Strength Margin Research Articles

Optimization of channels and I-shaped bended closed profiles with perforated walls

The article presents a continuation of the optimization of channel and I-shaped bended closed profiles (BCP) with tubular flanges and perforated walls made of rolled sheet products of both equal and different thicknesses. Such profiles are designed for light steel thin-walled structures (LSWS), which are distinguished by improved technical and economic indicators and mass demand in industrial and civil construction, which confirms the relevance of their further development. The purpose of the study is to show that the characteristics of LSWS can be further improved by shaping profiles, combining straight and round outlines of closed and open contours in a composite section, including their perforation. Through experimental design studies, solving optimization problems and variant design of the BCP, their design sections with a maximum margin of bending strength with a minimum mass have been refined. The originality of technical solutions is confirmed by patent examination. The channel BCP has extreme weight and strength with a relative height of cutouts in the wall of 1/1.87 and a ratio of width and height dimensions of 1/4.32. When the thickness of the shelves is 2 times the wall thickness, the strength and mass of the I-shaped BCP are extreme at a relative height of cutouts of 1/1.23 and a ratio of dimensions of 1/4.17, and when the thickness of the shelves is 0.6 of the wall thickness, the strength and mass of the BCP are extreme with a cutout height of 1/1.73 and a size ratio of 1/5.22. If the thicknesses of the shelves and the wall are equal, then the strength and mass of the BCP is extreme at a cutout height of 1/1.46 and a size ratio of 1/3.17.

Hyperelastic Constitutive Model Determination and Structural Optimization Based on High Vacuum Elastomer Sealing Structure

The stress analysis of rubber liner is widely used in the design of high vacuum elastomer sealing structure. It is very important to determine a reasonable constitutive model and establish a strength evaluation method suitable for failure mode. A series of mechanical properties tests of JY7766 fluororubber were completed in this paper, and material parameters under different constitutive models and strain levels were fitted. A model selection method based on stiffness relative deviation of liner as evaluation index was proposed, and the high precision constitutive model and material parameters with only 0.2% stiffness relative deviation was determined. At the same time, the consistency of crack propagation path and Mises stress distribution of liner was confirmed based on the comparison between theoretical calculation and the actual structure. Under the condition of ensuring the contact total stress of main sealing surface, the maximum Mises stress was reduced by 43.6% and the safety margin of structural strength was improved by optimizing the sealing groove size of a vacuum equipment. The test result showed that the optimized structure meet the requirement of sealing performance.

FIELD DISTORTION ARRESTERS WITH IMPROVED TIME LIMITS FEATURES AND INCREASED RELIABILITY

The article considers the features of the design of four-channel rail arresters with field distortion with improved time characteristics and presents the results of studies of their time characteristics. The need for these studies is associated with the widespread use of such dischargers in capacitive energy storage devices that serve as power sources for electrodynamic mass accelerators. At the present stage of the development of science and technology, the use of such accelerators is the most promising for creating experimental stands for modeling in laboratory conditions the processes of high-speed interaction of structural elements of aircraft with particles of different masses and different origins. According to the operating conditions of the experimental stands, in a wide range of changes in both particle masses and interaction velocities, the amplitude values of currents through the low-inductive load of the mass accelerator can vary from kiloamperes to several megamperes at acceleration times from units to hundreds of microseconds. With this in mind, capacitive energy storage devices are performed in a multi-module design. Each module of a capacitive energy storage device is switched to the load by its own switch. To expand the range of operation of the spark gap of the storage device, to obtain the time characteristics of the spark gap with small delay times, to exclude the probability of spontaneous operation of the spark gap, and to provide the stability of the discharge formation during parallel operation of the switches, the designs of four-channel rail spark gaps with field distortion with improved characteristics were developed, their experimental and theoretical studies were carried out.
 
 The results of the conducted studies show that the smallest value of the delay time and, accordingly, the spread of the delay time are obtained for a spark gap with field distortion with two control electrodes.
 
 It is shown that the obtained analytical expressions presented in the article and the empirical expression calculated for a spark gap with a field distortion with two control electrodes make it possible to determine the values of threshold voltages and delay times, taking into account the statistical delay time and the time of discharge formation.
 
 The value of the threshold voltage is determined, at which the process of direct transformation of the streamer into a spark discharge with high conductivity followed by a breakdown of the interelectrode gap is observed.
 
