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Introduction. The safety problem and the situation with accidents during the operation of elevator installations are elucidated. The role of elevator rope defects as a factor of dangerous incidents is indicated from the point of view of statistics. The malfunctions of the elevator mechanical equipment related to the defective indices of the ropes are listed. There is a difference in the documentary fixation of defective indices and rejection rates of ropes of lifting structures. Materials and Methods. The well-known approaches to the control of ropes of lifting structures were described. It was emphasized that visual inspection control (VIC) was required to identify such rejection rates of steel elevator ropes as geometry change, corrosion and wear, wire breaks, temperature exposure, etc. The rejection rate was presented in the form of a mathematical system. The technical condition of elevator ropes during the operation was integrally assessed by the totality of identified defects at a fixed length. The decision to create a software and hardware complex (PAC) for the practical implementation of visual and measuring control was validated. Results. The developed PAC VIC laboratory sample consisted of a hardware part, a video stream processing module, communicator for the server connectivity, specially designed software, and a client mobile application. PAC VIC implemented the following functions: – automatic detection and classification of the major significant rope defects based on a deep convolutional artificial neural network; – demonstration of a three-dimensional image of a rope and an image scanning algorithm with distortion compensation, according to which the metric characteristics of defects were fixed; – integral assessment of the technical condition of the rope according to the totality of detected defects; – color interpretation of the actual technical condition of the rope with subsequent transmission to the user's mobile device. Preliminary tests have shown the suitability of the PAC VIC for identifying defects. The reliability of the results for the identification and qualification of defects exceeded 80%. Work on deep learning of the system continues. Discussion and Conclusions. PAC VIC of elevator ropes provides eliminating the risks of visual control caused by the psychophysical state of a person. It works remotely and contactless. The solution proposed by the authors automatically evaluates the rejection rates according to five criteria: external wire breaks, surface wear, rope diameter change, undulation, traces of temperature exposure. An important result of the VIC of steel ropes using computer vision and artificial intelligence is an increase in reliability and safety during the operation of elevator equipment.

Introduction. Composite materials are the main way to reduce the weight of the aircraft structure and improve its flight performance. Methods of non-destructive testing enable to assess the technical condition of composite materials, as well as to determine stress concentrators in them to make a decision on the further operation of this control object. The paper presents an analysis of the use of composite materials in the aircraft design and ways to improve their flight performance through the application of composites. An acoustic-emission method for assessing crack resistance based on invariants was described. The study aimed at increasing the accuracy and efficiency of assessing the crack resistance of aircraft structures made of composite materials through the use of the acoustic emission method of non-destructive testing. Materials and Methods. The nomenclature of composite materials used in aircraft was given, and their physical and mechanical properties were compared. The acoustic emission method of non-destructive testing of composite materials based on invariant ratios was used. Results. A method for assessing the crack resistance of primary structural elements based on the invariants of acoustic emission processes, and a program apparatus complex based on it has been developed. Discussion and Conclusions. The results obtained can be used to determine the strength characteristics of composite materials by the acoustic emission method of non-destructive testing to assess the technical condition of primary structural elements in mechanical engineering, shipbuilding, and aircraft construction. The paper is recommended to researchers involved in the development of aircraft.

Introduction. The key stages of sludge processing technology are the destruction of conglomerates into metal and non-metal components, as well as the grinding of component particles to obtain secondary raw materials of the required granulometric composition. The use of a rotating electromagnetic field for processing grinding sludge makes it possibleto exclude the application of various means of destruction and grinding, avoiding contact interaction of agglomerates and the walls of the working chamber. Thus, the material consumption of technical means is reduced, and the efficiency of the destruction process is increased. The study aimed at establishing the features and basic patterns of sludge waste processing in devices with a rotating electromagnetic field. Materials and Methods. For the research, grinding sludge was used, which was a collection of conglomerates of arbitrary shape, consisting of 80-85 % of metal chips. An induction method was applied based on establishing the connection of the EMF induced in an induction sensor and the magnetic induction of a rotating electromagnetic field. The influence of induction on the nature of interaction between sludge particles in a rotating electromagnetic field was evaluated by changing the relative EMF signal induced in an inductive sensor. Results. As a result of experimental studies conducted using the induction method, it has been found that the dynamic characteristics of sludge waste conglomerates depend on the induction of a rotating field to a certain value. With an increase in the size of sludge conglomerates, with the same size of ferromagnetic particles entering it, the magnitude of the magnetic field induction required for their destruction decreased. With a decrease in the particle size of conglomerates, the field induction required for the destruction of conglomerate bonds increased. An increase in the number of particles in the conglomerate reduced the value of induction. The degree of destruction of the conglomerate and the grinding of its ferromagnetic particles depended on the duration of the rotating electromagnetic field induction. Discussion and Conclusions. The proposed induction method makes it possible to investigate the influence of electromagnetic field parameters on the change in the state of the magnetic vibrating layer, as well as to evaluate the kinematic characteristics of ferromagnetic medium particles in the magnetic vibrating layer.

Introduction. A new scheme of a flat statically determinate regular lattice is proposed. The lattice rods are hinged. The study aims at deriving a formula for the dependence on the number of panels of the first natural oscillation frequency of nodes endowed with masses, each of which has two degrees of freedom in the lattice plane. The rigidity of all rods is assumed to be the same, the supports (movable and fixed hinges) — nondeformable. Another objective of the study is to find the dependence of the stresses in the most compressed and stretched rods on the number of panels in an analytical form. Materials and Methods. An approximate Dunkerley’s method was used to determine the lower bound for the lattice natural frequency. The lattice rigidity was found in analytical form according to Maxwell-Mohr formula. The rod stresses and the reactions of the supports were determined from the equilibrium equations compiled for all lattice nodes. Generalization of the result to an arbitrary number of panels was performed by induction using Maple symbolic math operators for analytical solutions to a number of problems for lattices with different number of panels. Results. The lower analytical estimate of the first oscillation frequency was in good agreement with the numerical solution for the minimum frequency of the oscillation spectrum of the structure. Formulas were found for the stresses in four most compressed and stretched rods and their linear asymptotics. All required transformations were made in the system of Maple symbolic math. Discussion and Conclusions. The obtained dependence of the first frequency of lattice oscillations on the number of panels, mass and dimensions of the structure has a compact form and can be used as a test problem for numerical solutions and optimization of the structure.

Introduction. The article investigated one of the problems of creating exoskeletons — controlling the properties of magnetic rheological fluid in links of variable length with adjustable stiffness. Based on the research of domestic and foreign authors, the development and urgency of the topic was evaluated. The disadvantage of known exoskeleton models has been specified, i.e., the use of absolutely solid links, whose dynamics does not convey the dynamics of the human musculoskeletal system. The scientific research aimed at the formation of a new direction in the development of exoskeletons that accurately simulate the biomechanics of movements. Materials and Methods. Different states of structures of variable-length links with a magnetorheological fluid were studied. It has been noted that the links work on the principle of magnetic shock absorbers and consist of a piston rod, electromagnetic coils, and a housing filled with magnetorheological fluid. The ordering effect of an external magnetic field on the particles of a magnetorheological fluid was visualized and mathematically presented. The significance of such factors as time, charge density, magnetic field strength, as well as vectors of electric and magnetic induction, electric intensity and electric current density for this system was shown. The input parameter affecting the behavior of the magnetorheological fluid was determined. This was the magnetic field intensity. It was shown that the viscosity of the liquid varied depending on the shape of the magnetic particles (oblong or oblate ellipsoid). Results. The dependences that were fundamental for solving the task were investigated and visualized. The magnetic field strength and the angle between the vector directed along a straight line connecting the centers of two micron particles, and the vector of the external magnetic field strength were taken as the basic parameters. It was shown how the magnetic moment, voltage and its antisymmetric part depended on them. It was established that to control the properties of a magnetorheological fluid, it was required to change: – the external magnetic field intensity; – the angle between the external magnetic field intensity and the orientation vector between the dipoles. Two values of force were compared: one – for a given link design, and the other — fixed when walking in the lower leg of a person. The consistency of these indicators was established. Discussion and Conclusion. The scientific research results allowed us to present: – a method for controlling the properties of a magnetorheological fluid by an external magnetic field; – a variable-length link model with adjustable stiffness. The results obtained can be used in modeling multilink structures to create comfortable exoskeletons that interact synchronously with the human musculoskeletal system as a single human-machine system. The development is applicable to solving significant social and economic problems.

Introduction. One of the tasks of two-link manipulators of industrial robots that move the end-effector along complex trajectories (e.g., robot welder) is associated with the need for careful programming of their movement. For these purposes, manual programming methods or training methods are used. These methods are quite labor-intensive, and they require highly qualified service personnel. A possible solution to the problem of programming the manipulator movements is the simulation of motion with the calculation of angular coordinates. This can help simplify the geometric adaptation of the manipulator in the process of debugging the control program. Therefore, this work aimed at calculating coordinates for programming the control system of a two-link manipulator operating in an angular coordinate system and moving the end-effector along a complex trajectory (e. g., when welding car bodies). Materials and Methods. A two-link robot manipulator designed for cyclically repeating actions in an angular coordinate system was considered. The manipulator consisted of two rotating links: “arm” and “elbow”, which were fixed on the base. The base could rotate, which provided a third degree of freedom. This configuration increased the working area of the manipulator and minimized the area for its placement in production. The movement of the manipulator end-effector could be performed if the kinematics provided its positioning along three Cartesian and three angular coordinates. For software control of robots, including welding robots operating in an angular coordinate system and performing the movement of the end-effector along a complex trajectory, it was required to calculate the angular coordinates of the movement of the end-effector of a two-link articulated manipulator. The robot control system should determine the position of the tool in the angular coordinate system, converting it for user friendliness into x, y and z coordinates of the Cartesian coordinate system. Results. The relations of angular and Cartesian coordinates have been obtained. They can be used for calculating when programming the control system of a two-link manipulator of an industrial robot and organizing the exchange of information between the user and the control system, as well as for checking the accuracy and debugging the movement of the end-effector of an industrial robot through feedback. Discussion and Conclusion. The presented results can be used for software control of a welding robot operating in an angular coordinate system and performing a complex trajectory of the end-effector of a two-link articulated manipulator (gripper). A manipulator operating in an angular coordinate system can be used for contact spot welding when moving the end-effector along a complex trajectory using a positioning or contouring control system. These systems control the movement of the end-effector along a given trajectory with the help of technological commands.

