity are distinguished, and a basic experiment is formulated. The prediction of the material lifetime of structures under non-isothermal cyclic loads is carried out on the basis of the analysis of the durability of the combustion chamber edge of the diesel piston and the uncooled conical nozzle tip during heat changes. Calculated lifetime estimates based on the applied theory of inelasticity are compared with the results of experiments and traditional methods of lifetime estimation. Examples of estimating the lifetime of a structural element of a long-term lifetime power unit are also considered. The loading modes leading to a significant reduction in the lifetime are shown.

The influence of various factors on the workability of critical metallic parts of a gas turbine engine (GTE) is analysed and systematized. As shown, compressor blades fail as a result of foreign-objects’ damage, gas corrosion, and erosion. Compressor blade roots in most cases fail due to fretting wear caused by vibrations, while the fir-tree rim of turbine discs fails due to low-cycle fatigue (LCF) damage and creep. An increase in the radial gaps between the rotor and stator of the turbine reduces the thrust force and causes changes in the gas-dynamic loading of the engine components. Additional oxidation of metal parts is observed under the action of hot gases from the combustion chamber. The principles of material selection for manufacturing turbine blades and disks, concepts of alloying heat-resistant alloys, and modern methods of surface engineering due to applying protective oxidation-resistant coatings, in particular, chemical vapour deposition (CDV), physical vapour deposition (PVD), air plasma spraying (APS), etc., are also described. To predict the lifetime of turbine disks, it is proposed to use the modified Walker model and Miner’s rule. To specify the time before the failure of metal blades of the turbine, it is proposed to use the finite element method. To monitor the working-surfaces’ deformations of the gas turbine engine, it is recommended to use optical-digital methods.

Introduction. In the process of chrome plating of car parts, there is a change in the composition of the chrome plating bath, which affects the stability of the ongoing processes – the performance and quality of the chrome coating. Therefore, it is necessary to constantly monitor the chrome plating bath for the presence of foreign elements that can be formed during the operation of the bath during the reaction of the solution with the anode or cathode.Materials and methods. During the research, the necessary equipment was used, which made it possible to determine with sufficient accuracy the content of trivalent chromium and its effect on the electrolysis process – the performance and quality of chrome coatings. A well-known technique was used to determine the quality and performance.Results. When conducting studies of the obtained cold self-regulating chromium plating electrolyte, it was found that trivalent chromium has a significant effect on the stability of the chromium plating bath. The content of which can vary within 2...25 g/l during operation. As a result, it was found that the optimal amount of trivalent chromium is its content in the chromium plating bath from 2 to 15 g/l. With a lower or higher content, the electrolysis performance and the quality of the chrome coating decrease. It was also found that in order to maintain the optimal amount of trivalent chromium and increase the time for stable operation of the chromium bath, it is necessary to observe the ratio of the area of the anode and cathode (the coated surface of the part), the value of which is within 3...4.Discussion and conclusion. As a result of the conducted research, it will make it possible, under certain conditions, to carry out the process of chromium deposition from a cold self-regulating electrolyte, which will allow for stable chromium deposition at high productivity and the necessary quality of the coatings obtained. The main condition is to control and maintain the amount of trivalent chromium in the chromium plating electrolyte in the bath.