 The dependences of the static voltage on the pressure in the inner chamber of the spark gap with field distortion with improved time characteristics are given. It is shown that at a certain distance between the main electrodes at a pressure of 0,3-0,5 MPa, the arresters operate with a margin of electrical strength when the static breakdown voltage is 1,5-2 times higher than the operating voltage applied to the electrodes of the gas gap of the arrestor. This eliminates the possibility of spontaneous triggering of the dischargers of the capacitive energy storage.

ПРОГНОЗУВАННЯ ДОВГОВІЧНОСТІ ЦЕМЕНТОБЕТОННОГО ПОКРИТТЯ АВТОМОБІЛЬНИХ ДОРІГ ВІД ДІЇ ТРАНСПОРТНИХ ЗАСОБІВ

Abstract Introduction.In recent years, there has been a tendency to increase the intensity of vehicle traffic on highways around the world, the share of trucks and road trains with an increased number of axles, total load capacity, increased tire pressure is growing. Problems. When designing pavement, the required margin of strength of the layer material to repeat the load should be assigned depending on traffic intensity, traffic flow, its distribution across the width of the roadway, road life and the ability of the material to resist destruction from fatigue. Goal. Develop a method for predicting the durability of cement concrete pavement from the action of vehicles. Results. On the basis of the given theoretical researches it is offered to define a degree of damage of structure of a cement concrete covering from action of vehicles. As is known from the above analysis, the modulus of elasticity of cement concrete pavement on highways is variable from the time of loading, and also confirmed by the results of theoretical and experimental studies of scientists such as Solodkoy S.Y., Levitsky E.F., Chernigova V.A. , Radovsky B.S., Mozgovoy V.V., Sheikina AE etc. Therefore, tensile stresses arise from the action of vehicles in the cement-concrete pavement of highways and fatigue damage occurs over time. Due to the fact that the load of heavy vehicles increases every year, the pressure in the tire tire increases, which is transmitted to the cement-concrete pavement of highways. Conclusions. To predict the durability of cement-concrete pavement of roads from the action of vehicles, an analytical dependence is proposed, which takes into account the total traffic intensity determined by GBN B.2.3-37641918-557 and the maximum allowable amount of design load that can withstand cement-concrete pavement under horizontal tension. when bending. Keywords: highway, pavement, cement concrete, stress, vehicles, fatigue, crack resistance, durability.

Research on Probability Analysis Technology of Circular Section Cabin Socket Structure Based on APDL

In the strength design of sleeve joint structure, manufacturing tolerance and fit clearance are generally ignored. The load of connecting screw is usually calculated by the method of linear distribution. The contact force between screw and cabin is usually simulated by deterministic finite element method. The command flow of probability analysis for typical circular section socket structure is developed based on APDL. The uncertainty of manufacturing tolerance and fit clearance for socket structure is defined as random input variables, such as the cabin diameter, cabin hole position, and cabin aperture and so on. Monte Carlo method is used in probability analysis, and the input variables are random uniform distribution. The analysis results show that the transfer load of screws is redistributed under the probability analysis compared with the finite element analysis, and some screws bear larger load, while the nearby screws bear smaller load. At the same time, the load transferred by screw is not only affected by its own variables, but also by others. The probability analysis method can fully consider the influence of manufacturing tolerance of the structure, and evaluate the structural strength margin more accurately. It can not only prevent the harm caused by uncertainty of random manufacturing tolerance, but also prevent over design caused by conservative method.

Study of the installation for testing the insulation of electrical equipment with increased voltage

In the article, the authors investigated a device for testing the insulation of electrical equipment with increased voltage. Insulation in electrical devices is an essential design element. The dielectric strength of the insulation is determined by its ability to withstand the continuous rated voltage for which the installation is designed. But in some cases, the strength of the insulation may deteriorate due to moisture or defects. Defects can be air inclusions in solid or liquid dielectric. These air inclusions further create conditions for the occurrence of partial discharges. The article discusses the test schemes that exist today to determine the margin of dielectric strength of insulation. The article presents a diagram of the developed device of the installation for testing insulation based on a single design and technological component. The presented device has a smaller weight and size and more effective voltage gain. The results of mathematical modeling, proving an improvement in gain in comparison with analogs, are given.