Introduction. Robotic technologies serve as an important indicator of the technological and economic state of the country, they also affect the lives of individuals. Their development is a promising and urgent task affecting many aspects of the life of modern society. Currently, robotics is going through another stage of development, which has its own characteristics, new directions. The work aims at analyzing the situation and ways of development of this industry in the world and in our country, as well as the attitude of people to the use of robotic systems and their willingness to improve them. The topic under consideration is understudied. Materials and Methods. In the presented work, the historical aspects of the formation of unique robotic technologies are defined, the ratio of the number of manufacturers and consumers of robotic products in the world is specified, the areas of the robotic technology application are named. The central place in the research is given to the results of an online survey conducted by the authors. Its statistical analysis made it possible to study, using specific data, the factors that influence the spread of robotic systems and robotic technologies and contribute to them. Results. The survey results, on the one hand, showed a high assessment of the prospects of robotic systems given by the respondents, and confirmed that young people have an interest in robot-making technologies. On the other hand, they allowed us to note the high level of knowledge in the field of robotic technologies among engineering students and the presence of more than elementary knowledge of these technologies among representatives of other special fields. In the opinion of the authors, there are all prerequisites for the further successful development of these technologies. Discussion and Conclusions. The analysis of the use of robotics in the world and in our country, as well as the results of the survey conducted by the authors, enable to conclude that these technologies are developing and will continue to develop actively, and the interest of current students in this, confirmed by the answers to the questionnaire, will contribute to the wider introduction of robots into the lives of future generations.

Introduction. To develop new system modules of software to help employees with disabilities, it is required to work out an architectural solution for the interaction of all parts of the system. As a result of the analysis and design, it is necessary to obtain a software architecture that must meet a number of standard requirements. First of all, it should be safe. To do this, you should take into account the error logging system, event auditing, the possibility of disabling the functionality immediately after putting it into commercial operation, internal mechanisms for validating client input requests and server responses. This study is aimed at the development of basic system maintenance options, the analysis of exception cases under interacting with the user for further evaluation of the architecture efficiency, and the direct project development. Materials and Methods. The architectural decision was carried out using the Unified Modeling Language (UML), which helps to build visual images of the life cycle and interaction of all components of the system. The syntax of the UML deployment diagram was used to study the interaction of the main modules of the future system, and the syntax of the UML sequence diagram was used to process the lifecycle. A use case diagram was also applied to describe the main use cases. To study the interaction of the main modules of the future system, the UML deployment diagram syntax was used. For life cycle processing, the UML sequence diagram syntax was applied. In addition, a use case diagram was applied to describe the base use cases. Results. An architecture that has a scheme for the interaction of individual modules and systems, as well as options for using the software package for the future implementation of the software product, has been developed. The proposed system architecture meets the requirements of security, reliability (fault tolerance), and performance. The authors have fixed the functional requirements of the system of assistance to employees of enterprises with hearing problems for the possibility of their employment and work on the telecommunication Internet. Basic variations of system maintenance have been developed. Discussion and Conclusions. Building a competent architecture provides taking into account cases that go beyond the normal use of the system, and applying a fuzzy model to determine the system efficiency. Further in-depth description of deployment and operation options will enable to implement an efficient and productive system.

Introduction. In modern heavy-loaded friction units, metallopolymer coated bearings operating in the boundary friction mode are widely used. Their successful application is provided by the viscoelastic deformation of these coatings under load. To pass from boundary friction to liquid friction, it is required to create a bearing hydrodynamic wedge. Currently, the use of journal bearings with polymer-coated grooved support ring is hindered by the lack of a methodology for their calculation. This work analyzes a model of movement of a micropolar lubricant in the operating clearance of a journalbearing with a nonstandard support profile having a PTFE composite coating with a groove on the bearing surface. The study aims at establishing the dependence of the stable hydrodynamic regime on the width of the groove on the surface of the bearing profile. Materials and Methods. Tribological tests of journal bearings with a nonstandard bearing profile having a polymer coating with a groove on the surface were carried out on samples in the form of partial bushes (blocks). Using the equation of movement of a lubricant with micropolar rheological properties, as well as the continuity equation, new mathematical models were obtained that took into account the width of the groove, polymer coating, and nonstandard bearing profile. Results. A significant expansion of the applicability of design models of journal bearings with structural changes has been achieved. Polymer-coated bearings with a groove provided a hydrodynamic lubrication mode. The results obtained allowed us to evaluate the operational characteristics of the bearing: hydrodynamic pressure value, load capacity, and coefficient of friction. Discussion and Conclusions. The design of polymer coated journal bearing and a groove 3 mm wide on the surface of the liner provided a stable ascent of the shaft on the hydrodynamic wedge, which was validated experimentally. The experiments were carried out for journal bearings with a diameter of 40 mm with a groove 1–8 mm wide, at a sliding speed of 0.3–3 m/s and a load of 4.8–24 MPa.

This study aims at developing the concept of fragmentation of the frame to assess the load-bearing capacity of the floors. As a rule, a frame-rod design scheme is used under the finite elementmodeling of high-rise buildings made of monolithic reinforced concrete. Numerical experiments using volume-rod and volume-plate models of a repeating structural fragment were performed on a test example of a six-span three-storey monolithic reinforced concrete frame. Practical recommendations have been developed for the refined strength calcula-tion of the floors of monolithic reinforced concrete frames of multistorey buildings. Materials and Methods. Computational experiments were performed using the ANSYS Mechanical software package, in which the finite element method was implemented in the form of a displacement method. A plate-rod ensemble of finite elements was used to simulate the stress-strain state of a monolithic reinforced concrete frame. The refined calculation of the coupling zone of the floor slab and column under static loading was performed using solid, beam, truss and plate elements. Results. An engineering technique has been developed for numerical analysis of the stress-strain state of the coupling of the floor and the column of the reinforced concrete monolithic frame under static loading. The most accurate result was provided by a finite element model constructed using beam finite elements as reinforcing rods. Discussion and Conclusions. The developed technique of numerical modeling of the coupling of the floor and the column made it possible to estimate the real strength margin of this node, taking into account the real geometry of reinforcing grids, as well as to clarify the bearing capacity of a monolithic reinforced concrete frame under various loading scenarios.

Introduction. Life expectancy is, by definition, the average number of years a person can expect to live from birth to death. It is therefore the best indicator for assessing the health of human beings, but also a comprehensive index for assessing the level of economic development, education and health systems . From our extensive research, we have found that most existing studies contain qualitative analyses of one or a few factors. There is a lack of quantitative analyses of multiple factors, which leads to a situation where the predominant factor influencing life expectancy cannot be identified with precision. However, with the existence of various conditions and complications witnessed in society today, several factors need to be taken into consideration to predict life expectancy. Therefore, various machine learning models have been developed to predict life expectancy. The aim of this article is to identify the factors that determine life expectancy. Materials and Methods. Our research uses the Pearson correlation coefficient to assess correlations between indicators, and we use multiple linear regression models, Ridge regression, and Lasso regression to measure the impact of each indicator on life expectancy . For model selection, the Akaike information criterion, the coefficient of variation and the mean square error were used. R2 and the mean square error were used. Results. Based on these criteria, multiple linear regression was selected for the development of the life expectancy prediction model, as this model obtained the smallest Akaike information criterion of 6109.07, an adjusted coefficient of 85 % and an RMSE of 3.85. Conclusion and Discussion. At the end of our study, we concluded that the variables that best explain life expectancy are adult mortality, infant mortality, percentage of expenditure, measles, under-five mortality, polio, total expenditure, diphtheria, HIV / AIDS, GDP, longevity of 1.19 years, resource composition, and schooling. The results of this analysis can be used by the World Health Organization and the health sectors to improve society.

Introduction. For the effective use of unmanned aerial vehicles (UAV), it is required to take into account the impact of atmospheric environmental factors. Based on the existing level of development of the research and methodological apparatus, it is impossible to determine the probability of damage to the UAV under the conditions of complex exposure to atmospheric environmental factors and to assess the feasibility of further performance of the flight task. Violation of the UAV operation process is caused by the influence of atmospheric precipitation, wind and temperature conditions of the environment. The work aims at the development of a methodology for determining the probability of damage to UAV as a result of exposure to atmospheric environmental factors, as well as to evaluate the performance of the software package implementing the developed algorithm using triangular, trapezoidal, pentagonal, and Gaussian membership functions.Materials and Methods. A technique is proposed that makes it possible, using the theory of fuzzy logic, to determine the probability of damage to the UAV with inaccuracies and uncertainties in the description of atmospheric effects of the environment. It takes into account possible atmospheric forcing and enables to determine the probability of damage to the UAV under various atmospheric influences. The computational complexity of the algorithm implementing the technique depends significantly on the number of qualitative assessments of atmospheric impacts on UAV.Results. A method for determining the probability of damage to UAV as a result of exposure to atmospheric environmental factors based on fuzzy sets (triangular, trapezoidal, pentagonal, Gaussian) was proposed and tested. The use of fuzzy sets for estimating the conditions of the UAV application environment was described. An algorithm was developed to determine the probability of damage to the UAV as a result of exposure to atmospheric environmental factors. A computational experiment was carried out to determine the complexity of calculating the probability of UAV damage as a result of atmospheric forcing under various environmental conditions: «moderate conditions» at a wind speed of 3 m/s, precipitation intensity of 0.8 mm/h, and air temperature of 5 °C; «very heavy conditions» of the external environment at a wind speed of 12 m/s, precipitation intensity 3.5 mm/h, and air temperature of –6 ºС. It was established that the use of triangular membership functions to calculate the probability of damage to the UAV as a result of atmospheric forcing provided higher performance compared to the rest ones (trapezoidal, pentagonal, Gaussian).Discussion and Conclusions. The values of the UAV damage probabilities obtained during the implementation of the methodology under atmospheric environmental influences can be used at the pre-flight preparation stage and during the flight to assess the feasibility of further performance of the flight task. Based on the analysis of the application of the considered forms of membership functions, recommendations for their application are given. The use of algorithms with triangular membership functions will provide high performance of UAV control systems (UAV CS).

