"Department" Automobile transport "N.A. Kuzmin, G.V. Borisov LECTURES ON THE COURSE technical systems»» NIZHNY NOVGOROD 2015 Lecture Topics INTRODUCTION .. 1. ... "

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MINISTRY OF EDUCATION AND SCIENCE OF THE RF

FEDERAL STATE BUDGET

EDUCATIONAL INSTITUTION

HIGHER PROFESSIONAL EDUCATION

"NIZHNYGOROD STATE TECHNICAL

UNIVERSITY them. R.E. ALEXEEVA "

Department "Automobile transport"

N. A. Kuzmin, G. V. Borisov

COURSE LECTURE OUTLINE

"Fundamentals of the performance of technical systems" "

NIZHNY NOVGOROD

2015 G.

Lecture Topics INTRODUCTION ……………………………………………………………… ...

1. BASIC CONCEPTS, TERMS AND DEFINITIONS IN THE FIELD

………………………………………...

MOTOR VEHICLES

2. PERFORMANCE AND QUALITY OF VEHICLES ... ...

2.1. Operational properties of cars. ………………………

2.2. Realizable indicator of the quality of cars .. ……………… ...

3. PROCESSES OF CHANGE IN THE TECHNICAL STATE OF CARS IN OPERATION ……………………………………………….

Wear of the surfaces of parts .. …………………………… 3.1.

Plastic deformations and strength fractures of parts 3.2.

Fatigue failure of materials ………………………………… 3.3.

Corrosion of metals ………………………………………………….

Physical and mechanical or thermal changes in materials (aging) ……………………………………………… ..

4. OPERATING CONDITIONS OF CARS ………………………… ..

4.1. Road conditions ………………………………………………… ..

4.2. Transport conditions …………………………………………… ...

4.3. Natural and climatic conditions …………………………………

5. OPERATING MODES OF CARS

UNITS …………………………………………………………… ..

5.1. Non-stationary modes of operation of automotive units ... ..

5.2. Speed \u200b\u200band load modes of operation of automobile engines ………………………………………………………… ..

5.3. Thermal operating modes of car units ……………….

5.4. Running-in of vehicle units ……………………………………

6. CHANGE OF TECHNICAL CONDITION OF AUTOMOTIVE TIRES

………………………………………………………..

IN OPERATION

6.1. Classification and marking of tires ………………………………

6.2. Investigation of factors affecting tire life ……

BIBLIOGRAPHIC LIST

BIBLIOGRAPHIC LIST

1. Regulations on the maintenance and repair of the rolling stock of road transport / Minavtotrans RSFSR.– M.: Transport, 1988 –78 p.

2. Akhmetzyanov, M.Kh. Resistance of materials / M.Kh. Akhmetzyanov, P.V.

Gres, I.B. Lazarev. - M .: Higher school, 2007 .-- 334p.

3. Boucher, N.A. Friction, wear and fatigue in machines (Transport equipment): textbook for universities. - M .: Transport, 1987 .-- 223p.

4. Gurvich, I.B. Operational reliability of automobile engines / I.B. Gurvich, P.E. Syrkin, V.I. Chumak. - 2nd ed., Add. - M .: Transport, 1994 .-- 144p.

5. Denisov, V. Ya. Organic chemistry / V. Ya. Denisov, D.L. Muryshkin, T.V. Chuikova. - M .: Higher school, 2009. - 544p.

6. Izvekov, B.S. Modern car. Automotive terms / B.S. Izvekov, N.A. Kuzmin. - N. Novgorod: RIG ATIS LLC, 2001. - 320 p.

7. Itinskaya N.I. Fuels, oils and technical fluids: a handbook, 2nd ed., Rev. and add. / N.I. Itinskaya, N.A. Kuznetsov. - M .: Agropromizdat, 1989 .-- 304s.

8. Karpman, M.G. Materials science and technology of metals / M.G. Karpman, V.M. Matyunin, G.P. Fetisov. - 5th ed. - M .: Higher school. - 2008.

9. Kislitsin N.M. Durability of car tires in various driving modes. - N. Novgorod: Volgo-Vyatka book. publishing house, 1992 .-- 232p.

10. Korovin, N.V. General chemistry: a textbook for technical areas and special universities / N.V. Korovin. - 12th ed. - M .: Higher school, 2010. - 557s.

11. Kravets, V.N. Car tire tests / V.N. Kravets, N.M. Kislitsin, V.I. Denisov; Nizhny Novgorod. state tech. un-t them. R.E. Alekseeva - N. Novgorod: NSTU, 1976 .-- 56p.

12. Kuzmin, N.A. Automobile reference book-encyclopedia / N.A.

Kuzmin and V.I. Sands. - M .: FORUM, 2011 .-- 288p.

13. Kuzmin, N.A. Scientific basis processes of changing the technical state of cars: monograph / N.A. Kuzmin, G.V. Borisov; Nizhny Novgorod. state tech. un-t them. R.E. Alekseeva - N. Novgorod, 2012. –2 p.

14. Kuzmin, N.A. Processes and causes of changes in the performance of cars: a tutorial / N.А. Kuzmin; Nizhny Novgorod. state tech.

un-t them. R.E. Alekseeva - N. Novgorod, 2005 .-- 160 p.

15. Kuzmin, N.A. Technical operation of cars: patterns of change in working capacity: a tutorial / N.A. Kuzmin.

- M .: FORUM, 2014 .-- 208s.

16. Kuzmin, N.A. Theoretical foundations of ensuring the operability of cars: textbook / N.А. Kuzmin. - M .: FORUM, 2014 .-- 272 p.

17. Neverov, A.S. Corrosion and protection of materials / A.S. Neverov, D.A.

Rodchenko, M.I. Tsyrlin. - Minsk: Higher school, 2007. - 222s.

18. Peskov, V.I. Theory of the car: a tutorial / V.I. Sands; Nizhny Novgorod. state tech. un-t. - Nizhny Novgorod, 2006 .-- 176 p.

19. Tarnovsky, V.N. etc. Car tires: Device, work, operation, repair. - M .: Transport, 1990 .-- 272p.

INTRODUCTION

The rate of economic development in Russia and all countries of the world largely depends on the level of organization and operation of road transport (AT), which is associated with the mobility and flexibility of delivery of goods and passengers. These properties of AT are largely determined by the level of performance of cars and car parks in general. The high level of serviceability of the rolling stock of AT, in turn, depends on the reliability of vehicle structures and their structural components, the timeliness and quality of their maintenance (repair), which is the field of technical maintenance of vehicles (TEA). At the same time, if the reliability of the structure is laid down at the stages of design and production of cars, then the fullest use of their potential capabilities is ensured by the stage of real operation of vehicles (ATS) and only under the condition of effective and professional organization of TEA.

Intensification of production, increasing labor productivity, saving all types of resources - these are tasks that are directly related to the AT - TEA subsystem, which ensures the operability of the rolling stock. Its development and improvement are dictated by the intensity of development of the AT itself and its role in the transport complex of the country, the need to save labor, material, fuel and energy and other resources during transportation, technical maintenance (MOT), repair and storage of cars, the need to ensure the transport process of reliably working mobile composition, protection of the population, personnel and the environment.

The purpose of the field of TEA science is to study the regularities of technical operation from the simplest ones, describing the change in the operational properties and the levels of performance of vehicles and their structural elements (FE), which include units, systems, mechanisms, units and parts, to more complex ones that explain the formation of operational properties and operability during operation of a group (fleet) of cars.

The efficiency of TEA in a motor transport enterprise (ATP) is ensured by the engineering and technical service (ITS), which realizes the goals and solves the tasks of TEA. The part of the ITS, which is directly involved in production activities, is called the production and technical service (PTS) of the ATP. Production facilities with equipment, instrumentation are the production and technical base (PTB) of the ATP.

Thus, TEA is one of the AT subsystems, which in turn also includes a subsystem for the commercial operation of ATE (transportation service).

The purpose of this tutorial does not provide for the technical issues of organizing and implementing technical maintenance (MOT) and car repairs, optimization of these processes. The presented materials are intended for the study and development of engineering solutions to reduce the intensity of the processes of changing the technical state of vehicles, their units and assemblies under operating conditions.

The publication summarizes the research experience of scientific schools of the State Pedagogical Institute-NSTU professors I.B. Gurvich and N.A. Kuzmina in the field of thermal state and reliability of cars and their engines in the context of the analysis of the processes of changing their technical state in operation. Also presented are the results of studies on the assessment and improvement of reliability indicators and other technical and operational properties of cars and their engines at the design and testing stage, mainly on the example of cars of JSC "Gorkovsky car factory"And engines of JSC" Zavolzhsky Motor Plant ".

The materials presented in the textbook are the theoretical part of the discipline "Fundamentals of the performance of technical systems" of the profiles "Automobiles and Automotive Industry" and "Automobile Service" of the direction of training of the current state educational standard (GOS III) 190600 "Operation of transport and technological machines and complexes". The materials of the manual are also recommended as the initial theoretical prerequisites for scientific research of undergraduates in the specified direction of training in the professional educational program "Technical operation of cars" and for mastering the discipline " Contemporary problems and directions of development of structures and technical operation of transport and transport-technological machines and equipment ”. The publication is intended for students, undergraduates and postgraduates of other automotive areas, training profiles and specialties of universities, as well as for specialists engaged in the operation and production of automotive equipment.

1. BASIC CONCEPTS, TERMS AND DEFINITIONS

IN THE FIELD OF MOTOR VEHICLES

BASIC TECHNICAL CONDITION TERMS

CARS

A car and any vehicle (ATS) in its life cycle cannot fulfill its purpose without maintenance and repairs, which form the basis of TEA. The main standard in this case is the "Regulation on the maintenance and repair of the rolling stock of road transport" (hereinafter the Regulation).

For each special question on the operation of cars, there are also corresponding GOSTs, OSTs, etc. Basic concepts, terms and definitions in the field of TEA are:

Object - an object of a certain purpose. Objects in cars can be: an assembly, a system, a mechanism, an assembly and a part, which are usually called structural elements (FE) of a car. The object is the car itself.

There are five types of vehicle technical condition:

Serviceable condition (serviceability) - the condition of the car in which it meets all the requirements of the normative-technical and (or) design (project) documentation (NTKD).

Fault condition (malfunction) - the condition of the vehicle in which it does not meet at least one of the requirements of the NTKD.

It should be noted that serviceable cars do not actually exist, since every car has at least one deviation from the requirements of NTKD. This may be a visible malfunction (for example, a scratch on the body, a violation of uniformity paint coatings parts, etc.), as well as when some parts do not comply with the NTKD deviation of dimensions, roughness, surface hardness, etc.

Serviceable state (operability) - the state of the car, in which the values \u200b\u200bof all parameters characterizing the ability to perform the specified functions meet the requirements of the NTKD.

Inoperative state (inoperability) - the state of the car, in which the value of at least one parameter characterizing the ability to perform the specified functions does not meet the requirements of NTKD. An inoperative car is always faulty, and a working one may be faulty (with a scratch on the body, a blown out lamp of the cabin lighting, the car is faulty, but quite functional).

The limiting state is the state of a car or EC in which its further operation is ineffective or unsafe. This situation occurs when the permissible values \u200b\u200bare exceeded. operational parameters FE of the car. Upon reaching the limit state, repair of the FE or the car as a whole is required. For example, the inefficiency of the operation of automobile engines that have reached the limiting state is due to the increased consumption of motor oils and fuels, a decrease in the operating speeds of vehicles caused by a drop in engine power. The unsafe operation of such engines is caused by a significant increase in the toxicity of exhaust gases, noise, vibrations, and a high probability of sudden engine failure when driving in a stream of cars, which can create an emergency.

Events of changing technical conditions of vehicles: damages, failures, defects.

Damage - an event consisting in a violation of the serviceable state (loss of serviceability) of the vehicle's FE while maintaining its serviceable state.

Failure is an event consisting in a violation of the operational state (loss of performance) of the vehicle's FE.

A defect is a generalized event that includes both damage and failure.

The concept of rejection is one of the most important in TEA. The following types of failures should be distinguished:

Structural, production (technological) and operational failures are failures arising from a reason associated with imperfection or violation of: established rules and (or) standards for the design or construction of a car; the established process of making or repairing a car; established rules and (or) operating conditions of vehicles, respectively.