Error Estimation of Measured Exhaust Gas Temperature in Afterburner Mode in an Aero Gas Turbine Engine

In a turbofan engine, thrust is a key parameter which is measured or estimated from various parameters acquired during engine testing in an engine testbed. Exhaust Gas Temperature (EGT) is the most critical parameter used for thrust calculation. This work presents a novel way to measure and correct the errors in EGT measurement. A temperature probe is designed to measure EGT in the engine jet pipe using thermocouples. The temperature probe is designed to withstand the mechanical and temperature loads during the operation. Structural analysis at the design stage provided a strength margin of 90% and eigenfrequency margin of more than 20%. Thermal analysis is carried out to evaluate maximum metal temperature. Errors are quite high in high-temperature measurements which are corrected using the available methodologies. The velocity error, conduction error, and radiation error are estimated for the measured temperature. The difference of 97 K between the measured gas temperature and calculated gas temperature from measured thrust is explained. The estimated velocity error is 1 K, conduction error is 3 K, and radiation error is 69 K. Based on the error estimation, the measurement error is brought down to 24 K. After applying the above corrections, the further difference of 24 K between measured and estimated value can be attributed to thermocouple error of +/-0.4% of the reading for class 1 accuracy thermocouple, other parameter measurement errors, and analysis uncertainties. The present work enables the designer to calculate the errors in high-temperature measurement in a turbofan engine.

A MODEL FOR IMPROVING THE STRENGTH CHARACTERISTICS OF THE ELECTROMECHANICAL DRIVE OF A MOBILE ROBOT

Mobile robots are increasingly used in the most diverse spheres of human activities; accordingly, it is essential to ensure their reliable functioning, which in turn determines efficiency. Using appropriate calculations during design, it is possible to increase reliability and reduce the metal consumption of the machine samples being created. It is crucial that such calculations consider the loading modes in which the vehicle is used. The purpose of the presented work is to increase the technical and operational indicators of the electromechanical drive of mobile robots by selecting the input parameters in combination with the appropriate methods and techniques of design and mathematical modelling. In order to achieve the specified goal, the following main tasks of the research are defined: firstly, to improve the model of increasing reliability and reducing the metal consumption of mechanical components of mobile robots; and secondly, to calculate the mechanical components of mobile robots using the proposed model. Providing the necessary margin of strength with a simultaneous reduction in metal density is necessary for improving the electromechanical drive of a mobile robot and improving its characteristics in general. The paper presents a model and developed an algorithm for increasing the reliability and reducing the metal consumption of mechanical components of mobile robots. The method includes geometric, kinematic, dynamic, energy, technical and economic indicators' calculations, as well as strength and stiffness calculations. The calculations were performed for a small mobile robot with an electromechanical transmission, and the results of a study of the reliability and strength characteristics of the shaft of the mobile robotics platform were presented. The case of turning a mobile robot with the realization of the maximum torque, which is transmitted to one of the tracks, is considered. Based on the kinematic scheme of the electric transmission, a solid-state model of one of its elements (the traction star shaft of the crawler motor) was developed, for which, based on the schematized Serensen – Kinasoshvili diagram, the margin of safety was determined. The proposed model has been examined and successfully used to construct the experimental samples of mobile robots.

Збільшення запасу міцності різьбових з’єднань, що працюють при змінних навантаженнях

One of the most common types of plug-in connections are threaded connections. In any machine, unit, the number of parts of threaded connections (bolts, studs, nuts, washers, etc.) is calculated by dozens and hundreds of pieces. It follows from this that the issue of designing and calculating threaded connections is of great importance in the design of machines and devices. One of the most important elements of bolts and screws is the thread, which is the surface of the protrusion formed during the helical movement of an arbitrary flat contour on the side surface of a cylinder or cone. Threaded connections are widely used in various mechanisms (internal combustion engines, etc. products). Their use is due to simplicity, high load-bearing capacity, reliability, as well as the convenience of connecting and disconnecting parts. The calculation of tightened threaded connections operating under alternating stresses is a check calculation. Based on the simplified statement of the problem, the preliminary dimensions of the main elements of the threaded connection are determined. Then the layout of the connecting node is carried out, and after the design is fully determined, they begin to perform the verification calculation. In recent times, we have seen an increase in the interest of designers in the calculations of threaded connections operating under variable stresses. This is explained by the fact that in most mechanisms, in particular in the automotive industry, threaded connections work under variable stresses, but an incorrectly determined margin of strength of threaded connections leads to breakdowns and destruction of mechanisms. Thus, there is a need to study more accurate calculation formulas for determining the margin of strength of threaded connections, which is the result of a verification calculation.