Introduction. Properties of filled composites based on polytetrafluoroethylene allow them to work at high contact pressures, reciprocating nature of shear loads, and in a wide temperature range. Due to this, they are used as antifriction layers of bearing parts with ball segment. To simulate the mechanical behavior of such materials under operating conditions, adequate constitutive equations of elasto-viscoplasticity and methods of their identification according to the data of basic experiments are needed.Materials and Methods. The tensor-linear model of elasto-viscoplasticity should be identified according to the data of tests on free compression of samples. They were subjected to loading up to a maximum deformation of 10 %, allowed to remain, unloaded, and then, a similar loading cycle up to 160 MPa under constrained compression was carried out. The experiment with a composite based on polytetrafluoroethylene filled with 40 wt. % fine bronze, was conducted at room temperature. Tests for constrained compression were performed for two values of the strain rate, and for free compression – for three values of the strain rate in the range of 10-6 – 10-3 s-1. For the description, two models of elasto-viscoplasticity were considered, representing modifications of Swain and Kletschkowski’s models and corresponding to the connection of a viscoelastic or elastic nonlinear viscous element with a plastic or endochronic element. An integral operator with a Kohlrausch kernel was considered as a viscoelastic element.Results. The results of the constrained compression tests made it possible to separate the elastic relationship of volumetric deformations and average stresses from the constitutive relations. The data of free compression cycles at different strain rates were used to determine the material constants of the model. For this purpose, an efficient search algorithm based on the simplex method of minimizing the discrepancy was implemented. Both models discovered the importance of the plastic component (independent of the deformation rate) for a qualitative description of the stress cycling that accompanied the cyclic deformation, as well as their dependence on the strain rate.Discussion and Conclusions. Both models of elasto-viscoplasticity described correctly the behavior of the studied fluorocomposite under loading conditions close to the operating conditions of the antifriction layers of the bearing parts with ball segment. They can be considered as a basis for their further generalization, taking into account the dependence on temperature.

Introduction. The problem of controlling the lower-extremity powered exoskeleton motion was investigated. To solve it, it was proposed to use a program control and feedback control. The formation of control in the form of feedback required an assessment of the state of the exoskeleton (rotation angles, angular velocities, and accelerations of the links). The possibility of using an inertial measuring unit to estimate angular velocities and accelerations of exoskeleton links was considered. The work objective was to develop laws for the formation of the exoskeleton motion control, which could provide the stability of the program motion and use the measurements of encoders, micromechanical gyroscopes and accelerometers.Materials and Methods. Previously performed mathematical modeling of the exoskeleton dynamics was used to form a program control. It was proposed to equip the exoskeleton with inertial sensor units. This solution made it possible to evaluate the state vector of the exoskeleton and to use these estimates in a feedback loop. A mathematical model of measurements of these sensors was described. The proposed version is suitable for control systems of three-link exoskeletons of the lower extremities and can be expanded to the case of multi-link exoskeleton designs.Results. New laws of exoskeleton motion control based on a mathematical model of the system dynamics and using measurement information from encoders and inertial information sensors were proposed. Numerical simulation of exoskeleton motion was performed in the Wolfram Mathematica mathematical package. Its results confirmed the operability of the proposed control and the possibility of using an inertial sensor unit to assess the exoskeleton state. The numerical simulation results for the following program movements were presented: lifting the exoskeleton from a sitting position to a vertical position, and stabilization of the vertical equilibrium position.Discussion and Conclusions. The proposed control can be applied in exoskeletons for medical purposes, e.g., in the task of verticalization of patients with dysfunctions of the musculoskeletal system. The possibility of using measurement information obtained from inertial measurements units in the problem of estimating the state of exoskeleton links was demonstrated. The use of inertial sensors will make it possible to determine the angular acceleration of the exoskeleton links, avoiding numerical differentiation of the measurement information received from the encoders. The obtained estimates of angular acceleration allow us to introduce feedback on angular accelerations into the control system, which opens up the possibility of improving transients in controlling the exoskeleton motion.

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.

Introduction. One of the commonly used methods for assessing the dynamic characteristics of a material is the Taylor test, which establishes the relationship between the dynamic yield strength of a cylindrical sample material and its length after hitting a non-deformable barrier. The purpose of this work was to study the microhardness and determine the dynamic yield strength of copper samples for various impact velocities in the Taylor test.Materials and Methods. Experiments were carried out with cylindrical copper (M1) samples. The throwing conditions were selected on the ballistic stand, which provided the speed of the sample in the range of 150–450 m/s at the exit from the barrel. After the impact, the microhardness of the samples in the section plane was measured. The calculation of the dynamic yield strength was carried out according to the classical Taylor formula.Results. Experimental data are presented for cylindrical copper samples upon impact on a rigid wall with velocities in the range of 162–416 m/s, including configurations and sizes of images before and after impact. Microhardness distributions in the axial section of the samples were obtained. For each sample, the dependences of the averaged values of microhardness were constructed, which made it possible to identify four areas of deformation of the samples (the area of elastic deformations, plastic deformations, intense plastic deformations, the area of the material undergoing destruction) and determine their sizes. The dynamic yield strength of copper in the studied range of impact velocities was calculated.Discussion and Conclusions. The values of microhardness in the entire considered region and for all studied impact velocities exceeded the initial value. There was a significant increase in the value of the dynamic yield strength compared to its static value. The correlation of the maximum averaged values of microhardness and dynamic yield strength, which grew with increasing impact velocity, was identified.

Introduction. The problem of critical loads of a compressed orthotropic rectangular plate on an elastic base was considered. The following orthotropy parameters were set for the plate: Poisson coefficients, Young's modules for the main directions, and the shear modulus of the plate material. The components of the compressive load were uniformly distributed along two opposite edges of the plate and acted parallel to the coordinate axes. The edges of the plate were loosely pinched or pivotally supported. Cases were also considered when two parallel edges of the plate were free from loads, and the other two were freely pinched or pivotally supported.Materials and Methods. The problem was studied on the basis of a system of nonlinear Kármán-type equilibrium equations. The critical values of the load parameter were determined from a linearized problem based on a trivial solution. At the same time, the variational method in combination with the finite difference method was used to solve the boundary eigenvalue problem.Results. The problem was reduced to solving a parametric linear boundary eigenvalue problem. In case of boundary conditions of a movable hinge support, exact formulas of eigenvalues and eigenfunctions were given. While in case of free edge pinching, a variational method was used in combination with a finite-difference method, and a computer program for solving the problem was built. It was established that one or two eigenfunctions expressing the deflection of the plate could correspond to the critical value of the compressive load parameter at which the stability of the compressed plate was lost. The results of numerical calculations of the critical values of the compressive load at different values of the orthotropy parameters were presented, and graphs of the corresponding equilibrium forms were constructed. For the case of a long orthotropic plate on an elastic base, it was established that the main term of the asymptotic expansion of the solution to the linear eigenvalue problem was determined from the problem of critical loads of a compressed beam on an elastic base with an elastic modulus that coincides with the elastic modulus of the plate in the longitudinal direction.Discussion and Conclusions. The problem of critical loads of an orthotropic plate compressed in two directions lying on an elastic base was investigated. As the compressive load component increased along one direction, the critical value of the load compressing the plate along the other direction decreased. If an orthotropic plate was compressed by a load along a direction that corresponded to a greater bending stiffness, then the critical value of the loss of stability was greater than the critical value of the compressive load acting along the direction of a lesser bending stiffness. The presence of an elastic foundation increased the bearing capacity of the compressed plate.

Introduction. With the growth in the production and transportation of gas and oil, the urgency of the problem of tightness of the connection of pipes of the oil and gas range increases. The most common are coupling and streamline threaded connections. Threads of the buttress type, conical trapezoidal, and triangular threads are used. The tightness of the connection depends directly on their quality. The production of pipes and couplings is influenced by many factors. Examples include technological heredity, rigidity of technological equipment, its setting and resetting. The required connection quality is provided by the quality of the elements. The assembly should take into account the possibility of complete interchangeability. The second recommended option is a group assembling. In all cases, control operations are mandatory. The paper presents the results of studies on the distribution of pipe and coupling thread quality parameters in the batch.Materials and Methods. Fragments (tubular parts) of casing pipes with trapezoidal thread and increased tightness (CPTT) and with trapezoidal thread of the buttress profile were studied. They were randomly selected from different batches. When measuring, the samples were fixed in the chuck of 1I611P lathe. The measuring instrument was a clock type 0 accuracy class indicator with a stand. Generally accepted statistical methods were used to evaluate the data obtained.Results. The experiments have found how the tightness of the connection through the method of complete interchangeability is affected by the radial runout of the surfaces of the thread profile tops, the pipe chamfers, and the sealing belt.Discussion and Conclusions. Significant deviations of the values of the thread parameters from the permissible ones were found, which might cause a leak in the connection. Obtaining a high-quality and reliable connection is possible when assembling by the method of incomplete or group interchangeability.

