Causes of early wear or damage to the car engine. Causes of wear details. Main types of wear details. VII. Offers Commission

the main / Butter

The fact that the engine is a car's heart is understandable to everyone, and natural is the desire of every motorist to extend his life. The engine failures occur, as due to the fact that in the engine, something cloudy or was deregulated and due to wear. The latter has much more difficult consequences. But the wear, as a rule, does not occur suddenly and on individual manifestations it can be established that the engine, as it would have moved the line, which separates the natural wear, accompanying any normal operation from the intensive, at which the rapid and irreversible engine destruction occurs.

The main reasons for premature wear are:

1. "Dry friction" in contact pairs of conjugate parts

This in turn comes from the fact that the oil film, which should always disconnect all the many friction points, which come into contact with each other, moving parts, is squeezed and the avalanche-like metal destruction begins at these points. In addition, a sharp increase in temperature in the "dry friction" zone leads to the heating of the metal and the change in its properties, which in turn will cause further, even more sharp destruction, even if the root cause is eliminated. Simply put, the engine turns irretrievably "reverse". By the way, in this situation, many people have a strong desire to quickly sell the car for a reasonable price.

What are the main reasons leading to "dry friction"? There are only two of them. This or too much specific pressure in friction places from excess gaps or sharp dynamic loads leading to the punching of the oil film, or the "oil starvation" due to problems in the lubrication system.

2. Overheating of the engine

Every year, with the onset of warm days, many motorists meet on the road with raised hoods, from which couples valite. However, not everyone understands how dangerous for the engine even short-term overheating. Let's focus on this. Most vulnerable place From the point of view of overheating is a cylinder - a piston group. Maintaining the desired temperature modes is provided by the coolant, which should continuously remove the heat from the warm-up zone into the radiator. Heated in the combustion chamber is warm, when the heat sink is stopped, it is capable of raising the temperature in the combustion chamber several times in a few seconds. In this case, the piston rings, by virtue of their smaller mass and geometry, expand faster than the walls of the cylinders and turn into a kind of cutting tool that leaves deep nadrah cylinders on the walls.

The rings from overheating themselves lose their elasticity, as a result of which the engine loses its power, it starts to spend oil and without overhaul from this misfortune will not succeed. According to our observations, even one-time overheating of the engine never remains without consequences. And even short-term overheating, if it does not appear above the consequences described, then valve stem seals Most likely after that will have to change. It is for this reason that, when buying a car, it is more expedient to ask not about what mileage he has, but whether the engine did not overheat. This is especially true for cars, in which engines are substantially forced and have more intense temperature modes.

The characteristic mistake of many of our motorists is the desire to reach the house, despite the fact that the temperature arrow moves to the red zone. But it is not necessary to forget that the temperature sensor is most often in the radiator zone. Now imagine that according to one of the many reasons, the coolant movement slowed down or stopped at all. In this case, in the channels of washing cylinders, a steam plug is immediately formed and the temperature in a few seconds reaches critical values, while the arrow is just starting to move into the right. Even worse, the case is in cars that have only indication in the form of a light bulb.

A separate cause of many overheating is the effect of air conditioner. First, an additional radiator appears on the air flow of the air cooling radiator, this stream is very heated. Secondly, when the air conditioner is enabled, the engine receives a sufficiently high additional load. And thirdly, all this is dramatically aggravated when the engine is at idle, when the coolant circulation rate is minimal, and the share of the power of the conditioned air conditioning from the engine in this mode is approaching 50%. In this case, the cooling of radiators is provided only by an electric fan, which also creates an additional load. It is not surprising that very often when checking prestigious cars, we discover traces of high engine wear at small runs. The reason for this was most likely that when the nonsense owner of the car in hot weather was cooled in an office equipped with air conditioning, his driver did the same thing in his car.

How is the practical plan to avoid such phenomena and thereby extend the engine resource? If you bought a new car, then everything is simple - follow the requirement of instructions. If the car is supported, the smallest details are important in principle, indicating how the car has been exploited to you and what is the degree of its wear today. According to our statistics, after during the "pre-sale" expertise, not less than 60% of potential buyers from the purchase this car Refuse precisely according to the results of the engine check.

Many hope in such situations to help special additives. Here you have to be extremely careful and use them as potent medicines only on the prescription of specialists. A long-term study of this issue allows us to conclude that the use of some additives in preventive purposes can be very bad to end, and on the other hand, the target use of some additives on "well-explored target" gives a positive result.

In conclusion, I would like to give the owners of the supported cars several recommendations that could prevent the premature way out of order:

1. Do not soothing until you specify true reasons Such manifestations like tosol and oil consumption, as well as extraneous sounds from the engine, and even more so any signs of reducing oil pressure.

2. Under any circumstances, do not allow the short-term operation of the engine when the arrow approaches the temperature pointer to the red zone. The temperature indication system has inertia about 3-5 minutes, for which the cost of damage to your car can several times higher than the cost of the tow truck or towing.

3. The greatest loads, and, accordingly, wear to the rocker-piston group of the engine with sharp overclocks, so the pleasure of starting with slipping can not be denying only the owners relative to fresh and fairly powerful cars.

The main causes of the accelerated wear of the engine

Unreasonable replacement Oil and oil filterhe leads to the work of steam friction in adverse conditions.

This is due to the deterioration operational properties Motor oil (its viscosity changes, additives are produced, the addiction increases to the formation of sediments on the details and in the channels of the lubricant system, etc.) and a large number of wear products in the lubricant system (an extremely contaminated oil filter is opened by a bypass valve and oil passes by the filter element).