Dependent and independent failures - failures caused or not dependent, respectively, on the failures of other FE of the car (for example, when the oil pan breaks down, engine oil flows out - scuffing occurs on the rubbing surfaces of engine parts, parts jamming - dependent failure; tire puncture - independent failure) ...

Sudden and gradual failures - failures characterized by a sharp change in the values \u200b\u200bof one or more vehicle parameters (for example, a broken piston rod); or arising as a result of a gradual change in the values \u200b\u200bof one or more vehicle parameters (for example, a generator failure due to wear of the rotor brushes), respectively.

Failure is a self-correcting failure or a one-time failure that can be eliminated without any special technical intervention (for example, water ingress on the brake pads - the braking efficiency is broken until the water naturally dries up).

Intermittent failure is a recurring self-correcting failure of the same nature (for example, the disappearance of the emergence of a contact of the lamp of a light device).

Explicit and latent failures - failures detected visually or by standard methods and means of control and diagnostics; not detectable visually or by standard methods and means of control and diagnostics, but detected during maintenance or special diagnostic methods, respectively.

Degradation (resource) failure is a failure caused by natural processes of aging, wear, corrosion and fatigue in compliance with all established rules and (or) design, manufacturing and operation standards, as a result of which the car or its FE reach the limit state.

Basic concepts for maintenance and repair of cars:

Maintenance is a directed system of technical actions on the FE of a car in order to ensure its performance.

Technical diagnostics is a science that develops methods for studying the technical condition of cars and its CE, as well as the principles of constructing and organizing the use of diagnostic systems.

Technical diagnostics is the process of determining the technical condition of a vehicle's FE with a certain accuracy.

Restoration and repair is the process of transferring a car or its FE from a faulty state to a working one or from an inoperative state to a working one, respectively.

Serviced (unattended) object - an object for which maintenance is provided (not provided) by NTKD.

Recoverable (non-recoverable) object - an object for which, in the situation under consideration, restoration is provided for by the NTKD (not provided by the NTKD); for example, in industrial enterprises of the regional center, grinding of the necks is easily performed crankshaft engine, and in rural areas this is impossible due to lack of equipment.

A repaired (non-repairable) object is an object, the repair of which is possible and provided for by NTKD (it is impossible or not provided for by NTKD (for example, non-repairable objects in a car are: a generator belt, thermostat, incandescent lamps, etc.).

BASIC TERMS OF VEHICLE SPECIFICATIONS

Below we consider the terms (and their decoding) used in the field of ATE operation - in TEA and the organization of road transport. Most of them are listed in passports technical characteristics ATC.

The curb weight of a car, trailer, semitrailer is defined as the weight of a fully fueled vehicle (with fuel, oil, coolant, etc.) and equipped (with a spare wheel, tool, etc.) ATS, but without cargo or passengers, driver, other service personnel ( conductor, freight forwarder, etc.) and their luggage.

The total mass of a vehicle or vehicle consists of the curb weight, the weight of the cargo (in terms of carrying capacity) or passengers, the driver and other service personnel. In this case, the total mass of buses (city and suburban) should be determined for the nominal and maximum capacities. Gross mass of road trains: for a trailer train, it is the sum of the gross masses of the tractor and trailer; for a semitrailer vehicle - the sum of the unladen weight of the tractor, the weight of the personnel in the cab, and the total weight of the semitrailer.

The permissible (structural) total mass is the sum of the axial masses allowed by the vehicle design.

Estimated weights (per person) of passengers, service personnel and luggage: for cars - 80 kg (person's weight 70 kg + 10 kg of luggage); for buses: city - 68 kg; suburban - 71 kg (68 + 3); rural (local) - 81 kg (68 + 13); intercity - 91 kg (68 + 23). The attendants of buses (driver, conductor, etc.), as well as the driver and passengers in the cab of a cargo vehicle are accepted in calculations of 75 kg. The weight of a luggage compartment with a load installed on the roof of a passenger car is included in the total weight with a corresponding reduction in the number of passengers.

Carrying capacity is defined as the mass of the transported cargo without the mass of the driver and passengers in the cab.

Passenger capacity (number of seats). In buses, the number of seats for seated passengers does not include the seats of service personnel - driver, guide, etc. The capacity of buses is calculated as the sum of the number of seats for seated passengers and the number of seats for standing passengers at the rate of 0.2 m2 of free floor space per one standing passenger ( 5 people per 1 m2) according to the nominal capacity or 0.125 m2 (8 people per 1 m2) - according to the maximum capacity. The nominal capacity of buses is typical for peak-to-peak operating conditions.

Maximum capacity - the capacity of buses during peak hours.

The vehicle center of gravity coordinates are given for the equipped condition. The center of gravity is indicated in the figures with a special icon:

Ground clearance, entry and exit angles are given for GVW vehicles. The lowest points under the front and rear bridges of the vehicle are indicated in the figures with a special icon:

Control fuel consumption - this parameter is used to check the technical condition of the vehicle and is not a fuel consumption rate.

The reference fuel consumption is determined for a vehicle of full weight on a horizontal section of a paved road at a steady motion at a specified speed. The "urban cycle" mode (imitation of urban traffic) is carried out according to a special technique, in accordance with the relevant standard (GOST 20306-90).

Maximum speed, acceleration time, ascent to be overcome, coasting distance and braking distance - these parameters are given for a car of full weight, and for truck tractors - when they work as part of a road train of full weight. An exception is the maximum speed and acceleration time of passenger cars, for which these parameters are given for a car with a driver and one passenger.

Overall and loading heights, fifth wheel height, floor level, bus footrest heights are given for equipped vehicles.

The size from the seat cushion to the inner lining of the ceiling of passenger cars is measured with the cushion bent under the influence of the mass of a three-dimensional dummy (76.6 kg) using a retractable dummy probe, according to GOST 20304-85.

The vehicle run-out is the distance that a vehicle of full weight, accelerated to the specified speed, travels to a stop on a dry asphalt flat road with a neutral gear engaged.

Braking distance - the distance of the vehicle from the beginning of braking to a complete stop, usually given for tests of type "0"; check is carried out with cold brakes at full vehicle weight.

The sizes of brake chambers, cylinders and brake accumulators are designated by the numbers 9, 12, 16, 20, 24, 30, 36, which corresponds to the working area of \u200b\u200bthe diaphragm or piston in square inches. The sizes of chambers (cylinders) and associated energy storage devices are indicated by a fractional number (for example, 16/24, 24/24).

Vehicle base - for two-axle vehicles and trailers this is the distance between the centers of the front and rear axles, for multi-axle vehicles it is the distance (mm) between all axles through the plus sign, starting from the first axle. For single axle semitrailers, the distance from the center of the fifth wheel to the center of the axle. For multi-axle semitrailers, the base of the bogie (bogies) is additionally indicated through the plus sign.

The turning radius is determined by the track axis of the outer (relative to the steering center) front wheel.

The angle of free rotation of the steering wheel (play) is set when the wheels are in a straight line position. For power steering, readings should be taken with the engine running at the recommended minimum crankshaft speed (CMR) idle move engine.

Air pressure in tires - for cars, light-duty trucks and buses made on the basis of passenger cars, and their trailers, a deviation from the values \u200b\u200bspecified in the operating instructions by 0.1 kgf / cm2 (0.01 MPa) is allowed, for truck vehicles, buses and trailers to them - by 0.2 kgf / cm2 (0.02 MPa).

Wheel formula. The designation of the main wheel formula consists of two numbers, separated by a multiplication sign. For rear-wheel drive cars, the first digit indicates the total number of wheels, and the second - the number of driving wheels to which the engine torque is transmitted (in this case, two-wheel wheels are counted as one wheel), for example, for rear-wheel drive two-axle cars, 4x2 formulas are used (GAZ-31105, VAZ -2107, GAZ-3307, PAZ-3205, LiAZ-5256, etc.). The wheel formula of front-wheel drive cars is built the other way around: the first digit means the number of driving wheels, the second - their total number (2x4 formula, for example, VAZ-2108 - VAZ-2118). For all-wheel drive vehicles, the numbers in the formula are the same (for example, VAZ-21213, UAZ-3162 "Patriot", GAZ-3308 "Sadko", etc. have a 4x4 wheel arrangement).

For trucks and buses in the designation of the wheel arrangement there is a third digit 2 or 1, separated from the second digit by a dot. Number 2 indicates that the drive rear axle has dual-tire tires, and number 1 indicates that all wheels are single-tire. Thus, for two-axle trucks and buses with two-wheel drive wheels, the formula has the form 4x2.2 (for example, a GAZ-33021 car, LiAZ-5256, PAZ-3205 buses, etc.), and for cases of using single-wheel drive wheels - 4x2 .1 (GAZ-31105, GAZ-2217 "Barguzin"); the last wheel formula is usually also in off-road vehicles (UAZ-2206, UAZ-3162, GAZ-3308, etc.).

For three-axle vehicles, wheel formulas are used 6x2, 6x4, 6x6, and in a more complete form: 6x2.2 (tractor "MB-2235"), 6x4.2 (MAZx6.1 (KamAZ-43101), 6x6.2 (timber truck KrAZ- 643701) For four-axle vehicles respectively 8x4.1, 8x4.2 and 8x8.1 or 8x4.2.

For articulated buses, the fourth digit 1 or 2 is entered into the wheel arrangement, separated from the third digit by a dot. The number 1 indicates that the axle of the trailed part of the bus has a single-sided tire, and the number 2 has a double-sided tire. For example, for the Ikarus-280.64 articulated bus, the wheel arrangement is 6x2.2.1, and for the Ikarus-283.00 bus - 6x2.2.2.

ENGINE TECHNICAL CHARACTERISTICS

Generally known information on technical iCE characteristics presented here solely for reasons of the need to understand the subsequent information on markings and classifications of vehicles. In addition, most of these terms are given in the technical data sheets of the automatic telephone exchange.

The working volume of the cylinders (engine displacement) Vl is the sum of the working volumes of all cylinders, i.e. is the product of the working volume of one cylinder Vh by the number of cylinders i:

- & nbsp– & nbsp–

The volume of the combustion chamber Vc is the volume of the residual space above the piston at its position at TDC (Fig. 1.1).

The total volume of the cylinder Va is the volume of the space above the piston when it is at BDC. It is obvious that the total volume of the cylinder Va is equal to the sum of the working volume of the cylinder Vh and the volume of its combustion chamber Vc:

Va \u003d V h + Vc. (1.3) The compression ratio is the ratio of the total volume of the cylinder Va to the volume of the combustion chamber Vc, i.e.

Va / Vc \u003d (Vh + Vc) / Vc \u003d 1 + Vh / Vc. (1.4) The compression ratio shows how many times the volume of the engine cylinder decreases when the piston moves from BDC to TDC. The compression ratio is dimensionless. In gasoline engines \u003d 6.5 ... 11, in diesel engines - \u003d 14 ... 25.

The piston stroke and bore (S and D) determine the size of the engine. If the S / D ratio is less than or equal to one, then the engine is called short-stroke, otherwise it is called long-stroke. Most modern automotive engines are short-stroke.

Figure: 1.1. Geometrical characteristics of the crank mechanism of the internal combustion engine. Indicator power of the engine Рi - the power developed by gases in the cylinders. The indicated power is greater than the effective engine power by the amount of mechanical, heat and pumping losses.

The effective engine power Pe is the power delivered to the crankshaft. Measured in horsepower (hp) or kilowatts (kW). Conversion factor: 1 hp \u003d 0.736 kW, 1 kW \u003d 1.36 HP

The effective engine power is calculated using the formulas:

- & nbsp– & nbsp–

- engine torque, Nm (kgs.m); Is the rotation frequency where the crankshaft (CHVKV), min-1 (rpm).

nom The nominal effective power of the engine Pe is the effective power guaranteed by the manufacturer at a slightly reduced PMC. It is less than the maximum effective engine power, which is done due to the artificial limitation of the PMCV in order to ensure a given engine resource.

Liter engine power Pl - ratio of effective power to displacement. It characterizes the efficiency of using the engine displacement and has a dimension of kW / l or hp / l.

Weight power of the engine Pw - the ratio of the effective power of the engine to its weight; characterizes the efficiency of using the engine mass and has a dimension of kW / kg (hp / kg).