Introduction. In sheet and hull structures operating under pressure, destruction, as a rule, is localized along the transition line from the base metal to the weld metal. Methods of increasing the durability of butt-welded joints, which are aimed at reducing stress concentration and creating favorable residual compression stresses, are described.Materials and Methods. The tests were carried out on an installation for biaxial bending, which created a biaxial stress field. Factory-made coupons and samples with an additionally processed transition zone from the weld metal to the base metal were tested. The effectiveness of further processing is shown by the following methods:– abrading;– grit hardening;– abrading with grit hardening;– melting of the fusion line in argon without filler wire;– melting of the fusion line in argon with filler wire EP-410U;– melting of the fusion line without filler wire with plastic deformation between narrow rollers.Results. The origin, development of destruction, and its features were analyzed using different methods of further processing of joint welds. Confidence spans (95 %) of the origin and development of failures for joint welds and base metal were calculated. The efficiency of the proposed methods for further processing was evaluated.Discussion and Conclusions. An analysis of the effectiveness of methods for increasing the durability of butt-welded joints has shown that the creation of a smooth transition from the weld metal to the base metal reduces significantly the stress concentration. This provides increasing the number of cycles before the onset of destruction and the survivability of compounds. Due to compressive stresses in the near-weld area, it is possible to increase the durability of joint welds. The most effective methods of further processing of welds combine the reduction of stress concentration and the creation of residual compression stresses. The high-tech solution is remelting the transition zone in an argon medium with an additional EP-410U filler wire.

Introduction. Determination of mechanical properties of layered structures of highways is an urgent task. This is due, firstly, to the need to control the quality of new sections during the construction of highways. Secondly, to assess the condition of existing roads with the accumulation of damage and defects is of interest. The formation of multiple defects (cracks) changes the averaged viscoelastic properties of the components of the structure, specifically, the surface asphalt-concrete layers. The article discusses the use of neural network technologies to improve the accuracy of the recovery of viscoelastic properties. This approach is based on experimental methods. As an example, we can give the definition of the dynamic deflection of a structure from a falling weight, FWD.Materials and Methods. The elastic modulus of a three-layer structure was determined on the basis of a neural network. To find out the solution accuracy, it was compared to the results of mathematical modeling and experimental data.Results. The experimental and calculated parameters of the elastic modulus of individual layers of the road structure turned out to be very close. The proposed approach to determining the mechanical properties of materials of road structures allowed us to apply the obtained results to examination of the condition of individual elements and the entire road structure.Discussion and Conclusions. The prospects of using artificial intelligence to determine the mechanical properties of layered structures was shown. Further improvement of methods and tools for analyzing the behavior of road structures under dynamic loading will expand existing approaches to assessing the condition of road structures.

Introduction. Determining the tumor (nodule) characteristics in terms of the shape, location, and type is an essential step after nodule detection in medical images for selecting the appropriate clinical intervention by radiologists. Computer-aided detection (CAD) systems efficiently succeeded in the nodule detection by 2D processing of computed tomography (CT)-scan lung images; however, the nodule (tumor) description in more detail is still a big challenge that faces these systems.Materials and Methods. In this paper, the 3D clustering is carried out on volumetric CT-scan images containing the nodule and its structures to describe the nodule progress through the consecutive slices of the lung in CT images.Results. This paper combines algorithms to cluster and define nodule’s features in 3D visualization. Applying some 3D functions to the objects, clustered using the K-means technique of CT lung images, provides a 3D visual exploration of the nodule shape and location. This study mainly focuses on clustering in 3D to discover complex information for a case missed in the radiologist’s report. In addition, the 3D-Density-based spatial clustering of applications with noise (DBSCAN) method and another 3D application (plotly) have been applied to evaluate the proposed system in this work. The proposed method has discovered a complicated case in data and automatically provides information about the nodule types (spherical, juxta-pleural, and pleural-tail). The algorithm is validated on the standard data consisting of the lung computed tomography scans with nodules greater and less than 3mm in size.Discussion and Conclusions. Based on the proposed model, it is possible to cluster lung nodules in volumetric CT scan and determine a set of characteristics such as the shape, location and type.

Introduction. One of the most significant tasks facing road experts is to maintain the transport network in good condition. The process of selecting an appropriate approach to providing such condition is quite complex since it requires considering many parameters, such as the existing condition of the pavement, road category, weather conditions, traffic volume, etc. Recently, the rising trend of digitization in the industry has contributed to the use of artificial intelligence to address problems in several fields, including the bodies in charge of operational control over the status of roadways. Within the context of any control system, the main task of the control system is to carry out reliable forecasting of the operational state of the road in the medium and long term.Materials and Methods. This study investigated the possibility of using artificial neural networks to assess existing pavement characteristics and their potential application in developing road maintenance strategies. A back-propagation neural network was implemented, trained using data from 1,614 investigated sections of the M4 «DON» highway in the road network of the Russian Federation in the period from 2014 to 2018. Several models were developed and trained using the MATLAB application, each with a different number of neurons in the hidden layers.Results. The results of the models showed a convergence between the inferred paving state values and the actual values, as the multiple correlation coefficient (R2) values exceeded 92 % for most of the models during all learning stages.Discussion and Conclusions. The findings suggest that public road authorities may utilize the established models to choose the best road maintenance strategy and assign the most efficient steps to restore road bearing capacity and operation.

Introduction. A gravity conduit with a control valve and a pressure regulator in the gravity water-supply pipe is considered under conditions when the hydraulic regime of the water-supply system is not disturbed. In relation to such a system, the problems of converting the energy of local artificial hydraulic resistance into electricity are investigated.Materials and Methods. Literature that highlights the possibility of using microturbines for power generation in water systems was studied. The actual values noted by the continuous pressure recorder (logger) for 12 hours were presented, as well as the water consumption by the turbine at a given unit section (the average for a year), and the pressure differential. It was noted that the use of small hydroelectric power plants in water supply systems significantly reduced the cost of their operation. The indicators of water consumption in the hydroturbine unit during the year, broken down by months, were given. The maximum power at the turbine inlet was calculated. The principles of selecting the type of hydraulic turbine were described. The average efficiency values for different elements of the hydroturbine plant, the average parameters of the power of the small hydro and the corresponding indicators of the average monthly electricity generation were indicated.Results. Equipping the units under study with specially designed turbines can enable to obtain electrical energy through converting artificially created by local resistance and extinguished mechanical energy. It is possible to apply the approaches described in this article when replacing many of the pressure control units of the Yerevan City Network system. The productivity of a small hydro power plant was predicted, as well as the terms of its construction and operation — for 2 years and 30 years, respectively. The construction and maintenance costs were calculated in advance. The expected data on income, expenses, and net profit are given. It is indicated that it will potentially be close to 6 million drams per year. The analysis of the data allowed us to conclude that the internal rate of return will be at the level of 10.4%, and the payback period is 9 years.Discussion and Conclusions. We recommend replacing the regulator with a hydroturbine having the same hydraulic resistance and automatic flow control in the system. The conclusions were confirmed by the energy and economic indicators of the hydroturbine plant located on the section of the Arzakan — Yerevan main water pipeline.

Introduction. The paper presents a brief kinematic analysis, as well as the application of D'Alembert's principle to finding the relationship between the force parameters in the transmission mechanism of a robotic manipulator constructed from a twisted arm chain. The use of this transfer mechanism can enhance the life of the arm actuator, the accuracy of its positioning, and increase the workload compared to the flexible linkage actuators (twisted strings). The work aimed at obtaining dependences between the displacements of circuit elements, as well as their force parameters required to monitor the control system operation of these devices.Materials and Methods. In the course of solving the problem, an elementary segment (element) of the transmission chain was considered. To find the relationship between the loads in the element, the virtual displacement principle was used. When finding kinematic connections between displacements, a brief geometric analysis of the transmission chain element was carried out. To conduct a comparative analysis of the analytical dependences obtained, a simulation technique implemented on a graphical link model using the NX software package was applied.Results. In the course of the study, we obtained dependences for determining the magnitude of the moment developed on the input link, depending on the external workload and its rotation angle, as well as for defining the linear displacement of the output link. A simulation model of the actuator was constructed, which can be applied in the dynamic study of the actuator mechanism, taking into account the inertia of the links.Discussion and Conclusions. From the obtained analytical dependences, we determined the value of the angle of rotation of the input link of the mechanism element, at which the maximum torque value for a fixed workload on the output element was achieved, as well as the maximum linear displacement of the output link. The calculated values were in good agreement with similar values obtained from the results of the simulation experiment, which gave us the possibility of using analytical dependences in the formation of a robot control system. In addition, these dependences made it possible to provide the selection of actuators with the required force indicators.

Introduction. Over the past decade, global demand for pressure vessels has increased significantly, specifically in such industries as aviation, space, chemical, and oil and gas. Being under the constant impact of high internal pressure, the walls of the tanks are under increased stress, which can cause their sudden destruction. To eliminate this probability and improve the strength characteristics, the tanks are made in the form of metal cylinders with an internal coating of composite material consisting of resin reinforced with carbon fibers. This article aimed at studying the effect of the angle of inclination of carbon fiber on cylindrical tanks and determining the maximum destructive pressure using the finite element method of ANSYS program.Materials and Methods. Using the ANSYS program, a finite element model of a tank was created. It has a central part, which is a metal cylinder with an internal coating of composite material consisting of polymer reinforced with carbon fibers. At the ends of the tank, spiral wound hemispheres were placed. In these studies, SHELL 99 was used to model the layered composite material. The Tsai-Wu theory was used to determine the pressure tank failure criterion.Results. The cylindrical tank model was calculated for two types of fiber winding paths: annular and spiral, at different angles of their inclination. The results of the pressure value analysis for different fiber inclination angles showed that, starting from the angle value of 0° and up to 45°, it increased, and then, up to the angle value of 65°, it began to decrease. The critical pressure value for a carbon fiber reinforced tank was 207 MPa, which was obtained at a fiber angle of 45º.Discussion and Conclusion. Analysis of the studies showed that at a fiber inclination angle of 45º, the value of the maximum stress turned out to be the smallest, and the maximum possible destructive pressure at the same angle was 207 MPa. It follows, that the optimal fiber orientation angle to provide safe operation of the high-pressure tank is ± 45º, and the carbon fiber tank, calculated at the same fiber winding angle, has the maximum strength value.

