DIAGNOSTICS

Fundamentals of reliability theory

DIAGNOSTICS

Basics of reliability theory and

TUTORIAL

St. Petersburg

Ministry of Education and Science of the Russian Federation

State Educational Institution of Higher Professional Education

Northwest State Correspondence Technical University

Department of Car and Automotive

TUTORIAL

Institutomotomobile transport

Specialty

190601.65 - Cars and Automotive

Specialization

190601.65 -01 - technical operation of cars

Direction of bachelolavrov training

190500.62 - Operation of vehicles

St. Petersburg

Publisher SZTU

Approved by the Editorial Publishing Council of the University

UDC 629.113.02.004.5.

Fundamentals of reliability and diagnostics: Tutorial / Sost. Yu.N. Katsuba, [and others]. - SPb.: Publishing house SZTU, 2011.- 142 p.

The training manual was developed in accordance with state educational standards of higher professional education.

The textbook provides the concept of aging and restoring the machines and their components; Qualitative and quantitative reliability characteristics; Factors affecting the reliability of products; reliability as the main indicator of the quality of the car; methods of statistical analysis of the status of products, means and methods of state control; strategies and systems of working capacity; diagnostic parameters of the technical condition of the machines and their components; the place of diagnostics in the system of maintenance of the technical condition of cars; Classification of methods for diagnosing a technical condition; The concept of the reliability of the transport process.

Considered at the meeting of the department of cars and roads on November 10, 2011, Protocol No. 6, approved by the Methodological Council of the Institute of Automobile Transport November 24, 2011, Protocol No. 3.

Reviewers: Department of Car and Automotive Economy SZTU (Yu.I. Sennikov, Cand. Tech. Sciences, Prof.); V.A. Yanchelenko, Cand. tehn Sciences, Doc. Departments for the organization of transportation NWTU.

Compilers: Yu.N. Katsuba, Cand. tehn sciences, ass

A.B. Egorov, Cand. tehn science, prof.;

© Northwest State Correspondence Technical University, 2010

© Katsubu Yu.N., Egorov A.B. 2011.

Improving product quality cannot be ensured without solving the problem of improving the reliability of products, as reliability is the main defining property of quality.

Increasing complexity of technical devices, increasing the responsibility of functions performed by technical systems, increasing the requirements for the quality of products and the conditions of their work, which increased the role of automation of technical systems management - the main factors determined the main direction in the development of science on reliability.

The range of issues included in the competence of the theory of reliability is most fully formulated by Academician A.I. Berg: the theory of reliability establishes the patterns of failures and restoring the performance of the system and its elements, considers the influence of external and internal influences on processes in systems, creates the basics of calculating the reliability and prediction of failures, seeks ways to increase reliability when designing and manufacturing systems and their elements, and so Ways to maintain reliability during operation.

The problem of improving the reliability of products is particularly relevant for road transport. This problem is exacerbated as the design of the car themselves and increase the intensity of operation modes.

In solving issues of modernization of car park, the problem of improving reliability, as well as when creating the designs of a new generation and during the operation of modern cars.

When operating cars, it is important to know their design, as well as a mechanism for the failure of component parts (units, nodes and parts). Knowing the estimated time of failure of composite parts of cars can be prevented by their appearance. By solving these tasks, the theory of diagnostics is engaged.

Given the above, future specialists in the operation of the AT must have knowledge and skills in the field of improving and maintaining the reliability of AT when it is created, operation, maintenance and repair.

Section 1. Basics of reliability theory

I.. Basics of the theory of reliability and diagnostics.

1. Systems for maintaining the working state of cars.The essence of the planned warning system is that preventive impacts are performed forcibly without coordination of the actual necessity, and malfunctions and failures are eliminated during their occurrence. At the PPR, it is planned runs from the first effect to another of the same type.

The PPR system has types of preventive effects: EO: washing (cosmetic and in-depth), refueling J., polishing, installation of spikes, sanitary processing of vans and salons A / M ambulance. TO-1: Normated strictly after 4-5 thousand km of mileage, including operations: fasteners - periodic lift of threaded connections; lubricants, including the replacement of oil in the crankcase; Uncomplicated low-volume adjustments (fan belt tension). TO-2: incl. All works related to TO-1 + required adjustment work. CA: 2 times a year. It is planned to replace seasonal oils, tires, batteries, gaps in candles. Works are determined by the "Regulation on the TR".

Pros: 1) needed at low formation; 2) You can define the volume of work in advance, distribute them by day of the week. Cons: 1) Recommendations are developed on average observation results; 2) The system requires performing work sometimes without their need.

2. Calculation of the reliability of the car with a sequential and parallel inclusion of items. Under the complex system, the object that performs the specified functions, which can be dissected to the elements, each of which also performs certain functions and is in collaboration with other elements. Elements may have a variety of output parameters, which from the reliability position can be divided into three groups (type): XI - parameters whose change with output for the established levels of indicators leads to the loss of the element and system; X2 - the parameters participating in the formation of the output parameters of the entire system, for which it is difficult to judge the refusal of the element; Xs - parameters affecting the performance of other elements similarly to the change in external operating conditions of the system. For greater clarity of the possible types of output parameters, the system of two elements (on the example of the engine) can be represented by a structural scheme in the figured in Fig. 18 Scheme for power system XI - this is the bandwidth of the fuel gibber (if the jibeler is scored and the fuel does not arrive, the power system fails and refuses the engine), X2 - this is the wear of the fuel gibber (the fuel efficiency of the car is worsening), Xs - the rich mixture leads to overheating of the engine and makes it difficult to work the cooling system. In turn, the poor operation of the cooling system leads to the engine overheating and the formation of steam plugs in the power system is Xs. for element number 2, the bad work of the thermostat delays the engine warming, which leads to a decrease in the fuel efficiency of the car - this X2 the belt break leads to the refusal of the cooling system and the failure of the car - this XI For element number 2. In real complex systems, elements may have or all three types of output parameters or less (one or two). In many respects, it depends on the degree of dismemberment of the system on the elements. In the example considered, the power system and the cooling system themselves are complex systems. The car is a very complex system that can be divided into a large number of items. When analyzing the reliability of such a complex system, its elements are useful to divide into groups; 1.Elements, the refusal of which practically does not affect the performance of the car (damage to the abundance of the cabin, the corrosion of the wing). The refusal of such elements is usually considered isolated from the system. 2. The elements, the performance of which during the time interval or the developments, practically does not change (for a vehicle cleaning car, take into account the change in the state of the transmission crankcase does not make sense). 3. Elements, the restoration of the performance of which does not require significant costs of time and, practically, does not reduce the performance of the car performance (fan belt tension). 4. Elements whose failures lead to a vehicle failure and regulate its reliability. Due to the fact that the functioning of the car is associated with the performance of a variety of tasks in different operating conditions, the selection of elements to the specified groups can be problematic (the wiper failure in dry good weather does not lead to a car failure, and in the rain and slush - it leads to failure). Depending on the nature of the impact on the reliability of the complex system, its elements can be considered in series or in parallel (by analogy with the inclusion of light bulbs in the garland). In this case, the real structural scheme of the system should be a structural reliability scheme. We give an example of the structural circuit of the bearing assembly, consisting of the following elements; 1 - shaft, 2 - Bearing, 3 - Bearing housing, 4 - Bearing cover mounting screws (4 pcs.), 5 bearing lid. If the element fails leads to the failure of the system, then we can assume that the element is turned on sequentially. If, when the system fails, the system continues to function, the element is turned on in parallel. In accordance with this, the structural diagram of the bearing assembly will have the first element, however, with an increase in the operation to a value of 2, the probability of a second element failure may increase significantly. The third element under the values \u200b\u200bunder consideration remains, practically, trouble-free. Thus, to increase the reliability of the system consisting of sequentially included elements, it should be primarily increasing the reliability of the most "weak" elements. Equally increase the average resource of all elements of the system is impractical.