Net power is the maximum effective power delivered by a fully standardized engine.

“Gross” power - maximum effective power for completing the engine without some serial attachments (without an air cleaner, muffler, cooling fan, etc.) Specific effective fuel consumption ge - the ratio of the hourly fuel consumption GT, expressed in grams, to the effective power engine Pe; has units of measurement [g / kWh] and [g / hp .. h].

Since the hourly fuel consumption is usually measured in kg / h, the formula for determining this indicator is:

... (1.7) External speed characteristic of the engine - the dependence of the output parameters of the engine on the PMCV at full (maximum) fuel supply (Fig. 1.2).

- & nbsp– & nbsp–

UAZ-450, UAZ-4 ZIL-130, ZIL-157 ZAZ-968, RAF-977 KAZ-600, KAZ-608 GAZ-14, GAZ-21, GAZ-24, GAZ-53

- & nbsp– & nbsp–

In accordance with the new digital classification system in force in the country since 1966, each model of automatic telephone exchange is assigned an index consisting of at least four digits. Model modifications correspond to the fifth digit indicating the serial number of the modification. The export version of domestic car models has the sixth digit. The digital index is preceded by an alphabetic abbreviation indicating the manufacturer. The letters and numbers included in the full model designation give a detailed idea of \u200b\u200bthe car, since they indicate its manufacturer, class, type, model number, its modification, and if there is a sixth digit, the export version.

The most important information is given by the first two digits in the car brand. Their semantic meaning is presented in table. 1.2.

Thus, each number and dash in the designation of a car model carries its own information. For example, the difference in the spelling of GAZ and GAZ-2410 is very significant: if the first model is a modification of the GAZ-24 car, the designation of which is based on the previously operating system, then the last car model does not exist at all, since according to the modern digital designation

- & nbsp– & nbsp–

INTERNATIONAL MOTOR VEHICLE CLASSIFICATION

Of funds

In the rules of the UN Economic Commission for Europe (UNECE), the international classification of vehicles is adopted, which in Russia is standardized by GOST 51709-2001. vehicles... Safety requirements for technical condition and test methods "

(Table 1.4).

ATS of categories M2, M3 are additionally subdivided into: class I (city buses) - equipped with seats and places for transportation of passengers standing outside the aisles; class II (intercity buses) - equipped with seats, and it is also allowed to transport passengers standing in the aisles; class III (tourist buses) - designed to carry only seated passengers.

Vehicles of categories O2, O3, O4 are additionally subdivided into: semi-trailers - towed vehicles, the axles of which are located behind the center of mass of a fully loaded vehicle, equipped with a fifth wheel coupling that transfers horizontal and vertical loads to the tractor; trailers - towed vehicles equipped with at least two axles and a towing device that can move vertically in relation to the trailer and control the direction of the front axles, but transfers a negligible static load to the tractor.

Table 1.4 International ATC classification Cat.

Maximum Class and operational Type and general purpose ATS weight (1), t ATS ATS purpose

- & nbsp– & nbsp–

2. PERFORMANCE PROPERTIES

AND QUALITY OF CARS

2.1. OPERATIONAL PROPERTIES OF CARS

The efficient use of cars is predetermined by their main operational properties - traction and speed, braking, fuel and economic, cross-country ability, smooth running, handling, stability, maneuverability, carrying capacity (passenger capacity), environmental friendliness, safety and others.

Traction and speed properties determine the dynamics of the vehicle (necessary and possible acceleration when driving and starting off), the maximum speed of movement, the maximum amount of climbs to be overcome, etc. These characteristics provide the basic properties of the vehicle - engine power and torque, gear ratios in the transmission, vehicle weight, its streamlining characteristics, etc.

It is possible to determine the traction and speed indicators of the vehicle operation (traction characteristic, maximum speed, acceleration, time and acceleration path) both on the road and in the laboratory. Traction characteristic - the dependence of the traction force on the driving wheels Pk on the speed of the vehicle V. It is obtained either at all, or at some one gear. The simplified traction characteristic represents the dependence of the free traction force Pd on the vehicle hook on the speed of its movement.

Free pulling force is measured directly by dynamometer 2 (Fig. 2.1.) In laboratory conditions by tests on a stand.

The rear (driving) wheels of the car are supported by a belt thrown over two drums. An air cushion is created to reduce friction between the belt and its supporting surface. Drum 1 is connected to an electric brake, with which you can smoothly change the load on the driving wheels of the vehicle.

IN road conditions the traction-speed characteristic of a car can most easily be obtained using a dynamometer trailer, which is towed by a test car. Measuring with the help of a dynamograph the traction force on the hook, as well as the vehicle speed, it is possible to plot the curves of the dependence of Pk on V. In this case, the total tractive force is calculated by the formula Pk \u003d P "q + Pf + Pw. (2.1) where: P "d is the pulling force on the hook; Рf and Рw - resistance forces, respectively, to rolling and air flow.

The traction characteristic completely determines the dynamic properties of the car, however, its obtaining is associated with a large volume of tests. In most cases, when conducting long-term control tests, the following dynamic properties of the car are determined - the minimum stable and maximum speed; acceleration time and path; the maximum climbs that the vehicle can overcome with uniform movement.

Road tests are carried out with equal vehicle loads and no load on a horizontal rectilinear section of the road with a hard and even surface (asphalt or concrete). At the NAMI test site, a dynamometric road is intended for this. All measurements are made when the car drives in two mutually opposite directions in dry, calm weather (wind speed up to 3 m / s).

The minimum sustainable vehicle speed is determined in direct gear. Measurements are made on two successively located track sections 100 m long each with a distance between them equal to 200-300 m. Maximum speed the movements are determined in the highest gear when the car passes the measuring section 1 km long. The time taken to pass the measuring section is recorded with a stopwatch or photo gate.

- & nbsp– & nbsp–

Figure: 2.1. Stand for determining the traction characteristics of a vehicle Braking properties of vehicles are characterized by the values \u200b\u200bof maximum deceleration and braking distance. These properties depend on the design features of the vehicle brake systems, their technical condition, the type and wear of the tire treads.

Braking is the process of creating and changing artificial resistance to the movement of a car in order to reduce its speed or keep it motionless relative to the road surface. The course of this process depends on the braking properties of the car, which are determined by the main indicators:

maximum deceleration of the car when braking on roads with various types of surfaces and on dirt roads;

the limiting value of external forces, under the action of which the braked vehicle is reliably held in place;

the ability to provide a minimum steady-state vehicle speed downhill.

Braking properties are among the most important of the performance properties, primarily determining the so-called active security vehicle (see below). To ensure these properties modern cars, in accordance with Regulation No. 13 of the UNECE, are equipped with at least three braking systems - working, spare and parking. For cars of categories M3 and N3 (see Table 1.1), it is also prescribed to equip them with an auxiliary braking system, and cars of categories M2 and M3 intended for operation in mountainous conditions must also have an emergency brake.

Estimated indicators of the efficiency of the working and spare braking systems are the maximum steady-state deceleration

- & nbsp– & nbsp–

The effectiveness of these vehicle braking systems is determined during road tests. Before carrying out them, the vehicle must be run-in in accordance with the manufacturer's instructions. Besides weight load and its distribution over bridges must comply with technical specifications. The transmission and chassis assemblies must be preheated. In this case, the entire brake system should be protected from heating. Tire tread wear should be uniform and not exceed 50% of the nominal value. The section of the road on which the tests of the main and spare braking systems are carried out, and the weather conditions must meet the same requirements that are imposed on them when assessing the speed properties of the vehicle.

Since the effectiveness of the braking mechanisms largely depends on the temperature of the rubbing pairs, these tests are carried out under various thermal states of the braking mechanisms. According to the standards currently accepted in the country and the world, tests to determine the effectiveness of the working brake system are divided into three types: tests "zero"; tests I;

tests II.

Zero tests are designed to evaluate the performance of the service braking system when brakes are cold. In tests I, the efficiency of the working brake system is determined when the braking mechanisms are heated by preliminary braking; during tests II - with mechanisms heated by braking on a long descent. In the above-mentioned GOSTs for testing brake systems of vehicles with a hydraulic and pneumatic drive, the initial speeds from which braking should be performed, steady-state decelerations and braking distances, depending on the type of vehicles, are determined.

Efforts on the braking pedals are also regulated: the pedal of cars must be pressed with a force of 500 N, for trucks - 700 N. The steady-state deceleration during tests of type I and II must be, respectively, at least 75% and 67% of the decelerations during tests of type "zero" ... The minimum steady-state deceleration of vehicles in operation is usually allowed to be somewhat lower (by 10-12%) than for new vehicles.

As an estimate indicator of the parking brake system, the value of the limiting slope is usually used, at which it ensures the maintenance of the vehicle's full mass. The standard values \u200b\u200bof these slopes for new cars are as follows: for all categories M - at least 25%; for all N categories - at least 20%.

The auxiliary braking system of new cars must, without the use of other braking devices, ensure movement at a speed of 30 2 km / h on a road with a slope of 7%, with a length of at least 6 km.

Fuel efficiency is measured by fuel consumption in liters per 100 kilometers. In the real operation of vehicles for accounting and control, fuel costs are normalized by allowances (reductions) to the base (linear) rates, depending on the specific operating conditions. Rationing is made taking into account the specific transport work.

One of the main generalizing measures of fuel efficiency in the Russian Federation and in most other countries is the fuel consumption of a vehicle in liters per 100 km of the distance traveled - this is the so-called track fuel consumption Qs, l / 100 km. It is convenient to use the directional flow rate to assess the fuel efficiency of vehicles with similar transportation characteristics. To assess the efficiency of fuel use when performing transport work by vehicles of different carrying capacity (passenger capacity), a specific indicator is often used, which is called fuel consumption per unit of transport work Qw, l / t.km. This indicator is measured by the ratio of the actual fuel consumption to the performed transport work (W) for the transportation of goods. If the transport work involves the carriage of passengers, the flow rate Qw is measured in liters per passenger kilometer (l / pass km). Thus, the following relations exist between Qs and Qw:

Qw \u003d Qs / 100 P, Qw \u003d Qs / 100 mg and (2.2) where mg is the mass of the transported cargo, t (for a truck);

P is the number of transported passengers, pass. (for the bus).

Fuel efficiency is largely determined by the corresponding engine performance. This is, first of all, the hourly fuel consumption GT kg / h - the mass of fuel in kilograms consumed by the engine for one hour of continuous operation, and the specific fuel consumption ge, g / kWh - the mass of fuel in grams consumed by the engine in one hour of operation to obtain one kilowatt of power (formula 1.7) There are other estimated indicators of the fuel economy of cars. For example, the control fuel consumption is used to indirectly assess the technical condition of the vehicle. It is determined at given values \u200b\u200bof constant speed (different for different categories of cars) when driving on a straight horizontal road in top gear in accordance with GOST 20306-90.

More and more use is being made of integrated fuel efficiency estimates for special driving cycles.

For example, the measurement of fuel consumption in the main driving cycle is carried out for all categories of vehicles (except for city buses) by mileage along the measuring section in compliance with the driving regimes specified by a special cycle diagram adopted by international regulatory documents. Similarly, measurements of fuel consumption in the urban driving cycle are made, the results of which make it possible to more accurately assess the fuel efficiency of various vehicles in urban operating conditions.

Cross-country ability - the ability of a car to work in difficult road conditions without slipping the driving wheels and touching the lowest points on the unevenness of the road. Cross-country ability is the property of a car to carry out the transport process in deteriorated road conditions, as well as off-road and with overcoming various obstacles.

Poor road conditions include: wet and dirty roads; snow-covered and icy roads; soggy and bumpy roads, which impede the movement and maneuvering of wheeled vehicles, noticeably affecting their average speeds and fuel consumption.

When driving off-road, the wheels interact with various supporting surfaces that have not been trained for the transport process. This causes a significant decrease in vehicle speed (3-5 times and more) and a corresponding increase in fuel consumption. At the same time, the appearance and condition of these surfaces is of great importance, the entire nomenclature of which is usually reduced to four categories:

cohesive soils (clay and loam); incoherent (sandy) soils; swampy soils; virgin snow. The obstacles that the vehicle is forced to overcome include: slopes (longitudinal and transverse); artificial barrier obstacles (ditches, ditches, embankments, curbs); single natural obstacles (hummocks, boulders, etc.).

