Mobile Agricultural Machinery Research Articles

Advancement of Domestic Mobile Agricultural Machinery Powered by Electric Traction

Advancement of Domestic Mobile Agricultural Machinery Powered by Electric Traction

АЛГОРИТМ ЭКСПЕРСС-ОЦЕНКИ ВОЗДЕЙСТВИЯ НА ПОЧВУ ХОДОВЫХ СИСТЕМ ПРИЦЕПНЫХ ТРАНСПОРТНЫХ СРЕДСТВ

A reliable assessment of the level of impact on the soil from the propulsors of mobile agricultural machinery is possible only with an accurate measurement of the contour area of the contact surface of the tire with the support base. This indicator underlies all standard methods for determining the maximum normal pressure, maximum stresses and other indicators in the “wheel-soil” system. A simplified algorithm for determining the area of the contact patch of tires, which can be used both when assessing the level of pressure on the soil of existing trailed agricultural vehicles and newly developed ones, was proposed by the authors. In the first case, it is enough to measure the dimensional parameters of the tire mounted on the trailer: diameter, profile width, the amount of deformation under the influence of axial vertical load. In the second case, it is enough to take this data from catalogs with the technical characteristics of tires from specific manufacturers. The mathematical model used to determine the crosssectional area of the cylinder by the plane of the supporting surface located from the edge of the wheel at a distance equal to the tire deflection is the basis of the algorithm. The proposed methodology was tested by comparing the calculation results with the results of full-scale tests of 22 samples of agricultural tires installed on various types of transport and tractor units: carts, trailers, transfer bins. As a result of the research, a fairly high value of the modeling efficiency criterion was obtained (0.989), indicating a high level of convergence between the predicted (calculated) and observed (measured) values of the contact areas of the studied tire samples. Ease of use, versatility and accuracy sufficient for engineering calculations make the proposed algorithm convenient for wide practical use.

Technical overview of the main types, designs, and materials of brake pads for mobile agricultural machinery

Brake pads are a critical element of any machine, as they directly affect the safety of its use. Accordingly, the quality of brake pads, their resistance, and durability are key aspects that must be considered when developing braking systems for mobile agricultural machinery. The purpose of this study was to review scientific sources related to the study of the tribological properties of brake pads, their operating modes, and friction materials included in brake linings. The main parameters affecting the efficiency of brake pads were analysed and the main criteria for selecting materials for brake pads of mobile agricultural machinery were defined, namely, wear resistance, temperature resistance, and corrosion resistance. Accordingly, the materials used in the production of brake pads for such equipment must be capable of operating under any conditions, have high thermal conductivity, help reduce the wear rate, have a stable friction coefficient, and be environmentally friendly. The study focused on an overview of the types and design of brake pads, their systematisation by various features (by purpose; by design features; by friction material composition; by the presence of wear sensors) and composition (semi-metallic, non-asbestos organic, and ceramic). The study described modern components of friction materials for brake linings and found that they are usually composites formed by hot pressing coarse powders, which include many different components: a binder (thermosetting phenolic resins, often with rubber added), structural materials (metal, carbon, glass, and/or Kevlar fibres), fillers (mica and vermiculite), and friction additives (graphite and various metal sulphides). The study also assessed the main characteristics of friction material components used in the manufacture of brake linings. The findings of this study can provide researchers and scientists with useful information on the types and design of brake pads and the main materials used in the manufacture of brake linings and be useful for further practical development of braking mechanisms

К ФОРМИРОВАНИЮ МОДЕЛИ ЭФФЕКТИВНОСТИ ФУНКЦИО-НИРОВАНИЯ СЕЛЬСКОХОЗЯЙСТВЕННОГО ТРАКТОРА В СОСТАВЕ МТА ПРИ РАБОТЕ НА АЛЬТЕРНАТИВНЫХ ВИДАХ ТОПЛИВА