Introduction. The article presents an overview of modern neural network models for natural language processing. Research into natural language processing is of interest as the need to process large amounts of audio and text information accumulated in recent decades has increased. The most discussed in foreign literature are the features of the processing of spoken language. The aim of the work is to present modern models of neural networks in the field of oral speech processing.Materials and Methods. Applied research on understanding spoken language is an important and far-reaching topic in the natural language processing. Listening comprehension is central to practice and presents a challenge. This study meets a method of hearing detection based on deep learning. The article briefly outlines the substantive aspects of various neural networks for speech recognition, using the main terms associated with this theory. A brief description of the main points of the transformation of neural networks into a natural language is given.Results. A retrospective analysis of foreign and domestic literary sources was carried out alongside with a description of new methods for oral speech processing, in which neural networks were used. Information about neural networks, methods of speech recognition and synthesis is provided. The work includes the results of diverse experimental works of recent years. The article elucidates the main approaches to natural language processing and their changes over time, as well as the emergence of new technologies. The major problems currently existing in this area are considered.Discussion and Conclusions. The analysis of the main aspects of speech recognition systems has shown that there is currently no universal system that would be self-learning, noise-resistant, recognizing continuous speech, capable of working with large dictionaries and at the same time having a low error rate.

Introduction. The movement of the carrier and external factors (the effects of the atmosphere, temperature and pressure) degrade significantly the image quality of the servo optoelectronic systems (OES) and the positioning accuracy of the emitting OES. The issues of image quality improvement and the probability of keeping the image of the observation object (OO) on the optical axis of the servo EOS are considered.Materials and Methods. The development of an automatic control system for an optoelectronic device (ACS OED) involved solving a multi-criteria optimization problem taking into account a number of conflicting technical-andeconomic (TE) requirements. The determination of tolerated dynamic errors (TDE) of image stabilization was a key issue in the development of on-board optoelectronic devices (OOED). Lagrange equations of the second kind and the mixed Gilbert method made it possible to obtain a mathematical model of the CO OED. Then, the decomposition of a two-link ACS with nonlinear cross-couplings in the CO was performed. A functional diagram of the image formation model of the OOED was presented. The parameters of the matrix photodetector and the requirements for the dynamic error of the ACS OED, taking into account the permissible MTF of the OED, were listed. The functions of transferring modulation, as well as linear, harmonic and vibrational shift of the image corresponding to the permissible and achieved TDE were visualized. Logarithmic frequency characteristics were created in the Mathcad environment. The two-link control system of the OED with the specified parameters of the CO for the considered movement was presented as two independent azimuth and elevation control channels.Results. The processes of control of the on-board optoelectronic system in the stabilization and tracking modes were described. To study the dynamics of spatial control of the OOEP in accordance with the ACS methodology, a computer simulation model (CSM) of the digital automatic control systems (DACS) of the OED was developed. It was implemented in the Matlab environment and consisted of CSM CO, drives, proportional-integral-derivative (PID) controllers taking into account non-linearities, a central computing device (CCD), a guidance software device, a CSMcarrier that implemented the equations of motion. Harmonic vibrations of the carrier were described. The errors of tracking and stabilization in the tracking mode with an additional control action introduced in the form of a constant speed were determined. The dynamics of spatial control of the OOED was investigated. A computer simulation model of a digital automatic control system of an optoelectronic device, the results of modeling the DACS OED without considering the board movement, and the processes of OED control subject to movement were visualized.Discussion and Conclusions. The stabilization accuracy was calculated for the studied cases. It was established that the stabilization tens of times exceeded the previously stated indicators, and it tens of times reduced the requirements for the convergence of the laser beam and the laser radiation power when developing the optical path of the product in question. The proposed CSM can be used in the development of the on-board optoelectronic systems. In this case, the application of the presented methodology and CSM will help to reduce labor costs and minimize errors.

Introduction. Domestic and foreign works on the milling of complex-profile surfaces with a ball-end tool were analyzed. Methods of surface quality control and ways to provide amplitude parameters of roughness, based on research data and field experiments, were considered. Theoretical provisions on the determination of cutting forces and the results of vibroacoustic diagnostics were presented.Materials and Methods. The methods of correlation analysis, comparison and generalization of the results were applied. The data were calculated at different tool angles, taking into account the instantaneous cutting forces, and were fixed in the range of values of the variable feed per tooth (fz) and the angle of inclination of the surface (γ). The vibroacoustic diagnostic data and theoretical data of the presented model at different tool inclination angles were verified by experiment. Consequently, such methods can be used to predict surface roughness parameters.Results. The relationship between cutting forces, tool inclination angle, and vibroacoustic diagnostics data was found. A model of the cutting force and tool displacements was formulated taking into account the inclination of the surface. The optimal range of the inclination angle of the tool to the surface to be machined, at which the minimum values of the amplitude parameters of roughness were achieved, was determined. The sound vibrations obtained empirically, presented in spectral and wave forms, were in good agreement with data from other sources. This allowed us to conclude about the feasibility of forecasting and monitoring roughness parameters in real time through acoustics.Discussion and Conclusions. It was established that the growth of forces in the direction ae(X) and fz(Y) was observed at γ > 40°. This was due to the distribution of the components of the cutting force along the cutting edge and depended on the inclination of the surface. The amplitude parameters decreased when the angle increased from 10 to 40 degrees. The found interrelations of force analysis, processing directions, and vibroacoustic diagnostics have validated the use of vibroacoustic diagnostics to predict surface roughness. Acoustic diagnostics, regardless of the layout of technological equipment, enables to quickly adjust the sound device and assess the impact of cutting modes on roughness parameters.

Introduction. The article studies the problem of investigation of coupled nonstationary thermoelectroelastic fields in piezoceramic structures. The main approaches related to the construction of a general solution to the initial non-selfadjoint equations describing the process under consideration are briefly outlined. The work aims at constructing a new closed solution to the axisymmetric thermoelectroelasticity problem for a long piezoceramic cylinder.Materials and Methods. A long hollow cylinder whose electrodated surfaces were connected to a measuring device with large input resistance was considered. On the cylindrical surfaces of the plate, a time-varying temperature was given. The hyperbolic theory of Lord–Shulman thermo-electro-elasticity was used. The closed solution is constructed using a generalized method of finite integral transformations.Results. The developed calculation algorithm makes it possible to determine the stress–strain state of the cylinder, its temperature, and electric fields. In addition, it becomes possible to investigate the coupling of fields in a piezoceramic cylinder, as well as to analyze the effect of relaxation of the heat flow on the fields under consideration.Discussion and Conclusion. The use of assumptions about the equality of the components of the temperature stress tensor and the absence of temperature effect on the electric field allowed us to formulate a self-adjoint initial system of equations and construct a closed solution.

Introduction. Some of the major factors in the occurrence of vibration of units, causing fatigue failure of the housings of elements, pipelines, and failure of pump elements, are pulsations of the working medium in the hydraulic systems of machine tools, fuel feed systems of aircraft engines and liquid-propellant engine supply. This study aimed at the implementation of a method for determining the dynamic characteristics of a volumetric pump using special bench systems, and the comparison of the calculation results to the experimental data. The stages of calculating the dynamic characteristics of a volumetric pump were described, taking into account the pre-developed special bench systems on the example of an external gear pump with a capacity of 14 cm3 /rev. The implementation of V. P. Shorin's load variation method using special bench systems developed by the authors with predetermined dynamic characteristics was shown. The main stages of the methodology for determining the dynamic characteristics of a gear pump were described.Materials and Methods. Methods of spectral analysis of pulsating pressure were applied in the work. Pulsations of fluid flow at the pump outlet were determined using the impedance method, the method of load variation, and special bench systems.Results. The paper implemented a technique for determining the dynamic characteristics of a gear pump in the drive shaft speed range of 500-2500 rpm for four harmonic components of the vibration spectrum in a wide range of dynamic loads (from inertial to capacitive nature). The bench systems yielding the calculation of the dynamic characteristics of the pump with a minimum error based on the condition of matching the dynamic load and the source of vibrations were analyzed. The developed approach to the evaluation of the dynamic characteristics of the pump was verified through comparing the calculated and experimental data of pressure pulsations in the bench systems with choke, cavity and an extended pipeline at the pump outlet.Discussion and Conclusions. The method for determining the dynamic characteristics of a volumetric pump was implemented using special bench systems developed by the authors. The research results show that the gear pump under study can be considered as an independent source of flow fluctuations, for which the deviation of its own dynamic characteristics from the average values does not exceed 10% for the first harmonic component.

Introduction. Incipient fatigue damage in the metal superstructures of bridges creates certain threats to the safety of operation. Various methods of non-destructive testing are used for their timely detection and diagnosis. A modern and popular on-the-day solution is the method of infrared (IR) thermography. Due to the specifics of the operation of IR cameras, additional processing of recordings received from these cameras is required to obtain an accurate result. This work aims at presenting a method for processing thermofilms and describing the possibilities of its application under real conditions.Materials and Methods. A method for processing thermographic films was described. It provided detecting temperature anomalies using only information from the camera. The results of its application on the elements of existing metal bridge spans are presented.Results. It is shown that there are temperature anomalies for existing defects. This means that the defects continue to develop, which was confirmed by subsequent observations of their condition. In addition, a case of temperature anomaly in the defect-free external region was identified. This might be a sign of an incipient defect that could not be diagnosed by other methods. If the presence of this defect is confirmed during repeated examinations, it will be possible to diagnose hidden defects that have not yet come to the surface, and/or detect potentially collapsing places.Discussion and Conclusions. The IR thermography performance as a method of non-contact non-destructive testing is shown, as well as its operability on real objects under random load.