Using low-quality oil causes accelerated wear And the quick output of the engine is out. The oil that does not possess the entire complex of the properties necessary for the normal lubricant of the friction pairs, does not prevent the formation of scaling and the destruction of the working surfaces of high-loaded parts (parts of the gas distribution mechanism, piston rings, piston skirts, crankshaft liners, turbocharger bearings, etc.).

The increased tendency of poor-quality oils to the formation of resinous sediments can lead to clogging of oil channels and leave the friction pairs without lubrication, which will cause their accelerated wear, education of scaling and jamming. Such effects are possible in the case of oil application that does not correspond to the engine class (API, ACEA classification, and so on). For example, when the SF / CC is used instead of the recommended oil on the API of the SH / CD API.

Unsatisfactory condition of the air or fuel filter (Defects, mechanical damage), as well as various lootability of the intake system compounds lead to the ingress of abrasive particles (dust) into the engine and intensive wear, primarily cylinders and piston rings.

Low-time troubleshooting in the engine Or improper adjustments accelerate wear details. For example, "knocking" camshaft It is a source of continuous contamination of the lubricant system with metal particles. Invalid installation of the ignition advance, carburetor malfunction or engine control system, the use of non-referenced spark plugs cause detonation and a rival ignition that threaten the destruction of the pistons and surfaces of combustion chambers.

Overheating of the engine due to faults in the cooling system can lead to deformation of the head of the cylinder block (GBC) and the formation of cracks in it. Oil film in friction pairs with insufficient cooling becomes less durable, which leads to intensive wear of rubbing parts. Diesels have progars, pistons and other serious defects arise as a result of fuel equipment malfunctions.

Car operating modes Also affect the motor wear rate. The engine operation is mainly at the maximum loads and frequencies of rotation of the crankshaft, it may noticeably reduce its resource (by 20-30% or more). Excess the permissible number of revolutions leads to the destruction of parts.

About 70% of the engine wear falls on the start mode. Especially promoted resource reduction cold launchIf the engine is flooded with oil with inappropriate viscosity characteristic. At temperature -30 ° C, it is equivalent to a somewhat mileage of several hundred kilometers. This is due, first of all, with a high viscosity of oil at low temperatures - for its receipt (pumping) to friction pairs require more time.

Short trips on an immentable engine in winter They contribute to the appearance of deposits in the lubrication system and corrosion wear of the pistons, their rings and cylinders.

VIII. Conclusion of the commander of the military unit

VII. Offers Commission

Vi. The volume of completed modifications

V. Causes of early wear or damage

IV. TECHNICAL CONDITION

___________________________________________________________________________________________________________________________________________________________

(Furnishing Bulletinations)

______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Chairman of the Commission:__________________________________________________

Commission members: ____________________________________________________________________________

(Position, military rank, signature, surname)

____________________________________________________________________________

(Position, military rank, signature, surname)

Act is compiled in ____ copies.

ex. № 1 __________

ex. № 2 __________

ex. Number 3 __________

(Senior chief)

M. P. ________________________________________________________________________________________________________

(Position, military rank, signature, surname)

Passed: _________________________________________________________

(Position, military rank, signature, surname)

Accepted: _________________________________________________________

(Position, military rank, signature, surname)

"____" ________________ 200

1. The act is intended for registration of established technical condition, the need for repair and write-off of weapons and techniques taken by numbers and technical condition.

2. Act is compiled by the Commission of the Military Part (compound), association:

during the transfer of weapons and techniques within the military unit (warehouse) - in one copy and is approved by the commander of the part (head of the warehouse);

when transferring armaments (techniques) from one military unit to another, surrender to the repair part (enterprise) of association (center) - in three copies and is approved by the commander of the military unit. The first copy of the act is represented by a higher authority of the management of the relevant service, the second is sent together with weapons (technique), the third remains in the military unit;

when translating weapons (techniques) into the lower category of the previously established period, the extension of the resource and the service life - in two copies. Both copies are represented by the higher authority of the relevant service. After approval by the senior chief, the first copy of the act is returned to the military unit (to the warehouse);

with the write-off of weapons (techniques), filmed with the equipment of troops, as well as those who ended with the test or after the established period of operation - in two copies. Both copies of the act are sent in the prescribed manner to approve the boss, which is presented to this right. After approval, the first copy is returned to the military unit (to the warehouse);

when writing off the lost or prematurely incorporated weapons (techniques) - in two copies and is approved by the commander of the military unit (head of the warehouse). The first copy, together with the petition, is sent to the senior chief to receive the inspection certificate.

The signature of the commander of the military unit in Section VIII and the signature of the head, approved by the act, are assigned to mastic coat-made gerbers.

3. In column 2 of partition I, the act of the first line records the basic sample of weapons (equipment, equipment) to which the act is drawn up. The subsequent lines are recorded by its components, taken into account by numbers (engines, aggregates, guns, launchers, machine guns, radio-electronic receiving and transmitting devices, nodes, etc.), technical documentation.

4. In Section III, the Act records missing parts and items of ZIP (a card of noncompleteness is attached to the act), as well as technical documentation and fuel transmitted with weapons (technique). Here are recorded wheel tires and the percentage of their wear.

5. Section IV records: the date and place of the exit of weapons (techniques) is out of order; Specification with outdoor inspection, engine start and mileage testing (operating mode).