The development of the Russian agro-industrial complex provides for increasing the efficiency of the functioning of energy machines while simultaneously reducing energy and labor costs. A promising direction for saving diesel fuel and improving the environmental performance of mobile agricultural machinery is the use of alternative motor fuel. In modern agricultural machines, this will be reflected, first of all, in the parameters of the working process and its flow in the engine, as well as in the indicators of power, fuel efficiency and environmental friendliness of its operation, which, to one degree or another, will lead to changes in the indicators characterizing the operational properties of a machine-tractor unit. The functioning of the engine as a model can be presented in the form of a multi-level and multidimensional system in which the control flows will be indicators of the work process (effective power, indicator pressure, the amount of fresh charge entering the cylinders, etc.), fuel supply parameters (cyclic supply, fuel injection pressure, fuel temperature, etc.), which depend on the physicochemical and operational properties of the alternative fuel. The proposed model provides for the determination of the rational composition of the fuel, technical solutions for adapting the fuel system for the effective supply of alternative fuel to the engine cylinders with the required indicators, as well as determining their influence on the parameters of the operational efficiency of the tractor as part of machine-tractor unit. The obtained numerical values of the parameters of the diesel operating process and fuel supply, depending on the physical-chemical properties of the alternative fuel used, make it possible to determine the performance indicators of the tractor as part of machine-tractor unit and evaluate the efficiency of its operation on various alternative types of fuels, in comparison with using petroleum diesel fuel.

Conceptual directions for the development of driverless agricultural mobile power units

BACKGROUND: Currently, major global developers and manufacturers in the field of mobile agricultural machinery are working on the development of agricultural robotic systems. Particular attention is paid to the development of universal driverless mobile power units (MPU) capable of performing various technological operations autonomously, without human intervention. In the future, this makes it possible to exclude the operator from the MPU control process and to reconsider approaches to the issue of increasing the efficiency of technological operations. The existing trend of productivity improvement by increasing the main parameters of the unit, such as operating width, operating velocities, load capacity, etc., may change to an alternative path consisting in the use of numerous autonomous small-sized units comparable in performance (a swarm of agricultural robots). Thus, the use of driverless control systems makes it possible to use conceptually new approaches to the development of agricultural MPUs. In this regard, it becomes relevant to conduct the study aimed at identifying promising conceptual directions for the development of driverless MPUs and evaluating the efficiency of their application. AIM: Identification of conceptual directions for the development of driverless driverless MPUs and a theoretical assessment of the efficiency of their application. METHODS: The study object was the MPU transformation in the context of the development of driverless control systems. The study was based on scientific publications on the development of robotic agricultural tools, informational data of manufacturers of agricultural tractors and control systems for agricultural machinery. In the course of the study, such methods as information analysis, synthesis, methods of performance analysis of agricultural units and analysis of present cost of performing technological operations, adapted for driverless MPUs by the VIM, were used. RESULTS: The prospects for the introduction of driverless MPUs, the existing digital and intelligent control systems of MPUs and the main factors hindering their development are analyzed. A classification of agricultural MPUs according to automation levels is proposed. The main directions of development are identified and conceptual models of driverless MPUs are proposed: universal driverless MPUs (driverless tractors) with keeping the existing traction class and power classification, universal (multifunctional) low-power driverless MPUs of the only traction class, separate power modules capable of being combined into a single driverless unit based on the coupled agricultural machine. The method is proposed and the equivalent number of driverless MPUs of each conceptual model for each traction class is calculated. An assessment of the impact of the use of the proposed conceptual models of driverless MPUs on the arable unit performance and the present cost of arable operations has been carried out. CONCLUSIONS: Conceptual models for the advancing of driverless MPUs have been developed and comparative calculations of the efficiency of their application as part of arable units, helping to assess the possible prospects for their use, have been made.