3. Basic concepts, definitions, properties and reliability indicators.During the operation of the car, its quality is usually worsens by changing the indicators. Reliability is a quality property, since it is manifested only for a long time. Reliability is expressed by four parameters: a) reliability - the property of the object continuously maintain a working condition for some time, the indicators are the average operation for failure; b) durability - the property of the object to maintain performance before the limit state with the necessary interruptions for maintenance, indicators are the average service life, the average resource; c) maintainability - the property of the object, which consists in its adaptability to the detection, elimination of failures and malfunctions, the indicators are the frequency, the specific labor intensity, the number of tools used; d) Sustainability - the property of the object to maintain the established quality indicators in the process of storage, transportation, indicators are the average and gamma percentage of storage. The main terms and concepts are: a) failure - changing one or more indicators of the specified object parameters, leading it into an inoperable condition; b) a malfunction - the state when the object does not respond to at least one of the requirements of the regulatory and technical documentation; c) failure - a self-configuration. By origin or reasons for the appearance of failures and malfunctions are divided into three types: a) structural, production, and operational.

4. Processes change the properties of structural materials affecting the reliability of the car.In the design of the car, very diverse materials are used: various metals, plastics, rubber, fabric, glass. As the car is exploited, the properties of structural materials are also varying very diverse. Consider the most essential processes: Temperature softening- Characteristic for metals and other materials. With increasing temperature for different metals, their strength characteristics (yield strength) are more or less reduced. For example, when the engine overheating, jumpers can be taken out with piston rings. Fatigue- softening of metals during cyclic loads, leading to the destruction of parts at stresses. Sources of cyclic loads may be the conditions of the natural functioning of the part (for example, when the gear is running, the tooth perceives the load, then "resting", again perceives the load, etc.), vibration loads, etc. Intercrystalline corrosion -this is the process of diffing (seeping) oxygen into the crystal lattice of the metal. This process reduces the fatigue strength of the parts. Flooding -this is the process of hydrogen diffounding in the crystal lattice of metals, which leads to increasing the brittleness and decrease in the fatigue strength of the part. Flooding can occur when the mode of electroplating coatings can be impaired. Intercrystalline adsorption (Rebinder effect)this is the process of softening parts due to the propagating action of molecules falling into cracks or cuts.

The change in the properties of non-metallic materials is very diverse and should be considered separately in each case.

5. Processing the results of truncated tests of durability of parts and aggregates.The appearance of this technique is due to the stretching of the observation of failures and the desire to get the result as rather. In the processing of truncated tests, the curve of the probabilities of the failure first build a numeric characteristics (average resource or gamma percentage resource). Without a significant reduction in the accuracy of the definition of the average resource, the durability tests can be stopped (safe) after the refusal of 60 ....70 the number of test cars. Having placing test results x1 x2, x1 ... In order to increase resources, it is possible to calculate the probabilities of failures corresponding to the obtained values \u200b\u200bof random variables, dividing the sequence number of the random variable to the number of test cars. . Applying probabilities on the schedule and spending the curve through them, you can get the law of probability distribution. With a small number of tests of cars N \u003d 1, the curve is significantly shifted and the inventive results should be used by the formula :. The second reception that increases the accuracy of the test results is the use of special probabilistic paper when the curve of the probability distribution law is applied to a chart with nonlinear scales, the order of constructing nonlinear scales is determined by the type of probability distribution law for the normal law of the ordinate linear, and the scale of the abscissa (probabilities) is non-linear . This scales can be constructed using a special table, or by uniform postponing quantile values \u200b\u200bindicating the likelihood corresponding to the value of quantile, or directly graphic construction. Applying values \u200b\u200bagainst the corresponding values \u200b\u200bon probabilistic paper and spending direct line through the obtained points, we obtain the desired probability distribution. The numeric characteristics of the resulting distribution of random variables are determined by the position of the distribution line relative to the coordinate axes on the graph, for example, for a normal law when testing durability, the average resource corresponds to the probability of 0.5.

6. Determination of durability indicators for truncated on the left. Tests truncated to the left - there is a moment of refusal, and the moment of starting the work of the subject unknown is unknown. Watching a large group of multi-industrial cars of one model on a relatively small segment of time or work, you can get information about the durability of their units or parts. This period of time should be quite large so that you can have failures, but at the same time the probability of successive two or more failures on one A / m should be extremely small. Since 6 ... 8 points are enough to build the distribution law, then it is possible to choose a segment of 0.25 of the alleged average part of the part.

The results of the observation are recorded in the table: breaking the possible service life at the intervals we will have a histogram (Fig.), Which characterizes the likelihood of observing failures R;, in intervals T,. If the probability distribution is close to a normal law, then with a large period of service life, the probability of failures are reduced, since the main share of the details have already refused earlier. Practically, old a / m details denied more often than new ones. This is explained by the fact that there are not only the first (installed at the factory) details, but also established repair of repair. Thus, to build the law of probability distribution, it is necessary from the observed number of failures to eliminate the failures of the parts established during repairs or adjust the observed (experimental) probabilities. For the output of the formula that allows you to adjust the experienced probabilities, consider the graph of possible outcomes of events for objects that have different developments or service life. On the column, the state of refusal is shown by a cross, and the working condition - a circle, the probability of refusal for the first interval - for the second - ... The probability of the detail in the first period will coincide with the experimental probability, which is determined by the results of monitoring the group of new cars, . Instead of the refused part during repair, the car will be installed another detail, which can also refuse the second period. The probability of two failures in a row will be expressed by the product of the probabilities of failures and will be equal. In the second period, the details established at the factory can probably be observed with a probability that we are looking for. T. about. The experimental probability of the removal failures in the age group A / M will be equal to P2 ° \u003d p, 2 + P2. Where Р2 \u003d p2 ° - p, 2. Similar to the third period can be recorded . Transforming we get expression :. Comparing the expressions obtained, we see a general trend that is written as follows: The advantage of this method of evaluating the durability of the details is that, having come to ATP with a large multi-expanded car park, an engineer after a year of work has the ability to determine the average life of all parts. Knowing the average annual car mileage along the average service life, it is easy to determine the average resource, which allows you to evaluate the reliability of cars and plan the consumption of spare parts.

7. Determination of the norm of spare parts that guarantees the specified probability of the absence of downtime of cars due to lack of parts. The calculation allows you to determine such norms of the stock of parts, which, with any advanced probability, guarantee the absence of a downtime of the car due to the lack of parts during the planned period. The calculation method is acceptable for any number of cars, if the resource of the parts is described by the exponential law (failures are sudden), and can also be distributed to large groups of cars, heterogeneous on time and deadlines, when the resource is described by any law of probability distribution. In the first and in the second case, when the failures of normalized parts occur on different cars and are not related to each other, the number of failures for the planned time interval is described by Poisson's law. A is the average consumption of spare parts for the planned period. When there is a possibility that the random number of failures will be less than this stock, will express the sum of the probabilities a \u003d p (k \u003d 0) + p (k \u003d 1) + p (k \u003d 2) + ... + p (k \u003d on ). Using Poisson's Law, you can record For the convenience of calculating the rewrite formula, carrying a constant multiplier into the left part of equality. Knowing the average consumption of spare parts and setting the required probability of downtime due to lack of spare parts calculate the left part of equality, and then begin to count the sum of the right part of the sequential integrity of the number to the point when the amount of the amount reaches the value of the left part of the equality. The number to the equality will be achieved, and will be the desired norm of spare parts on. Based on the considered formulas, a table of relative standards of spare parts, providing a given probability of downtime due to lack of parts. Analyzing table values, you can see a very important pattern: the larger the average consumption of spare parts, the closer the value ρ to one, i.e., at high average expenditures, a minor excess of average reserves ensures a high probability of non-downtime due to lack of spare parts. Thus, warehouses should not be at the entrance to production, but at the output of production. To guarantee the lack of downtime at ATP with a small Park, a / m should have a reserve of bearings several times greater than their average consumption, and in the warehouse of the bearing plant of excessive reserves it is not necessary, with a minor increase in consumption, the requests of all consumers will be satisfied with a very high guarantee.