Background. The problem of aging in assessing and analyzing the durability of any living and technical systems has always been and remains a burning one, and medicine and technology in any foreseeable past have tried to find ways and means of solving it. However, no significant progress has yet been made. The most important thing in solving the problem of durability of structurally and functionally complex technical systems (SFTSS) has always been considered to find theoretical and experimental methods for combating aging. So, for SFSTS in the XX century, the methods of the theory of long-term strength have successfully proven themselves. Through the efforts of such outstanding scientists of our country as A. S. Pronikov, V. S. Ivanova, K. V. Frolov, N. L. Makhutov, V.N. Chuveldiev and others, great success has been achieved in the development of approaches to the description of various levels of aging of SFSTS structural materials. Achievements in this area have been implemented in a large number of theoretical methods and state standards. However, the number of defects and failures in SFSTS at various stages of their life cycle continues to be high. This often happens even in such critical systems as space, aviation, transport, oil and gas main pipelines. But there were also pleasant surprises: the development of dynamics and thermodynamics in the 19th and 20th centuries in the works of R. Yu. Clausius, D. W. Gibbs, L. Boltzmann, A. M. Lyapunova, V. I. Vernadsky, A. N. Kolmogorova, I.R. Prigozhin, new ideas were proposed to significantly increase the reliability of calculating the durability indicators (resource, service life and their residual values) of the SFSTS. In this regard, it is impossible not to pay attention to the fact that in our country regularly (with a period of approximately 10–15 years) new state standards for the reliability of complex systems are issued. The purpose of this article is to solve the problems of a comprehensive assessment and analysis of aging in the theory of durability of structural materials of SFSTS equipment elements using methods and models of modern statistical theory of reliability. Materials and methods. Functional Analysis Operator Theory and Statistical Reliability Theory. Results and conclusions. On the basis of modern achievements of statistical methods of the theory of reliability, moreover, new approaches were proposed to describe the levels of aging of structural elements of SFSTS equipment. As a result, a set of methods for assessing and analyzing the effect of aging on durability indicators has been developed, presented in the form of a detailed block diagram.

The work is devoted to development of the method of restoration of worn press tools from 3Kh3M3F steel for extrusion of non-ferrous alloys by mechanized hardfacing with self-shielded flux-cored wire. The advantages and disadvantages of different classes of hardfacing materials are considered and use of 50Kh6V2GSMFA steel is proposed. In the case of hardfacing with selfshielded flux-cored wire the alloying part of this steel provides a higher hardness at high working temperatures of pressing, due to a complex hardening of the martensite matrix with carbides of tungsten, chromium and other elements, as well as additional hardening by vanadium nitride. It allowed increasing the tool life. Moreover, alloying by chromium at the level of 5.5 – 6.0% improved adhesion to the processed metal. Resistance to thermal erosion and thermal fatigue strength of the deposited layer was increased by selection and optimization of gas-slag-forming components. Industrial trails of hardfaced steel 50Kh6V2GSMFA, first applied for restoration and hardening of the hot pressing matrices from 3Kh3M3F steel, were conducted at LLC “ZCM” (city of Bakhmut). Compared to new unsurfaced matrices, those restored by hardfacing demonstrated 2.4…2.5 times higher durability, while working diameter drawdown after 5 pressing cycles decreased three times. Total cost of matrix restoration by surfacing is 1.5 – 20 times lower than that of a new matrix from 3Kh3M3F steel. [ABSTRACT FROM AUTHOR]

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The article studies reliability of technically complicated goods as complex customer characteristics; the most informative indicators, i.e. service life; the dependence of durability on economic characteristics of the product; trends of reducing service life of goods and possible negative economic and ecological after-effects were shown; an attempt was made to compare customer costs on different stages of the product life cycle. The authors provide requirements to manufacturers' responsibility and product sellers concerning warranty periods and service life, service support and repair of technically complicated goods, legal consequences of product breakdown within the frames of warranty periods and service life. Statistics given by Rospotrebnadzor dealing with faulty technically complicated products was analyzed. Summarized information of recommended service life and average amount of work per breakdown fixed in relative inter-state standards was provided. The stated information was compared with figures of durability and reliability in today's practice of manufacturing and selling house-hold electric machines and devices. On the basis of EU guidelines one variant of legal way of resolving the problem of attaining the optimum service life for customers and manufacturers was proposed. The authors give recommendations on fixing obligatory requirements on limiting use of short-life and difficult to utilize materials in details of technically difficult goods.