ОБЕСПЕЧЕНИЕ ЭКСПЛУАТАЦИОННОЙ НАДЕЖНОСТИ СЕЛЬСКОХОЗЯЙСТВЕННОЙ ТЕХНИКИ С УЧЕТОМ РЕГИОНАЛЬНЫХ ОСОБЕННОСТЕЙ

The technical equipment of agricultural production in Russia is characterized by a low level of energy supply. In the regions of the country, where a sharp decrease in technical equipment has been stabilized, there is a decrease in the number of machines that have developed a standard service life. (Research purpose) The research purpose is assessing the operational reliability of agricultural machinery taking into account the regional features of the maintenance system, capital repairs and modernization of machinery. (Materials and methods) It was noted that in the Republic of Bashkortostan, a program is being implemented to subsidize the costs of agricultural producers for capital repairs and modernization of equipment, which has significantly increased the availability factor of tractors and combines while increasing their standard service life. (Results and discussion) It was established that the operational reliability of agricultural machinery is largely ensured taking into account the regional characteristics of the maintenance and repair system, which is determined by the leading and coordinating role of the regional Ministry of Agriculture in the field of state support for the technical service system of agricultural machinery, scientific, technical and personnel policy. The directions of activity of the engineering service of the Ministry of Agriculture of the Republic of Bashkortostan have been identified: subsidizing technical service enterprises; development of tools and technologies for maintenance and repair (import substitution); coordination of work for the serial production of new types of equipment; organization of interaction with industrial enterprises; search and development of constructive solutions to improve the design of components and assemblies; creation of zonal service centers by dealers in the territory of supervised regions; advanced training and retraining of engineering personnel; creation of a systematic catalog database data on tractor parts and mobile agricultural machinery; the development of the secondary market and the trade-in system of agricultural machinery. (Conclusions) Measures of influence on the system of maintenance and repair were determined, taking into account regional peculiarities in the field of state support for the system of technical service of agricultural machinery, scientific, technical and personnel policy of the region.

Issues Of Introduction Of Mobile Power Plants Based On Renewable Energy Sources And A Multifunctional Electric Tractor

For the effective development of the agricultural sector, solving the problems of timely and sufficient power supply is relevant. Due to the absence or inefficiency of the wiring of centralized power supply systems in remote areas, fertile lands are gradually going out of circulation. Based on the study of the experience of developed countries in solving the above problems, the corresponding conclusions were made on the transfer of mobile agricultural machinery to electric drive, the development and production of mobile mini-electric tractors for processing and harvesting in local conditions, mobile power stations based on renewable energy sources for remote territories.
 
 In the agricultural sector, electric energy is mainly consumed for irrigation and electric drive of various equipment and installations. For example, for the introduction of drip irrigation and electric tractors in remote areas from centralized power supply lines in Uzbekistan, the mobile method of power supply is considered effective. The developed prototype of the Solar-Wind mobile power plant can generate an average of 4.5-4.7 kWh in the daytime, and 0.8-1.0 kWh of electric energy in the evening hours. The annual production of electric energy is more than 20,000 kWh of electric energy. Taking into account the return of fertile lands into circulation, and the cost of the resulting crop, the payback of the station does not exceed 4-5 years.

Analysis of ways to ensure the reliability and safe operation of electrified technological equipment in life systems

The authors show the period of energy development in the USSR and modern Russia since the fifties of the last century, during which the path of continuous electrification of the country was passed. Vacuum electronics and used electromechanical devices were replaced with semiconductor ones. The miniaturization of control systems has been ensured, the reliability of the operation of electrical equipment has been increased (by repeated duplication of control circuits, the introduction of ultra-large economical integrated circuits). This is confirmed by all smartphone users. Based on the analysis of traumatism and accidents, the possibility of further reducing the traumatism of workers, including the proposed author's solutions, was confirmed. By analyzing the problems of energy saving during the operation of diesel generators, possible ways to reduce fuel consumption during the operation of electrical equipment of enterprises have been clarified. It is noted that the most effective method of energy saving is the use of stationary diesel power plants of natural gas as fuel. When operating mobile agricultural machinery and transport, the most effective method of energy saving is the use of liquefied propane-butane as a fuel, which is actively introduced into modern practice. Modern electrical technologies for accounting for the operation of mobile equipment reduce energy consumption. The shortcomings of most modern devices for automated collection of information on the accounting of consumed energy are also shown.