8. Definition of periodicity, then parallel to the included systems that smoothly change their characteristics.Consider replacing the oil in the engine. As the engine is working, lubricating properties are filled into
Carter oils gradually deteriorate, leading to an increase in the intensity of the wear of parts
Engine. Express the value of the wear formula i \u003d a - xb, where x - oil production, A and B -
Empirical coefficients. If we replace the oil through a hto kilometers, then with each replacement

the nature of the increasing wear will be repeated. According to the technical and economic method of determining the periodicity, the target function of the specific costs.

. We define an unknown engine resource from the following considerations. If, during the time before replacing the oil, the engine is flashed by AI \u003d A * XHMO, then the limit on the technical conditions of wear 1PR will be achieved when developing Substituting the value of the resource to the target function, we obtain the formula with one desired unknown - periodicity: We take a derivative about this formula by hee equating it to zero. From here, we express the optimal periodicity of oil replacement: The resulting formula can be simplified by entering the value of the minimum resource of the engine operating without replacing the oil. From condition Express:

9. Definition of periodicity, then parallel to the included systems discretely change their characteristics. As an example of the system under consideration, a full-flow filter can be received for oil purification, which refuses to mechanically destroy the filtering element or climbing it when the oil begins to pass through the reduction valve with crude. Consider the nature of the wear of the engine details as far as possible (Fig.) With the refused filter, the wear intensity is high and motor wear (curve 1) can be achieved when the filter is guaranteed, the wear intensity is low (curve 2) and the engine will be able to work . Filters are often manufactured non-separable and replaced in a planned manner with frequency during which the filter may refuse. For a particular engine, wear is expressed by a broken line 1, and its resource random variable. Find optimal frequency of filter replacement using the target function of total specific costs: . Obviously, if, if (filters are not replaced), then. In addition to the periodicity, the reliability of the filter itself will also be affected on the engine resource, which can be represented by the trouble-free curve. As the car is working, the probability of trouble-free operation of the filter will change from 1 to, the average reliability of the filter can be determined by isometric area under the loaning curve by integrating . Knowing the fetility of the filter, you can find the average engine resource, as a mathematical expectation in two values \u200b\u200band. Substituting the value of the resource into the target cost function, we get. The optimal frequency can be determined at a minimum of costs from the condition since the analytical solution is difficult to perform, it is possible to use a numerical solution, finding the average reliability of the filter by area under the curve on a given segment, you can find such a value that will give minimal total costs.

10. Definition of frequency of consistently included systems.

Sequentially included systems include the aggregates and systems of the car, the refusal of which leads to the loss of the working capacity of the car without serious damage to other systems, is the instruments of the power supply system, ignition, start, etc.

Maintenance and repair of sequentially included systems for need leads to high costs, including possible fines for flight breakdowns, the need to tow the car into the garage, etc. Regulated by these systems under ATP or a hundred requires costs. We define the optimal frequency of the consistently included systems using

the law of the distribution of probability of its developments for refusal. Under the prescribed periodicity, the likelihood of a system failure in road conditions probability that the refusal will be prevented when planned, . The refusal may be observed in the interval, on average, the refusal will occur when developing, which can be found by the formula: . Thus, part of a / m will refuse and serviced, on average when developing, and part - when developing. You can find an average developing at which consistently included systems will be served as a mathematical expectation :. Similarly, you can find the average system maintenance costs:, where - the coefficient, taking into account the maintenance at the next system, which refused earlier and was serviced by the need. If all systems are serviced in a planned manner, if only those systems that have not been denied and not served in the scheduled manner and are not serviced by the need, then. Knowing average service costs and an average developing at which the maintenance can be recorded by specific total costs, i.e., the target function for determining the frequency.

The frequency of which in which the specific costs will be minimal is optimal. We will conduct a qualitative analysis of the specific costs: when probabilities,, if, the system will not be serviced in a planned manner ,,,. Optimal frequency can be found in a numerical solution, having expenses of costs in the planned manner and the average cost of eliminating the system failures, as well as the curve of the law of probability distribution of the system. The character of changing specific costs is shown in the figure.

11. The essence of the diagnosis method for diagnostic parameters.The technical diagnostics is the knowledge branch that studies signs of car malfunctions, methods, means and algorithms for determining its technical condition without disassembly, as well as technology and the organization of the use of diagnostic systems in technical operation processes. The diagnosis is the process of determining the technical condition of the object without its disassembly, according to the external signs, by changing the values \u200b\u200bthat characterize its condition and comparison with the standards. The diagnosis is carried out according to the algorithm (combination of consecutive actions) established by the technical documentation. A complex that includes an object, means and algorithms form a diagnostic system. Diagnostation systems are divided into functional when the diagnostics are carried out in the process of operation objects, and the test, when the object is changed when diagnostic parameters change artificially. Universal systems are distinguished, intended for several different diagnostic processes, and special, providing only one diagnostic process. The purpose of the diagnosis to identify object malfunctions, determine the need for repair or then evaluate the quality of the work performed or confirm the suitability of the diagnosed mechanism to operate to the next service. It is required to make a diagnosis of a set of features: ; ; ; - probability of diagnostic parameters- diagnosis

II.. Licensing and certification in road transport.

1. Activities licensed in the field of road transport, the procedure for obtaining a license.In accordance with the law, the provision provides for the licensing of passenger transport by road, equipped for transportation of more than eight people. Licensing of passenger transport by road is carried out by the Ministry of Transport of the Russian Federation, which laid these duties on RTI. The Ministry of Transport of the Russian Federation in the field of vehicles is entrusted with licensing authority of only three activities: the transportation of passengers by buses, transportation of passengers with passenger cars and transportation of goods. The licensed type of activity provides a relevant license. License requirements and conditions in the implementation of passenger and cargo transportation by road are: a) fulfillment of the requirements established by federal laws; b) the compliance of motor vehicles stated to carry out traffic; c) compliance with the individual entrepreneur and employees by qualifying requirements; d) availability in the state of the legal entity of officials responsible for ensuring the safety of road traffic. The license is a document, which is a permit for the implementation of a specific type of activity with the obligatory compliance with licensing requirements. To obtain a license, the license applicant provides the following documents to the licensing authority: 1) a statement with an indication of a legal entity, legal form, addresses, for IP: F. I.O., Passport details, indication of the activity; 2) a copy of the constituent document or a copy of the certificate of registration of IP; 3) a copy of the registration certificate in the tax inspectorate; 4) a copy of the qualifications documents; 5) a copy of the Documents of the BDD specialist; 6) information about vehicles; 7) Receipt of payment for licensing. The decision to issue a license must be issued within 30 days. The license is not more than 5 years.

2. Technical regulations and other documents used in certification.Technical Regulations - a document that adopted by the International Agreement of the Russian Federation ratified in the manner prescribed by the legislation of the Russian Federation or federal law and establishes compulsory and execution requirements for technical regulation facilities (products, processes of production, operation, storage, transportation). Then the regulations are accepted in purposes: a) protecting the life or health of citizens; b) property of individuals or legal entities, state or municipal property; c) environmental protection, life or animal health and plants; d) preventing actions that are misleading purchases (consumers of services). The adoption of technical regulations for other purposes is not allowed. Unlike the mandatory execution of technical regulations, the standard, as a basis for certification, is a regulatory document developed on the basis of consensus approved by a recognized body aimed at achieving the optimal degree of streamlining in a particular area. Standard is a document in which the characteristics of the production and characteristics of production, exploitation, storage, transportation, transportation, implementation are established for voluntary repeated use.