IDENTIFICATION OF COVID-19 PANDEMIC INFLUENCE ON COUNTRY MACROECONOMIC STABILITY

During 2020-2021 the world community united the efforts to counteract the destructive impact of the COVID-19 pandemic not only on the life and health of the population but also on the state of country macroeconomic stability. The main task faced by the representatives of state authorities at the stage of the active development of the pandemic was the development and implementation of effective and quick tools to contain the spread of the coronavirus infection along with interventions to maintain the business and population well-being. In turn, during 2020-2021 scientists from all over the world focused their efforts on a multifaceted analysis of the causes, features and consequences of the pandemic in various spheres of life. The main goal of this study is to analyze the impact of the COVID-19 pandemic on the main parameters of the country macroeconomic stability and formalize the changes in patterns of this impact for a sample of European countries. The analysis was conducted for a sample of 15 European countries, including: Albania, Bulgaria, Croatia, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Moldova, Poland, Romania, Serbia, Slovakia, Slovenia and Ukraine during 2015–2021. The time range of the study covers both the pre-pandemic period and pandemic period. This will make it possible to assess the margin of macroeconomic stability in the countries before the outbreak of the pandemic, to reveal the scale of its destructive influence during the active stage of the pandemic, and also to find out the key changes in the analyzed parameters of macroeconomic stability in the pandemic and pre-pandemic periods. The literature review on a certain topic conducted in the work revealed that the most relevant indicators of the state of macroeconomic stability are GDP growth, %; the level of employment of the population, calculated according to the methodology of the International Labor Organization, %; consumer price index, %; current account balance, % of GDP. To fulfill the task set within the scope of the work, several stages were implemented: 1) determination by means of statistical analysis with calculation of the average levels of the relevant indicators for the sample of countries, their chain and base growth rates of the patterns of change in the determinants of macroeconomic stability in the countries included in the sample, in the pre-pandemic and pandemic period periods; 2) performing a cluster analysis using Ward clustering and constructing dendrograms in the Stata 14.2/SE software product for a selected group of countries in 2015, 2019, 2020 and 2021; 3) determination of patterns of macroeconomic stability in 15 European countries and patterns of their change caused by the impact of the COVID-19 pandemic. The results of the statistical and cluster analysis generally show that the COVID-19 pandemic has damaged the macroeconomic stability of the 15 European countries but the scale of the destructive impact is not the same: countries with a greater margin of strength and stability of macroeconomic indicators in the pre-pandemic period more easily passed the stage of high turbulence caused by the coronavirus pandemic, while states that were characterized by macroeconomic instability for several years before the pandemic suffered more devastating consequences in 2020-2021. According to the results of the study, it was established that the pandemic had the most detrimental effect on the state of macroeconomic stability in Croatia and Slovenia, which led to a change in patterns of the ratio of determinants of macroeconomic stability and their transition in 2021 to a worse cluster, while Slovakia even moved to a more stable cluster in 2020-2021. The obtained research results can be useful both to representatives of state authorities in the context of the formation of a post-pandemic recovery strategy, and to representatives of the academic community – for deepening scientific research in this direction.

СТРАТЕГІЧНА ПОВЕДІНКА КОМПАНІЙ В УМОВАХ ВІЙНИ ТА ПОВОЄННОГО ВІДНОВЛЕННЯ

The article is devoted to the problem of formation of strategic behavior of companies, development of effective business strategies in the context of ensuring their survival, recovery and qualitative renewal. To achieve the objectives of the study, the following general scientific methods were used: analysis and synthesis, induction and deduction, comparison. The state and problems faced by domestic companies after the beginning of the war in Ukraine are analyzed. It is established that the business that is focused on the local market, in particular micro-, small- and medium-sized businesses, whose financial strength margin is smaller or much smaller compared to large businesses, has been particularly affected. In these conditions, companies should make effective managerial decisions on the formation of their strategic behavior, the implementation of which is conditionally divided into three consecutive stages: to survive, to keep the business "afloat"; to recover, to adapt to new realities; and thirdly, to lay the foundation and successfully update in the future. The company's strategy should meet its main objectives at a particular stage, reflect what the business needs to operate, and the success of its implementation will be determined by the appropriate "decision tree", which focuses on how, given the situation, to effectively confront the main challenges, resume work and function effectively. It is proposed that at the stage of survival, companies should implement a reduction strategy with an emphasis on capital preservation and cost reduction. At the stage of recovery, it is advisable for companies to implement a stabilization strategy, form a clear program of measures to restore the business, carry out a full or partial change in the business configuration, build new operating models, apply methods and technologies to expand the customer base, establish logistics and effective communications, enter new markets or expand existing ones, build strong relationships with partners, use new technologies for the organization of production and labor. At the stage of renewal, the company should implement certain strategic changes within the growth strategy that will optimize business processes and update the business model. It is concluded that the choice of alternative strategic behavior of the company and justification of business strategy is one of the key factors of its success at the stages of survival, recovery and renewal.

