. Electrolytic-plasma treatment (EPT) is a promising method for improving the operating characteristics of metal materials. Anodic electrolytic-plasma hardening is a variation of EPT. This technology makes it possible to saturate the surface of the processed parts with atoms of light non-metallic elements, included in the composition of the electrolyte used. Limitations to the widespread use of electrolytic-plasma hardening in industry are associated with a number of process features, expressed in the uneven heating of the workpieces, as well as the need for them to be slowly immersed into the electrolyte to avoid disruption of the heating process. The paper presents the results of a study of the influence of operating voltage on the maximum heating temperature and the distribution of temperature zones during electrolytic-plasma heating of cylindrical samples made of VT6 titanium alloy. It has been established that electrolytic-plasma treatment in an ammonium chloride solution at an operating voltage of 200 to 260 V ensures heating of samples to a temperature of 1200 °С. The highest heating temperature is observed at a voltage of 260 V, and the lowest at 200 V. At the same time, samples undergoing processing are characterized by the presence of a temperature gradient along the height (maximum heating is observed in the most submerged part of the sample). During the EPT process, up to six distinct temperature zones are identified , but no more than five such zones exist simultaneously. Reducing the length and diameter of the samples leads to their more uniform heating. In this case, the size of the zones with the highest temperature increases due to the reduction or disappearance of the least low temperature zones. The opposite pattern is observed with increasing sample length.

The paper considers the technological process of manufacturing fluoroplastic sealing rings, consisting in forced feeding and pulling a polymer tape blank between rotating rollers, plastic bending of the tape in the deformation zone toa given curvature by twisting it on a drive roller and the subsequent operation of cutting off the strip after obtaining a ring of the required diameter. This technology has high productivity due to the automation of the full cycle of manufacturing a split ring and the continuity of the process allowing to minimize waste, reduce the labor intensity and energy intensity of production. The most difficult issue in developing the proposed technology is the design of the working tool, its dimensions and geometry, as well as the power and kinematic parameters of the device that ensure the production of fluoroplastic rings of the required accuracy. The complexity of the issue lies in the fact that fluoroplastic has a number of features that manifest themselves during deformation, and its mechanical behavior under force exposure differs significantly from the behavior of known classical materials. However, unlike other polymers, fluoroplastic is a high-density material and has a structure with a high degree of crystallinity, therefore, as studies show, its behavior under load, as well as the mechanism and sequence of deformations in it, are in many ways similar to the behavior of metals, which allows to use methods and approaches adopted in the mechanics of solid deformable bodies for fluoroplastic. According to the proposed technology, a fluoroplastic tape blank, pulled between rotating rollers and subjected to bending in the deformation zone, experiences pure bending with the occurrence of elastic and residual deformations, of which it is the latter that give the product the necessary shape and ensure the production of a ring of the required diameter. To solve this problem, it is necessary to perform the corresponding force and geometric calculations of the process. Force calculation is aimed at determining the force parameters of bending that create the maximum possible irreversible deformations in the deformed product with the minimum possible elastic recovery (springing) after leaving the deformation zone, and the geometric calculation is aimed at fulfilling force conditions. Based on a study of the stress state during bending of fluoroplastic tape, taking into account the different rigidity of fluoroplastic under tension and compression, as well as the kinematic calculations of the elements of the working unit of the installation, the diameters of the forming roller that creates the necessary bending forces in the deformation zone and the cutting roller-caliber that ensure obtaining a ring of the required diameter are determined. The calculation methods developed by the authors are in fairly accurate agreement with the results of experimental studies.

The purpose of the work is to increase the productivity of machining complex-profile surfaces of parts. To achieve this goal, the tasks of studying the kinematic and geometric features of the use of rotating cutting tools are solved, providing processing of cylindrical, conical, spherical and flat surfaces of a part at one workplace in one or two installations. Analytical research methods are used, which made it possible to obtain formulas for calculating the linear processing speed when the tool is embedded in the workpiece, in the cutting zone and at the tool exit from the workpiece, to determine changes in the inclination angle of the tool cutting edge in the instrumental, static and kinematic coordinate systems. Schemes for machining the surfaces of a part on a CNC machine by interpolating the cutting trajectory by rectilinear movements of the cutting edge are considered. The influence of the discreteness of the cutting edge movements on the quality of the resulting surface of the part at the recommended values of the cutting mode is estimated. The research results can be used in the development of control programs for CNC machines by selecting a rational machining scheme with tangential movement of the cutting edge and adjusting the values of linear velocity during embedding, during the cutting process and the exit of the cutting edge from the workpiece, which ensures an increase in machining productivity.