3. The basic concepts of certification, its forms and participants.Certification translated from Latin means "done true". Certification is a procedure by which the third party certifies in writing that properly identified products, the process, the service meets the specified requirements. The certification system is: the central body; rules and procedure for certification; regulations; The procedure for inspection control. Certificate targets are: a) certificate of compliance of products, production processes, operation, transportation standards and terms of contracts; b) promoting purchases in the choice of products, works and services; c) improving the competitiveness of products, works, services in the Russian and international market; d) creating conditions for ensuring the free movement of goods through the territory of the Russian Federation. Certification may be mandatory or voluntary, which is directly related to the presence or absence of accepted technical regulations. To carry out certification, systems are created, including: 1) the central body, which manages the entire system; 2) certification bodies; 3) rules and provisions of certification; 4) regulatory documentation. The system is usually organized by the industry principle. The certification body is a physical or legal person accredited in the prescribed manner. Functions of the certification authority: a) performs confirmation of conformity; b) issues a certificate; c) presents the right to apply the sign of the market for the market (with mandatory) or compliance (with voluntary); d) suspend or terminate the certificate issued. To register a voluntary certification system, it is necessary: \u200b\u200ba) evidence of state registration of a legal entity or IP; b) an image of a conformity mark; c) Receipt payment receipt (registration occurs within 5 days). The law provides 2 types of mandatory certification: 1) conformity declaration; 2) Certification of conformity. Declaration of compliance is carried out: a) adoption of the Declaration on Compliance on the basis of its own evidence; b) adoption of the Declaration on Compliance on the basis of its own evidence and evidence obtained with the participation of the certification authority or accredited testing laboratory.

The basics of the theory of reliability and diagnostics are presented in relation to the most capacious system of the system of the system - a car - the road - environment. Basic information about the quality and reliability of the car as a technical system. The main terms and definitions are given, indicators of reliability of complex and dissected systems and methods for their calculation are given. Attention is paid to the physical basics of car reliability, methods for processing reliability information and methods for reliability testing. The scene and the role of diagnosing in the system of maintenance and repair of cars in modern conditions are shown.
For university students.

The concepts of "quality" and "reliability" of machines.
The life of modern society is unthinkable without using the most diverse design and purpose of machines that convert energy, materials, information, change the lives of people and the environment.
Despite the tremendous diversity of all machines, in the process of their development use uniform criteria to assess the degree of their perfection.

In terms of market relations, the creation of most new machines requires compliance with the most important conditions for competitiveness, namely, give them new features and high technical and economic indicators of their use.
For efficient use of machines, it is necessary that they have high quality and reliability.

INTERNATIONAL STANDARD ISO 8402 - 86 (ISO - International Organization Standartization) gives the following definition: "Quality is a set of properties and characteristics of products or services that give them the ability to satisfy the conditioned or alleged needs."

TABLE OF CONTENTS
Preface
Introduction
Chapter 1. Reliability is the most important property of product quality
1.1. The quality of products and services is the most important indicator of the successful activity of the enterprises of the transport and road complex
1.2. The concepts of "quality" and "reliability" of cars
1.3. Reliability and universal problems
Chapter 2. Basic concepts, terms and definitions adopted in the field of reliability
2.1. Objects considered in the area of \u200b\u200breliability
2.1.1. General concepts
2.1.2. Classification of technical systems
2.2. The main states of the object (technical system)
2.3. Transition object to various states. Types and characteristics of the refusals of technical systems
2.4. Basic concepts, terms and definitions in the field of reliability
2.5. Reliability indicators
2.6. Reliability criteria for non-standard systems
2.7. Reliability criteria for restored systems
2.8. Durability indicators
2.9. Sustainability indicators
2.10. Indicators of maintainability
2.11. Complex reliability indicators
Chapter 3. Collection, analysis and processing of product reliability data
3.1. Goals and tasks of collecting information and assess the reliability of cars
3.2. Principles of collecting and systematization of operational information on the reliability of products
3.3. Construction of empirical distribution and statistical assessment of its parameters
3.4. The laws of distribution of the time of operation before the failure, most commonly used in the theory of reliability
3.5. Laplas transformation
3.6. Trust interval and confidence probability
Chapter 4. Reliability of complex systems
4.1. Complex system and its characteristics
4.2. Reliability of dismembered systems
Chapter 5. Mathematical models of reliability of operation of technical elements and systems
5.1. General model of reliability of the technical element
5.2. General model of reliability of systems in terms of integral equations
5.2.1. Basic notation and assumptions
5.2.2. Matrix of states
5.2.3. Matrix transitions
5.3. Models of reliability of non-standard systems
Chapter 6. The life cycle of the technical system and the role of scientific and technical preparation of production to ensure the requirements of its quality
6.1. Structure of the life cycle of the technical system
6.2. Comprehensive product quality assurance system
6.3. Quality level assessment and reliability management
6.3.1. International Standards Quality ISO Series 9000-2000
6.3.2. Quality control and its methods
6.3.3. Methods of quality control, defect analysis and their causes
6.4. Featuring Economic Management of Reliability
6.5. Seven simple statistical methods for assessing the quality used in ISO 9000 standards
6.5.1. Classification of statistical quality control methods
6.5.2. Data bundle
6.5.3. Graphic representation of data
6.5.4. Chart Pareto
6.5.5. Causal chart
6.5.6. Diagram scattering
6.5.7. Checklist
6.5.8. Control Card
Chapter 7. The physical essence of the processes of changing the reliability of the structural elements of cars during their operation
7.1. Causes of performance loss and damage to machine elements
7.2. Physico-chemical processes of material destruction
7.2.1. Classification of physico-chemical processes
7.2.2. Processes of mechanical destruction of solids
7.2.3. Material aging
7.3. Refuses for strength parameters
7.4. Tribological failures
7.5. Types of wear of car parts
7.6. Refuses for corrosion parameters
7.7. Wear chart and methods for measuring car wear
7.8. Methods for determining the wear of machine parts
7.8.1. Periodic measurement of wear
7.8.2. Continuous measurement of wear
7.9. The effect of residual deformations and aging of material wear
7.10. Evaluation of the reliability of elements and technical systems of cars when they are designing
7.11. The most common ways and methods for ensuring and predicting the reliability used when creating machines
Chapter 8. Maintenance and repair system
8.1. Maintenance and repair systems of machines, their essence, content and principles of construction
8.2. Requirements for maintenance and repair system and methods for determining the frequency of their conduct
8.3. Functioning of the machine in extreme situations
Chapter 9. Diagnostics as a method of controlling and ensuring the reliability of the car during operation
9.1. General Diagnostics Information
9.2. Basic concepts and terminology of technical diagnostics
9.3. Diagnostic value
9.4. Diagnostic parameters, determination of the limit and permissible values \u200b\u200bof the parameters of the technical condition
9.5. Principles of car diagnostics
9.6. Organization of car diagnostics in the system of maintenance and repair
9.7. Types of car diagnostics
9.8. Diagnosing car aggregates during repair
9.9. Diagnosing the state of the cylindrophone group
9.10. Concept of diagnosing technology in modern conditions
9.11. Technical diagnostics - an important element of technological certification of service enterprises
9.12. Management of reliability, technical condition of machines based on the results of diagnosis
9.13. Car diagnostics and safety
9.14. Diagnostics of the brake system
9.15. Diagnostics of headlight headlights
9.16. Diagnostics of suspension and steering
Conclusion
Bibliography.

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TEST

Basics of the theory of reliability and diagnostics

The task

According to the results of tests, the following source data for estimating reliability indicators was obtained for reliability according to the plan.

5 selective values \u200b\u200bof developments to failure (unit of measurement: th. Hours): 4.5; 5.1; 6.3; 7.5; 9.7.

5 selective values \u200b\u200bof developments before censorship (i.e. 5 products remained in the working condition by the end of the test): 4.0; 5.0; 6.0; 8.0; 10.0.

Determine:

Point estimate of the average operation to failure;

With the trust probability of the lower trust borders and;

Build on scale the following graphics:

distribution function;

probability of trouble-free work;

upper confidence border;

lower confidence border.

Introduction

The calculated part of the practical work contains an assessment of reliability indicators for specified statistical data.