SCIENTIFIC RATIONAL FOR THE ASSESSMENT OF PROFESSIONAL COMPETENCE AND SAFETY OF OPERATORS OF MOBILE AGRICULTURAL MACHINERY

A regression equation has been obtained to predict the professional competence and labor safety of operators of mobile agricultural machinery. The influence of such factors as "injury hazard of the MSHT during the restoration of its working capacity, professional competence, working conditions at the workplace" on the safety indicator of the operation of a forage harvester is considered.

EFFICIENCY OF CONVERSION OF DIESEL POWER MEANS TO GAS-DIESEL OPERATION MODE

Today, the use of compressed natural gas as fuel for internal combustion engines is becoming a global trend. Stavropol Krai is one of the leaders among all regions of Russia in this matter, the level of gasification of which is 99.8 percent. Such a high level of gasification of the region serves as a catalyst for the leadership of the region in the use of natural gas as a motor fuel. (Research purpose) The research purpose is determining the effectiveness of the transfer of mobile agricultural machinery and stationary equipment to gas engine fuel. (Materials and methods) Developed the program "Calculation of efficiency of conversion of diesel power facilities to gas-diesel mode of operation". The initial data concerning the specific operating conditions of agricultural machinery are entered for the operation of the program. As a result, the program analyzes the input data and issues a calculation. (Results and discussion) It is possible to output data in the table and determine the most appropriate brands of equipment to transfer them to the gas-diesel mode of operation in the first place. The program provides general recommendations on the organization of the provision of gas-diesel equipment with compressed natural gas, taking into account the individual characteristics of the location of the farm and the brand composition of gas-diesel equipment. (Conclusions) The developed software tool allows you to answer the most pressing questions of an applied nature at both the economic and logistical level; significantly simplify the transfer of diesel power facilities to the gas-diesel mode, as well as reduce the risks of unplanned costs associated with the need to organize the provision of equipment with gas using means of delivery and storage of compressed natural gas.

Path Tracking of a 4WIS–4WID Agricultural Machinery Based on Variable Look-Ahead Distance

Aiming to solve the problem of the low path-tracking accuracy of mobile robots in agricultural environments, the authors of this paper propose a path-tracking method for agricultural machinery based on variable look-ahead distance. A kinematic model of the four wheel independent steering–four wheel independent drive (4WIS–4WID) structure based on pure pursuit was constructed to obtain the functional equation of the current position and the four-wheel steering angle. The fuzzy controller, which takes the lateral deviation and heading deviation as input and the look-ahead distance in a pure pursuit model as output, was designed to obtain the look-ahead distance that changes dynamically with the deviation of mobile agricultural machinery. The path-tracking performance of 4WIS–4WID agricultural machinery in three scenarios (1 m, −90°; 1 m, 0°; and 0 m, 90°) with different initial deviations was tested using a pure pursuit model based on a variable look-ahead distance. The obtained field test results showed an average deviation of 19.7 cm, an average tracking time of 5.1 s, an average stability distance of 203.9 cm, and a steady state deviation of 3.1 cm. The results showed that the proposed method presents a significant path-tracking performance advantage over a fixed look-ahead distance pure tracking model and can be a reference for high-quality path-tracking methods in automatic navigation research.