Introduction. Grinding sugar beet should be carried out with minimal losses in centrifugal beet cutters with specially designed knives that provide frequent and constant chaotic longitudinal-lateral cutting of circular conductive beet knots. The objective of the work is to increase the reliability of the knives of centrifugal beet cutters by structural and technological strengthening in the process of their production and restoration. Materials and Methods. The state of the cutting edges of the knives was determined by using the micrometric measurement of the wear and deformation of the edges. Physical and mechanical indicators were analyzed based on the values of wear resistance, microhardness, and bending endurance. Results. The analyzes of the defective state of the knives of centrifugal beet cutters and theoretical studies of the grinding process have allowed formulating the factors affecting the permeability of the beet chips and the efficiency of their grinding with knives of a special diamond-shaped design. Experimental studies have made it possible to establish dynamically substantiated design parameters of an improved knurled knife. Discussion and Conclusion. The proposed measures ensured an increase in the durability of knives by 27–30%, the relative wear resistance of cutting edges by 20%, the limit of endurance of cutting edges for bending by 25% and a shift increase in the length of chips by 18–20% with an increase in its permeability by 16–18%.

Durability indexes are presented as a consequence of some deterministic properties inherent in the system and (or) their elements, and it is proposed to determine the durability indexes on the basis of analysis of these properties. The most important for estimating the durability are properties related to the lifetime, and the deterministic properties basic for determining the indexes of durability, can be represented by the function of the dependence of the lifetime on the parameter defining the operational conditions. Estimating the durability indexes is reduced to identification of the deterministic properties representing the dependence of the lifetime on the parameter defining the operational conditions. An example of estimating the durability of pipes of superheaters of steam boilers demonstrates the proposed approaches with relatively less complexities. This particular example shows that deterministic properties can have a significant influencing on the durability due to significant differences between the density function of the parameter defining the operational conditions and the density function of the lifetime. The proposed approaches can be recommended for use to estimate the durability indexes of unique technical systems, such as high-power steam boilers and nuclear power reactors, which are usually manufactured in single batches, as well as to estimate the durability indexes of any systems at the stage of their development in order to compare the durability of different constructions.

The object of the study is durability of expansion joints in bridge structures; the subject of the research is the vibration response of a structure obtained under conditions of natural operation. Diagnostics of the road bridge expansion joints has been carried out in order to identify characteristic dependences between the value of structure vibration response and types of expansion joint designs during the period of their operation while taking into account the features of the bridge structure. For this purpose, we have tested the methodology for collecting and processing data on the vibration response of the structure under natural conditions of its operation. The paper presents results of data collection on the coverage topology which have been obtained while using three-dimensional scanning method. Data collection on the vibration response of the structure has been carried out by measuring the vibration velocity and deformation of the structure. The data obtained are analyzed. As a result of testing and analysis of the obtained data, the main characteristics have been revealed: the value of base unevenness, the amplitude of vibration velocity and vibration displacement of the structure elements. Two main parameters of the dynamic impact have been assigned, adjusted for the mass of a moving vehicle, which can be used as main parameter for assessing the magnitude of the dynamic impact. A comprehensive method for assessing the dynamic impact on bridge structures has been developed and proposed in the paper, and its use will make it possible to differentiate various designs of expansion joints according to the magnitude of the dynamic impact of vehicles. This, in its turn, will contribute to formulate new recommendations on the use of specific types of expansion joints for various categories of highway, which will increase operational durability of expansion joints and the structure as a whole.