Introduction. The article elucidates increasing the efficiency of turn-milling of powdered metal high-speed steel products. Turn-milling can be used as an alternative to the traditional turning method. The article describes advantages of the turn-milling method. A review of studies devoted to improving the surface quality of parts when turning by milling is given. The work aims at determining the effect of cutting modes on the surface roughness by the orthogonal turning method through milling powdered high-speed steel with a monolithic cutter.Materials and Methods. Statistical analysis methods based on the creation of a mathematical model for predicting microgeometric deviations of the treated surface were used. An experimental research method was applied to verify the adequacy of the mathematical model. The experiment was planned according to the non-composite design proposed by Box and Behnken. The experiment was carried out on a turning machining center with a driving tool. Powdered highspeed steel BÖHLER S390 MICROCLEAN was used as sample material for the experiment. A monolithic carbide milling cutter served as a cutting tool. During the experiment, the cutting speed, milling width, and feed per tooth varied. The roughness of the treated surface was measured by a contact profilometer.Results. A mathematical model of the formation of surface roughness depending on the processing modes was developed. During the experiments, the effect of cutting speed, tool feed, and radial cutting depth on the roughness of the treated surface was determined. It was established that the dependence of roughness on feed had a linear character over the entire investigated range of cutting modes. In turn, the dependence of roughness on the cutting speed and cutting width had a parabolic character. The results obtained allowed us to achieve the roughness of the treated surface Ra = 1.85 without reducing the processing performance. Discussion andConclusions. The developed mathematical model reflects the impact of cutting modes on the surface roughness when turning high-speed steel with a monolithic cutter. The results of the conducted research can be used to determine the optimal cutting modes that provide a given surface quality in the manufacture of real parts under the production conditions. It is recommended to continue the research with the control of additional output parameters, such as temperature and vibration. Reducing the effect of regenerative self-oscillations on the roughness of the treated surface can be reached through assigning the cutting modes based on the results of a modal analysis of the process system.

Introduction. To search for effective methods of finishing and stripping of long-length parts, it is advisable to create a rotary-screw process system of a pass-through type. Its main working element is a screw rotor, which is a combination of flat elements of various shapes and sizes, multidirectional with respect to the helical lines around the perimeter. The purpose of this study is to justify the intensity of the machining process in devices equipped with a screw rotor.Materials and Methods. Metal removal is accepted as the main parameter determining the intensity of the machining process in screw rotors. Within the framework of the presented study, processing was performed on an experimental rotary-screw installation. The processing medium consisted of molded abrasive pellets of the PT 10x10 brand. The research conditions were as follows: loading volume (without part) — 60 %; rotor speed — 50 rpm; processing time – 30, 60, 90 min; rotor axis tilt angles — 0о and 5о. The influence of treatment modes and conditions on the process intensity was considered on plate samples with dimensions of 80×10×1 mm made of aluminum alloy D16T. To determine metal removal, the samples were weighed on Ohaus AX223 analytical balance before and after processing.Results. The patterns of metal removal from samples at different processing times, the location of samples in the working area of a screw rotor with different angles of inclination, and its speed are presented.Discussion and Conclusions. The regularities established in the course of research indicate the efficiency of rotaryscrew process systems for solving problems on the finishing treatment of long-length parts. The main factors that control such processing in devices with a screw rotor and affect its intensity (and, as a consequence, the process performance) are the screw rotor speed, the shape of the perimeter, and the axis angle.

Introduction. The paper considers an axisymmetric problem of elasticity theory for a radially inhomogeneous transversally isotopic nonclosed sphere containing none of the 0 and 𝜋 poles. It is believed that the elastic moduli are linear functions of the radius of the sphere. It is assumed that the side surface of the sphere is fixed, and arbitrary stresses are given on the conic sections, leaving the sphere in equilibrium. The work objective is an asymptotic analysis of the problem of elasticity theory for a radially inhomogeneous transversally isotropic sphere of small thickness, and a study of a three-dimensional stress-strain state based on this analysis.Materials and Methods. The three-dimensional stress-strain state is investigated on the basis of the equations of elasticity theory by the method of homogeneous solutions and asymptotic analysis.Research Results. After the homogeneous boundary conditions set on the side surfaces of the sphere are met, a characteristic equation is obtained, and its roots are classified with respect to a small parameter characterizing the thickness of the sphere. The corresponding asymptotic solutions depending on the roots of the characteristic equation are constructed. It is shown that the solutions corresponding to a countable set of roots have the character of a boundary layer localized in conic slices. The branching of the roots generates new solutions that are characteristic only for a transversally isotropic radially inhomogeneous sphere. A weakly damping boundary layer solution appears, which can penetrate deep away from the conical sections and change the picture of the stress-strain state.Discussion and Conclusions. Based on the solutions constructed, it is possible to determine the applicability areas of existing applied theories and propose a new more refined applied theory for a radially inhomogeneous transversally isotropic spherical shell.

Introduction. The significance of machine learning under the conditions of digital transformation of industry, and methods of implementing deep learning to provide the performance of trust management systems are considered. The necessity of using convolutional artificial neural networks for deep machine learning is determined. Various technologies and architectures for the implementation of artificial neural networks are briefly considered; a comparative analysis of their performance is carried out. The work objective is to study the need to develop new approaches to the architecture of computing machines for solving problems of deep machine learning in the trust management system implementation.Materials and Methods. In the context of digital transformation, the use of artificial intelligence reaches a new level. The technical implementation of artificial neural systems with deep machine learning is based on the use of one of three basic technologies: high performance computing (HPC) with parallel data processing, neuromorphic computing (NC), and quantum computing (QC).Results. Implementation models for deep machine learning, basic technologies and architecture of computing machines, as well as requirements for trust assurance in control systems using deep machine learning are analyzed. The problem of shortage of computation power for solving such problems is identified. None of the currently existing technologies can solve the full range of learning and impedance problems. The current level of technology does not provide information security and reliability of neural networks. The practical implementation of trust management systems with deep machine learning based on existing technologies for a significant part of the tasks does not provide a sufficient level of performance.Discussion and Conclusions. The study made it possible to identify the challenge of the computation power shortage for solving problems of deep machine learning. Through the analysis of the requirements for trust management systems, the external challenges of their implementation on the basis of existing technologies, and the need to develop new approaches to the computer architecture are determined.

Coronavirus, also known as COVID-19, was first detected in Wuhan, China, in December 2019. It is a family of viruses ranging from the common cold to severe acute respiratory syndrome (SARS). The symptoms of such a virus are similar to those of a cold or seasonal allergies. Like other respiratory viruses, it is mainly transmitted through airborne droplets when coughing or sneezing. Therefore, the recognition of COVID-19 requires careful laboratory analysis, and the reduction of recognition resources is a major challenge. On 11 March, 2020, the World Health Organization (WHO) declared COVID-19, caused by SARS-CoV-2, a pandemic, as there had been an exponential increase in cases worldwide, and demand for intensive beds and related structures had far exceeded existing capacity. The first examples of this are the regions of Italy. Brazil registered the first case of SARS-CoV-2 on 02/26/2020. Transmission of the virus in this country shifted very quickly from imported cases to local and, finally, community missions, with the Brazilian federal government announcing national community transmission on 03/20/2020. As of March 23, in the state of São Paulo with a population of about 12 million people, where the Israelita Albert Einstein Hospital is located, 477 cases of the disease and 30 related deaths were registered, and on March 27, there were already 1223 cases of COVID-19 with 68 concomitant deaths. To slow the spread of the virus in the state of São Paulo, quarantines and social distancing measures were introduced. One of the motivations for this challenge is the fact that, in the context of an extensive healthcare system with the possible limitation of SARS-CoV-2 testing, it is not practical to test every case, and test results can only be used in testing the target subpopulation. The study objective is to build a model based on machine learning that can predict the detection of SARS-CoV-2 from medical data. For this, various classification models of machine learning are compared, and the best one to predict coronaviruses is determined. The comparison is based on individuals in class 1, i.e., those with a positive test. Therefore, it is required to determine the machine learning model with the best response and F1 score for class 1.Materials and Methods. An open-source data set from the Israelita Albert Einstein Hospital in São Paulo, Brazil, was taken as a basis. The following machine learning models were used for the study: RandomForests (RF), K-Nearest Neighbor (KNN), Support Vector Machine (SVM), Logistic Regression (LR), Decision Tree (DT) and AdaBoost (AB), as well as the 10-time cross-validation technique. Some machine learning performance measures, such as accuracy, recall, and F1 score were evaluated.Results. Out of a total of 5,644 people tested during the COVID-19 pandemic, 5,086 people tested negative and 558 people tested positive. At the same time, support for machine vectors showed the best results in detecting coronavirus with a recall of 75 % and an F1 score of 60 % compared to models: Random drill, KNN, LR, AB, and DT.Discussion and Conclusions. It was found that when using AB algorithms, greater accuracy is achieved, but the stability of the LSVM algorithm is higher. Therefore, it can be recommended as a useful tool for detecting COVID-19.

Introduction. Mechanical vibrations are widespread in the production processes. The drives of machines and mechanisms are mainly electromechanical, so mechanical reactive power is transformed into electrical reactive power of the network, impairing the quality of electricity. This explains the significance of considering the mechanical reactive power, and, as a consequence, the urgency of the presented study. The research objective is to detail the types of mechanical power under harmonic vibrations.Materials and Methods. The literature on the issues of dynamics, kinematics, vibrations, transformation of motion in oscillatory systems, etc., has been studied. Theoretical, mainly mathematical methods of research are used.Results. The powers developed under elastic deformations, forced harmonic vibrations of an inert body, and vibrations associated with gravitational influence, as well as reactive, active, full powers in the complex formulation, and mechanical powers in the vector representation are mathematically interpreted.Discussion and Conclusions. Under the mechanical harmonic vibrations, along with the sign-positive thermal power, sign-variable reactive powers develop, characterizing the reversibility of kinetic and potential energies. The total mechanical power satisfies the Pythagorean formula. The concept of mechanical reactive, active, and total powers generalizes the corresponding concepts of power from electrical engineering, and thus manifesting electromechanical dualism.