The paper analyzes the advantages and disadvantages of three-layer orthotropic slabs. It is shown that when developing the design of such slabs, it is necessary to work out the technology for connecting elements within the structure. The use of laser welding is effective for joining elements of small thicknesses. Such welding of sheet elements with a thickness of 12–50 mm has a number of limitations, and the strength characteristics of the joints have not been sufficiently studied. Therefore, in the manufacture of heavy-duty structures, three-layer orthotropic steel plates are often used; the plates are connected to each other using electric arc welding. Current experience shows that a significant number of weld intersections at joints requires compliance with a certain technological sequence of work to reduce deformations that occur during welding and prevent the occurrence of cracks during operation in areas with negative temperatures, as well as quasi-static and variable loads. An analysis of the stress-strain state of the slab was carried out using the ANSYS multifunctional software package. The model and full-scale slabs were tested for lateral loads. It has been established that due to welding stresses, it is possible that the actual geometry of the slab may deviate from the design one. By comparing the results of vertical movements of theoretical calculations and full-scale tests, the results of deviations are substantiated. After conducting experiments and inspecting the test samples at the points where the elements are connected to each other, the destruction of the slotted seams was not detected. When the maximum load applied to the slab model was reached, cracks were detected in the welds located along the perimeter of the cover slab. It has been revealed that in the design of welded three-layer plates, in the places where the sheets intersect, the weld is a concentrator of defects. The use of manual or semi-automatic welding contributes to the initiation of cracks under variable loads and operation at low temperatures. This problem requires the identification of crack-dangerous zones in three-layer slabs using non-destructive testing methods and experimental studies of the strength of various technical solutions using structural and welding stress concentrators.

All types of improved pavements operate under extreme conditions in terms of loads and temperatures. The degree of these influences is modeled by standardized tests, which, as a rule, reproduce only the load at a constant temperature. Based on these results, requirements are imposed on the materials of structural layers that do not fully reflect a number of features of their performance in road pavements. In fact, the main temperature effects and temperature-physical changes occurring in asphalt concrete are not taken into account, which can lead to insufficient durability and reliability. These changes include the material's response to temperature fluctuations, which can cause infrastructural changes and lead to increased cracking and poor performance. In our work, we conducted research to determine the thermophysical parameters of the material of the upper structural layers of road pavement, such as the coefficients of thermal conductivity, heat capacity, and thermal expansion (compression). A distinctive feature of our experiments was the tracking and determination of thermophysical indicators in the dynamics of the process of temperature changes. The article presents the results of local experimental studies of prototypes of asphalt concrete to determine the coefficients of thermal linear expansion, thermal conductivity and heat capacity at given temperature differences. Given the importance of these characteristics, it is necessary to reconsider the requirements for materials of structural layers in order to ensure that realistic operating conditions are simulated and actual temperature changes are taken into account. The main result of the research can be considered the developed methodology for further work, in which it is planned to take into account the gradient and rate of temperature change, the size of the stone aggregate, and the change in rheological characteristics depending on the temperature change. 

The purpose of the work is to establish the characteristics of the stress state of composite building reinforcement during tensile tests, caused by errors in the centering of the composite rod when installed in anchor couplings. A calculation scheme and a corresponding differential equation describing the stress-strain state of the rod have been compiled. Analytical dependencies were obtained to determine the bending moment and the stresses caused by it. A calculation estimate of bending stresses was made in comparison with the nominal tensile stresses of the rod. It is shown that bending stresses are unevenly distributed along the length of the rod and reach their highest values near the ends of the test couplings. Bending stresses increase in proportion to the eccentricity of the installation of the rod in the test anchor couplings and decrease with increasing length of the rod working part. Using the example of fiberglass reinforcement with a nominal diameter of 6 mm, manufactured in accordance with СТБ (STB) 1103–98, a calculation estimate of these stresses was made for a wide range of changes in the eccentricity of the composite rod in the anchor couplings location and the length of the working part of the test sample. It is shown that the use of short samples should be accompanied by an increase in the accuracy of rod centering in test anchor couplings. A method convenient for engineering calculations is proposed for determining bending stresses and total stresses in a composite rod. The research results can be used in engineering practice and in the educational process when training specialists in construction and chemical technology.