Evaluation of the reliability indicator is the numerical values \u200b\u200bof the indicators defined by the results of observations of objects under operating conditions or special reliability tests.

When determining reliability indicators, two options are possible:

- The type of the Distribution Distribution Act is known;

- The type of Distribution Distribution Act is not known.

In the first case, parametric estimates are used, in which they first estimate the parameters of the distribution law included in the calculated formula of the indicator, and then determine the indicator of reliability as a function from the estimated parameters of the distribution law.

In the second case, non-parametric methods are applied, in which reliability indicators are assessed directly according to experimental data.

1. Brief theoretical information

trouble-free trust distribution

Quantitative indicators of reliability of rolling stock can be determined by representative statistical data on refusals obtained during operation or as a result of special tests set taking into account the characteristics of the design, the presence or absence of repairs and other factors.

The initial set of observation objects is called the general population. The coverage of the aggregate distinguish 2 types of statistical observations: solid and sample. Complete observation when each element of the aggregate is studied, with significant costs of assets and time, and sometimes generally physically impossible. In such cases, it is resorted to selective observation, which is based on the allocation from the general population of some of its representative part - a selective aggregate, which is also called the sample. According to the results of the study of the trait in the selective aggregate make an opinion on the properties of the trait in the general population.

The selective method can be used in two versions:

- simple random selection;

- Random selection in typical groups.

The division of the sample aggregate on typical groups (for example, according to the models of gondola cars, by the years of construction, etc.) gives a gain with accuracy when evaluating the characteristics of the entire general population.

As it were, selective observation was not delivered, the number of objects is always of course, and therefore the volume of experienced (statistical) data is always limited. With a limited amount of statistical material, it is possible to obtain only some estimates of reliability indicators. Despite the fact that the true values \u200b\u200bof reliability indicators are not accidental, their estimates are always random (stochastic), which is associated with the chance of sampling objects from the general population.

When calculating the assessment, usually tend to choose this method so that it is wealthy, unstable and efficient. A wealthy is an assessment, which, with an increase in the number of observation objects, converges in probability to the true value of the indicator (SELL 1).

The estimate is called an assessment, the mathematical expectation of which is equal to the true magnitude of the reliability indicator (SL. 2).

An estimate is effective, the dispersion of which compared with the dispersions of all other estimates is the smallest (SL. 3).

If the conditions (2) and (3) are performed only with n, striving to zero, then such estimates are called respectively asymptotically unbearable and asymptotically effective.

Wealthiness, failure and efficiency are qualitative characteristics of estimates. Conditions (1) - (3) allow for a finite number of objects N observation to record only approximate equality

a ~ B (n)

Thus, assessment of the reliability indicator in (n), calculated by a selective set of volume N objects applied as an approximate value of the indicator of reliability for the entire general population. Such an assessment is called point.

Given the probabilistic nature of reliability indicators and significant variation of statistical data on failures, when using point estimates of indicators instead of the true values \u200b\u200bof their values, it is important to know what the limits of a possible error, and what is its probability, that is, it is important to determine the accuracy and accuracy of the assessments used. It is known that the quality of the point estimate is higher than on the greater statistical material it is obtained. Meanwhile, the point assessment itself does not bear any information about the amount of data on which it is received. This determines the need for interval estimates of reliability indicators.

The source data for evaluating reliability indicators is due to the observation plan. The source data for the plan (N v z) are:

- selective values \u200b\u200bof developments to failure;

- Selective values \u200b\u200bof the operations of machines remaining workable during observations.

The operation of machines (products), which remained operational during the tests, is called the operation before censorization.

Censure (clipping) to the right is an event that leads to the termination of tests or operational observations of the object before the failure (limit state).

The causes of censorship are:

- the abundance of the beginning and (or) end of testing or operation of products;

- removal from testing or operation of certain products for organizational reasons or due to the failures of the components, the reliability of which is not investigated;

- translation of products from one application mode to another in the process of testing or operation;

- The need to assess reliability before the failures of all studied products.

Working before cranventment is the work of an object from the start of tests before censorization. The sample, the elements of which are the values \u200b\u200bof developments to failure and prior to censorization, is called censored sample.

A single censored sample is a censored sample, in which the values \u200b\u200bof all the developments before censorization are equal to each other and no less than the greatest developments before failure. If the values \u200b\u200bof the developments before censorization in the sample are not equal to each other, then this sample is repeatedly censored.

2. Evaluation of reliability indicators by non-parametric method

1 . During the failure, it is built to the overall variationaries to censorship to censorship to censorship; 4.5; 5.0 *; 5.1; 6.0 *; 6.3; 7.5; 8.0 *; 9.7; 10.0 *.

2 . Calculate the point estimates of the distribution function by the formula:

; ,

where is the number of workable products of the Jth failure in the variational series.

;

;

;

;

3. Calculate a point estimate of the average work before the refusal by the formula:

,

where;

;

.

;

thousand hour.

4. The point estimate of trouble-free work for the operation of thousands of hour is determined by the formula:

,

where;

.

;

5. Calculate point estimates by the formula:

.

;

;

;

.

6. According to the calculated values \u200b\u200band build graphs of the distribution functions of the operation and reliability functions.

7. The lower confidence border for the average developing to failure by calculating the formula:

,

where is the quantile of the normal distribution corresponding to the likelihood. Accepted on the table, depending on the trust probability.

By the condition of the task, the trust probability. Select from the table corresponding to it.

thousand hour.

8 . The values \u200b\u200bof the upper trust border for the distribution function calculated by the formula:

,

where is the quantile chi-square distribution with the number of degrees of freedom. Accepted on the table, depending on the trust probability q..

.

Figured brackets in the last formula mean the taking of the integer part of the number enclosed in these brackets.

For;

for;

for;

for;

for.

;

;

;

;

.

9. The values \u200b\u200bof the lower confidence limit of the probability of trouble-free operation are determined by the formula:

.

;

;

;

;

.

10. The lower confidence limit of the probability of trouble-free operation at a given time for thousand hours is determined by the formula:

,

where; .

.

Respectively

11 . According to the calculated values \u200b\u200band we build graphs of the functions of the upper trusting border and the bottom trust border as the previously constructed models of point estimates and

Conclusion

In the study of the test results of products on reliability according to plan, the values \u200b\u200bof the following reliability indicators were obtained:

- point estimate of the average operation before the refusal of thousand hours;

- point estimate of the probability of trouble-free work for the development of thousand hours;

- with the trust probability of the lower trust borders of thousand hours and;

According to the found values \u200b\u200bof the distribution function, probability of trouble-free operation, the upper trust border and the lower trust border are built graphs.

Based on the calculations, you can solve similar tasks with which engineers face production (for example, during the operation of wagons at w.).

Bibliography

1. Quirkin E.M., Kalikhman I.L. Meritality and statistics. M.: Finance and Statistics, 2012. - 320 p.

2. Reliability of technical systems: Reference / Ed. I.A. Ushakov. - M.: Radio and Communication, 2005. - 608 p.

3. Reliability of machine-building products. Practical guide to normalization, confirmation and provision. M.: Publishing House Standards, 2012. - 328 p.

4. Methodical instructions. Reliability in the technique. Methods for estimating reliability indicators for experimental data. RD 50-690-89. Introduce P. 01.01.91 M.: Publishing House of Standards, 2009. - 134 p. Group T51.

5. Bibles L.N., Smirnov N.V. Tables of mathematical statistics. M.: Science, 1983. - 416 p.

6. Kiselev S.N., Savodikin A.N., Ustich P.A., Zaidadinov R.I., Burchak G.P. Reliability of mechanical railway transport systems. Tutorial. M.: Miit, 2008-119 p.

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Introduction The value of the theory of reliability

in modern technique.

The current period of development of the technique is characterized by the development and implementation of complex technical systems and complexes.