In the article, the author published the full-scale experiment results on an existing steel-reinforced concrete road bridge, carried out to determine the actual parameters of the operation regime of the interconnection elements — flexible pin stops. This work was carried out as part of the author’s dissertation research in the field of improving methods for testing the elements’ endurance of the steel-reinforced concrete superstructures interconnection and is a development of the previously conducted comprehensive comparative analysis of existing models for testing endurance. The article gives a detailed description of the conditions for conducting and methods of a two-stage experiment, which includes short-term and long-term parts, as well as a detailed description used for processing experimental data for each of the stages. Based on the results of the experiment’s short-term part, when compared with the results of finite element modeling of the operation of the stops, the possibility of using existing computational models to describe the actual model operation was confirmed. Also, within the framework of the short-term part, according to the conducted dynamic tests results with the moving load passage through the threshold, the presence of a significant dynamic component of the resulting forces in the interconnection stops was revealed. During the second long-term part of the experiment, a continuous recording of stresses in the interconnection elements from the passage of an unregulated traffic flow over the bridge was made. The article presents both direct survey data (tensograms) and the results of their further processing in terms of damage accumulation analysis; also, the accumulated damages values from actual traffic loads are compared with the expected values in the calculation according to some design standards. Intermediate conclusions based on the experiment results are formed and directions for future work within the scope of this study are indicated.

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The article deals with the problem of stable operation of various structures of drainage systems on heavy soils in the natural and climatic conditions of the Novgorod region during the first years after construction and after 30 years of operation. The experiment examines the effectiveness of drainage using shallow drainage structures with the depth of 70 cm and two variants of medium-deep drainage (110 cm) with filling the drainage trench with sand-gravel mixture (PGS) and wood chips to the arable horizon. Analysis of groundwater dynamics showed that the rate of groundwater decline in the early spring period in the first years of operation on all experimental variants was approximately the same: 2.0-2.4 cm/day. In recent years in the shallow drainage variant, the decrease in ground water levels occurred more slowly (2.3 cm/day) compared to the standard drainage variants (3.8-3.9 cm/day). The average humidity of the root layer of the soil during the growing season in experimental closed drainage systems has not increased for 30 years. The average moisture reserves for the growing season in the experimental systems were: 177 mm in the shallow drainage variant in 1991, 168 mm in 2018; 165 and 154 mm for the standard drainage with drainage chips backfill, respectively; 164 and 123 mm in the PGS backfill variant, respectively. The highest reliability and durability were shown by collectors with PGS backfill of the drainage trench, which have maintained a consistently high efficiency over a thirty-year period. During the drought period, shallow drainage systems provided more favorable conditions according to the degree of moisture in the root layer: in 2018, the shortest period of moisture lack in the root layer of the soil (10 days) was observed in shallow drainage systems, and the longest (1 month) - in systems with backfill of the drainage trench with PGS.

The article gives the description of the calculation and experimental assessment of the durability and other characteristics of the resistance to wear-and-fatigue damage to a “shaft – liner” active system under regular and irregular loading for mechano-sliding fatigue, developed on the basis of the energy criterion of limiting states. The methodology is based on the nonlinear hypothesis of the wear-and-fatigue damage accumulation, takes into account the influence of different in nature hardening-softening processes associated with the class of material (cyclically hardening, softening, or stable), the nature of irregular loading, the properties of a corrosive environment and other factors. An algorithm for calculating the durability, taking into account the loading history, is developed. An example of calculation is considered. The curves of sliding and mechano-sliding fatigue of the active system “shaft (0.45 % carbon steel) – liner (siluminum)” are constructed.

Introduction. The article examines the problem of choosing a material and method for increasing the wear resistance of construction machines elements. The performance of construction machines is affected by the reliability of the parts used. The selection of materials for their manufacture allows to calculate the probability of how such elements will affect its ability to work and productivity.Materials and methods. In the process of determining the material and the method for increasing the wear resistance of construction machines, structural steels with various chemical compositions were selected: lowcarbon 08ps (as a model material), 10, 20.30, St3 and low-alloy steels 09G2S and 10HSND, as well as high-carbon steel 65G and boron steel 30MnB5. The methods as high temperature annealing, normalization, injection and high temperature release, thermocyclic processing, cold plastic deformation, thermocyclic processing of steels after cold plastic deformation were used.Results. During the experiment, it was found that both for low-carbon 08ps, 10, 20, 30, St3, and for low-alloy structural steels 09G2S and 10HSND, as well as for high-carbon steel 65G and for boron-containing steel 30MnB5, an increase in the number of TCT cycles (thermal cycling) leads to an increase in the strength properties of the metal. With an increase in the number of cycles over 3-6, the increase in strength properties slows down significantly. Conclusion. In contrast to heat treatment, TCO allows to identify the positive effect of alloying on strength and plastic properties to a greater extent. At the same time, significantly increasing the strength and plasticity, it is possible to obtain previously unattainable values of the work of destruction of alloy steels in the process of various types of loading. Accordingly, the preliminary preparation of steel for the production of individual elements of machines and mechanisms will increase their strength and wear resistance.