ПЛОЩАДЬ КОНТАКТА ШИНЫ С ОПОРОЙ, КАК ФУНКЦИЯ ВЕРТИКАЛЬНОЙ НАГРУЗКИ И ВНУТРИШИННОГО ДАВЛЕНИЯ

A comprehensive increase in the efficiency of mobile agricultural machinery is impossible without taking into account the level of impact of its movers on the soil, while the most important target is to improve the coupling qualities of tractors and agricultural machines, including by increasing the size of the contact area of the mover with the supporting base. The dimensions of the contact surface at the soil-tire interface will determine the specific pressure of the pneumatic wheeled equipment on the soil, which in turn determines the level of environmental safety of the “mechanized vehicle – environment – crop” system. Agricultural tires, widely used in the Russian Federation, were chosen as objects of research, in total 22 options. The studies were carried out at vertical load levels from 10 to 60 kN and tire pressure from 50 to 500 kPa. As a result of the research, the authors proposed a method for determining the contour area of the contact of modern wheel propellers, with a change in external (wheel axle load) and internal (in-tire pressure) factors. The level of adequacy of the mathematical model, calculated by the Nash–Sutcliff modeling efficiency criterion, was 0.991. Simplicity and sufficient accuracy for engineering calculations make it quite suitable for practical use.

MOBILE AGRICULTURAL MACHINERY: SOURCES OF INJURIES AND WAYS TO ELIMINATE THEM

The results of research related to injury of operators of mobile agricultural machinery due to absence or imperfection of safety interlocks design are given. Information is given on the level of injuries of agricultural workers due to harmful and (or) dangerous working conditions, including due to the imperfection of agricultural equipment in terms of labor protection parameters. The components of harmful and (or (dangerous working conditions and their share in non-compliance with regulatory requirements guaranteeing the regulatory framework of the country for safety and harmlessness of work are named. Specific data are given for eight enlarged groups of economic activity on labor protection indicators (the number of injured and dead) for comparison as of the beginning of 2021 and 2019. The share for the same conditions of the number of workers, including the share of workers in harmful and (or) dangerous working conditions, employed in heavy work and work with labor process strain, is given. As an example, the imperfection of dump trucks and self-unloading trailers is given in terms of blocking the spontaneous uncontrolled lowering (fall) of their bodies, which usually cause severe and fatal injuries. The complex of measures that prevent injuries is regarded.

Increasing the reliability of machines and the efficiency of their use in transportation processes in agro-industrial production using service logistics methods

The article considers the problem of increasing the reliability of machines and the efficiency of their use when transporting agricultural products. Increasing the reliability of machines at agro-industrial production enterprises is considered on the basis of improving the strategy of their technical maintenance and repair. At the same time, logistic service methods are used to provide the fleet of cars with the necessary spare parts. The theoretical justification of the formation of the composition of spare parts at the enterprise, its limitations and the supply system is given. It is noted that in the processes of providing the necessary spare parts, the logistics center takes control. The main factors affecting the efficiency of spare parts supply organization have been identified. On the basis of the cost function, optimal management based on logistic models is considered. Comparative analysis proved the advantage of the developed system of technical maintenance and repair along with the existing planned preventive system. This is, first of all, an increase in the probability of trouble-free operation and the availability ratio of KamAZ vehicles and mobile agricultural and mobile agricultural machinery of the John Deere family.

Modern trends in the formation of occupational pathology when working on mobile agricultural machinery

Introduction. There are currently several works in the scientific literature devoted to studying the influence of working conditions on mobile agricultural machinery on the occupational morbidity of workers on the example of individual regions. Still, Russian Federation did not conduct such studies before. The study aims to analyze working conditions and current trends in the formation of occupational pathology when working on mobile agricultural machinery in the Russian Federation. Materials and methods. The paper uses the results of long-term sanitary-hygienic and ergonomic studies of working conditions when working on mobile agricultural machinery and data on the level of occupational morbidity (PZ) of farmworkers of the Russian Federation in 2011-2017. Results. Microclimatic discomfort, dustiness and gas contamination of the working area air, industrial noise, general and local vibration, physical overload, forming harmful operating conditions (classes 3.2-3.4), occupational risk categories from medium to very high characterize working on mobile agriculture machinery. From 2011 to 2017, researchers have identified 960 agricultural machine operators with 1052 occupational diseases in the Russian Federation, formed mainly under the influence of physical factors and physical overloads. In the nosological structure of occupational diseases (OD), the first place is occupied by vibration disease (VD), the second by radiculopathy (RP), and the third by sensorineural hearing loss. Researchers characterize the current trends in the nosological structure by a significant increase in the prevalence of radiculopathy against the background of a decrease in diagnosis cases of vibration disease. Conclusions. Working conditions when working on mobile agricultural machinery remain harmful and pose a high risk of developing occupational radiculopathy, vibration disease and sensorineural hearing loss. It should be taken into account when developing measures to prevent occupational pathology for agricultural machine operators.