Rehabilitation of deteriorated asphalt concrete pavements is an important task for the road industries in many countries. Roads built earlier with non-rigid road surfaces cannot cope with the growth of transportation load. Therefore, asphalt-cement composites of various compositions are widely used in the practice of road construction. In the article several variants of obtaining asphalt-cement composites are proposed. Several compositions based on asphalt granulate were selected for  the experiment. Rubber crumb additive was introduced into bitumen in order to obtain an elastic transition zone due to the deformative properties of rubber particles reinforcing the asphalt binder. As reinforcement of the semi-rigid material, we used dispersed fibers of flax, cellulose and an additive in the form of a solution of polyvalent metal salts capable of creating additional structural bonds in the transition zone between the cement stone and the asphalt-binder. Experimental studies have shown a decrease in the angle of internal friction, which confirms the high stability of deformation without breaking the continuity of dispersed-reinforced material from asphalt granulate in a wide range of transport loads. Compositions with rubber crumb and linen fiber showed the best deformative qualities and resistance to repeated loads. The addition of crumb rubber modifies the bitumen film, and particles of undissolved rubber increase the elasticity of the material. Due to this, at rather large deformations (0.98 mm) and multiple loading, the stability of the samples is preserved (fracture work is 3.80 J). The introduction of linen fiber, which has high tensile strength and increased stiffness, allows to reinforce the transition layer in such a way that at sufficiently high strains (0.73 mm) and high work of destruction (2.69 J) the material remains stable. The resulting material can be used in load bearing areas.

The object of the study is new design solutions for metal protective screens based on elements made of rolled sheets, half-pipes and guide pipes. Metal protective screens are used in the construction of underground transport structures  using a closed method. The protective screen prevents deformations and subsidence of the surface of overlying soil layers, road and railway bed. During the construction of tunnel-type structures under existing transport communications, the conditions for the safe operation of roads and railways must not be violated. In this case, special attention is paid to subsidence of the overlying soil layers. The magnitude of subsidence affects the possibility to operate roads and reduce the speed or completely stop traffic on the railway. Therefore, the stress-strain state of the proposed metal protective screens was studied using a calculation model developed on the basis of the finite element method. To improve the accuracy of calculating internal for-ces on punching individual structural elements of a metal protective screen, the Romberg method was used. The proposed designs and technologies of protective screens retain the advantages of those currently used, while simultaneously reducing the costs of constructing a protective screen, since the design solutions under study require less effort to push through indivi-dual elements, and, as a consequence, use less powerful equipment. Calculations of the stress-strain state of the proposed designs of protective screens have shown their viability. As a criterion for checking the operability, the maximum stresses perceived by individual parts of the structures were considered; they do not exceed the yield strength of the selected steel, and the maximum vertical and horizontal displacements of individual parts of the screens were calculated, which do not exceed those specified in the requirements of the Rules for Technical Operation of Railways in the Republic of Belarus and the Instructions for Current Maintenance of Railway Tracks in the Russian Federation. This confirms the operability of the proposed metal protective screens.

The transport and logistics systems of most states of the Eurasian continent at the present stage of their development are in a stage of active transformation. This process is evolutionary in nature. However, due to the impact of external factors (pandemic, trade wars, sanctions, etc.), the dynamics of transformation processes take on non-linear development trajectories. The study of the characteristics of such processes is of fundamental and applied interest for transport and economic science. Developments on this issue are used to determine priorities for the development of infrastructure facilities of transport and logistics systems. The purpose of the study is to develop an approach to the transformation of transport and logistics systems. In the article, the authors analyzed the dynamics of volumetric performance indicators of individual types of transport and characterized their systemic interconnectedness in serving market needs. High variability in the average transportation distance by road transport was revealed with a general reduction in transportation volumes. This circumstance indicates a redistribution of the transport capacity of road carriers to main routes due to changes in foreign trade relations under the influence of external factors. High variability reduces the quality and increases the cost of transportation on local and intraregional routes. The article proposes a set of measures to level out the negative effects in the operation of certain types of transport, which are caused by the influence of external factors; transformation of transport and logistics systems is necessary. Transformation projects should provide for the systematic development of infrastructure in promising directions for the delivery of foreign trade cargo for the prompt redistribution of cargo flows along national sections of international transport corridors. It is also necessary to ensure that the throughput capacities of transport and logistics infrastructure facilities are balanced with the future parameters of cargo flows in compliance with reservation standards. To organize the interaction of different modes of transport and redistribute cargo flows along multimodal routes, it is necessary to form a network of multimodal transport and logistics centers of the hub type.