The main concepts that are used in this discipline are the concepts of a complex dynamic system and a technical device (TU) or an element included in the system. Under complexity is usually understood erected Systems from individual elements, while considered not just the amount of elements, but their interaction. The interaction of the elements and their properties change over time. The complexity of the interaction of elements and their number are two aspects of the concept of a complex dynamic system. The complexity of the system is determined not so much by the number of elements as the amount of connections between the elements themselves and between the system and the environment.

Complex dynamic systems are systems oversaturated with internal bonds of elements and external connections with an environment.

We define a complex dynamic system as the formation of elements of various nature, which have some functions and properties that are missing from each of the elements, and can function, statically correlacing in some range with the environment, and due to this, to maintain its structure during the continuous change in the interacting elements by complex dynamic laws.

Complex dynamic systems are essentially nonlinear systems, the mathematical description of which is not always possible at the present stage.

Any complex dynamic system is created to solve a certain theoretical or production task. Due to the deterioration of the properties of the system during operation, there is a need for periodic maintenance, the purpose of which to maintain the system's ability to perform its functions. Therefore, information processes are fundamental to complex dynamic systems. The cyclicity of information processes is provided by the feedback mechanism. Based on information on the behavior of the system, its condition is organized, taking into account the results of which the subsequent management of the system is corrected.

When designing technical systems, it is necessary to provide maintenance issues in the process of intended exploitation. Among other problems of designing and creating a complex:

Compliance with the specific technical requirements;

Efficiency of the complex, taking into account the tests and conditions for the intended exploitation;

Development of technical means of maintenance of the complex and mathematical support for them;

Ensure the fitness of the complex to work in the link "Man - Machine" and others.

Thus, during the design of the complex, focus on all marked, related issues in general, and not on each individual one.

You can design a complex that meets the specified technical requirements, but not to satisfy the requirements of economic, maintenance requirements and the functioning of the complex in the "Man - Machine" link. Consequently, the problem of creating a complex must be solved from the position of the system approach. The essence of this approach can be demonstrated on a simple example. Suppose we are selected by one car each of the available brands. Then we appeal to the group of experts with a request to study them and choose the best carburetor, then choose the best engine, distributor, transmission, etc. until we collect all the automotive parts from different cars. We are unlikely to be able to assemble a car from these parts, and if you succeed, it will hardly work well. The reason is that individual parts will not approach each other. Hence the conclusion: it is better when the parts of the system are well suited to each other, even if they work separately and not excellent than when excellent parts are not suitable for each other. This is the essence of the system approach.

Sometimes the improvement of one part of the complex leads to the deterioration of the technical characteristics of the other, so the improvement loses its meaning. A systematic approach to analyzing the phenomena under consideration provides for the use of a complex of various mathematical methods, modeling methods and conducting experiments.

The proposed course considers the decision of the private tasks of the maintenance of complex systems and their elements by the analytical method and the features of solving more complex objectives of operation by the method of statistical modeling are noted. In practice, the implementation of the methods obtained will lead to the analysis of the complex from the positions of the system approach.

The main signs of a complex system or technical device (TU) are as follows:

Possession of a certain integrity of the target and promoting the development of optimal outputs from the existing set of inputs; Optimality of outputs should be assessed by a predetermined optimality criterion;

Performing a large number of different functions that are carried out by a plurality of part in the system;

The complexity of functioning, i.e. The change in one variable entails the change in many variables and, as a rule, is non-linear;

High degree of automation;

The ability to describe the perturbation in a quantitative measure.

Operation of a complex TU is a continuous process that includes a number of activities requiring planned, continuous impact on that to maintain it in working condition. Such activities include: scheduled maintenance, recovery of performance after failure, storage, preparation for work, etc. The above definition of operation does not cover all the activities that make up the process of operation of complex systems. Therefore, under operation, in a broad sense, it is necessary to understand the process of using that intended and maintaining it in a technically good condition.

The state of that is determined by the set of values \u200b\u200bof its technical characteristics. During operation, the technical characteristics of the device change continuously. For the organization of operation, it is important to distinguish between the states that correspond to the extreme or permissible (boundary) values \u200b\u200bof the technical characteristics that correspond to the working state, the failure, the state of maintenance, storage, recovery, etc. For example, the engine is in working condition if it provides the necessary thrust, provided that the values \u200b\u200bof all other characteristics are within the limits established in the technical documentation. The engine must be in terms of maintenance, if the values \u200b\u200bof its technical characteristics have reached the corresponding limits. In this case, its immediate use is impossible for its intended purpose.

The main task of the theory of exploitation is to scientific prediction of the states of complex systems or that and production using special models and mathematical methods for the analysis and synthesis of these models, recommendations on the organization of their operation. When solving the main objective operation, a probabilistic statistical approach is used to predict and managing the states of complex systems and modeling operational processes.

Some questions of the theory of operation, such as predicting the reliability of TU under operating conditions, the organization of restoration of the TU during the task, diagnostics of failures in complex systems, determination of the required number of spare elements, etc., received sufficient development in the theory of reliability, theory of recovery and theory of mass maintenance , in technical diagnostics and theory of stock management.

1. Basic concepts and definitions

reliability theory.

The theory of reliability is the science of methods for ensuring and preserving reliability in the design, manufacture and operation of systems.

The ability of any product or system to maintain its initial technical characteristics during operation are determined by their reliability. The physical meaning of reliability is the ability to maintain its characteristics in time.

Operating characteristics are also readiness for use, reducibility, maintenance parameters. Reliability can be defined as an independent operational characteristic of TU and serve as component of other performance.

Under reliability It is understood as the property of the specified functions, while maintaining its operational indicators in the specified limits within the required period of time or the required operation under certain operating conditions.

As follows from the definition, reliability depends on which functions performs the product in time, during which these functions must be fulfilled, and on operating conditions.

Any product has many operational indicators and must be strictly coordinated in each case when the technical parameters or the TU property should be considered when determining its reliability.

In this regard, the concept is introduced performance which is defined as the state of the one in which it is capable of performing specified functions with parameters set by the requirements of technical documentation. The introduction of the concept of performance is necessary to determine the technical parameters and properties of the proper functions of the specified functions and the permissible boundaries of their change.

From the definition of reliability, it also follows that reliability is the ability to maintain its initial specifications in time. However, even the most reliable one cannot maintain its initial technical characteristics during unlimited time. Therefore, to talk about reliability without defining a specific period of time, during which these characteristics should be ensured, meaningless. In addition, the real reliability of each that largely depends on the operating conditions. Any predetermined value of reliability is valid only for specific operating conditions, including the modes of use of that.

In reliability theory, the concepts of the element and system are introduced. The difference between them is purely conditional and is that in determining reliability, the element is considered indivisible, and the system is represented as a set of individual parts, the reliability of each of which is determined separately.

Concepts element and system are relative. For example, it is impossible to assume that the aircraft is always a system, and one of its engines is an element. The engine can be considered an item if it is possible to consider it as a single integer when determining the reliability. If it is disclosed to components (combustion chamber, turbine, compressor, etc.), each of which has its own reliability value, the engine is a system.

Quantify or measure reliability, it is much more complicated than measuring any technical characteristics. As a rule, only the reliability of the elements is measured, for which special, sometimes quite complex and long-term tests are carried out or the results of observations of their behavior are used.

System reliability is calculated on the basis of data on the reliability of elements. As a starting data, events consisting in violating the performance of that and called failures are used as the start of the quantitative reliability values.

Under refusal The event is understood, after which the one ceases to perform (partially or completely) its functions. The notion of refusal is the main in the theory of reliability and the correct clarification of his physical entity is the most important condition for the successful solution to the issues of reliability.

In some cases, the system continues to perform the specified functions, but with some elements, disruptions of technical characteristics appear. This state of the element is called a malfunction.

Fault - The state of the element in which it at the moment does not correspond to at least one requirements established both in relation to the main and secondary parameters.

Consider some other concepts characterizing the performance of TU. In some cases, it is required that that not only worklessly worked for a certain period of time, but, despite the presence of failures in interruptions in the work, would remain in general the ability to perform specified functions for a long time.