MODEL AND ALGORITHMS FOR DETERMINING THE LOCATION AND POSITION OF AGRICULTURAL MACHINERY DURING THE MOVEMENT

The subject of research is the navigation subsystem of autonomous control system to determine the location and position of agricultural machinery during the movement. The purpose of the work is to develop and research model and algorithms to determine the location and position of mobile agricultural machinery using a physical model. The following tasks are solved in the article: development of agricultural machinery physical model to collect information from sensors during movement, further development and research of applicability of algorithms for location and position determination. The following methods are used: methods of mathematical statistics, methods of information systems theory and data processing, methods of random signals filtration. The following results were obtained: during research, the agricultural machinery physical model to collect information from sensors during movement was created. The model includes a GPS receiver, an accelerometer, gyroscope and infrared encoders, to count the rotation of the wheels, as well as its own four wheelbase of agricultural machinery. The modernized GPS coordinate filtration algorithm using a geochex algorithm is proposed, which according to several successively obtained GPS coordinates calculates the hash received coordinates; if the coordinates have the same hash, it can be argued that the vehicle is in the segment of the area that corresponds to this hash. To determine the physical model position during the movement data from the accelerometer and the gyroscope was processed using Savitzky-Golay and Madgwick filters. With the use of wheels’ rotation data, the odometric algorithms for movement and location determining of the agricultural machinery physical model in motion were implemented. Conclusions: to improve the accuracy of estimating the location and position agricultural machinery, algorithms complexation of indicators from different navigation systems should be used to reduce the total error. Research results can be applied in the development of new and modifications of existing navigation subsystems of agricultural machinery autonomous control systems.

Creation of theoretical bases of tribotechnologies of running-in and restoration as means of effective increase of operational wear resistance of motor transport and mobile agricultural machinery

The bases for creation of theoretical bases of tribotechnologies of running-in and restoration of conjugations of details of systems and units of motor transport and mobile agricultural machinery are defined. The specifics of selective transfer on the surface of contacting parts of machines and creation of servito films, formation of coatings during running-in and restoration from antifriction materials, which are a part of additives in motor and transmission oil, are considered. A number of tribophysicochemical processes that occur in the conjugations of parts materials and how they affect the creation of tribotechnologies of running-in and restoration are clarified. The creation of tribotechnologies using geomodifiers is considered. It is proposed to build a single theory of tribotechnologies of running-in and recovery on the basis of the mechanism of triboplasm formation in the conjugations of parts of systems and units of machines. It is also proposed to add to this the thermofluctuation theory of S.M. Zhurkova taking into account the change of dilaton and compression bonds of atoms of materials of tribocouples of details with creation of local areas of deformations of compression and tension and zones of thermoplastic deformation.