According to the level of cross-country ability, cars are divided into three categories:

1. Cars of limited passability - designed for year-round operation on paved roads, as well as on unpaved roads (cohesive soils) in the dry season. These cars have a wheel arrangement of 4x2, 6x2 or 6x4, i.e. are non-four-wheel drive. They are equipped with tires with road or universal tread pattern, have simple differentials in the transmission.

2. Cross-country vehicles - designed for the implementation of the transport process in poor road conditions and on certain types of off-road. Their main distinguishing feature is all-wheel drive (wheel formulas are used 4x4 and 6x6), the tires have developed lugs. The dynamic factor of these cars is 1.5-1.8 times higher than that of road cars. Structurally, they are often equipped with locking differentials, have automatic tire pressure control systems. Cars of this category are capable of wading water obstacles up to 0.7-1.0 m deep, and for insurance they are equipped with self-pulling means (winches).

3. Wheeled vehicles of high cross-country ability - designed to operate in complete off-road conditions, to overcome natural and artificial obstacles and water obstacles. They have a special layout scheme, an all-wheel drive wheel arrangement (most often 6x6, 8x8 or 10x10) and other structural devices for increasing cross-country ability (self-locking differentials, tire pressure control systems, winches, etc.), a floating hull and a propeller on the water, etc. etc.

Ride smoothness is the ability of a car to move at a given speed range on uneven roads without significant vibration and shock effects on the driver, passengers or cargo.

Under the smooth running of the vehicle, it is customary to understand the totality of its properties that provide, within the limits set by regulatory documents, the limitation of shock and vibration effects on the driver, passengers and transported goods from the unevenness of the road surface and other sources of vibration. Smooth running depends on the disturbing effect of sources of vibrations and vibrations, on the layout characteristics of the vehicle and on the design features of its systems and devices.

Smooth running, along with ventilation and heating, seating comfort, weather resistance, etc. determines the comfort of the vehicle. Vibration loading is created by disturbing forces, mainly when the wheels interact with the road. Irregularities with a wavelength of more than 100 m are called the macro-profile of the road (it practically does not cause vibrations of the car), with a wavelength of 100 m to 10 cm - a micro-profile (the main source of vibrations), with a wavelength of less than 10 cm - roughness (can cause high-frequency vibrations) ... The main devices that limit vibration are the suspension and tires, and elastic seats for passengers and the driver.

Vibrations increase with an increase in the speed of movement, an increase in engine power; the quality of roads has a significant effect on the vibrations. Body vibrations directly determine the ride smoothness. The main sources of vibrations and vibrations during vehicle movement are: road irregularities; uneven operation of the engine and imbalance of its rotating parts; imbalance and a tendency to excite vibrations in cardan shafts, wheels, etc.

The main systems and devices that protect vehicles, drivers, passengers and transported goods from vibrations and vibrations are: vehicle suspension; pneumatic tires; engine mount; seats (for driver and passengers); cab suspension (on modern cargo vehicles). To accelerate the processes of damping the arising vibrations, damping devices are used, of which the most widespread are hydraulic shock absorbers.

Controllability and stability. These properties of ATS are closely related, and therefore they should be considered together. They depend on the same parameters of mechanisms - steering, suspension, tires, mass distribution between axles, etc. The difference lies in the methods of evaluating the critical parameters of vehicle movement. The parameters characterizing the stability properties are determined without taking into account the control actions, and the parameters characterizing the controllability properties are determined taking them into account.

Controllability is the property of a vehicle controlled by a driver in certain road and climatic conditions to ensure the direction of movement in exact accordance with the driver's influence on the steering wheel. Stability is the property of the vehicle to maintain the direction of movement set by the driver when exposed to external forces that tend to deflect it from this direction.

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The main processes causing a decrease in the performance of machines are considered: friction, wear, plastic deformation, fatigue and corrosion damage of machine parts. The main directions and methods of ensuring the operability of machines are given. Methods for assessing the performance of elements and technical systems in general are described. For university students. It can be useful for specialists in the service and maintenance of cars, tractors, construction, road and utility vehicles.

Technical progress and machine reliability.
With the development of scientific and technological progress, more and more complex problems arise, for the solution of which it is necessary to develop new theories and research methods. In particular, in mechanical engineering, due to the increasing complexity of the design of machines, their technical operation, as well as technological processes, generalization and a more qualified, rigorous engineering approach to solving problems of ensuring the durability of equipment are required.

Technological progress is associated with the creation of complex modern machines, instruments and working equipment, with a constant increase in quality requirements, as well as with a tightening of operating modes (an increase in speeds, operating temperatures, loads). All this was the basis for the development of such scientific disciplines as the theory of reliability, tribotechnics, and technical diagnostics.

CONTENT
Foreword
Chapter 1. The problem of ensuring the operability of technical systems
1.1. Technological progress and machine reliability
1.2. The history of the formation and development of tribotechnics
1.3. The role of tribotechnics in the system of ensuring the operability of machines
1.4. Triboanalysis of technical systems
1.5. The reasons for the decrease in the performance of machines in operation
Chapter 2. Properties of working surfaces of machine parts
2.1. Part working surface profile parameters
2.2. Probability characteristics of profile parameters
2.3. Contact of working surfaces of mating parts
2.4. Structure and physical and mechanical properties of the material of the surface layer of the part
Chapter 3. Basic provisions of the theory of friction
3.1. Concepts and definitions
3.2. Interaction of working surfaces of parts
3.3. Thermal processes accompanying friction
3.4. Influence of the lubricant on the friction process
3.5. Factors determining the nature of friction
Chapter 4. Wear of machine elements
4.1. General pattern of wear
4.2. Wear types
4.3. Abrasive wear
4.4. Fatigue wear
4.5. Wear when seizing
4.6. Corrosion-mechanical wear
4.7. Factors affecting the nature and intensity of wear of machine elements
Chapter 5. Influence of lubricants on the performance of technical systems
5.1. Purpose and classification of lubricants
5.2. Lubrication types
5.3. Mechanism of lubricating action of oils
5.4. Properties of liquid and grease lubricants
5.5. Additives
5.6. Requirements for oils and greases
5.7. Changes in the properties of liquid and plastic lubricants during operation
5.8. Formation of a comprehensive criterion for assessing the state of machine elements
5.9. Restoration of the performance properties of oils
5.10. Restoring machine performance using oils
Chapter 6. Fatigue of materials of machine elements
6.1. Conditions for the development of fatigue processes
6.2. Mechanism of material fatigue failure
6.3. Mathematical description of the process of material fatigue failure
6.4. Calculation of fatigue parameters
6.5. Estimation of fatigue parameters of part material by accelerated test methods
Chapter 7. Corrosion destruction of machine parts
7.1. Classification of corrosion processes
7.2. Mechanism of corrosive destruction of materials
7.3. Influence of a corrosive environment on the nature of the destruction of parts
7.4. Conditions for Corrosion Processes
7.5. Types of corrosion destruction of parts
7.6. Factors influencing the development of corrosion processes
7.7. Methods for protecting machine elements from corrosion
Chapter 8. Ensuring the operability of machines
8.1. General concepts of machine health
8.2. Planning machine reliability indicators
8.3. Machine Reliability Program
8.4. Life cycle machines
Chapter 9. Evaluation of the performance of machine elements
9.1. Presentation of the results of triboanalysis of machine elements
9.2. Determination of performance indicators of machine elements
9.3. Machine Life Optimization Models
Chapter 10. Performance of the main elements of technical systems
10.1. Operability power plant
10.2. The performance of transmission elements
10.3. Efficiency of chassis elements
10.4. The operability of electrical equipment of machines
10.5. Methodology for determining the optimal durability of machines
Conclusion
List of references.

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• Materials Science Course in Questions and Answers, Bogodukhov S.I., Grebenyuk V.F., Sinyukhin A.V., 2005
• Reliability and diagnostics of automatic control systems, Beloglazov I.N., Krivtsov A.N., Kutsenko B.N., Suslova O.V., Shirgladze A.G., 2008

Ministry of Education and Science of the Russian Federation

Saratov State Technical University

A.S. Denisov

Basics of technical systems performance

Textbook

Approved by the UMO of universities of the Russian Federation for education

in the field of transport machines

and transport and technological complexes

as a textbook for university students,

students in specialties

"Service of transport and technological

machinery and equipment (Automotive

transport) "and" Automobiles and automobile

economy »areas of training

"Exploitation land transport

and transport equipment»

Saratov 2011

UDC 629.113.004.67

Reviewers:

Department "Reliability and repair of machines"

Saratov State Agrarian University

them. N.I. Vavilova

Doctor of Technical Sciences, Professor

B.P. Zagorodsky

Denisov A.S.

D 34 Basis of technical systems performance: Textbook / A.S. Denisov. - Saratov: Sarat. state tech. un-t, 2011 .-- 334 p.

ISBN 978-5-7433-2105-6

The textbook provides data on the content of various technical systems. The elements of the mechanics of destruction of machine parts are analyzed. The regularities of wear, fatigue failure, corrosion, plastic deformation of parts during operation are substantiated. Methods of substantiation of standards for ensuring the operability of machines and their correction according to operating conditions are considered. The regularities of satisfying service needs are substantiated using the provisions of the queuing theory.

The textbook is intended for students of the specialties "Service of transport and technological machines and equipment (Automobile transport)" and "Automobiles and automotive industry", and can also be used by employees of car service, auto repair and transport companies.

UDC 629.113.004.67

© Saratov State

ISBN 978-5-7433-2105-6 Technical University, 2011

Denisov Alexander Sergeevich -doctor of Technical Sciences, Professor, Head of the Automobiles and Automotive Industry Department, Saratov State Technical University.

In 2001 he received the academic title of professor, in 2004 he was elected an academician of the Academy of Transport of Russia.

Scientific activity of Denisov A.S. is devoted to the development of the theoretical foundations of the technical operation of cars, the substantiation of the system of regularities of changes in the technical state and indicators of the efficiency of using cars during operation in various conditions He developed new methods for diagnosing the technical state of vehicle elements, monitoring and controlling their operating modes. Theoretical developments and experimental research Denisova A.S. contributed to the founding and approval of a new scientific direction in the science of machine reliability, which is now known as "Theory of the formation of resource-saving maintenance and repair cycles of machines."

Denisov A.S. has over 400 publications, including: 16 monographs and textbooks, 20 patents, 75 articles in central journals. Under his scientific supervision, 3 doctoral and 21 candidate dissertations were prepared and successfully defended. At the Saratov State Technical University, Denisov A.S. created a scientific school that develops the theory of machine service, well known already in the country and abroad. He was awarded the honorary badges "Honorary Worker of Transport of Russia", "Honorary Worker of Higher Professional Education of the Russian Federation".

INTRODUCTION

Technique (from the Greek word techne - art, craftsmanship) is a set of means of human activity created to carry out production processes and satisfy the non-production needs of society. The technique includes all the variety of complexes and products, machines and mechanisms, industrial buildings and structures, devices and assemblies, tools and communications, devices and devices.

The term "system" (from the Greek systema - whole, made up of parts) has a wide range of meanings. In science and technology, a system is a set of elements, concepts, norms with relationships and connections between them, forming a certain integrity. An element of the system is understood as a part of it, designed to perform certain functions and indivisible into parts at a given level of consideration.

This paper deals with a part of technical systems - transport and technological machines. The main attention is paid to cars and technological car service equipment. Over the entire service life, the costs of ensuring their operability are 5 - 8 times higher than the costs of manufacturing. The basis for reducing these costs are the regularities of changes in the technical condition of machines during operation. Up to 25% of failures of technical systems are caused by errors of service personnel, and up to 90% of accidents in transport, in various power systems are the result of erroneous actions of people.

The actions of people, as a rule, are justified by the decisions they make, which are selected from several alternatives based on the information collected and analyzed. Information analysis is based on knowledge of the processes occurring when using technical systems. Therefore, when training specialists, it is necessary to study the patterns of changes in the technical state of machines during operation and methods of ensuring their performance.