Debt security forecasting models

The paper examines models for predicting Ukraine's debt security. The main purpose of the paper is to reveal the theoretical and practical component of debt security forecasting of various types of forecast models that can be used to predict debt parameters. In the course of the study, attention is focused on debt forecasting as a factor in minimizing financial and debt shocks. The interpretation of the definition of debt security in a broad and narrow sense is given. The linear trend model of forecasting debt indicators is studied and it is concluded that it acts as a fundamental element in the process of debt forecasting, but cannot guarantee high quality planning of future indicators. A study was also conducted in the context of medium-term forecasting using ARIMA and multivariate regression models, which showed satisfactory qualitative characteristics in the process of simulating future debt security parameters. Forecasting of financial and debt parameters using ARIMA models, in the context of econometric and statistical quality, showed a sufficient level of adequacy of regression equations. The ARIMA model for simulating future values of debt parameters is characterized by an approximate value of the integral debt security indicator to the regulatory level. Based on the obtained models, a comparative characteristic of the studied models is carried out with a comparison of the obtained results of the integral debt security indicator and calculation of the absolute financial strength margin indicator based on them. Based on the results of the study, it can be concluded that the use of ARIMA models and multiple regressions is the optimal method for predicting debt with a high level of adequacy of the simulated values and rather low labor costs in the procedural context. Priority areas of future research are highlighted.

Methodology for calculating rope drums for stability

. The problems of the stability of rope drums are quite urgent. The rope drum is in most cases a thin-walled shell, which, under the influence of external pressure from the rope, can lead to loss of stability. The stability issues of the drum shell, which is loaded with rope turns, are very important, because the safety and reliability of the rope hoist is directly related to them The studies carried out made it possible to obtain a new method for calculating the stability of cylindrical shells, which takes into account not only the length of the shell, but also the rigidity of the connection with the head. In addition, a calculation formula was obtained to determine the critical pressure of the oval shell, which gives a fairly good agreement with the experiments of American scientists. The work also considered the effect of the difference in wall thickness on the critical load of the drum. The studies carried out made it possible to conclude that the parameters of the rope drums make it possible to completely eliminate the need to install rings and stiffeners. Also as a result of research it was found that the shell of the crane drum under the influence of a radial load cannot lose stability. Studies have shown that in all cases the stability margin of the rope drum shell is greater than the strength margin. In this case, the load created by the rope wound on the drum is considered, with the ratios of the radius of the drum and the rope typical for crane construction. In addition, a coefficient was established that takes into account the elasticity of the shell-head joint. The studies carried out have shown that such initial deviations of the drum shell shape as ovality do not give a significant increase in the critical load. The results obtained are quite important, since they allow reducing the metal consumption of the rope drum shell and at the same time ensuring its reliable operation. A decrease in metal consumption is achieved by reducing the thickness of the shell and the absence of the need to install rings and stiffeners. This will lead to a decrease in metal consumption and energy consumption of the crane itself, and also simplifies the technology of manufacturing a rope drum.

Проектирование рамы автономного летательного аппарата с применением композиционных материалов

The paper considers approaches to creating a new type of unmanned aircrafts - quadcopters. It is stated that the efficiency of a quadcopter directly depends on its frame design and the structural materials used. The approaches to designing the aircraft frame using computer-aided design tools (SolidWorks package) are described. The stress maps obtained during the strength study for the frame beam made of carbon fiber allow asserting a large margin of structural strength. The strength calculation carried out predetermined the need to take into account the influence of additional factors (the air flow created by the traction screws). The existing restrictions on the maximum size of the rotating propellers predetermined the design of the quadcopter frame taking into account the maximum number of possible aerodynamic effects that determine the stability of flight characteristics by minimizing interference from air turbulence, as well as from possible natural phenomena. The designed quadcopter frame has special aerodynamic surfaces that allow for a stable flight path in a volatile air environment. The generated torque is determined by the characteristics of the traction screw motors. The influence of the isosurface air flow on the design of the quadcopter was evaluated.