РАЗРАБОТКА МОБИЛЬНОГО КОНТРОЛЬНО-ДИАГНОСТИЧЕСКОГО УСТРОЙСТВА

Service and repair of operating and servicing organizations are largely equipped with outdated, low-power, highly specialized bench equipment from former specialized enterprises and do not always meet the technical requirements of the manufacturer, especially for conducting quality control programs for the repair of powerful and modern tractors. These circumstances together reduce the reliability of the obtained diagnostic parameters and may lead to the risk of errors in determining the technical readiness of the repaired equipment, in particular, internal combustion engines, transmission units and chassis, hydraulic drive. (Research purpose) The research purpose is in developing a mobile control and diagnostic device for monitoring the power and fuel consumption of the internal combustion engine, as well as the quality of repair of hydrostatic transmission and hydraulic drive units. (Materials and methods) The article presents an analysis of scientific works on improving methods for diagnosing energy indicators of mobile agricultural machinery, as well as conducted extensive research on the use of axial plunger pumps and throttling the flow of liquid injected by them with a constant and variable cross-section throttle for engine braking. (Results and discussion) Authors developed an experimental model of a mobile control and diagnostic device and experimentally tested the methods for determining its parameters and control and diagnostic operations. (Conclusions) The use of the proposed mobile control and diagnostic device will eliminate excessive fuel consumption by tractors when reducing the effective power of their internal combustion engines below the permissible limits, and will also allow the diagnosis of hydrostatic transmission units in the conditions of agricultural and service enterprises and exclude the sending of serviceable units with unused resources for repair.

Development of mineral fertilization complex mechanization

The intensification of agriculture, its saturation with heavy machines, and the growth in the energy saturation of tractors put forward new tasks that cannot be solved without the development of theoretical and applied research in the field of soil mechanics. It became necessary to study the mechanical processes occurring in the soil when it interacts with the working bodies of tillage machines and the running systems of mobile agricultural machinery. Industrial technologies are based on the effective use of chemicals. The effectiveness of fertilization depends on the quality of their application (uniformity and place of delivery to the plant roots). In recent years, the annual volume of mechanized work per hectare has increased several times. Intensive industrial technologies are based on the effective use of chemicals. A successful increase in the efficiency of the use of all types of fertilizers and chemical plant protection products is possible only on the basis of an integrated quality management system for performing technological processes, including interrelated organizational and social measures. The article describes intensive and industrial technologies that are based on the effective use of chemical agents. A successful increase in efficiency, the use of all types of fertilizers and chemical plant protection products is possible only on the basis of an integrated quality management system for performing technological processes, including interrelated organizational, technological and social measures.

Justification of risk-based approach of operation of mobile agricultural equipment on example of details of separate units of tractors

It is shown that in order to justify the extension of the service life of the machine beyond the resource set by the developers, it is necessary to focus on the allowable risks of accidents that can lead to accidents. After all, today for mobile agricultural machinery, the operation of which is associated with high-risk work, the concept of acceptable (acceptable) risk is not used, which does not allow to assess the danger of being on fields, farms and roads without machinery, with exhaustion of installed resources. The purpose of researches is to justify the permissible risk of exploitation of mobile agricultural machinery, in array of details and elements of constructions which have accumulated defects (damage). This paper analyzes the kinetics of accumulation of operational defects in the array of parts of individual components (systems) of tractors. MTZ-80 tractors (82) were chosen as the object of research, as one of the most common in Ukraine. To detect cracks, a developed eddy current flaw detector was used, the sensitivity of which allowed to find cracks several millimeters or larger in length without preparing the surface of the controlled parts. It is shown that the kinetic dependences of the accumulation of operational defects in the parts of tractor units in the analyzed range of service life are monotonically increasing, which can be described by exponential functions with a sufficiently high reliability. It is noted that the obtained dependences are similar to the kinetic dependences of the accumulation of static and dynamic (fatigue) damage obtained as a result of laboratory tests of samples of construction materials, which allows to use approaches to the criteria of the limit state of laboratory samples due to the power load to establish the boundary life of mobile agricultural machinery. However, the kinetics of the intensity of the occurrence of operational cracks in the array of tractor parts is not monotonous and has a maximum in the range of about 11-13 years of operation. This service life can be used as a criterion to stop the operation of the tractor, to carry out defectoscopy of parts and to replace defective parts. With such a long service life of the tractor, there is the greatest probability of sudden destruction of the tractor components and the creation of emergencies.