This work was prepared in accordance with the educational standard for the discipline "Fundamentals of technical systems performance" for specialty 23100 - Service of transport and technological machines and equipment (road transport). It can also be used by students of the specialty "Automobiles and Automotive Industry" in the study of the discipline "Technical Operation of Cars", specialty 311300 "Mechanization of Agriculture" in the discipline "Technical Operation of Motor Vehicles".

BASIC CONCEPTS IN THE FIELD OF PERFORMANCE OF TECHNICAL SYSTEMS

Transcript

1 Federal Agency for Education Syktyvkar Forestry Institute branch of the state educational institution of higher professional education "St. Petersburg State Forestry Academy named after S. M. Kirov" Technical operation of cars "," Fundamentals of the theory of reliability and diagnostics "for students of specialties" Service of transport and technological machines and equipment ", 9060" Automobiles and automobile economy "of all forms of education Second edition, revised Syktyvkar 007

2 UDC 69.3 О-75 Considered and recommended for publication by the Council of the Forestry Faculty of the Syktyvkar Forestry Institute May 7, 007 Compiled by: Art. teacher R.V. Abaimov, Art. teacher P. A. Malashchuk Reviewers: V. A. Likhanov, Doctor of Technical Sciences, Professor, Academician of the Russian Academy of Transport (Vyatka State Agricultural Academy); AF Kulminsky, Candidate of Technical Sciences, Associate Professor (Syktyvkar Forestry Institute) BASES OF PERFORMANCE OF TECHNICAL SYSTEMS: O-75 method. manual for the disciplines "Fundamentals of technical systems performance", "Technical maintenance of cars", "Fundamentals of the theory of reliability and diagnostics" for stud. special "Service of transport and technological machines and equipment", 9060 "Automobiles and automotive industry" of all forms of education / comp. R. V. Abaimov, P. A. Malashchuk; Sykt. forest. in-t. Ed. second, revised Syktyvkar: SLI, p. The methodological manual is intended for practical exercises in the disciplines "Fundamentals of technical systems operability", "Technical operation of cars", "Fundamentals of the theory of reliability and diagnostics" and for the performance of tests by correspondence students. The manual contains the basic concepts of the theory of reliability, the basic laws of distribution of random variables in relation to road transport, the collection and processing of materials on reliability, general instructions for choosing options for the task. The tasks reflect the construction of structural diagrams, test planning and take into account the basic laws of distribution of random variables. A list of recommended literature is provided. The first edition was published in 004. UDC 69.3 R. V. Abaimov, P. A. Malashchuk, compilation, 004, 007 SLI, 004, 007

3 INTRODUCTION During the operation of complex technical systems, one of the main tasks is to determine their operability, that is, the ability to perform the functions assigned to them. This ability to a large extent depends on the reliability of products, laid down during the design period, implemented during manufacture and maintained during operation. Systems reliability engineering covers various aspects of engineering. Thanks to engineering calculations of the reliability of technical systems, it is guaranteed to maintain an uninterrupted supply of electricity, safe movement of vehicles, etc. For a correct understanding of the problems of ensuring the reliability of systems, it is necessary to know the basics of the classical theory of reliability. The methodological manual contains the basic concepts and definitions of the theory of reliability. The main qualitative indicators of reliability are considered, such as the probability of failure-free operation, frequency, failure rate, mean time to failure, and the failure flow parameter. Due to the fact that in the practice of operating complex technical systems in most cases one has to deal with probabilistic processes, the most frequently used laws of distribution of random variables that determine the reliability indicators are considered separately. Reliability indicators of most technical systems and their elements can be determined only by test results. In the methodological manual, a separate part is devoted to the methodology for collecting, processing and analyzing statistical data on the reliability of technical systems and their elements. To consolidate the material, it is envisaged to perform a test, consisting of answers to questions on the theory of reliability and solving a number of problems. 3

four . RELIABILITY OF VEHICLES .. TERMINOLOGY ON RELIABILITY Reliability is the property of cars to perform specified functions, keeping their performance within the specified limits during the required operating time. Reliability theory is a science that studies the laws governing the occurrence of failures, as well as ways to prevent and eliminate them to maximize the efficiency of technical systems. The reliability of the machine is determined by the reliability, maintainability, durability and preservation. Automobiles, as well as other reusable machines, are characterized by a discrete operation process. Failures occur during operation. It takes time to find and eliminate them, during which the machine is idle, after which operation is resumed. Serviceability is the state of the product in which it is capable of performing the specified functions with the parameters, the values \u200b\u200bof which are established by the technical documentation. In the case when the product, although it can perform its basic functions, does not meet all the requirements of technical documentation (for example, a car fender is dented), the product is functional, but defective. Reliability is the property of a machine to remain operational for a certain operating time without forced interruptions. Depending on the type and purpose of the machine, the operating time to failure is measured in hours, kilometers, cycles, etc. Failure is such a malfunction, without the elimination of which the machine cannot perform the specified functions with the parameters established by the requirements of the technical documentation. However, not every malfunction can be a failure. There are such failures that can be eliminated during the next maintenance or repair. For example, during the operation of machines, weakening of the normal tightening of fasteners, violation of the correct adjustment of units, assemblies, control drives, protective coatings, etc. are inevitable. If they are not timely 4

5 eliminated, this will lead to machine failures and time-consuming repairs. Failures are classified: according to the effect on the performance of the product: causing a malfunction (low tire pressure); causing a failure (breakage of the alternator drive belt); by source of occurrence: constructive (due to design errors); production (due to a violation of the manufacturing process or repair); operational (use of substandard operational materials); in connection with the failures of other elements: dependent, caused by the failure or malfunction of other elements (seizure of the cylinder mirror due to a broken piston pin); independent, not caused by the failure of other elements (tire puncture); by the nature (patterns) of occurrence and the possibility of predicting: gradual, resulting from the accumulation of wear and fatigue damage in the machine parts; sudden, unexpected and associated mainly with breakdowns due to overload, manufacturing defects, material. The moment of the onset of the failure is random, independent of the duration of operation (blown fuses, breakage of chassis parts when hitting an obstacle); by the impact on the loss of working time: eliminated without loss of working time, that is, during maintenance or during non-working hours (between shifts); eliminated with the loss of working time. Signs of object failures are direct or indirect effects on the observer's sense organs of phenomena characteristic of an inoperative state of an object (drop in oil pressure, the appearance of knocks, a change in temperature, etc.). five

6 The nature of the failure (damage) is the specific changes in the object associated with the occurrence of the failure (wire breakage, deformation of the part, etc.). The consequences of failure include phenomena, processes and events that have arisen after the failure and in direct causal connection with it (engine shutdown, forced downtime for technical reasons). In addition to the general classification of failures, which is the same for all technical systems, for individual groups of machines, depending on their purpose and nature of work, an additional classification of failures is applied according to the complexity of their elimination. According to the complexity of elimination, all failures are grouped into three groups, while taking into account such factors as the method of elimination, the need for disassembly and the laboriousness of eliminating the failures. Durability is the property of a machine to maintain its operational condition to the limit with the necessary breaks for maintenance and repairs. Longevity is quantified by the total life of the machine from the start of operation to retirement. New machines should be designed so that the service life in terms of physical wear and tear does not exceed obsolescence. The durability of machines is laid down during their design and construction, is ensured during production and maintained during operation. Thus, the durability is influenced by structural, technological and operational factors, which, according to the degree of their influence, allow us to classify durability into three types: required, achieved and actual. The required durability is set by the design specification and is determined by the achieved level of technology development in this industry. The achieved durability is due to the perfection of design calculations and manufacturing processes. Actual durability characterizes the actual use of the machine by the consumer. In most cases the required durability is greater than the achieved one, and the latter is greater than the actual one. At the same time, 6

7 cases when the actual durability of the machines exceeds the achieved one. For example, with a mileage rate before overhaul (CR) equal to 0 thousand km, some drivers, with skillful operation of the car, achieved a mileage without major repairs of 400 thousand km or more. Actual longevity is divided into physical, moral, and technical and economic. Physical durability is determined by the physical wear and tear of a part, assembly, machine to their ultimate state. For units, physical wear of the basic parts is decisive (for the engine, the cylinder block, for the gearbox, the crankcase, etc.). Moral durability characterizes the service life beyond which the use of a given machine becomes economically impractical due to the appearance of more productive new machines. The technical and economic durability determines the service life beyond which the repair of this machine becomes economically impractical. The main indicators of the durability of machines are technical resource and service life. A technical resource is the operating time of an object before the start of operation or its resumption after medium or major repairs before the onset of the limiting state. Service life is the calendar duration of the object's operation from its beginning or renewal after medium or major repairs to the onset of the limit state Maintainability is the property of a machine, which is its adaptability to prevention, detection, and elimination of failures and malfunctions by carrying out maintenance and repairs. The main task of ensuring the maintainability of machines is to achieve optimal costs for their maintenance (MOT) and repair with the highest efficiency of use. The succession of maintenance and repair technological processes characterizes the possibility of using typical maintenance and repair technological processes of both the machine as a whole and its component parts. Ergonomic characteristics serve to assess the convenience of performing all maintenance and repair operations and should exclude operational

8 walkie-talkies, requiring the performer to be in an uncomfortable position for a long time. The safety of performing maintenance and repairs is ensured with technically sound equipment, compliance with safety standards and rules by the executors. The properties listed above together determine the level of maintainability of the object and have a significant impact on the duration of repairs and maintenance. The suitability of the machine for maintenance and repair depends on: the number of parts and assemblies requiring systematic maintenance; service intervals; availability of service points and ease of operation; ways of connecting parts, the possibility of independent removal, availability of places for gripping, ease of disassembly and assembly; from the unification of parts and operating materials both within the same car model and between different models automobiles, etc. Factors affecting maintainability can be combined into two main groups: design and engineering and operational. The design and design factors include the complexity of the design, interchangeability, ease of access to units and parts without the need to remove adjacent units and parts, ease of replacement of parts, reliability of the design. Operational factors are related to the human operator's ability to operate machines and the environmental conditions in which these machines operate. These factors include experience, skill, qualifications of maintenance personnel, as well as technology and methods of organizing production during maintenance and repair. Preservation is the property of a machine to resist the negative impact of storage and transportation conditions on its reliability and durability. Since work is the main state of the object, the influence of storage and transportation on the subsequent behavior of the object in operation is of particular importance. 8

9 Distinguish between the preservation of an object before commissioning and during operation (during breaks in work). In the latter case, the shelf life is included in the service life of the object. To assess the preservation, the gamma percentage and the average shelf life are used. The gamma percent shelf life is the shelf life that will be achieved by an object with a given probability of gamma percent. The average shelf life is called the mathematical expectation of the shelf life ... QUANTITATIVE INDICATORS OF MACHINE RELIABILITY When solving practical problems related to the reliability of machines, a qualitative assessment is not enough. To quantify and compare the reliability of different machines, appropriate criteria must be introduced. Such applied criteria include: the probability of failure and the probability of failure-free operation during a given operating time (mileage); failure rate (failure density) for non-repairable products; failure rate for non-repairable products; failure streams; average time (mileage) between failures; resource, gamma-percentage resource, etc. ... Characteristics of random variables A random variable is a value that, as a result of observations, can take different values, and it is not known in advance which ones (for example, MTBF, labor intensity of repair, duration of downtime in repair, uptime, number of failures at some point in time, etc.). 9

10 Due to the fact that the value of a random variable is not known in advance, the probability (the probability that the random variable will be in the range of its possible values) or frequency (the relative number of occurrences of a random variable in the specified interval) is used to estimate it. A random variable can be described in terms of the arithmetic mean, mathematical expectation, mode, median, range of the random variable, variance, standard deviation, and coefficient of variation. The arithmetic mean is the quotient of dividing the sum of the values \u200b\u200bof a random variable obtained from experiments by the number of terms of this sum, ie, by the number of experiments N N N N, () where is the arithmetic mean of the random variable; N number of experiments performed; x, x, x N separate values \u200b\u200bof a random variable. The mathematical expectation is the sum of the products of all possible values \u200b\u200bof a random variable by the probabilities of these values \u200b\u200b(P): X N P. () Between the arithmetic mean and the mathematical expectation of a random variable, there is the following relationship with a large number of observations, the arithmetic mean of a random variable approaches its mathematical expectation. The mode of a random variable is its most probable value, that is, the value corresponding to the highest frequency. Graphically, the highest ordinate corresponds to fashion. The median of a random variable is such a value for which it is equally likely whether the random variable is greater or less than the median. Geometrically, the median defines the abscissa of the point whose ordinate divides the area bounded by the distribution curve.