Aim. The research aims to develop mathematical models for evaluating the reliability of two-story frame systems under the seismic impact, covering all possible ways of transition to the mechanism state due to the formation of plastic hinges in the frame nodes. Methods. The study is based on the application of the theory of Markov random processes in continuous time and their discrete states to describe the transition of a system into a different state. Such states include faults resulting from the formation of plastic hinges in the frame nodes. Results. Possible schemes of forming plastic hinges in two types of statically indeterminate frames under horizontal seismic impact are described: in the frame of a 2-story industrial building with a large-span upper floor and with the support of the roof truss on the heads of columns and a two-story two-span frame of a simple regular structure with rigid nodes. Possible states are noted and transition graphs are compiled, which are typical for the frames under consideration in the case of rigid disks of floor slabs during seismic impact, represented as a stationary random process. By representing the transition of systems to the states under consideration caused by the formation of plastic hinges in one or another sequence under seismic action in the form of a Markov random process in continuous time and discrete states, systems of first-order differential equations describing these transitions are obtained. Having solved them by applying the Laplace transform, analytical expressions for estimating the probabilities of finding frame systems in the states under consideration and expressions for estimating the probabilities of failure-free operation of these systems are obtained. Conclusion. By constructing transition graphs covering all possible states of frame systems during the formation of plastic hinges in nodes under seismic action and describing the process of frame transitions from one state to another by a Markov random process in continuous time and discrete states, analytical expressions for evaluating the probabilities of these system states, as well as their reliability and survivability under seismic action, can be obtained.

A methodology for the determination of number of cycles before the destruction of structure elements exposed to cyclic loading (tension-compression) has been developed. The analysis of the structure element static and dynamic stress-strain state with a usage of numerical methods of finite and boundary elements in order to determine the stress concentration zones is carried out. Model cracks that are placed in the highest stress concentration zones are selected. A database of model cracks is proposed. The initial length at which crack development begins is determined with a usage of the stress intensity factor threshold value. For each crack from the database, a critical number of cycles during which the crack grows to unacceptable sizes, is found based on the Paris criterion. A method for determining stress intensity factors for a structure element with cracks is proposed. The problem is reduced to solving singular integral equations. To obtain a numerical solution of these equations, the boundary element method is used. Densities, which appear as unknown functions in the considered integral equations, are used to calculate stress intensity factors. The analytical and numerical solutions of singular equations are compared. The critical number of cycles for plates with isolated cracks and cracks chains, cracks located at the elements holes and boundaries is determined. It was established that at the same loading level, a smaller critical number of cycles corresponds to a structure element with cracks that are in close proximity to the technological hole. An analysis of the fatigue crack development at holes in an elastic-plastic statement in order to determine the number of cycles before destruction is made, estimated number of cycles before the fatigue crack appearance is given.