Introduction. Transverse vibrations of a bimorph consisting of two piezomagnetoelectric layers and located in the alternating magnetic field are investigated. Piezomagnetoelectric layers are multilayer composites with alternating piezoelectric and piezomagnetic layers. The mechanical and physical properties of such a composite are given by known effective constants.Materials and Methods. The applied theory of multilayer plate vibrations takes into account the nonlinear distribution of electric and magnetic potential in piezoactive layers in the longitudinal and transverse directions. On the basis of this theory, the stress-strain state, the dependences of deflection, electric and magnetic potentials on the volume ratio of the composition of the hinged bimorph, are investigated. The electric potential is assumed to be zero at all electrodes, while the magnetic potential is zero at the inner boundary and unknown at the outer boundaries. Therefore, the distribution of electric and magnetic potentials in the middle of the layer are unknown functions. In the case of the magnetic potential, the distribution at the outer boundary is also unknown. In the problem, the Kirchhoff hypotheses for mechanical characteristics were accepted. The use of the variational principle and the quadratic dependence of the electric and magnetic potentials on the thickness of piezoactive layers made it possible to obtain a system of differential equations and boundary conditions.Results. When the volume ratio of the composition of piezoactive bimorph materials changes, the electric potential in the middle of the layer changes nonlinearly. The magnetic potential in the middle of the layer and at the outer boundary increases almost linearly with an increase in the volume percentage of BaTiO3. The dependence of the deflection in the middle of the layer is determined.Discussion and Conclusions. An applied theory for calculating transverse vibrations of a bimorph with two piezomagnetoelectric layers is constructed. The dependence of the characteristics of the stress-strain state, electric and magnetic fields on the volume fractions of piezomagnetic and piezoelectric materials, is investigated.

Introduction. The launch vehicle (LV) in flight and the dynamic components of loads from the impact of a trapezoidal wind gust are considered. It is proposed to determine the dynamic components of the force factors using analytical solutions for the structure points accelerations. The work objective is to create a technique for selecting the duration of the standard gust, under the influence of which maximum loads are provided in the sections of the LV structure.Materials and Methods. The launch vehicle is presented as an uneven beam. The description of its vibrations is reduced to a system of independent ordinary differential equations that determine the motion of an equivalent system of oscillators. The equation of oscillator vibrations under the action of a trapezoidal pulse load is solved by the overlay method, and it is reduced to the calculation of the Duhamel integral. It is proposed to get the parameters of an equivalent system of oscillators based on the results of the calculation of dynamic characteristics for a finite element LV model in the Nastran program.Results. Analytical relations for the LV structure point accelerations under the action of a trapezoidal wind gust are given. For the beam model, test calculations of accelerations were carried out according to the technique proposed in this paper. These data are compared to the results of finite element modeling. With the help of analytical solutions, dependences are constructed that determine the nature of the change in the magnitude of the bending moment for different sections of the launch vehicle when the duration of the wind gust varies.Discussion and Conclusions. The presented technique provides building an equivalent dynamic model of systems with a large number of degrees of freedom on the example of a LV and obtaining analytical solutions for accelerations of points of a mechanical system under trapezoidal external action. These solutions are applicable for the study of dynamic loads. The analysis results enable to select the duration of the wind gust, at which maximum loads are reached in the sections of the LV structure. Calculations based on the analytical solutions are very economical in terms of time spent. They can be used in design calculations for preliminary assessment of loading.

Introduction. This paper discusses tribomechanical characteristics of experimental hard alloys with a modified cobalt binder under friction without lubrication on hard-to-cut materials – stainless steel and titanium alloy. The research objective is to evaluate the process of friction interaction for each friction pair according to a number of parameters, and to determine the optimal combinations of “experimental hard alloy – structural material” on the basis of the established tribological indicators.Materials and Methods. Tribological tests of hard alloys were carried out using a cylinder-to-disc friction scheme for different sliding speeds and temperatures under constant load without the use of lubricants. Comparison of the friction interaction process was carried out by the frictional force, volumetric wear and roughness of the friction tracks on the counterbody. Stainless steel 12H18N9Т and titanium alloy ВТ3-1 were used as counterbody materials. The resistance of experimental compositions to the abrasive type of wear was determined through measuring the surface dynamic microhardness on a scanning nanohardness tester by analyzing the thickness of the scratches caused by the indenter.Results. According to the results of surface microindentation, the experimental alloys 2.22 (binder 5.65% Co + l.8% Mo + 0.6% Ti) and 2.23 (binder 5.1% Co + 2.7% Mo + 0.61 % Ti) are characterized by the highest microhardness. For these materials, the average scratch width at various forces was minimal. During tribological tests, the best frictional characteristics were recorded for stainless steel in combination with experimental alloy 2.22, and for the friction pair “titanium alloy VT3-1 — hard alloy 2.23”. The friction of this combination of materials was characterized by low friction coefficients with a low level of fluctuations, minimal wear of samples, and changes in the initial microrelief of their surfaces.Discussion and Conclusions. As a result of the research, the optimal friction pairs from the point of view of tribological interaction were established, specifically “titanium alloy VT3-1 — hard alloy 2.23” and “stainless steel 12X18N9T – hard alloy 2.22”. The frictional interaction for these combinations of materials is characterized by minimal volumetric wear, which will contribute to increasing the wear resistance of the tool in the areas of elastic contact on the front and rear surfaces.

The use of data mining and machine learning tools is becoming increasingly common. Their usefulness is mainly noticeable in the case of large datasets, when information to be found or new relationships are extracted from information noise. The development of these tools means that datasets with much fewer records are being explored, usually associated with specific phenomena. This specificity most often causes the impossibility of increasing the number of cases, and that can facilitate the search for dependences in the phenomena under study. The paper discusses the features of applying the selected tools to a small set of data. Attempts have been made to present methods of data preparation, methods for calculating the performance of tools, taking into account the specifics of databases with a small number of records. The techniques selected by the author are proposed, which helped to break the deadlock in calculations, i.e., to get results much worse than expected. The need to apply methods to improve the accuracy of forecasts and the accuracy of classification was caused by a small amount of analysed data. This paper is not a review of popular methods of machine learning and data mining; nevertheless, the collected and presented material will help the reader to shorten the path to obtaining satisfactory results when using the described computational methods

Introduction. Welded joints in large-sized metal structures (e.g., in the structures of ship hulls) subject to low-cycle fatigue are considered. The characteristic appearance of soft interlayers, which are significantly plastically deformed under working loads, was noted. Deformation of the metal structure with damage, especially in the form of cracks, reduces the strength and reliability of structural elements and joints. Pre-deformation negatively affects plasticity; therefore, much depends on the residual plasticity of the cracking material. At the same time, with a decrease in residual plasticity, such an important reliability indicator as the resistance of the material to crack propagation — the fracture toughness – decreases. The paper is devoted to the development of a model that includes analytical dependences for assessing the crack resistance of metal structures and their welded joints with soft interlayers according to the crack resistance limit for all crack sizes.Materials and Methods. The theory and methods of linear mechanics of materials destruction, structural-mechanical approach are used. The calculation results were analyzed and compared to the experimental data and other analytical solutions. The numerical experiment was performed for the ferrite-perlite steel grades of 10, 50, 22K, St3sp, etc., widely used in industry, as well as for alloy steels hardened to medium and high strength of 30KhGSA, 37KhN3A, etc. Results. Analytical dependences are obtained for calculating the relative crack resistance limit according to three main known mechanical characteristics of the state of the material of the soft interlayer of the welded joint.Discussion and Conclusions. The results obtained can be used to assess the crack resistance of pre-deformed structural elements and welded joints (including those with soft interlayers) operating under a transverse load. The results of experimental data and analytical calculations are shown in dimensionless form, which enables to obtain invariant results with respect to the fracture toughness limit.

Introduction. The paper submits the analysis of existing design solutions of flow dividers used to synchronize hydraulic drives of working bodies of technological and mobile machines. The market demands for multithreaded throttle flow dividers without valves with the controlled division ratio, such as multi-axle vehicle chassis, are identified. The objective of the work was to analyze the possibility and rationale for developing a throttle four-way flow divider without valves with sensing elements of the Venturi tube type. The solution should provide the synchronicity of movement (rotation) of more than three working bodies of technological and mobile machines.Materials and Methods. A patent search for the designs of hydraulic flow dividers is carried out, and systems that require the division of the hydraulic fluid flow into more than two executive bodies are considered. An upgrade option, which allows dividing the flow into four branches, is proposed for the design of a three-channel throttle flow divider without valves.Results. The urgency of developing a multithreaded throttle flow divider without valves for application in industrial and mobile machines is validated. Two types of four-flow dividers are considered, their weaknesses are indicated. It is noted that the development of a multithreaded throttle flow divider based on the designs created in 1989 and 1991 will reduce the number of hydraulic pumps and get rid of the series connection of double-flow dividers. In this way, it is possible to reduce pressure losses in the hydraulic system and implement adaptive control of hydraulic motors of multi-motor mobile machines. The possibility to obtain a divider/combiner into four flows by adding an outlet chamber connected to the membrane chamber through a channel entering the Venturi nozzle on the basis of a three-flow throttle divider is shown. The principle of operation of such equipment is described.Discussion and Conclusions. The principles of construction of throttle flow dividers without valves are considered. An upgrade option is proposed to increase the number of division channels from three to four. However, to validate the operability of this design, a numerical analysis of the various modes of operation of the divider is required — calculation of the reduced volumetric stiffness of its working cavities. The information obtained can be used to modernize the hydraulic units of technological and mobile machines, increase their reliability, manufacturability, and efficiency. The issues that need to be solved in further research are identified.