Mechanical Behavior of Titanium Based Metal Matrix Composites Reinforced with TiC or TiB Particles under Quasi-Static and High Strain-Rate Compression.

The mechanical behavior of titanium alloys has been mostly studied in quasi-static conditions when the strain rate does not exceed 10 s−1, while the studies performed in dynamic settings specifically for Ti-based composites are limited. Such data are critical to prevent the “strength margin” approach, which is used to assure the part performance under dynamic conditions in the absence of relevant data. The purpose of this study was to obtain data on the mechanical behavior of Ti-based composites under dynamic condition. The Metal Matrix Composites (MMC) on the base of the alloy Ti-6Al-4V (wt.%) were made using Blended Elemental Powder Metallurgy with different amounts of reinforcing particles: 5, 10, and 20% of TiC or 5, 10% (vol.) of TiB. Composites were studied at high strain rate compression ~1–3·103·s−1 using the split Hopkinson pressure bar. Mechanical behavior was analyzed considering strain rate, phase composition, microstructure, and strain energy (SE). It is shown that for the strain rates up to 1920 s−1, the strength and SE of MMC with 5% TiC are substantially higher compared to particles free alloy. The particles TiC localize the plastic deformation at the micro level, and fracturing occurs mainly by crushing particles and their aggregates. TiB MMCs have a finer grain structure and different mechanical behavior. MMC with 5 and 10% TiB do not break down at strain rates up to almost 3000 s−1; and 10% MMC surpasses other materials in the SE at strain rates exceeding 2200 s−1. The deformation mechanism of MMCs was evaluated.

Optimization Design of the Lower Rocker Arm of a Vertical Roller Mill Based on ANSYS Workbench

The lower rocker arm is an important part of the vertical roller mill and its lightweight design is of great significance for reducing the mass and production cost of the roller mill. Firstly, the strength and deformation distribution of the lower rocker arm under working load were analyzed by ANSYS Workbench to determine the maximum stress and maximum deformation. The parts with large strength margin were used as the basis for the optimal design. During the analysis, firstly, the arm body of the lower rocker arm was determined part of the lightweight design. Secondly, the mass of the lower rocker arm was taken as the optimization target, the stress and displacement generated by the load of the lower rocker arm were taken as the constraint conditions, the structural size of the internal cavity of the lower rocker arm was taken as the optimization design parameter, and the mathematical model of the optimization design was established. Finally, the structural size of the internal cavity of the lower rocker arm was optimized by using the response surface optimization module and multi-objective genetic algorithm in ANSYS Workbench. The optimum results show that, compared with the original design model, the lower rocker mass was reduced by 346.3 kg and the decrease was about 5.29%, while the strength and deformation were nearly unchanged. Therefore, by optimizing the design, the material is saved and the cost is reduced, which can provide a reference basis for the design and light weight of the lower rocker arm.

Calculation of the chain drum with elastic fingers of potato harvesting machines

In agricultural machines, chain transmission is widely used, the main advantage of which is a high load capacity. Therefore, in this article, the methodology for calculating chain drives in mechanical drives of agricultural machinery, namely in mechanical drives of potato harvesters, is presented. As a result of experimental and theoretical studies, the availability and safety margin of the selected chain drive of a loosening drum with elastic fingers of a potato harvesting machine was confirmed. In potato-harvesting machines, the movement of the executive working bodies is carried out. Analysis of the design of domestic and foreign potato harvesters showed that it is possible to obtain a good quality of potato harvesting in difficult soil and climatic conditions due to the use of machines of a simpler design with a mesh number of working bodies, but at the same time with their rational layout, the correct choice of transmission drives and ensured optimal modes work. The advantage of these transmissions is their large load capacity and the ability to work under dynamic loads. Therefore, in these investigations, the works are analyzed and the theoretical foundations and methods for calculating the working capacity of the wearable chain and the margin of strength of the chain transmission for dynamic loads are presented. As a result of the experimental theoretical research, the reliability of the working capacity and the strength reserve of the selected chain drive of the drum with elastic pulleys of the potato harvester is supported.