11 divisions in half. For symmetric modal distributions, the arithmetic mean, mode and median coincide. The scattering range of a random variable is the difference between its maximum and minimum values \u200b\u200bobtained as a result of tests: R ma mn. (3) Dispersion is one of the main characteristics of the dispersion of a random variable around its arithmetic mean. Its value is determined by the formula: D N N (). (4) The variance has the dimension of the square of a random variable, so it is not always convenient to use it. The standard deviation is also a measure of dispersion and is equal to the square root of the variance. σ N N (). (5) Since the mean square deviation has the dimension of a random variable, it is more convenient to use it than the variance. The standard deviation is also called standard, fundamental error, or fundamental deviation. The standard deviation, expressed in fractions of the arithmetic mean, is called the coefficient of variation. σ σ ν or ν 00%. (6) The introduction of the coefficient of variation is necessary for comparing the dispersion of quantities with different dimensions. For this purpose, the standard deviation is unsuitable, since it has the dimension of a random variable.

12 ... Probability of machine trouble-free operation Machines are considered to operate trouble-free if, under certain operating conditions, they remain functional for a given operating time. Sometimes this indicator is called the reliability factor, which estimates the probability of no-failure operation over the operating time or in a given interval of machine operating time under specified operating conditions. If the probability of a car's trouble-free operation during a run of l km is equal to P () 0.95, then out of a large number of cars of this brand, on average, about 5% lose their operability earlier than after a kilometer. When observing the N-th number of cars per run (thousand km) under operating conditions, it is possible to approximately determine the probability of failure-free operation P (), as the ratio of the number of properly operating machines to the total number of machines monitored during the operating time, i.e., P () N n () NN n / N; (7) where N is the total number of machines; N () the number of properly working machines to run; n the number of failed machines; the value of the considered operating time interval. To determine the true value of P (), you need to go to the limit P () n / () N n lm at 0, N 0. N The probability P (), calculated by formula (7), is called a statistical estimate of the probability of no-failure operation. Failures and reliability are opposite and incompatible events, since they cannot appear simultaneously in a given machine. Hence, the sum of the probability of no-failure operation P () and the probability of failure F () is equal to one, i.e.

13 P () + F (); P (0); P () 0; F (0) 0; F () ... 3. Failure rate (density of failures) The failure rate is the ratio of the number of failed products per unit time to the initial number of those under supervision, provided that the failed products are not restored or replaced with new ones, i.e. f () () n, (8) N where n () is the number of failures in the considered operating time interval; N the total number of items under supervision; the value of the considered operating time interval. In this case, n () can be expressed as: n () N () N (+), (9) where N () is the number of properly working products per operating time; N (+) the number of properly working products per operating time +. Since the probability of failure-free operation of products to the moments and + is expressed: N () () P; P () N (+) N +; N N () NP (); N () NP (+) +, then n () N (0) 3

14 Substituting the value of n (t) from (0) into (8), we get: f () (+) P () P. Passing to the limit, we get: f () Since P () F (), then (+ ) P () dp () P lm for 0. d [F ()] df (); () d f () d d () df f. () d Therefore, the failure rate is sometimes called the differential law of distribution of the time of failure of products. By integrating the expression (), we obtain that the probability of failure is: F () f () d 0 By the value of f (), one can judge the number of products that can fail at any time interval. The probability of failure (Fig.) In the operating time interval will be: F () F () f () d f () d f () d. 0 0 Since the probability of failure F () at is equal to one, then: 0 (). f d. four

15 f () Fig .. Probability of failure in a given interval of operating time .. 4. Failure rate The failure rate is understood as the ratio of the number of failed products per unit of time to the average number of working without failure for a given period of time, provided that the failed products are not restored or replaced with new ones. From the test data, the failure rate can be calculated by the formula: λ () n N cf () (), () where n () is the number of failed products for the time from to +; the considered operating time interval (km, h, etc.); N cp () is the average number of products without failures. The average number of fail-safe products: () + N (+) N Nср (), (3) where N () is the number of fail-safe products at the beginning of the considered operating time interval; N (+) the number of trouble-free products at the end of the operating time interval. five

16 The number of failures in the considered operating time interval is expressed: n () N () N (+) [N (+) N ()] [N (+) P ()]. (4) Substituting the values \u200b\u200bof N cf () and n () from (3) and (4) into (), we obtain: λ () NN [P (+) P ()] [P (+) + P ()] [P (+) P ()] [P (+) + P ()]. Passing to the limit at 0, we obtain Since f (), then: () λ () [P ()]. (5) P () () f λ. P () After integrating formula (5) from 0 to we get: P () e () λ d. 0 At λ () const, the probability of failure-free operation of products is equal to: P λ () e ... 5. Failure flow parameter At the moment of operating time, the failure flow parameter can be determined by the formula: 6 () dmav ω (). d

17 The operating time interval d is small, and therefore, with an ordinary flow of failures in each machine during this interval, no more than one failure can occur. Therefore, the increment in the average number of failures can be defined as the ratio of the number of failed machines dm over the period d to the total number N of machines under observation: dm dm N () dq avg, where dq is the probability of failure over the period d. From here we get: dm dq ω (), Nd d, i.e. the parameter of the flow of failures is equal to the probability of failure per unit of operating time at the moment. If instead of d we take a finite time interval and denote by m () the total number of failures in the machines during this time interval, then we obtain a statistical estimate of the parameter of the failure flow: () m ω (), N where m () is determined by the formula: N where m (+) N (+); m () mn N () m (+) m () The change in the parameter of the flow of failures in time for most of the repaired products proceeds as shown in Fig. A rapid increase in the flow of failures occurs in the section (the curve goes up), which is associated with the exit from building parts and 7 the total number of failures at a point in time the total number of failures at a point in time.,

18 units with manufacturing and assembly defects. Over time, parts run in and sudden failures disappear (the curve goes down). Therefore, this section is called a running-in section. On the site, the failure streams can be considered constant. This is the normal operating area of \u200b\u200bthe machine. It is mainly sudden failures that occur here, and wear parts change during maintenance and preventive maintenance. In section 3, ω () increases sharply due to the wear of most units and parts, as well as the basic parts of the machine. During this period, the machine usually arrives at overhaul... The longest and most significant section of the machine is. Here the parameter of the failure rate remains almost at the same level while the operating conditions of the machine are constant. For a car, this means driving in relatively constant road conditions. ω () 3 Fig .. Change in the flow of failures from operating time If the parameter of the flow of failures in a section, which is the average number of failures per unit of operating time, is constant (ω () const), then the average number of failures for any period of machine operation in this section τ will be : m avg (τ) ω () τ or ω () m avg (τ). τ 8

19 MTBF for any period τ at the -th section of work is equal to: τ const. m τ ω (τ) av. Consequently, the mean time between failures and the parameter of the flow of failures, provided it is constant, are reciprocal values. The failure flow of a machine can be viewed as the sum of its failure flows. individual nodes and details. If the machine contains k failing elements and for a sufficiently long period of operation the mean time between failures of each element is, 3, k, then the average number of failures of each element for this operating time will be: m cf (), m (), ..., m () Wed cfk. Obviously, the average number of machine failures for this operating time will be equal to the sum of the average number of failures of its elements: m () m () + m () + ... m (). + avg av av avg Differentiating this expression by operating time, we obtain: dmav () dmav () dmav () dmav k () dddd or ω () ω () + ω () + + ω k (), i.e., the parameter the failure flow of a machine is equal to the sum of the parameters of the failure flow of its constituent elements. If the parameter of the flow of failures is constant, then such a flow is called stationary. This property is possessed by the second section of the curve for changing the flow of failures. Knowledge of the reliability indicators of machines allows you to make various calculations, including calculations of the need for spare parts. The number of spare parts n spare parts per operating time will be equal to: 9 k

20 n sp ω () N. Taking into account that ω () is a function, for a sufficiently large operating time in the range from t to t we obtain: n sp N ω (y) dy. In fig. Figure 3 shows the dependence of the change in the parameters of the flow of failures of the KamAZ-740 engine under operating conditions in the conditions of Moscow, as applied to cars, the operating time of which is expressed in a kilometer. ω (t) L (mileage), thousand km Fig. 3. Change in the flow of engine failures under operating conditions 0

21. LAWS OF DISTRIBUTION OF RANDOM VALUES DETERMINING THE RELIABILITY INDICATORS OF MACHINES AND THEIR PARTS Based on the methods of the theory of probability, it is possible to establish patterns in the event of machine failures. In this case, experimental data obtained from the results of tests or observations of the operation of machines are used. In solving most of the practical problems of operating technical systems, probabilistic mathematical models (i.e., models that are a mathematical description of the results of a probabilistic experiment) are presented in integral-differential form and are also called theoretical distribution laws of a random variable. For a mathematical description of the experimental results, one of the theoretical distribution laws is not enough to take into account only the similarity of experimental and theoretical graphs and the numerical characteristics of the experiment (coefficient of variation v). It is necessary to have an understanding of the basic principles and physical laws of the formation of probabilistic mathematical models. On this basis, it is necessary to conduct a logical analysis of the cause and effect relationships between the main factors that affect the course of the process under study and its indicators. A probabilistic mathematical model (distribution law) of a random variable is the correspondence between possible values \u200b\u200band their probabilities P () according to which each possible value of a random variable is assigned a certain value of its probability P (). When operating machines, the following distribution laws are most characteristic: normal; logarithmically normal; Weibull distribution law; exponential (exponential), Poisson distribution law.

22 .. EXPONENTIAL LAW OF DISTRIBUTION The course of many processes of road transport and, consequently, the formation of their indicators as random with the total influence of all the others. The normal distribution is very convenient for the mathematical description of the sum of random variables. For example, the operating time (mileage) before the maintenance is made up of several (ten or more) shift runs that differ from one another. However, they are comparable, i.e. the influence of one shift run on the total operating time is insignificant. The complexity (duration) of performing maintenance operations (control, fastening, lubricating, etc.) consists of the sum of the labor inputs of several (80 and more) mutually independent transition elements, and each of the terms is quite small in relation to the sum. The normal law also agrees well with the results of the experiment on evaluating the parameters characterizing the technical condition of a part, assembly, unit and car as a whole, as well as their resources and operating time (mileage) before the first failure occurs. These parameters include: intensity (rate of wear of parts); average wear of parts; changing many diagnostic parameters; the content of mechanical impurities in oils, etc. For the normal distribution law in practical problems of technical operation of cars, the coefficient of variation is v 0.4. The mathematical model in differential form (i.e., differential distribution function) has the form: f σ () e () σ π, (6) in integral form () σ F () e d. (7) σ π

23 The law is two-parameter. The parameter mathematical expectation characterizes the position of the scattering center relative to the origin, and the parameter σ characterizes the stretching of the distribution along the abscissa axis. Typical graphs f () and F () are shown in Fig. 4.f () F (), 0 0.5-3σ -σ -σ + σ + σ + 3σ 0 а) b) Fig. 4. Graphs of theoretical curves of differential (a) and integral (b) distribution functions of the normal law From fig. 4 that the graph f () is symmetrical with respect to and has a bell-shaped appearance. The entire area bounded by the graph and the abscissa axis, to the right and to the left of is divided by segments equal to σ, σ, 3 σ into three parts and is: 34, 4 and%. Only 0.7% of all values \u200b\u200bof a random variable go beyond three sigma. Therefore, the normal law is often referred to as the three sigma law. It is convenient to calculate the values \u200b\u200bof f () and F () if expressions (6), (7) are transformed to a simpler form. This is done in such a way that the origin of coordinates is moved to the axis of symmetry, that is, to a point, the value is presented in relative units, namely in parts proportional to the standard deviation. To do this, it is necessary to replace the variable value with another, normalized, i.e., expressed in units of the standard deviation 3