Introduction. Providing people with high quality drinking water has always come first. However, its transportation through pipeline systems was often associated with some problems, such as the temperature of the water and the environment, as well as the possibility of water hammer on certain pipe sections. This was especially true for systems that use polyethylene pipes. Temperature is a key factor affecting the flexibility properties of polyethylene pipes, and it affects not only the design, but also the investment in the development of water supply networks. The purpose of these studies was to study the effect of water and ambient temperature on the density, properties of the pipe material and the speed of propagation of a hydraulic shock wave in polyethylene pipes.Materials and Methods. In the experiments performed, the method of field research was used, when tests are carried out on specialized equipment on samples specially made for the pursued purposes. Here, samples of high-density polyethylene pipes were used, which were subjected to tensile tests on a tensile testing machine, and each experiment was carried out three times.In the course of the experiments, the samples were exposed to certain temperature regimes (both external and internal), while the influence of the hydrodynamic pressure of the liquid in the pipe was also investigated, as a result of the change in time of the liquid velocity in its sections. To do this, the samples were supplied with liquid under a certain pressure in order to find out the influence on the pipes of an effect known as water hammer.Results. In the course of the research, it was found that the value of the elastic modulus of high-density polyethylene PE100 decreases with increasing water temperature, and the decrease at a temperature of 60° C reaches 60.21% compared to its value at a water temperature of +4° C. Based on the results of experiments to determine the effect of the elastic modulus of polyethylene with increasing temperature, an exponential equation was derived to calculate the value of the polyethylene coefficient as a function of time E = 1.312e-0,01t with the correlation coefficient R2 = 0.988 ; and based on the results of the studies carried out to calculate the value of the propagation velocity of a hydraulic shock wave, an exponential equation was derived as a function of time C = 275.9e-0,01t with the coefficient correlation R2 = 0.987 .Discussion and Conclusions. In the course of the research, it was found that such a phenomenon as water hammer has a harmful effect on the pipe walls, which, if possible, should be avoided even at the design stage of the water supply network. During the experiments, it was found that with an increase in temperature, the values of the elastic modulus of polyethylene decreased with a simultaneous decrease in the values of the propagation velocity of the hydraulic shock wave.

Introduction. Truss structures are widespread in construction due to a number of advantages, such as economy, versatility, and scalability. Accordingly, their modeling and calculation are urgent tasks in the design of building structures. Automatic solution to these problems causes an increase in design efficiency, calculation accuracy, and lower costs. The objective of the study is to examine the functionality and operation algorithm of the software module developed by the authors that generates the geometry of two-dimensional truss structures for subsequent modeling.Materials and Methods. Following the research of the widespread truss configurations, the classification of chords available in the software under consideration is given. The method of parameterizing a truss structure is provided. This method includes base geometric parameters of the structure such as dimensions, model construction rules, and additional features, as well as a comprehensive algorithm. The software is developed in JavaScript.Results. The software module has been integrated into a web application for calculating two-dimensional rod structures. To illustrate the functionality of the software, the examples of user interface are given as well as an example problem. The example includes configuration and calculation of an inclined truss structure. The results, such as support reactions and internal forces with axial force diagram, are provided.Discussion and Conclusions. Using this software module within the framework of the tool for calculating rod structures allows for the simplified process of modeling and calculating complex truss structures, design time, and resource reduction. The software module provides tools for specifying various types of structures, applying loads and assigning properties of a rod system, which makes it a useful instrument for design engineers.

Introduction. The paper analyzes the application of composite materials as the main determining method of reducing the mass of the airframe and an unmanned aerial vehicle. Advanced nondestructive testing methods provide assessing the technical condition of these materials, as well as determining stress concentrators on the airframe and an unmanned aerial vehicle with high accuracy in order to make a decision on the further operation of this object under control. The objective of the work was to increase the accuracy and efficiency of the assessment of crack resistance of composite materials through the acoustic emission control.Materials and Methods. This paper presents the nomenclature of composite materials used in the construction of various aircraft, including unmanned aerial vehicles. The most possible probable defects of these materials due to the influence of operational factors are presented. The applied methods of nondestructive testing of composite material and selection of the most suitable one according to specific advantages were compared. An experiment was carried out to determine the strength limits of carbon fiber using a hardware and software complex by acoustic emission method. The research results are presented in the form of drawings projected by the hardware and software complex.Results. The application of the acoustic-emission method of composite material control is described.Discussion and Conclusions. The results obtained experimentally can be used in the process of determining the strength limits of various composite materials by the acoustic emission method of nondestructive testing to assess the technical condition in mechanical engineering, shipbuilding, and aircraft construction. The paper is recommended to researchers involved in the design of aircraft and unmanned aerial vehicles.

Introduction. This paper studies the capability of different types of artificial neural networks (ANN) to predict the modulus of elasticity of pavement layers for flexible asphalt pavement under operating conditions. The falling weight deflectometer (FWD) was selected to simulate the dynamic traffic loads and measure the flexural bowls on the road surface to obtain the database of ANN models.Materials and Methods. Artificial networks types (the feedforward backpropagation, layer-recurrent, cascade back- propagation, and Elman backpropagation) are developed to define the optimal ANN model using Matlab software. To appreciate the efficiency of every model, we used the constructed ANN models for predicting the elastic modulus values for 25 new pavement sections that were not used in the process of training, validation, or testing to ensure its suitability. The efficiency measures such as mean absolute error (MAE), the coefficient of multiple determinations R2, Root Mean Square Error (RMSE), Mean Absolute Percent Error (MAPE) values were obtained for all models results.Results. Based on the performance parameters, it was concluded that among these algorithms, the feed-forward model has a better performance compared to the other three ANN types. The results of the best four models were compared to each other and to the actual data obtained to determine the best method.Discussion and Conclusions. The differences between the results of the four best models for the four types of algorithms used were very small, as they showed the closeness between them and the actual values. The research results confirm the possibility of ANN-based models to evaluate the elastic modulus of pavement layers speedily and reliably for using it in the structural assessment of (NDT) flexible pavement data at the appropriate time.

Introduction. The concept of estimating the dynamic parameters of the “base — weakened layer — block” system is proposed, taking into account the physical nonlinearity of the material and the kinematic method of excitation of vibrations. In accordance with this approach, the physical nonlinearity of the base and block material is considered using the Drucker- Prager model. The weakened layer is modeled by 3D spring finite elements. The verification procedure of the proposed methodology is carried out on the example of the dynamic calculation of the “base — weakened layer — slope” system.Materials and Methods. The computational experiments were performed using the ANSYS Mechanical software package in combination with a nonlinear solver based on the Newton-Raphson procedure. SOLID45 volumetric finite elements were used to discretize the computational domains. Combined elastic-viscous elements COMBIN14 were used to simulate the displacement of the block relative to the fixed base.Results. An engineering technique for the dynamic analysis of the stress-strain state of the “base — weakened layer — block” spatial system with kinematic method of excitation of vibrations is developed. The accuracy and convergence of the proposed method is investigated using specific numerical examples.Discussion and Conclusion. Based on the mathematic simulation performed, it is shown that the developed technique provides assessing the risks of the occurrence of real landslide processes caused by external non-stationary impacts.

Introduction. The paper is devoted to the study on free oscillations of the sensing element of a micromechanical R-Rtype gyroscope of frame construction developed by the Kuznetsov Research Institute of Applied Mechanics, taking into account the nonorthogonality of the torsion axes. The influence of the instrumental manufacturing error on the accuracy of a gyroscope on a movable base in the case of free oscillations is studied. The work objective was to improve the device accuracy through developing a mathematical model of an R-R type micromechanical gyroscope, taking into account the nonorthogonality of the torsion axes, and to study the influence of this error on the device accuracy. The urgency of the problem of increasing the accuracy of micromechanical gyroscopes is associated with improving the accuracy of inertial navigation systems based on micromechanical sensors.Materials and Methods. A new mathematical model that describes the gyroscope dynamics, taking into account the instrumental error of manufacturing the device, and a formula for estimating the error of a gyroscope, are proposed. The dependences of the state variables obtained from the results of modeling and on the basis of the experiment are presented. Methods of theoretical mechanics and asymptotic methods, including the Lagrange formalism and the Krylov-Bogolyubov averaging method, were used in the research.Results. A new mathematical model of the gyroscope dynamics, taking into account the nonorthogonality of the torsion axes, is developed. The solution to the equations of small oscillations of the gyroscope sensing element and the estimate of the precession angle for the case of a movable base are obtained. A comparative analysis of the developed model and the experimental data obtained in the case of free oscillations of the gyroscope sensing element with a fixed base is carried out. The analysis has confirmed the adequacy of the constructed mathematical model. Analytical expressions are formed. They demonstrate the fact that the nonorthogonality of the torsion axes causes a cross-influence of the amplitudes of the primary vibrations on the amplitudes of the secondary vibrations of the sensing element, and the appearance of an additional error in the angular velocity readings when the gyroscope is operating in free mode.Discussion and Conclusions. The results obtained can be used to improve the device accuracy using the algorithm for analytical compensation of the gyroscope error and the method for identifying the mathematical model parameters.

Introduction. The thermal calculation of a volumetric structure using the finite element method is considered. According to the plans of the Ministry of Energy of the Russian Federation, a powerful wind energy industry will be created in the country in the coming years. In this regard, calculations in the production of building structures of wind power plants are currently becoming a challenge. The production of such fiberglass structures is a complex thermochemical process, including the polymerization of the binder under strictly specified thermal conditions. The work objective is to develop a method for three-dimensional finite element calculation of the non-stationary heating mode of a complexshaped composite structure.Materials and Methods. The determination of the temperature fields of a complex-shaped structure made of inhomogeneous materials causes using numerical methods and, first of all, the finite element method. The finite element modeling of the behavior of composite materials under molding is still incomplete. For its partial solution, the well-known heat conduction equation is adapted for a specific problem based on the first law of thermodynamics. New finite element models describing the thermal fields in the structure during its manufacture are proposed. The accuracy of modeling thermal processes is specified. Numerical simulation of heating is carried out.Results. The solution to the problem was performed in the multifunctional software complex ANSYS with the implementation of the calculation method in the parametric programming language APDL. The temperature fields of the blade elements of wind power plants at the stage of their manufacture were calculated, which made it possible to identify the characteristic features of the production process of these structures and to obtain recommendations for clarifying the process of their gluing.Discussion and Conclusions. The results obtained can be used in thermal calculations of elements of complex layered structures made of composite materials in wind power, mechanical engineering, aircraft, shipbuilding, instrumentation, etc.