Modern gas turbine engines operate under changing temperature loads. Therefore, one of the important characteristics of the protective coatings used on the turbine blades is their high resistance to the occurrence and development of cracks under mechanical and thermal loads. The applied effective systems of internal heat removal of the cooled turbine blades lead to an increase in their heat stress. At present, cracks arising from thermal fatigue are one of the common defects of the protective coatings used on turbine blades. The heat resistance of coatings at high temperatures is determined by three factors: the shape of the part on which the coating is applied, the thickness of the coating and the phase composition of the surface layers or the maximum aluminum content in the coating. Therefore, when choosing a protective coating for these operating conditions, it is important to know the impact of these factors on the thermal stability of the coating. The paper presents a comparative study of various coatings on their resistance to crack formation under cyclic temperature change. The dependence of the heat resistance of the considered coatings on the method of their application and phase-structural state is established. Especially valuable is the established mechanism of formation and propagation of thermal fatigue cracks depending on the phase composition of the initial coating. It is shown that the durability of protective coatings with cyclic temperature change depends on the chemical composition of the coating and the method of its formation. The dependence of the formation of thermal fatigue cracks on the samples with the coatings under study on the number of cycles of temperature change is established.

Introduction. The behavior in the course of a time of geogrid material with random nonlinear viscoelastic characteristics under tension is analysed. Parameters of viscoelasticity are represented in form of Gaussian random vector. The components of this vector are taken from experimental data. Aim of the research. The objective of this research is the analysis of influence of different factors (value of applied load and the application of load in the form of random value instead of dead one, number of realizations, change of given level of strain) on providing of needed service life of geogrid material with given reliability level. Here reliability is interpreted as function of probability of non-failure. The first crossing of some given level by random strain is considered as a failure. The strain value corresponding to yield limit of geogrid material is accepted as the given level of longitudinal strain. Methods. The realizations of Gaussian random vector of viscoelastic parameters of material with given correlation matrix were imitated by means of linear transformation method. Results. It is demonstrated that longitudinal strain is Gaussian nonstationary random process which stochastic analysis can be made on base of 10 000 realizations. The dependencies on time of mathematical expectation and standard deviation of random longitudinal strain as well as function of probability of non-failure are found. Conclusion. It is shown that durability estimation found on base of the deterministic problem solution is overestimated in comparison with stochastic problem solution if the condition of given service life providing with some reliability level is set up.

Investigations have been carried out in respect of structural steel and titanium alloy fatigue at various cyclic loading frequencies and these investigations have made it possible to reveal regularities in changes of parameters pertaining to fatigue resistance and stability behaviour of the tested materials. A change in cyclic loading frequency affects duration of a single (during one cycle) stay of the material in the loaded state and it has an impact on its durability. In addition, with an increase in frequency of load cycles, deformation rate becomes higher, and stress build-up time is decreasing, while distortion of a crystal lattice is increasing due to reduction of time for development of a weakening process. This process is accompanied by an increase in intensity of grain crushing into fragments and blocks, and their disorientation. Tests on cyclic strength of the studied material samples have been carried out at various frequencies and at a room temperature according to the following loading schemes: cantilever cyclic transverse bending of a flat sample; cantilever bending with rotation of a cylindrical sample; axial tension on a pulsating cycle. Quantitative estimates of a fatigue resistance index in the form of slope tangent in a left branch of the fatigue curve to a cycle axis have been used in order to analyze and evaluate performance and stability of the tested materials. Methods for mathematical statistics have been applied to process the obtained results. Graphic dependences of fatigue curves have been plotted in logarithmic coordinates that allowed to obtain straightening of approximating lines for experimental data. The investigations have revealed that loading frequency has an ambiguous effect on fatigue resistance due to some differences in materials in respect of their reaction to changes in a load spectrum within different areas of the fatigue process, but at the same time it has been found that an increase in fatigue strength leads to a slope decrease in the fatigue curve regardless of a decrease or an increase in a load frequency. The paper proposes a new approach to assess a cyclic strength and durability of materials, and it comprises a system of parameters including a relative coefficient of limited endurance, a correlation coefficient and a slope tangent of the fatigue curve. Behavior dynamics for real machine parts and structures made of these alloys under operating conditions has been indicated in the paper.