24 z σ, (8) and set the value of the standard deviation equal, i.e., σ. Then in the new coordinates we obtain the so-called centered and normalized function, the distribution density of which is determined: z ϕ (z) e. (9) π The values \u200b\u200bof this function are given in the Appendix. The integral normalized function will take the form: (dz. (0) π zzz F0 z) ϕ (z) dz e This function is also tabulated, and it is convenient to use it in calculations (Appendix) ... The values \u200b\u200bof the function F 0 (z) given in the Appendix are given at z 0. If the value of z turns out to be negative, then the formula F 0 (0 z) should be used. The function ϕ (z) satisfies the relation z) F (). () ϕ (z) ϕ (z). () The inverse transition from the centered and normalized functions to the original is done by the formulas: f ϕ (z) σ (), (3) F) F (z). (4) (0 4

25 In addition, using the normalized Laplace function (Appendix 3) zz Ф (z) e dz, (5) π 0, the integral function can be written in the form () Ф F + (6) σ Theoretical probability P () of hitting a random variable normally distributed in the interval [a< < b ] с помощью нормированной (табличной) функции Лапласа Ф(z) определяется по формуле b Φ a P(a < < b) Φ, (7) σ σ где a, b соответственно нижняя и верхняя граница интервала. В расчетах наименьшее значение z полагают равным, а наибольшее +. Это означает, что при расчете Р() за начало первого интервала, принимают, а за конец последнего +. Значение Ф(). Теоретические значения интегральной функции распределения можно рассчитывать как сумму накопленных теоретических вероятностей P) каждом интервале k. В первом интервале F () P(), (во втором F () P() + P() и т. д., т. е. k) P(F(). (8) Теоретические значения дифференциальной функции распределения f () можно также рассчитать приближенным методом 5

26 P () f (). (9) The failure rate for the normal distribution law is determined: () () f λ (х). (30) P PROBLEM. Let the breakdown of the springs of the GAZ-30 car obey the normal law with parameters 70 thousand km and σ 0 thousand km. It is required to determine the characteristics of the reliability of the springs for a run x 50 thousand km. Decision. The probability of failure of springs is determined through the normalized normal distribution function, for which we first determine the normalized deviation: z. σ Taking into account that F 0 (z) F0 (z) F0 () 0.84 0, 6, the probability of failure is F () F0 (z) 0, 6, or 6%. Probability of no-failure operation: Failure rate: P () F () 0.6 0.84, or 84%. ϕ (z) f () ϕ ϕ; σ σ σ 0 0 taking into account that ϕ (z) ϕ (z) ϕ () 0.40, the frequency of failures of springs f () 0.0. f () 0.0 Failure rate: λ () 0, 044. P () 0.84 6

27 When solving practical problems of reliability, it is often necessary to determine the operating time of a machine for given values \u200b\u200bof the probability of failure or failure-free operation. It is easier to solve such problems using the so-called quantile table. Quantiles are the value of the function argument corresponding to the given value of the probability function; Let us denote the function of the probability of failure under the normal law p F0 P; σ p arg F 0 (P) u p. σ + σ. (3) p u p Expression (3) determines the operating time p of the machine for a given value of the probability of failure P. The operating time corresponding to a given value of the probability of no-failure operation is expressed: х х σ u p p. The table of quantiles of the normal law (Appendix 4) gives the values \u200b\u200bof the quantiles u p for probabilities p\u003e 0.5. For probabilities p< 0,5 их можно определить из выражения: u u. p p ЗАДАЧА. Определить пробег рессоры автомобиля, при котором поломки составляют не более 0 %, если известно, что х 70 тыс. км и σ 0 тыс. км. Решение. Для Р 0,: u p 0, u p 0, u p 0,84. Для Р 0,8: u p 0,8 0,84. Для Р 0, берем квантиль u p 0,8 co знаком «минус». Таким образом, ресурс рессоры для вероятности отказа Р 0, определится из выражения: σ u ,84 53,6 тыс. км. p 0, p 0,8 7

28 .. LOGARITHMICALLY NORMAL DISTRIBUTION Logarithmically normal distribution is formed if the course of the process under study and its result are influenced by a relatively large number of random and mutually independent factors, the intensity of which depends on the state achieved by the random variable. This so-called proportional effect model considers some random variable with an initial state of 0 and a final limit state n. The change in the random variable occurs in such a way that (), (3) ± ε h where ε is the intensity of the change in random variables; h () a reaction function showing the nature of the change in a random variable. h we have: For () n (± ε) (± ε) (± ε) ... (± ε) Π (± ε), 0 0 (33) where П is the sign of the product of random variables. Thus, the limit state: n n Π (± ε). (34) 0 From this it follows that the logarithmically normal law is convenient to use for the mathematical description of the distribution of random variables, which are the product of the initial data. From expression (34) it follows that n ln ln + ln (± ε). (35) n 0 Consequently, under a logarithmically normal law, the normal distribution is not the random variable itself, but its logarithm, as the sum of random equal and equally independent quantities.

29 r. Graphically, this condition is expressed in the elongation of the right side of the curve of the differential function f () along the abscissa axis, that is, the graph of the curve f () is asymmetric. In solving practical problems of technical operation of automobiles, this law (at v 0.3 ... 0, 7) is used to describe the processes of fatigue failure, corrosion, operating time before loosening of fasteners, and changes in backlash. And also in those cases where technical change occurs mainly due to wear of friction pairs or individual parts: linings and drums of brake mechanisms, discs and friction clutch linings, etc. The mathematical model of the logarithmically normal distribution has the form: in differential form: in integral form: F f (ln) (ln) (ln a) σln e, (36) σ π ln (ln a) ln σln ed (ln), (37) σ π ln where is a random variable whose logarithm is normally distributed; a mathematical expectation of the logarithm of a random variable; σ ln is the standard deviation of the logarithm of the random variable. The most characteristic curves of the differential function f (ln) are shown in Fig. 5. From fig. 5 that the graphs of the functions are asymmetric, elongated along the abscissa axis, which is characterized by the parameters of the distribution form σ. ln 9

30 F () Fig. 5. Typical graphs of the differential function of the logarithmically normal distribution For the logarithmically normal law, the change of variables is performed as follows: z ln a. (38) σ ln z F 0 z are determined by the same formulas and tables as for the normal law. To calculate the parameters, the values \u200b\u200bof the natural logarithms ln for the middle of the intervals are calculated, the statistical mathematical expectation a: Values \u200b\u200bof the functions ϕ (), () a k () ln (39) m and the standard deviation of the logarithm of the considered random variable σ N k (ln a) ln n. (40) According to the tables of probability densities of the normalized normal distribution, ϕ (z) is determined and the theoretical values \u200b\u200bof the differential distribution function are calculated by the formula: f () 30 ϕ (z). (4) σln

31 Calculate the theoretical probabilities P () of hitting a random variable in the interval k: P () f (). (4) The theoretical values \u200b\u200bof the cumulative distribution function F () are calculated as the sum of P () in each interval. The lognormal distribution is asymmetric about the mean of the experimental data - M for data. Therefore, the value of the estimate of the mathematical expectation () of this distribution does not coincide with the estimate calculated by the formulas for the normal distribution. In this regard, it is recommended to determine the estimates of the mathematical expectation M () and the standard deviation σ by the formulas: () σln a + M e, (43) σ (σ) M () (e) ln M. (44) Thus, for generalization and dissemination of the results of the experiment, not the entire general population using the mathematical model of the log-normal distribution, it is necessary to apply estimates of the parameters M () and M (σ). Failures of the following car parts obey the logarithmically normal law: driven clutch discs; front wheel bearings; frequency of loosening of threaded connections at 0 nodes; fatigue failure of parts during bench tests. 3

32 PROBLEM. During bench tests of the car, it was found that the number of cycles to failure obeys a logarithmically normal law. Determine the resource of the parts from the condition of absence 5 of destruction Р () 0.999, if: a Σ 0 cycles, N k σln (ln a) n, σ Σ (ln ln) 0, 38. N N Solution. According to the table (Appendix 4) we find for P () 0.999 Uр 3.090. Substituting the values \u200b\u200bu р, and σ in the formula, we get: 5 0 ep 3.09 0, () cycles .. 3. THE LAW OF WEIBULL DISTRIBUTION The Weibull distribution law is manifested in the model of the so-called "weak link". If the system consists of groups of independent elements, the failure of each of which leads to the failure of the entire system, then in such a model the distribution of time (or mileage) of reaching the limiting state of the system is considered as the distribution of the corresponding minimum values \u200b\u200bof individual elements: c mn (;; ...; n). An example of using Weibull's law is the distribution of the resource or the intensity of the change in the parameter of the technical state of products, mechanisms, parts, which consist of several elements that make up a chain. For example, the resource of a rolling bearing is limited by one of the elements: a ball or roller, more specifically a cage section, etc. and is described by the specified distribution. According to a similar scheme, the limiting state of the thermal clearances of the valve mechanism occurs. Many products (units, assemblies, vehicle systems) in the analysis of the failure model can be considered as consisting of several elements (sections). These are gaskets, seals, hoses, pipelines, drive belts etc. The destruction of these products occurs in different places and with different operating time (mileage), however, the product resource as a whole is determined by its weakest section. 3

33 The Weibull distribution law is very flexible for assessing vehicle reliability indicators. It can be used to simulate the processes of sudden failures (when the distribution shape parameter b is close to one, i.e. b) and failures due to wear (b, 5), as well as when the causes that cause both of these failures act together ... For example, fatigue failure can be caused by the combination of both factors. The presence of quench cracks or a notch on the surface of a part, which is a manufacturing defect, usually causes fatigue failure. If the original crack or notch is large enough, it can itself cause the part to break if a significant load is suddenly applied. This will be the case of a typical flash failure. The Weibull distribution also describes well the gradual failure of vehicle parts and assemblies caused by aging of the material in general. For example, damage to the body of cars due to corrosion. For the Weibull distribution in solving the problems of technical operation of automobiles, the value of the coefficient of variation is within v 0.35 0.8. The mathematical model of the Weibull distribution is set by two parameters, which determines a wide range of its application in practice. The differential function has the form: the integral function: f () F b a () a 33 b e b a b a, (45) e, (46) where b is the shape parameter, affects the shape of the distribution curves: at b< график функции f() обращен выпуклостью вниз, при b > bulge up; and the scale parameter characterizes the stretching of the distribution curves along the abscissa axis.

34 The most characteristic curves of the differential function are shown in Fig. 6.F () b b, 5 b b 0.5 Fig. 6. Characteristic curves of the differential Weibull distribution function At b, the Weibull distribution is transformed into an exponential (exponential) distribution, at b into the Rayleigh distribution, at b, 5 3,5 the Weibull distribution is close to normal. This circumstance explains the flexibility of this law and its wide application. The calculation of the parameters of the mathematical model is carried out in the following sequence. The values \u200b\u200bof natural logarithms ln are calculated for each value of the sample and auxiliary quantities are determined to estimate the parameters of the Weibull distribution a and b: y N N ln (). (47) σ y N N (ln) y. (48) Determine the estimates of the parameters a and b: b π σ y 6, (49) 34

35 γ y b a e, (50) where π 6.855; γ 0.5776 Euler's constant. The thus obtained estimate of the parameter b for small values \u200b\u200bof N (N< 0) значительно смещена. Для определения несмещенной оценки b) параметра b необходимо провести поправку) b M (N) b, (5) где M(N) поправочный коэффициент, значения которого приведены в табл.. Таблица. Коэффициенты несмещаемости M(N) параметра b распределения Вейбулла N M(N) 0,738 0,863 0,906 0,98 0,950 0,96 0,969 N M(N) 0,9 0,978 0,980 0,98 0,983 0,984 0,986 Во всех дальнейших расчетах необходимо использовать значение несмещенной оценки b). Вычисление теоретических вероятностей P () попадания в интервалы может производиться двумя способами:) по точной формуле: P b b βh βb β, (5) (< < β) H где β H и β соответственно, нижний и верхний пределы -го интервала по приближенной формуле (4). Распределение Вейбулла также B является асимметричным. Поэтому оценку математического ожидания M() для генеральной совокупности необходимо определять по формуле: B e M () a +. (53) b e 35