Results of post-irradiation examinations of mixed nitride pins with gas and liquid metal sub-layers

Today the investigations have been completed on helium-bonded fuel pins with mixed uranium-plutonium nitride of BN-600/BN-800, BN-1200 and BREST reactors types after irradiation as a part of ten EFAs of BN-600 reactor up to maximum burn-up of 7.5; 6.0 and 4.5at%, respectively. Also the PIE of mixed nitride pins of BREST type with helium and lead sub-layers after intermediate tests to maximum burn-up of 4,8 and 3,9at% as part of dismountable EFAs of BOR-60 reactor are over. As a result of postirradiation examinations, the main intra-fuel pin processes that affect on materials properties change and fuel pins state, their relationship with the initial nitride state were identified. The regularities and quantitative characteristics of nitride swelling, the behavior of fission products, cladding corrosion and mechanical properties change are revealed. The average for the irradiation time rate of fuel swelling in cross sections near the core midplane in gas-bonded pins of different EFAs irradiated in BN-600 reactor is equal to (1.6 - 2.0) %/at%. According to the results of irradiation in BOR-60 reactor, the fuel swelling rate in lead-bonded pins is lower than in helium-bonded pins: 1.4 ± 0.2 and 1.7 ± 0.2 %/at%, respectively. The presence of carbon and oxygen impurities in the fuel can lead to local areas of claddings carburization and oxidation, randomly distributed along the height and perimeter of its inner surface. The key characteristics of the fuel that determine the cladding carburization and oxidation, and ways to prevent them, are determined. Cladding corrosion in lead-bonded pin is caused by selective dissolution of cladding steel components. The maximum depth of the corrosion zone is located in the upper part of the fuel column and is equal to 40 microns. The results of cladding mechanical tests obtained using longitudinal segment samples and tubular samples loaded by internal gas pressure showed the significant margin of strength and ductility of cladding materials along the entire height of fuel pins both at nominal operating temperatures and at room temperature. High values of strength characteristics indicate a weak influence of corrosion on the strength of studied claddings materials. The mechanical cladding properties of a lead – bonded pins have the same pattern of change along the pin height depending on irradiation and testing temperatures, as of fuel pins with helium sublayer, keeping enough ductility in the area of low-temperature irradiation embrittlement. So, for example, at irradiation and test temperatures of 350-380 °C, the values of the strength limit from 1070 to 1200 MPa were obtained with the values of the total elongation of not less than 2 %. Thus, the results of post-irradiation examinations confirmed the performance of mixed nitride pins at the achieved test parameters and the possibility of their irradiation prolongation to higher fuel burn-up.

ИСПОЛЬЗОВАНИЕ ОПЕРАЦИОННОГО АНАЛИЗА В КАЧЕСТВЕ ИНСТРУМЕНТА УПРАВЛЕНИЯ КОММЕРЧЕСКОЙ ОРГАНИЗАЦИЕЙ В КРИЗИСНОЙ ЭКОНОМИКЕ

The article explores the possibilities of using operational analysis tools for managing a commercial organization in a crisis economy. The approaches to the use of indicators of the profitability threshold and the margin of financial strength to prevent the insolvency and bankruptcy of the organization are considered. The target function of the economic activity of a commercial organization has been formalized. The possibilities of regulating the strength of the operating leverage to reduce the loss of the company's profit with a decrease in sales in the context of the economic crisis have been studied.

Statistical and Reliability Study on Shear Strength of Recycled Coarse Aggregate Reinforced Concrete Beams.

The consumption of structural concrete in the construction industry is rapidly growing, and concrete will remain the main construction material for increasing urbanization all over the world in the near future. Meanwhile, construction and demolition waste from concrete structures is also leading to a significant environmental problem. Therefore, a proper sustainable solution is needed to address this environmental concern. One of the solutions can be using recycled coarse aggregates (RCA) in reinforced concrete (RC) structures. Extensive research has been conducted in this area in recent years. However, the usage of RCA concrete in the industry is still limited due to the absence of structural regulations appropriate to the RCA concrete. This study addresses a safety margin of RCA concrete beams in terms of shear capacity which is comparable to natural coarse aggregates (NCA) concrete beams. To this end, a database for reinforced concrete beams made of recycled coarse aggregates with and without shear reinforcement was established, collecting the shear specimens available from various works in the existing literature. The database was used to statistically identify the strength margin between RCA and NCA concrete beams and to calculate its safety margin based on reliability analysis. Moreover, a comparability study of RCA beams was conducted with its control specimens and with a database for conventional RC beams.