The article discusses the issues of increasing the durability of road-building machines. As a subject of research, friction units are considered, the details of which are made of gray iron. On the basis of a comprehensive technical and economic analysis of hardening methods for cast iron parts, it was established that chemical-heat treatment has the best combination of criteria. The methods used in practice for hardening cast irons are of little use in the conditions of repair production due to the complexity of technological processes and equipment. In addition, the thickness of the hardened layer usually does not exceed 0.3 mm. The paper discusses the main aspects of the application of new technology of surface hardening, formulated recommendations for its use, depending on the service purpose details. An assessment of the technical level of the proposed solutions compared with traditional technologies of hardening of cast iron.

The article presents materials on the study of the issue of increasing the resistance of technically complex twisted wire products-steel rope. The authors studied in detail the mechanisms and factors of formation of defects that lead to steel rope rejection. The cause abrasion and breakage of the wire strands in the locks (nodes) to couple the pusher is lack of mobility due to the lack of necessary quantity of lubricant for normal operation of a steel rope. The lubricants used in the manufacture of steel rope and its operation do not meet the requirements for durability, which leads to a decrease in the service life (loading cycles) established by the manufacturer. To solve the problem of increasing the resistance of steel ropes, the authors propose a new method of forming an antifriction powder coating based on molybdenum disulfide (MoS2) in the locks (nodes) of the coupler and on the surface of the wire by injection under pressure of compressed air antifriction powder material and fixing it on a complex surface by local hardening using a ball-rod hardener. Experimental tests of the surface layer of steel wire rope of different material coated with antifriction powder showed that the coefficient of friction is reduced from 3 to 9 times, and their wear resistance increased from 4 to 20 times. The main conclusions characterizing nanoscale pattern micro/nanoprobes the original surface of the sample, the steel wire rope of carbon steel according to GOST 1050 and GOST 14959. With anti-friction coating (MoS2), powder. From the presented drawings, the surface coated with molybdenum disulfide (MoS2) in comparison with the untreated becomes more flat, the micro-steps are rounded.

Objectives The use of additive technologies is one of the promising areas for improving the production of products for various purposes in the transition to a digital economy. Method. Layered construction of objects of complex shape in accordance with the developed solid-state model from materials with different mechanical and thermal properties allows directionally controlling the distribution of various components in the volume of the composite material and forming topological structures that provide a rational balance between various performance characteristics and reliability of the product. Result. Based on experimental studies, it has been established that reinforcing topological reinforcement of 3D printing objects made from ABS plastic with a composite consisting of carbon fibers and ED-20 epoxy resin, along with an increase in flexural strength and tensile strength, contributes to an increase in thermal conductivity of the material by more than 18% and thermal diffusivity - by 20%. A computer simulation of elementary cells of a composite material consisting of a polymer matrix, carbon fiber and special core inclusions with high thermal conductivity was performed, which made it possible to further increase thermal conductivity depending on the relative fiber diameter and the percentage of the additional component in an amount from 46 to 75%. Conclusion It is shown that additive technologies are an effective tool for creating universal topologies that allow technologically managing a combination of both mechanical and thermophysical properties of structural materials by determining the rational relative position of their components depending on the purpose and level of achievement of the required characteristics.

Introduction. The author presents the results of the reliability analysis of the structural systems in spans of bridges.Materials and methods. The analysis of published materials for the purpose of using them in the design of reinforced concrete bridges, in connection with changes in design standards and tightening of regulatory requirements for safety is made by the author.Results. The results of surveys of slab superstructures indicate the reliability and durability of typical structures operated under normal conditions, but in emergency situations there is a danger of progressive collapse. Therefore, in such conditions, split schemes of multi-span structures are unacceptable. The research tasks to ensure the durability of slab superstructures are formulated. In particular, the task of developing the method of durability calculation in case of one of the pillars failure in the continuous span structure, taking into account the dynamic effect is illustrated.Discussion and conclusion. Changes in design of slab structures of bridge cause the necessity to study the reliability and failure in emergency situations.