The property of that maintenance with the necessary interruptions for maintenance and repairs to the limit state defined in the technical documentation is called durability . The ultimate states of that may be: breakdown, limiting wear, power drop or performance, accuracy decreased, etc.

This may lose performance not only during operation, but also in the process of long-term storage, as a result of aging. To emphasize the property, the concept of persistence, which makes the meaning of the reliability of TU under storage conditions, has been introduced.

Persistence It is called the property of the following operational indicators during and after the storage and transportation period established in the technical documentation.

Important in determining the operational characteristics of TU has the concepts of service life, efficiency and resource.

Service life The calendar duration of operation is called that until the emergence of the limit state specified in the technical documentation. Under arabity It is understood as the duration (in hours or cycles) or the volume of the work of TU (in liters, kilograms, T-km, etc.) before the appearance of refusal . Resource The total operating time is called the limit state specified in the technical documentation.

2. Quantitative measure of reliability of complex systems

To select rational measures aimed at ensuring reliability, it is very important to know the quantitative indicators of the reliability of elements and systems. The peculiarity of the quantitative characteristics of reliability is their probabilistic statistical nature. Hence the features of their definition and use. As practice shows the same type of one, such as cars, even being manufactured at one factory, show a different ability to maintain their performance. In the process of operation, the refusals of the one occur in the most unexpected, unforeseen moments. There is a question, are there any patterns in the appearance of failures? Exist. Only for their establishment should be observed not for one, but for many of those in operation, and for processing observation results, apply methods of mathematical statistics and probability theory.

The use of quantitative reliability estimates is necessary when solving the following tasks:

Scientific substantiation of requirements for newly created systems and products;

Improve the quality of design;

The creation of scientific methods of testing and controlling the level of reliability;

Justification of ways to reduce economic costs and reducing time for the development of products;

Improving the quality and stability of production;

Development of the most efficient methods of operation;

An objective assessment of the technical condition in operation;

Currently, in the development of reliability theory allocated two main directions :

Progress of technology and improving the technology of manufacturing elements and systems;

Rational use of elements when designing systems - synthesis of reliability systems.

3. Quantitative Reliability Indicators

elements and systems.

The quantitative indicators of reliability of elements and systems include:

Reliability coefficient R. G. ;

Probability of trouble-free operation for a certain time P. ( t. ) ;

Average work before the first refusal T cf. for non-standard systems;

Working on failure t. cf. For restored systems:

Failure intensity λ( t. ) ;

Average recovery time τ cf. ;

μ( t. ) ;

Reliability function R. G. ( t. ).

Definitions of these quantities:

R. G. – probability to catch the product in a working condition.

P. ( t. ) - the likelihood that for a given period of time ( t. ) The system will not refuse.

T cf. - Mathematical expectation of system operation time before the first refusal.

t. cf. - Mathematical expectation of the system of operation between consistent failures.

λ( t. ) - mathematical expectation of the number of failures per unit of time; For a simple failure stream:

λ( t. )= 1/ t. cf. .

τ cf. - Mathematical expectation of system recovery time.

μ( t. ) - mathematical expectation of the number of recovery per unit of time:

μ( t. ) \u003d 1 / τ cp.

R. G. ( t. ) - Change the reliability of the time system.

4. Classification of systems for the purpose of calculating reliability.

Systems for the purpose of calculating reliability are classified by several features.

1. According to the features of functioning during the application:

Disposable systems; These are the reuse of which it is impossible or inexpedient for any reason;

Reusable systems; These are the system reuse of which it is possible and can be carried out after executing the system of functions assigned to it for the previous application cycle.

2. By adaptability to restoration after the appearance of failures:

Recoverable if their performance, lost in refusal, can be restored during operation;

Unstasted if their performance, lost during failure, is not subject to recovery.

3. For maintenance:

Not served - systems whose technical condition is not controlled during operation and measures are not carried out aimed at ensuring their reliability;

Served - systems whose technical condition is monitored during operation and relevant measures to ensure their reliability are held.

4. By type of implemented maintenance:

With periodic service - systems in which reliability measures are implemented only when planned repair and preventive work through predetermined intervals T O. ;

With a random service period - systems in which reliability measures are implemented at random intervals corresponding to the appearance of failures or the achievement of the limiting system for the state-efficiency;

With a combined service - systems in which, in the presence of planned repair and preventive work, there are elements of service with a random period.

5. Classification of system systems.

The reliability indicators are dependent only on the reliability indicators of the elements, but also the methods of "connection" of elements into the system. Depending on the method of "connection" of the elements into the system, flowcharts are distinguished: a. serial (main compound); b. parallel (redundant compound); in. Combined (in the flowchart, the main and redundant connection of the elements and the elements); See fig. one.

Fig. 1. Structures of systems for the purpose of calculating reliability.

The classification of the system structure to the main or reserved does not depend on the physical relative placement of elements in the system, it depends only on the influence of the failures of the elements on the reliability of the entire system.

The main structure of the system is characterized by the fact that the failure of one element causes the failure of the entire system.

The redundant structures of the system are called such in which the refusal occurs in the refusal of all or a certain number of elements that make up the system.

Reserved structures can be with general reservation, reservation by groups of elements and with element reservations (see Fig. 2, or., B., C.).

Figure 2. Reservation options for systems.

The classification belonging of the system according to the structure is not constant, but depends on the purpose of the calculation. The same system can be primary and reserved; For example, what "connection" do the engines of the four-dimensional aircraft? The answer is twofold.

If we consider the system from the point of view of the technique serving the aircraft, the engines are "connected" sequentially, because The aircraft cannot be released on the flight if at least one engine will be faulty; Thus, the failure of one element (engine) means the failure of the entire system.

If we consider the same system in flight, then from the point of view of pilots, it will be redundant, because The system will refuse completely with the failure of all engines.

6. Classification of failures and faults of systems and elements.

Failures have a different nature and are classified for several features. The main ones are as follows:

- influence of refusal to safety : dangerous, safe;

- the impact of refusal to work the main mechanism : leading to a dump; reduced performance of the main mechanism; not leading to a sinking mechanism;

- the nature of elimination of refusal : urgent; not urgent; compatible with the work of the main mechanism; not compatible with the work of the main mechanism;

- external manifestation of refusal : explicit (obvious); implicit (hidden);

- duration of elimination of refusal : short-term; long;

- the nature of the occurrence of refusal : Sudden; gradual; dependent; independent;

- the reason for the occurrence of refusal : structural; manufacturer; operational; erroneous; natural;

- the time of refusal : when storing and transporting; during the start period; before the first overhaul; After superficial repair.

All listed types of failures have a physical nature and are considered technical.

In addition to them, technological failures may occur in systems consisting of autonomous elements (machines, mechanisms, devices).

Technological - these are refusals associated with the implementation of individual elements of auxiliary operations that require stopping the operation of the main mechanism of the system.

Technological failures arise in cases:

Performing operations preceding the operation cycle of the main mechanism of the system;

Performing operations following the main mechanism cycle, but not compatible with the implementation of the new cycle;

The cycle of working out the main mechanism of the system is less than the cycle of testing the auxiliary element in the process;

The technological operation performed by any element is incompatible with the operation of the main mechanism of the system;

Transition of the system to a new state;

Mind of operational working conditions of the system of the system to the agreed passport characteristics of the system mechanisms.

7. Main quantitative dependencies when calculating systems for reliability.

7.1. Statistical analysis of the work of elements and systems.

The qualitative and quantitative characteristics of the reliability of the system are obtained by analyzing the statistical data on the operation of elements and systems.

In determining the type of the distribution law of a random variable, to which the intervals of the trouble-free operation and the recovery time, the calculations are performed in the sequence:

Preparation of experienced data; This operation is that primary sources about the operation of systems and elements are analyzed to identify clearly erroneous data; Statistical is radically presented in the form of variational, i.e. placed as increasing or decrease in random variable;

Construction of a random variable histogram;

Approximation of the experimental distribution of theoretical dependence; Checking the correctness of the approximation of the experimental distribution of theoretical using the criteria of consent (Kolmogorov, Pearson, omega-square, etc.).