36. 4. EXPONENTIAL LAW OF DISTRIBUTION The model of the formation of this law does not take into account the gradual change of factors influencing the course of the process under study. For example, a gradual change in the parameters of the technical condition of a car and its units, assemblies, parts as a result of wear, aging, etc., and considers the so-called non-aging elements and their failures. This law is most often used when describing sudden failures, operating time (mileage) between failures, labor intensity maintenance etc. For sudden failures, an abrupt change in the technical condition indicator is characteristic. An example of a sudden failure is damage or destruction when the load instantly exceeds the strength of the object. At the same time, such an amount of energy is reported that its transformation into another form is accompanied by a sharp change in the physicochemical properties of the object (part, node), causing a sharp drop in the strength of the object and failure. An example of an unfavorable combination of conditions, causing, for example, shaft breakage, can be the action of the maximum peak load when the most weakened longitudinal shaft fibers are in the load plane. As the car ages, the proportion of sudden failures increases. The conditions for the formation of an exponential law correspond to the distribution of the mileage of units and assemblies between subsequent failures (except for the mileage from the start of commissioning until the moment of the first failure for a given unit or unit). The physical features of the formation of this model are that during repair, in the general case, it is impossible to achieve the full initial strength (reliability) of the unit or unit. The incompleteness of the restoration of the technical condition after the repair is explained by: only partial replacement of the failed (faulty) parts with a significant decrease in the reliability of the remaining (non-failed) parts as a result of their wear, fatigue, misalignment, tightness, etc .; using spare parts of lower quality in repairs than in the manufacture of cars; a lower level of production during repairs in comparison with their manufacture, caused by small-scale repairs (impossibility of complex 36

37 mechanization, the use of specialized equipment, etc.). Therefore, the first failures characterize mainly the structural reliability, as well as the quality of manufacture and assembly of cars and their units, and the subsequent ones characterize the operational reliability, taking into account the existing level of organization and production of maintenance and repair and supply of spare parts. In this regard, it can be concluded that starting from the moment the unit or unit runs after its repair (usually associated with disassembly and replacement of individual parts), failures appear similarly sudden and their distribution in most cases obeys an exponential law, although their physical nature is in mainly a joint manifestation of wear and fatigue components. For an exponential law in solving practical problems of technical operation of cars v\u003e 0.8. The differential function has the form: f λ () λ e, (54) integral function: F (λ) e. (55) The graph of the differential function is shown in Fig. 7.f () Fig. 7. The characteristic curve of the differential function of exponential distribution 37

38 The distribution has one parameter λ, which is related to the mean value of a random variable by the ratio: λ. (56) The unbiased estimate is determined by the normal distribution formulas. The theoretical probabilities P () are determined by an approximate method according to formula (9), in an exact way according to the formula: P B λ λβh λβb (β< < β) e d e e. (57) H B β β H Одной из особенностей показательного закона является то, что значению случайной величины, равному математическому ожиданию, функция распределения (вероятность отказа) составляет F() 0,63, в то время как для нормального закона функция распределения равна F() 0,5. ЗАДАЧА. Пусть интенсивность отказов подшипников ОТКАЗ скольжения λ 0,005 const (табл.). Определить вероятность безотказной работы подшипника за пробег 0 тыс. км, если из- 000км вестно, что отказы подчиняются экспоненциальному закону. Решение. P λ 0,0050 () e e 0, 95. т. е. за 0 тыс. км можно ожидать, что откажут около 5 подшипников из 00. Надежность для любых других 0 тыс. км будет та же самая. Какова надежность подшипника за пробег 50 тыс. км? P λ 0,00550 () e e 0,

39 PROBLEM. Using the condition of the above problem, determine the probability of no-failure operation for 0 thousand km between runs of 50 and 60 thousand km and mean time between failures. Decision. λ 0.005 () P () e e 0.95. MTBF is equal to: 00 thousand. km. λ 0.005 PROBLEM 3. At what mileage will 0 gears of gearboxes fail from 00, ie P () 0.9? Decision. 00 0.9 e; ln 0.9; 00ln 0.9 thousand km. 00 Table. Failure rate, λ 0 6, / h, various mechanical elements Name of the element Gearbox transmission Rolling element bearings: ball roller bearings Plain bearings Seals of elements: rotating translationally moving Shaft axes 39 Failure rate, λ 0 6 Limits of change 0, 0.36 0.0, 0 0.0, 0.005 0.4 0.5, 0, 0.9 0.5 0.6 Average value 0.5 0.49, 0.45 0.435 0.405 0.35 The exponential law describes the failure of the following parameters fairly well: the operating time to failure of many non-recoverable elements of electronic equipment; operating time between adjacent failures in the simplest flow of failures (after the end of the running-in period); recovery time from failures, etc.

40. 5. THE LAW OF POISSON DISTRIBUTION The Poisson distribution law is widely used to quantitatively characterize a number of phenomena in the queuing system: the flow of cars arriving at the service station, the flow of passengers arriving at city transport stops, the flow of customers, the flow of subscribers taking out to automatic telephone exchanges, etc. This law expresses the probability distribution of a random variable of the number of occurrence of some event for a given period of time, which can only take integer values, i.e., m 0, 3, 4, etc. The probability of occurrence of the number of events m 0, 3, ... over a given period of time in Poisson's law is determined by the formula: P (ma) m (λ t) tm, a α λ eem! m !, (58) where P (m, a) the probability of occurrence of some event during the considered time interval t is equal to m; m is a random variable representing the number of occurrences of an event during the considered period of time; t time interval during which some event is investigated; λ is the intensity or density of an event per unit of time; α λt is the mathematical expectation of the number of events for the considered period of time..5 .. Calculation of the numerical characteristics of Poisson's law The sum of the probabilities of all events in any phenomenon is equal to, m a α ie e. m 0 m! The mathematical expectation of the number of events is: X a m m α α α (m) m e a e e a m 0 !. 40

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This course work consists of two chapters. The first chapter is devoted to the practical use of the theory of technology reliability. In accordance with the assignment for the course work, the following indicators are calculated: the probability of failure-free operation of the unit; unit failure probability; probability density of failure (distribution law of a random variable); resource recovery completeness factor; recovery function (leading function of the flow of failures); failure rate. Based on the calculations, graphical images of a random variable, a differential distribution function, a change in the intensity of gradual and sudden failures, a scheme for the formation of the restoration process and the formation of a leading restoration function are built.
The second chapter of the course work is devoted to the study of theoretical foundations technical diagnostics and mastering the methods of practical diagnostics. This section describes the purpose of diagnostics in transport, develops a structural and investigative model of steering, considers all possible methods and means for diagnosing steering, analyzes in terms of completeness of troubleshooting, labor intensity, cost, etc.

LIST OF ABBREVIATIONS AND SYMBOLS 6
INTRODUCTION 6
MAIN PART 8
Chapter 1. Basics of practical use of the theory of reliability 8
Chapter 2. Methods and tools for diagnosing technical systems 18
LIST OF USED LITERATURE 21

Work contains 1 file

FEDERAL EDUCATION AGENCY

State Educational Institution of Higher Professional Education

"Tyumen State Oil and Gas University"

Branch of Muravlenko

Department of EOM

COURSE WORK

by discipline:

"Basics of technical systems performance"

Completed:

Student of the STEz-06 group D.V. Shilov

Checked by: D.S. Bykov

Muravlenko 2008

annotation

This course work consists of two chapters. The first chapter is devoted to the practical use of the theory of technology reliability. In accordance with the assignment for the course work, the following indicators are calculated: the probability of failure-free operation of the unit; unit failure probability; probability density of failure (distribution law of a random variable); resource recovery completeness factor; recovery function (leading function of the flow of failures); failure rate. Based on the calculations, graphical images of a random variable, a differential distribution function, a change in the intensity of gradual and sudden failures, a scheme for the formation of the restoration process and the formation of a leading restoration function are built.

The second chapter of the course work is devoted to the study of the theoretical foundations of technical diagnostics and the assimilation of methods of practical diagnostics. This section describes the purpose of diagnostics in transport, develops a structural and investigative model of steering, considers all possible methods and tools for diagnosing steering, analyzes in terms of completeness of troubleshooting, labor intensity, cost, etc.

Assignment for term paper

Option 22. Main bridge.
160	160,5	172,2	191	161,7		100	102,3	115,3	122,7	150
175,5	169,5	176,5	192,1	162,2		126,5	103,6	117,4	130	147,7
166,9	164,7	179,5	193,9	169,6		101,7	104,8	113,7	130,4	143,4
189,6	179	181,1	194	198,9		134,9	105,3	124,8	135	139,9
176,2	193	181,9	195,3	199,9		130,5	109,6	122,2	136,4	142,7
162,3	163,6	183,2	196,3	200		133,8	107,4	114,3	132,4	146,4
188,9	193,5	185,1	195,9	193,6		122,5	108,6	125,6	138,8	144,8
158	191,1	187,4	196,6	195,7		105,4	113,6	126,7	140	138,3
190,7	168,8	188,8	197,7	193,5		133	111,9	127,9	145,8	144,6
180,4	163,1	189,6	197,9	195,8		122,4	113,6	128,4	143,7	139,3

List of abbreviations and conventions

ATP - motor transport company

SV - random variables

TO - maintenance

UTT - technological transport management

Introduction

Automobile transport is developing qualitatively and quantitatively at a rapid pace. At present, the annual growth of the world car fleet is 10-12 million units, and its number is more than 100 million units.

In the machine-building complex of Russia, a significant number of branches of production and processing of products are united. The future of motor transport enterprises, organizations of the oil and gas production complex and enterprises of the communal sector of the Yamal-Nenets region is inextricably linked with their equipment with high-performance equipment. The operability and serviceability of machines can be achieved by timely and high-quality performance of work on their diagnosis, maintenance and repair.

At present, the automotive industry has been tasked with reducing the specific metal consumption by 15-20%, increasing the service life and reducing the labor intensity of maintenance and repair of cars.

The effective use of equipment is carried out on the basis of a scientifically grounded preventive maintenance and repair system, which allows ensuring the efficient and serviceable condition of the machines. This system allows you to increase labor productivity based on ensuring the technical readiness of machines with minimal costs for these purposes, improve the organization and improve the quality of maintenance and repair of machines, ensure their safety and extend the service life, optimize the structure and composition of the repair and maintenance base and regularity its development, accelerate scientific and technological progress in the use, maintenance and repair of machines.

Manufacturing plants, acquiring the right to independently trade their products, must at the same time be responsible for its performance, provision of spare parts and organization of technical service throughout the entire service life of the machines.

The most important form of participation of manufacturers in the technical service of machines is the development of corporate repair of the most complex assembly units (engines, hydraulic transmissions, fuel and hydraulic equipment, etc.) and the restoration of worn parts.

This process can go along the path of creating their own production facilities, as well as with the joint participation of existing repair plants and mechanical repair shops.

The development of scientifically based technical service, the creation of a service market and competition impose stringent requirements on technical service providers.

With the existing growth in the rate of road transport at enterprises, an increase in the quantitative composition of the car fleet of enterprises, it becomes necessary to organize new structural divisions of the ATP, whose task is to carry out maintenance and repair work of road transport.

An important element of the optimal organization of repairs is the creation of the necessary technical base, which predetermines the introduction of progressive forms of labor organization, an increase in the level of mechanization of work, equipment productivity, and a reduction in labor costs and funds.

Main part

Chapter 1. Basics of practical use of the theory of reliability.

The initial data for calculating the first part of the course work are operating time to failure for fifty of the same type of units:

Operating time to first failure (thousand km)

160	160,5	172,2	191	161,7
175,5	169,5	176,5	192,1	162,2
166,9	164,7	179,5	193,9	169,6
189,6	179	181,1	194	198,9
176,2	193	181,9	195,3	199,9
162,3	163,6	183,2	196,3	200
188,9	193,5	185,1	195,9	193,6
158	191,1	187,4	196,6	195,7
190,7	168,8	188,8	197,7	193,5
180,4	163,1	189,6	197,9	195,8

Operating time to second failure (thousand km)304,1

331,7 342,6 296,1 271 297,5 328,7 346,4 311,4 302,1 310,7 334,7 338,4 263,4 304,7 314,1 336,6 334 323,7 280,7 316,7 343,5 338,1 302,8 276,7 318 341,6 335,1

Random variablesmTBF (from 1 to 50) are arranged in ascending order of their absolute values:

L 1 \u003d L min ; L 2 ; L 3 ;…; L i ;… L n-1 ; L n \u003d L max , (1.1)

where L 1 ... L n – realization of a random variable L;

n -number of realizations.

L min \u003d 158; L max \u003d 200;