6. Section V records the causes of early wear or damage and investigation data. The base sample on which the system is mounted is a separate conclusion about its technical condition, the category and type of necessary repair are determined. In this case, an additional instance of the act is sent to the head of the service, which takes into account the base sample.

7. In the manufacture of blanks, the acts on the automotive equipment are not printed: the reverse side of the first sheet; The name of the second, third and fourth details of paragraphs 4, 8 and paragraph 6 of section II; Section VI.

8. When drawing up an act on the write-off of production equipment in Section VIII, if necessary, the chief accountant (head of the Financial Service) confirms its balance value and the amount of wear.

In this article, we will look at the three most typical causes of damage to the components of the engines and we describe situations that lead to the occurrence of breakdowns. The most frequent causes of damage can be called abrasive engine wear due to dirt, hydraulic blow and increased oil consumption.

Abrasive engine wear

Abrasive wear is the result of the scratching or cutting effects of solid particles of conjugate parts, as well as the result of falling on the surface of the dust parts made by air or brought with lubricant. Most often, the abrasive wear of the engine is manifested in the form of an increased oil consumption.

The study of damaged parts reveals a different nature of damage:

on the piston skirt, a wide matte contact spot is formed by the largest side load and from the opposite side;
the profile of processing profile on the piston skirt is noted;
on the skirt of the piston, piston rings, the wall or sleeve of the cylinder are formed thin furrows in the course of the movement;
piston rings and their grooves have wear in height;
in the piston rings there is an increased thermal gap, the edges of the rings become extremely sharp;
wear working edges outlooking Ring;
the piston finger has a furrowing of a wave-like profile;
abrasive wear leaves its traces and on other details, for example, on the valve terminal.
In case of damage caused by abrasive wear, several types of defects can be distinguished:
If only one cylinder is damaged and the first piston ring is worn much stronger than the third, then the contamination fall into the combustion chamber through the cylinder intake system, that is, from above. The reason for this is either depressurization, or mud sediments that were not removed before repair work.
If several cylinders are damaged or all cylinders and the first piston ring is worn much stronger than the third, then the contamination falls into the combustion chamber through general System Inlet of all cylinders. The reasons for this situation are explained by depressurization and / or destroyed or absent air filter.
If the third piston ring is worn much stronger than the first, then should be proceeding from the fact that dirty is motor oil. Oil contamination occurs or for the reason that the engine crankcase was not cleaned, and / or due to the dirty oil fog separator.

Elimination of defects and prevention lies in checking the inlet system for tightness, verification and replacement air filterThe installation of the engine crankcase, as well as suction pipes, should be cleaned before assembly. During repair work, cleanliness should be observed.

Water hammer

Hydraulic punch is a powerful source of energy. And this energy can have a crushing effect on many engine components: the piston is destroyed or deformed, the rod is strung out or breaks, jumper piston Ring The damaged piston has signs of static breakdown, the piston finger breaks down.

The reason for this defect is fluid (water or fuel), which fell into the combustion chamber. Since neither water nor fuel is susceptible to compression, with hydraulic impact there is a sharp force on the piston, piston finger, connecting rod, cylinder head, engine crankcase, bearings and crankshaft.

Too much liquid can be in the combustion chamber for the following reasons: water enters the combustion chamber through the inlet system (for example, when driving on the surface, with water); Water turns out to be in the combustion chamber due to defective gaskets. Due to the faulty injector nozzle into the combustion chamber, too much fuel falls.

Elevated oil consumption

Small oil consumption is a normal phenomenon. It varies depending on the type of engine and the mode of its operation. If the oil consumption norms prescribed by the manufacturer are exceeded, then we can talk about such a thing as an increased oil consumption. Possible reasons Increased flow:

Due to the depressurization of the turbocharger. Oil circulation line in the turbocharger system is clogged or clocked. Due to the increasing pressure in the oil circuit, the oil is squeezed out of the turbocharger into the suction channel and in the gas carriage system.
In the combustion chamber, the oil falls with fuel, for example, due to the wear of high pressure fuel pump, the lubricant of which is usually carried out through the engine oil circuit.
An intersected intake system allows particles of dirt to get into the combustion chamber, which leads to its increased wear.
With incorrectly adjusted piston protrusion, piston strikes are possible on the cylinder head. As a result, oscillations arise that affect the fuel injectors. The nozzle at the same time ceases to be closed completely, therefore too much fuel fall into the combustion chamber, and the fuel is overdose.
Oil has developed its resource. The consequence of the exceedable oil replacement intervals are blockage and / or the destruction of the filter paper, as a result of which the crude oil begins to circulate in the oil circuit.
Curved or twisted connecting rods lead to a violation of the movement of the piston, which entails a violation of the required sealing of the combustion chamber. In the most critical cases, the pumping effect of piston rings is possible. At the same time, the oil is actively fed to the combustion chamber.
If the piston rings are broken, overwhelmed or incorrectly installed, then these circumstances can lead to insufficient sealing between the combustion chamber and the engine crankcase. Due to such a sealing disorders, oil can get into the combustion chamber.
The cylinder head bolts are tightened incorrectly. This can lead to deformations, and hence both the tightness of the oil circuit.
Due to the worn pistons, the piston rings and the contact surface of the cylinder increases the volume of breakthrough gases. And it leads to excess pressure in the engine crankcase. With too high pressure, it is possible to extrude oil fog through ventilation of the engine crankcase in the combustion chamber.
Due to too high level Oils The crankshaft is immersed in the oil bath, which leads to the formation of oil fog. And if the oil is too old or poor-quality, then the formation of and oil foam is possible. Then the oil fog and foam together with breakthrough gases fall through the ventilation of the engine into the suction channel, and therefore in the combustion chamber.
In case of failures, overflow is possible in the combustion process. Due to the oil dilution with fuel, wear of the pistons, piston rings and the working surface of the cylinders are repeatedly enhanced.
When the cylinder breaks, for example, due to old and / or incorrectly tightened cylinder head bolts, piston rings lose the ability to seal between the combustion chamber and the engine crankcase. Thus, the oil fog can get into the combustion chamber. With particularly strong deformations, even the appearance of the pumping effect of piston rings is possible, that is, such a situation when the oil is simply pumped into the combustion chamber.
The poor-quality processing of the cylinder with poor honinging its working surface prevents the oil to hold the oil to hold. This leads to a significant increase in the wear of such conjugate parts as pistons, piston rings and operating surfaces of cylinders, and, consequently, to insufficient sealing of the engine crankcase. When using clogged or lured honing heads, a graphite layer is based on the working surface of the cylinder. That is, the so-called insulating shirt occurs. It significantly reduces the oil consuming potential, which leads to increased wear, first of all, with a cold start.

Send your good work in the knowledge base is simple. Use the form below

Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.

Posted on http://www.allbest.ru/

Introduction

1.1 Abrasive wear
1.2 fatigue wear
1.3 Wearing during jealous

Conclusion

Introduction

In the process of operation of the car, as a result of the impact on it, a number of factors (the impact of loads, vibrations, moisture, air flows, abrasive particles, when hitting the car dust and dirt, temperature effects, etc.), there is an irreversible deterioration of its technical condition associated with wear and damage to its details, as well as a change in a number of their properties (elasticity, plasticity, etc.). Wearing hydro-erosive abrasive

The change in the technical condition of the car is due to the work of its nodes and mechanisms, the impact of external conditions and storage of the car, as well as random factors. Random factors include hidden defects of car parts, congestion of construction, etc.

The main permanent reasons for changing the technical condition of the car during its operation was wear, plastic deformations, fatigue destruction, corrosion, as well as physico-chemical changes in the material of parts (aging).

1. Types of destruction of metal surfaces

To effectively manage the processes of changes in the technical condition of the machines and justify the activities aimed at reducing the intensity of the wear of the parts of the machines, in each particular case, to determine the type of wear of the surfaces. To do this, set the following characteristics: type of relative movement of surfaces (friction contact scheme); the character of the intermediate medium (type of lubricant or working fluid); The main wear mechanism.

In the mating machines, there are four types of relative movement of working surfaces of parts: sliding, combustion, blow, oscillation (moving having the nature of relative oscillations with an amplitude of 0.02-0.05 mm).

In the form of the intermediate medium, wear is distinguished by friction without lubricant, by friction with a lubricant material, with friction with abrasive material. Depending on the properties of materials of parts, lubricant or abrasive material, as well as on their quantitative relations in conjugations, during operation, the destruction of surfaces of various species arise.

Wear separated into the following types: Mechanical (abrasive, hydro and gas abrasive, erosion, hydro and gas - erosive, cavitation, fatigue, wear during the jamming, wear during fretting); corrosion-mechanical (oxidative, wear during fretting corrosion); Wearing under the action of electric current (electro-erosion).

Mechanical wear occurs as a result of mechanical effects on the friction surface.

Corrosion-mechanical wear is a consequence of a mechanical impact, accompanied by a chemical and (or) electrical interaction of the material with the medium.

The electro-erosion is called the erosion wear of the surface as a result of the exposure of discharges during the passage of the electric current. In the machines, this type of wear is found in elements of electrical equipment in generators, electric motors, as well as in electromagnetic starters.

In real conditions, there are simultaneous types of wear at the same time. However, as a rule, it is possible to establish a leading type of wear, limiting the durability of parts, and separate it from other concomitant types of destruction of surfaces, which slightly affect the performance of the conjugation.

The mechanism of the main type of wear is determined by studying worn surfaces. Observing the nature of the manifestation of the wear of the friction surfaces (the presence of scratches, cracks, traces of coloring, the destruction of oxide film) and knowing the properties of the materials of parts and lubricant material, as well as the data on the presence and nature of the abrasive, intensity of wear and the mode of conjugation, can be fully justified. On the form of wear of the conjugation and develop measures to increase the durability of the machine.

1.1 Abrasive wear

Abrasive is called the mechanical wear of the material as a result of mainly cutting or scratching effects on it of abrasive particles located in a free or fixed state. Abrasive particles, having a higher than metal, hardness, destroy the surface surface and dramatically increase their wear. This type of wear is one of the most common. In road vehicles, more than 60% of wear can be abrasive. Such wear is found in the details of pivot compounds, open bearings of sliding, parts of the working bodies of road vehicles, details running parts and etc.

The main source of abrasive particles in the interface of the machines is the environment. In 1 m3 of air contains from 0.04 to 5 g of dust, 60 ... 80% consisting of suspended particles of minerals. Most of the particles have dimensions D \u003d 5 ... 120 μm, i.e. commensurate with gaps in pairing road machines. The main components of dust: SiO2 silicon dioxide, FE2O3 iron oxide, Al, Ca, Mg, Na compounds and other elements.

In determining the type of wear of the elements of machines, it is necessary to distinguish from hydro and gas-abrasive wear erosion, hydrogazoerosium and cavitation wear.

The erosion is called the mechanical wear of the surface as a result of the effect of fluid flow and (or) gas.

Hydro-erosive (gas - erosion) wear is erosion wear as a result of the effect of fluid flow (gas).

Cavitational is called hydro-erosive wear when the solid body moves relative to the liquid, in which gas bubbles slam close near the surface, which creates a local pressure or temperature. The wear of this species is most often found in the elements of pipelines and in collectors in the absence of abrasive particles in the working fluid or gas. For road and building machines, erosion types of wear are not characteristic.

1.2 fatigue wear

The fatigue is called mechanical wear as a result of fatigue destruction when re-deforming the microvapors of the material of the surface layer. Such wear is observed in most pairs of road machines as a concomitant type of wear. It occurs both by friction of rolling and with friction slip.

The process of fatigue wear is usually associated with repeated voltage cycles in contact or slipping. In the process of the interaction of surfaces in their upper layers there are fields of stresses. Scheme of voltage distribution when the cylinder contact with the plane calculated by the method of finite elements. In the process of friction on the working surface of parts, the maximum compression voltages arise, and in the depth of the material of the part, the directed tangent voltages with a maximum of a distance from the contact point are distributed.

The intensity of fatigue wear is determined by the following factors: the presence of residual stresses and surface voltage concentrators (oxides and other major inclusions, dislocations); surface quality (micropographs, pollution, dents, scratches, scratches); Load distribution in the conjugation (elastic deformation, skew parts, clearance); type of friction (rolling, sliding or rolling with slippage); The presence and type of lubricant material.

There are two models of the process of fatigue wear of the material. The theory of fatigue wear, developed by a group of scientists under the leadership of I.V. Krageelsky. According to this theory, wear particles from the friction surface can be separated and without the introduction of microprips of one part to the surface layers of another detail of the conjugation. Wearing can occur due to the fatigue of microvipos of the material arising from multiple compressive and stretching efforts.

The fatigue wear is most often observed under high contact loads while rolling and slipping one surface on another. In such conditions, there are, for example, gear wheels, severe gears and rolling bearings, gear crowns. The fatigue wear of the working surfaces of parts is accompanied by an increase in noise and vibration as wear increases.

The fatigue wear of the material may be moderate and progressive. Conventional moderate wear for most friction pairs is not dangerous, and details that have fatigue damage can be used for a long time. Progressive wear occurs at high contact stresses, accompanied by intense destruction of the surface and can lead to a breakdown of parts (for example, the gear tooth).

With intense abrasive wear of the working surfaces, their destruction occurs faster than the formation of fatigue cracks, therefore, as a rule, pitting is not observed in such cases.

The fatigue wear is also manifested in the interaction of parts from elastomeric materials. The elastic properties of these materials make it possible to reproduce the roughness of the opposite solid surface during the slip process, which, in turn, leads to a multiple cyclic loading of the material. If the protrusions of the irregularities of the solid surface have a rounded shape and do not cause abrasive wear, the damage may occur in the subsurface layers of the elastomer under the action of repeating stresses of compression, stretching and alternating tangent stresses. This fatigue mechanism causes the wear of relatively low intensity, which increases significantly under the action of cyclic stresses for a long time.

1.3 Wearing during jealous

Wearing during the jamming occurs as a result of setting, the deep breaking of the material, transfer it from one friction surface to another and exposure to the irregularities on the conjugate surface. Wearing this species is one of the most dangerous and destructive. It is accompanied by a durable compound of contacting friction surfaces. In the process of friction, the relative movement of the surfaces leads to the separation of the metal particles of one surface and adding them to another firm surface.

In the mechanism of wear when she has an important role plays atomic molecular interaction of parts of parts, occurring during convergence of surfaces. Unlike the wear of other species, which requires a certain time on the development of the process and the accumulation of destructive damage, while jamming the destruction of the surface occurs rather quickly and leads to severe forms of damage (scams and sinks).

The process of forming metal bonds depends on the properties of conjugate surfaces (their nature, hardness), as well as on the methods of their processing. In the presence of oxide films on the surface of the metals, the process of jamming also depends on the properties of these oxides. Protective films that firmly connecting with the main metal and capable of rapidly restored during the destruction, prevent the collection of metals.

Wearing for the shealing of metals occurs due to violation of the rule of a positive gradient mechanical properties In the depth under friction conditions without lubricant or with its insufficient amount. In the friction of rolling under the conditions of boundary lubrication, wear is also observed caused by grasp materials and jamming. Classroom occurs at a local grease film breaking and installing metal contact. This is possible not only with the termination of the supply of lubricant, but also due to the overall overload of the conjugation, a sharp increase in oil temperature in surface layers, local temperature flashes, etc.

Wearing during the jail is most often found in gear engagement. By the ability to confront hot transmission of all types in the same conditions of loading, the gears can be positioned in the following order: cylindrical transmissions with internal and external engagement; conical transmissions with straight, oblique and spiral teeth; Hypoon and screw transmissions having the lowest contamination resistance. This is explained by the fact that hypoid and screw gears have the greatest slip of the teeth in the engagement. Wear when jealous is also found in ball and roller bearingsIn severe loaded rolling supports.

1.4 Corrosion-mechanical wear

Corrosion-mechanical wear is characterized by the process of friction material that has entered into chemical interaction with the medium. At the same time, new, less durable chemical compounds are formed on the metal surface, which during the operation of the pairing are removed with wear products. The corrosion-mechanical wear includes oxidative wear and wear during fretting corrosion.

The oxidative is called wear, in which the basic effect on the destruction of the surface has a chemical reaction of material with oxygen or oxidizing environment. It occurs when rolling with lubricant or without lubricant. The speed of oxidative wear is small and is 0.05 ... 0.011 μm / h. The process is activated with an increase in temperature, especially in a humid environment.

Wearing with fretting-corrosion is the corrosion-mechanical wear of contacting bodies with small oscillatory relative movements. This type of wear differs from wear with the fretting of mechanical wear of contacting bodies with low oscillatory relative movements. The main difference lies in the fact that the wearing in fretting occurs in the absence of an oxidizing environment without the manifestation of the chemical reaction of materials of parts and wear products with oxygen. Considering this, it is not difficult to draw an analogy in the mechanisms for the development of wear at fretting and fretting-corrosion.

Wearing during fretting and fretting-corrosion usually occurs on the conjugate surfaces of the shafts with the wheels pressed on them, clutches and rings of rolling bearings; on the axes and hubs of the wheels; on the support surfaces of the springs; on the protracted joints, the fitted surfaces of the knaps and grooves; On the supports of engines and gearboxes. Prerequisite The occurrence of fretting corrosion is the relative slippage of the conjugate surfaces, which can be caused by vibration, reciprocating movement, periodic bend or twisting of the conjugate parts. The fretting process is accompanied by a setting, oxidation, corrosion and fatigue destruction of micro components.

As a result of fretting-corrosion, the surface endurance limit is reduced by 3-6 times. On the surfaces of parts in places of conjugates, nozzles, baking sheets, feed, sinks, as well as surface microcracks are formed. A distinctive feature of wear due to freaking-corrosion is the presence of sink friction surfaces, in which compressed oxides having a specific color are concentrated. In contrast to the wear of other species with fretting corrosion, wear products in the main mass cannot exit the contact area of \u200b\u200bthe working surfaces of parts.

Wearing with fretting-corrosion entails a violation of the dimensional accuracy of the connection (if part of the wear products finds output from the contact zone) or jamming and jamming of detachable connections (if wear products remain in the friction zone). For fretting corrosion, a low rate (about 3 mm / s) of the relative movement of surfaces and the path (0.025 mm) of friction equivalent to the amplitude of oscillations, with a frequency of oscillations up to 30 Hz and above; Localization of surface damage on valid contact sites due to small relative displacements; Active oxidation

When the interaction of elastomeric materials with metal parts is also observed a phenomenon of setting. Elastomer wear out if the friction coefficient between it and the solid surface is quite large, and the strength of the elastomer on the rupture is small. If the surface layers of the material are in a state of maximum deformation, then a scratch or a small crack appears in the direction perpendicular to the slide direction. Next, there is a gradual breaking of a part of the elastomer elastic material, which is in a state of setting with a solid surface. At the same time, the elastomer layer, separated from the surface, is twisted into the roller and forms a particle of wear. The intensity of the elastomer wear in this case is significantly depends on the temperature, load and type of lubricant material. Selecting the lubricant taking into account the external conditions and elastic properties of the elastomer, you can completely eliminate this type of wear.

The process of wear during fraging corrosion under friction conditions without lubricant can be divided into three stages.

The first stage is accompanied by the destruction of protrusions and oxide films due to cyclically repeated oscillatory relative movements of contacting surfaces under the action of high loads. The processes of hardening materials and plastic deformation of the protrusions of microdelnics, causing convergence of surfaces. Rapid of surfaces causes molecular interaction and setting the metal in separate points of contact. Destruction due to the fatigue of protrusions and setting nodes generates wear products, part of which is oxidized. This stage is characterized by elevated wear with monotonously decreasing wear rate.

In the second stage, fatigue damage accumulates in surface layers. In the friction zone, a corrosion-active medium is formed under the action of oxygen air and moisture. A electrolytic medium is created between the surfaces, which intensify the process of oxidation of metal surfaces and their corrosion destruction. For this stage, the stabilization of the wear process is characteristic, a decrease in the wear rate compared with the velocity rate at the first stage.

In the third stage, due to fatigue corrosion processes, the sophisticated surface layers of metals begin to intensively collapse with gradually increasing speed. The process has a corrosion-fatigue nature of destruction.

The intensity of the destruction of surfaces during phreatic corrosion depends on the amplitude and frequency of oscillations, load, properties of the materials of parts and the environment.

2. Basic causes of wear and body damage

Worn and damage to the body may be caused by various reasons. Depending on the cause of the malfunction, they are divided into operational, structural, technological and arising due to improper storage and body care.

During operation, elements and body nodes experience dynamic stresses from bending in a vertical plane and twisting, load from their own mass, weight of cargo and passengers.

Significant stresses are also contributed to the wear of the body and its assemblies, which arise as a result of the body fluctuations not only when it moves on the irregularities and possible jokes and shocks when driving on these irregularities, but also due to the operation of the engine and the errors in balancing the rotating knots of the car chassis (especially cardan shafts), as well as as a result of the bias of the center of gravity in the longitudinal and transverse directions.

Loads can be perceived by the body completely if the car does not have a chassis frame, or partly when installing the body on the frame.

Studies have shown that the variables by the magnitude of the voltage act on the elements of the body during the operation of the car. These stresses cause fatigue accumulation and lead to fatigue destruction. Fatigious destruction begin in the area of \u200b\u200bstress accumulation.

In bodies of cars entering overhaulThere are two basic groups of damage and faults: damage appearing as a result of increasing changes in the body.

These include natural wear, arising in the process of normal technical operation of the car, as a result of a constant or periodic impact on the body of such factors such as corrosion, friction, rotting of wooden parts, elastic and plastic deformations, etc.; Malfunctions, the appearance of which is associated with the action of a person and are a consequence of constructive flaws, factory undersensation, violations of the body of the body and maintenance rules (including emergency), poor-quality repair of the body.

In addition to normal physical wear, during the operation of the car in heavy conditions Or as a result of the violation of the norms of care and prevention, an accelerated wear may occur, as well as the destruction of individual parts of the body.

Characteristic types of wear and body damage during the operation of the car are metal corrosion arising on the surface of the body under the influence of chemical or electromechanical effects; violation of the density of rivet and welded joints, cracks and ruptures; Deformation (dents, skews, deflection, warping, rejected).

Corrosion is the main type of wear of the metal body of the body.

In the metal parts of the body, the electrochemical type of corrosion is most often found, in which the metal reacts with an electrolyte solution adsorbed from the air, and which appears as a result of both the direct injection of moisture on the unprotected metal surface surfaces and as a result of condensate formation in its inter-branch space ( Between the internal and outer panels of doors, sides, roofs, etc.). Corrosion is particularly developing in places, difficult to access and clean in small gaps, as well as in flanging and edge bending, where the moisture that periodically falls into them can be maintained for a long time.

Thus, dirt, salt and moisture, which stimulate the process of corrosion development can be collected in the wheeled niches; The bottom of the body is not sufficiently resistant to the effects of corrosion factors. The composition of the corrosion has a great influence on the atmosphere, its pollution with various impurities (emissions of industrial enterprises, such as sulfur dioxide, formed as a result of fuel combustion; ammonium chloride, falling into the atmosphere due to evaporation of seas and oceans; solid particles in the form of dust), and Also ambient temperature and other solid particles contained in the atmosphere or on the surface of the body from the canvas are also caused abrasive wear of the metal surface of the body. With increasing temperature, the corrosion rate increases (especially in the presence of aggressive impurities and moisture content in the atmosphere).

Winter coatings of the road Salt to remove snow and ice, as well as the work of the car on sea coasts lead to an increase in the corrosion of the car.

Corrosion destruction in the body are also found as a result of contacting steel parts with details made of some other materials (duralumin, rubber containing sulfur compounds, plastic based on phenolic resins and others, as well as as a result of metal contact with parts made of very wet lumber. containing a noticeable amount of organic acids (formic et al.).

Thus, studies have shown that during contact steel with poly-isobutylene, the rate of metal corrosion per day is 20 mg / m2, and at the contact of the same steel with a silicone rubber - 321 mg / m2 per day.

This type of corrosion is observed in places of formulation of various rubber seals, in places of adjustment to the body of chrome decorative details (headlights, etc.).

To the emergence of corrosion on the surface of the body parts, contact friction also provides a place with the simultaneous effect of the corrosion medium and friction, with the oscillatory movement of the two metal surfaces relative to each other in the corrosion medium. This type of corrosion is subject to the door around the perimeter, the wings in the places of connecting them to the body bolts and other metal parts of the body.

When car painting, the body carefully prepared to the color of the body surfaces and contaminated air may occur. This is not enough high-quality coating also leads to corrosion of the body.

The process of corrosion of the body occurs either evenly on a significant area (surface corrosion is shown in Figure 1), or the corrosion is in the thickness of the metal, forming deep local destruction - sinks, stains in separate points of the metal surface (point corrosion is shown in Figure 2).

Figure 1 - surface corrosion on the wing of the car.

Figure 2 - point corrosion by car.

Solid corrosion is less dangerous than the local, which leads to the destruction of the metal parts of the body, the loss of strength to the sharp decrease in the limit of corrosion fatigue and the corrosion fragility characteristic of the body facing.

Depending on the working conditions that contribute to the occurrence of corrosion, parts and components of the body can be divided into having open surfaces facing a canvas (bottom of the floor, wings, wheel arches, door thresholds, the bottom of the radiator cladding), on having surfaces that are in The limits of body volume (frame, trunk, top of the floor), and on having surfaces that form a closed isolated volume (hidden parts of the frame, bottom of the outdoor door facing, etc.).

Corps cracks occur when they hit due to violation of the technology of metal processing technology (shock multiple steel treatment in cold condition), poor build quality in the manufacture or repair of the body (significant mechanical efforts when connecting parts), as a result of the use of low quality steel, the effects of metal and corrosion With the subsequent mechanical load, defects of assembling nodes and parts, as well as not enough durable knot design.

Cracks can be formed in any part or part of the metal case, but most often in places prone to vibration.

Figure 3 shows the main body damage on the example of the car gas - 24.

Figure 3 - Damage found in the Body of the car GAZ-24 "Volga"

1 - cracks on the mudguard; 2 - disruption of the welded connection of the strut or the rush of the govik with the frame of the frame; 3 - cracks on the strut; 4 - cracks on the front panel and the mudguards of the front wheels; 5 cracks on windows racks; 6 - deep dents on the windows rack panel; 7 - skew of the windows opening; 8 - Bracket front seats; 9 - cracks on the body base casing; 10 - disruption of welded bodies parts; 11 - reinforcing gutter; 12 - dents on outdoor panels closed with details with inner, irregularities remaining after editing or richtovka-13 - local corrosion at the bottom of the rear window; 14 - the separation of the pandexes in the places of attachment or cracks on the racks; 15 and 16 - local corrosion of the trunk cover; 17 - Targeting bracket of the trunk lock; 18 - local corrosion in the rear of the body base; 19 - dents on the bottom of the cow's rear panel in the mounting places rear Lights; 20 - local corrosion at the bottom of the mudguard - 21 - corrosion raid and other small mechanical damage; 22 - local corrosion arch wheel; 23 - rear wing mudguard rushing; 24 - a violation of the welded. In combination of mudguard with an arch; 25, 32 - cracked on the basis of the seats fastening places; 26 - Local corrosion at the rack rear door And on the basis of the body. An exciting rear spar amplifier; 27 - cracks on the basis of the body in places of attachment of the rear springs and others brackets; 28 - dents on the panel of the rack and the reckling of the central rack; 29 - separation of holders of the locks of the lock and the body door loop; 30 - local corrosion at the bottom of the middle side of the sidewall; 31 - local corrosion and cracks of the base base of the body; 33 - Dissars of door openings of the body; 34 - solid corrosion of base thresholds; 35 - dents on spars base base (gaps); 36 - breaking the thread on the plates of fixing fixture and door loops; 37 - Out of the door lock cover; 38 - dents (possibly with breaks) on the sidewall panel of the body; 39 - local corrosion at the bottom of the front rack; 40 - impaired anti-corrosion coating; 41 - Gay-coderzhatley separation; 42 - concurrentness of the coordinates number 1; 43 - cracks on the front panel in the places of the strut; 44 - separation of the mounting bracket front buffer; 45 - cracks on the radiator shield; 46 - local corrosion on the amplifier split; 47 - Cracks in places of fastening of the spar; 48 - attenuation of the rivet connection of the bracket; 49 - Developing holes under the finger of the spring earrings and the front bracket of the rear springs; 50 - separating the amplifier of the body base of the body; 51 - wear of the shock absorber fastening; 52 - Cracks in mounting places brackets fuel tank; 53 - dents with sharp corners or gaps on the bottom panel; 54 - solid corrosion on the bottom of the rear panel; 55 - cracks in the depreciation places; 56 - Cracks on the Cardan Shaft Casing

Destruction of welded connections in nodes whose details are connected point weldingAs well as in continuous welds of the body can occur due to poor-quality welding or impact of corrosion and external forces: the vibration of the case under the action of dynamic loads, uneven distribution of goods during loading and unloading body.

Destruction data are presented in Figure 4.

Figure 4 - destruction of welded compounds under the influence of corrosion

Worn as a result of friction occurs in the details of the reinforcement, axes and holes of the loops, the upholstery, in the holes of the rivet and bolted connections.

Celers and are released in the panels, as well as defamations and bias in the body appear due to residual deformation when they hit or poorly performed works (assembly, repair, etc.).

The concentration of stresses in the compounds of individual elements of the housing in openings for doors, windows, as well as the joints of the elements of large and low rigidity can be the cause of the destruction of parts if they are not enhanced.

In the structures of the body, the necessary hard connections are usually provided, strengthening individual sections. additional details, squeezing the ribs of stiffness.

However, in the process of long-term operation of the body and in the process of its repair, separate weak links can be revealed in the body housing that require gain or change the design of nodes to avoid the appearance of secondary breakdowns.

Conclusion

To change the technical condition of the car, conditions of operation are significantly influenced by: road conditions (technical category of road, view and quality of road surface, slopes, climbs of descent, radii of rounding road), conditions of movement (intensive city traffic, road traffic), climatic conditions ( ambient temperature, humidity, wind load, solar radiation), seasonal conditions (summer dust, dirt and moisture in autumn and spring), environmental aggression (sea air, salt on the road in winter, reinforcing corrosion), as well as transport conditions ( Loading a car).

As a result of the execution of the abstract, the main types of car body destruction of the car were studied.

These include such destruction as fatigue wear and corrosion-mechanical wear.

To reduce corrosion parts of the car and primarily the body needs to maintain their purity, carry out timely care for the paintwork and its restoration, to produce anticorrosive treatment of hidden body cavities and other prone corrosion details.

To prevent fatigue destruction and plastic deformations, it is strictly followed by the rules of operation of the car, avoiding its work on the limit modes and with overloads.

List of sources used

1 basics of performance of technical systems of studies. For universities V.A. Zorin Academy, 2009. - 206 p.

2 Reliability of vehicles "Fundamentals of the theory of reliability and diagnostics" / V. I. Calm. - Orenburg: Publishing house OGU, 2000. - 100 p.

3 Reliability of mobile machines / K.V. Schurin; M-in education and science grew. Federation: OGU, 2010. - 586 p.

4 Increasing the durability of transport machines: studies. Manual for universities / V. A. Bondarenko [and others]. - M.: Mechanical Engineering, 1999. - 144 p.

5 Basics of Reliability Theory motor vehicles: study.-method. Hands. For students in the event. Forms of training specialties "150200, 230100" / V. I. Rosidoye. - Orenburg: OGU, 2000. - 36 p.

Posted on Allbest.ru.

...

Causes of early wear or damage to the car engine. Causes of wear details. Main types of wear details. VII. Offers Commission

1. "Dry friction" in contact pairs of conjugate parts

2. Overheating of the engine

The main causes of the accelerated wear of the engine

Send your good work in the knowledge base is simple. Use the form below

Similar documents

Editor's Choice