According to observations, conducted in various fields of technology, the flow of failures and recovery is the simplest, i.e. It has the ordinary, stationary and lack of amersion.

The reliability of complex systems is subject to the exponential law, which is characterized by dependencies:

Probability of trouble-free operation:

Time distribution function of trouble-free operation:

Distribution of time distribution of trouble-free operation:

	f (T)

These dependencies correspond to the simplest failure flow and are characterized by constants:

Failure intensity λ( t. ) = const. ;

Intensity of recovery μ( t. ) = const. ;

Working on failure t. cf. \u003d 1 / λ ( t. ) = const. ;

Recovery time performance τ cp \u003d 1 / μ ( t. ) = const. .

Parameters λ( t. ), t. cf. ; μ( t. ) and τ cf. - obtained as a result of processing a variational series by timing observation of elements and systems.

7.2. Calculation of the reliability coefficient of elements.

The reliability coefficient of the element is determined according to the statistical processing of variational series by formulas:

or (1)

as well as in terms of failure and recovery intensity λ( t. ) and μ( t. ) :

. (2)

In industrial transport systems, technical and technological failures should be distinguished. Accordingly, the characteristics of the reliability of elements in technical and technological relations are technical coefficients r. T. I. and technological r ci reliability of elements. The reliability of the element as a whole is determined by the dependence:

r. G. I. = r. T. I. · r ci . (3)

7.3. Calculation of the technical reliability of the system.

The reliability of the main system (system sequentially connected elements) is determined if there is only technical failures dependency:

with the equal elements:

where n. - the number of sequentially connected elements in the system;

In calculating the quantitative indicators of redundant and combined system structures, it is necessary to know not only their reliability, but also the unreliability of the element; Since reliability r I. And unreliability q I. The element make up the total amount of probabilities, equal to one, then:

q I. =(1 - r I. ) . (6)

The unreliability of the redundant system (with parallel connection of the elements) is defined as the probability that all elements of the system have been denied, i.e.:

(7)

Reliability, respectively, to determine the dependence:

(8)

Or, with the same elements

, (9)

where m. - Number of backup elements.

Power ( m. + 1) When calculating the reliability of the system, it is explained by the fact that in the system one element is required, and the amount of backups can vary from 1 to m. .

As already noted, reservation in combined systems can be a single, group of elements and element. Reliability indicators of systems depend on the type of reservation in the combined system. Consider these variants of various ways to develop the system.

Reliability of combined redundant systems with general reservation (system redundancy) is determined by addiction:

(10)

with an equalized elements (consequently, subsystems):

(11)

The reliability of combined systems with reservation by groups of elements is determined sequentially; First, the reliability of the reserved subsystems are determined, then the reliability of the system of successively connected subsystems.

The reliability of combined systems with element (separate) redundancy is determined sequentially; First define the reliability of block elements (element reserved by one, two, etc. m. Elements), then - the reliability of the system of sequentially connected block elements.

The reliability of the block element is equal to:

; (12)

R. to J. With element reservation, it is:

; (13)

or at the equalized elements:

(14)

Consider example Calculation of the reliability of the system without reservation and with various forms of its development (redundancy).

A system consisting of four elements is given (see Fig. 1.):

	r. 1 = 0,95		r. 2 = 0,82		r. 3 = 0,91		r. 4 = 0,79

Figure 1. Block diagram (main) system.

Reliability of the main system:

0.95 · 0.82 · 0.91 · 0.79 \u003d 0.560.

The reliability of the combined system with a general (system) reservation will be equal to (see Fig. 2):

r. 1 = 0,95

r. 2 = 0,82

r. 3 = 0,91

r. 4 = 0,79

r. 1 = 0,95

r. 2 = 0,82

r. 3 = 0,91

r. 4 = 0,79

Figure 2. Flow diagram of the combined system during system reservation.

1- (1- 0,560) 2 = 1 – 0,194 = 0,806.

The reliability of the combined system during reservation by groups of elements will depend on how elements will be grouped; In our example, elements are grouping as follows (see Fig. 3):

r. 1 = 0,95

r. 2 = 0,82

r. 3 = 0,91

r. 4 = 0,79

r. 1 = 0,95

r. 2 = 0,82

r. 3 = 0,91

r. 4 = 0,79

Figure 3. Block diagram of the combined system when reservation by groups of elements.

Reliability of the first subgroup R. O1 of the 1st and 2nd sequentially connected elements will be equal to:

0.95 · 0.82 \u003d 0.779;

Reliability of the first subgroup block element:

= 1- (1- 0,779) 2 = 0,951.

Reliability of the second subgroup R. op Of the 3rd and 4th sequentially connected elements will be equal to:

0.91 · 0.79 \u003d 0.719.

Reliability of the block element of the second subgroup:

= 1 – (1 – 0,719) 2 = 0,921.

System reliability R. ks. Of the two successively connected subsystems will be equal to:

0.951 · 0.921 \u003d 0.876.

Reliability of the combined system R. to J. With element reservation, it is equal to the product of the reliability of block elements consisting of each of the same system element (see Fig. 4)

r. 1 = 0,95

r. 2 = 0,82

r. 3 = 0,91

r. 4 = 0,79

r. 1 = 0,95

r. 2 = 0,82

r. 3 = 0,91

r. 4 = 0,79

Figure 4. Flow diagram of a combined system with element reservation.

The reliability of the block element is determined by the formula:

;

For the first element: r J. 1 = 1 – (1 – 0,95) 2 = 0,997;

For the second element: r J. 2 = 1 – (1 – 0,82) 2 = 0,968;

For the third element: r J. 3 = 1 – (1 – 0,91) 2 = 0, 992;

For the fourth element: r J. 4 = 1 – (1 – 0,79) 2 = 0,956.

For the system sequentially connected block elements:

0.997 · 0.968 · 0.992 · 0.956 \u003d 0.915.

As the calculation example shows, the more connections between the system elements, the higher its reliability.

7.4. Calculation of the technical readiness of the system.

The system's readiness parameters in the presence of technical and technological failures is determined by the formula:

.

where r. G. I. - technical reliability of the element;

r ci - technological reliability of the element;

r. G. I. - generalized reliability of the element.

When reserving elements, the change in technical and technological reliability occurs in different ways: technical - according to a multiplicative scheme, technological - according to an additive scheme, and the maximum technological reliability can be equal to one.

From here, with twofold reservation of the item, we obtain its reliability of the block element:

With an arbitrary number of backup elements M:

where M is the number of backup elements.

The readiness of the combined systems is determined similar to the definition of reliability in the presence of only technical failures, i.e. The readiness of block elements is determined, and according to their indicators the availability of the entire system.

7. Formation of the optimal structure of the system.

According to the results of calculations, the development of the structure of the system is its reliability asymptotically approaches unity, while the cost in the formation of the system increases according to linear dependence. Since the operational performance of the system is a product of its reliability on the nominal (passportable) performance, then the increasing increase in the costs of the system for the formation of the system when its reliability will result in the cost of its reliability, will result in the cost of the performance unit and the further development of the system structure will become economically inappropriate. Thus, the solution to the question of the expedient reliability of the system is an optimization task.

The target system optimization function is:

where - the total system costs; - achieved on the basis of these costs the coefficient of the preparedness of the combined system.

PRI MERS Source Conditions: The main type system is set (see Figure):

Figure 5. Structure of the main system, reliability indicators

elements and conditional costs of elements.

It is required to determine the optimal multiplicity of the reservation of the third element of the system (the remaining items are not reserved).

Decision:

1. Determine the reliability of the main system:

0.80 · 0.70 · 0.65 · 0.90 \u003d 0.328.

2. Determine the cost of the main system:

C o \u003d\u003d 20 + 30 + 12 + 50 \u003d 112 cu

3. Determine the specific costs of achieving this coefficient of readiness of the main system: