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PARAMETERS OF THE WORKING SURFACE OF AUTOMOTIVE TRACTOR
ENGINE PARTS IN THE ENGINE WORKING PROCESS
Kasimov Ilkhomjon
PhD., Associate Professor
Department of Automotive Engineering and Transport
+998 97 272 07 37
Annotation:
Parameters of the working surface of parts of automotive and tractor engines play
an important role in the efficient operation of the engine. Working surfaces, such as piston,
cylinder, and valve surfaces, their smoothness, rigidity, and dimensions determine the engine's
performance. Optimal working surfaces contribute to effective control of temperature and
pressure in the working medium, reducing friction. Also, the surface parameters increase service
life and reduce the risk of malfunctions. Therefore, ensuring the quality of the working surfaces
and their correct adjustment guarantees uninterrupted and reliable engine operation.
Keywords
: Tractor, engine, working surface, parameters, efficiency
Introduction.
It is known that the components that determine the service life of internal combustion
engines include the crankshaft, bearing inserts, cylinder liner, and piston ring. One of the
convenient and simple methods for increasing their working period is rubbing them together and
mutually polishing them under optimal conditions.
Until recently, friction smoothing of friction surfaces was understood as an increase in the
contact support surface between the joint parts as a result of mechanical cutting and crushing of
micro-roughs on their surfaces. It is said that the increase in this contact surface leads to a
decrease in the amount of load on their unit surface during operation and, as a result, a sharp
decrease in wear y. Recently, the idea has been put forward that the wear resistance of joint parts
e depends not only on the increase in the supporting surfaces but also on the quality of the parts'
surfaces [1].
The quality of friction surfaces depends on the type of material, microstructure, physical-
mechanical and chemical properties, macro- and microgeometry, the type of heat treatment, and
the quality of grinding under optimal conditions [2].
Small contact surface of friction surfacesleads to an increase in the specific load, and as a result,
the local pressure and temperature on the friction surfaces increase sharply. According to
Professor N.G. Polyushkin [3], who analyzed Bowden's experiments, the local temperature can
reach 1000°C without oil friction. As a result, the peaks of the microplatitudes on the rubbing
surfaces collide with each other, become spot-welded, and merge in an instant, forming
"bridges," but they immediately break under the influence of the friction force, and small
particles and even whole grains separate from the rubbing surfaces.
When the pressure between the friction surfaces of the parts is small, elastic collisions occur, and
when the pressure is high, the collision becomes plastic. In the latter case, friction leads to plastic
displacement of the material of the outer layer of the parts, and as a result, the friction surfaces
become polished. For this reason, when the friction surfaces of parts are mutually smoothed,
their polishing occurs and an amorphous layer is formed. In this case, as a result of the
displacement of the material of the peaks of the micro-roughness on the surfaces into a plastic
state, the depressions of the micro-roughness are partially filled.
Result and discussion
. Details manufactured on metal-cutting machines have uneven surfaces
due to machining. It consists of microscopic heights and depressions invisible to the eye, and
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they represent surface roughness [5]. For example, after choning the cylinder liner, the root mean
square value of the height of the microplatforms will be Ra=0.4-0.8. In addition, due to the
uncertainty of the machine-piece-tool system, the surfaces of the parts deviate from the ideal
geometric shape. Its magnitude depends on the physical and mechanical properties of the
material from which the part is made, the condition of the machine tool, the cutting regime, the
condition of the cutting tool, etc. [4].
When assembling engines, the mutual arrangement of the friction surfaces of the connecting
parts - piston and sleeve, piston and piston ring, connecting rod and piston pin, connecting rod
and crankshaft journals and bearings - has a deviation from the ideal geometric arrangement.
All these deviations are microgeometric deviations, which lead to a violation of the accuracy of
the relative positioning of the cylindrical surfaces of the parts during engine assembly. Such
distortions include deviations from the geometrically correct positioning of the parts' axes: non-
parallelism, non-perpendicularity, and adjacent beats. [5].
The presence of such deviations leads to the fact that the actual support friction surface, on
which the surfaces of the joint parts are in contact with each other, is very small. This, in turn,
leads to an increase in the load on the unit friction surface by tens of times. This situation was
proven in the experiments conducted by Bowden and Taylor. When studying the influence of
pressure on the contact surface of a steel plate with a total surface area of 21 cm
2
, they found that
at a total load of 3 kg, the contact surface is 1/170000 of the total surface, and at a load of 300 kg,
the contact surface is 1/130 of the total surface. As can be seen from the experiment, the contact
area of the surfaces increases with increasing load.
K.K. Nuriev stated that when smoothing the friction surfaces of movable joints, the roughness
heights of micro-roughnessning decrease by up to 70% compared to the initial value and
expressed it as follows:
S
R
=1,4∙(
R
zD
+
R
zd
)
(1.1.)
S
R
mkm
2
where - surface area
RzD, Rzd
- micro-roughness of the contact surfaces of two parts in a friction pair;
1.4
- a coefficient that takes into account a decrease in the height of micro-roughness of each part
of the friction pair by up to 70% compared to the initial value.
In A.V. Makarov's article, the great Leonardo da Vinci, based on his experiments, discovered the
basic laws of friction and introduced the concept of the coefficient of friction to science, as a
result of which he rejected the idea of creating a perpetual motion machine. He emphasized here
that with the development of transmission electron microscopy, it became possible to determine
the highly dispersed crystalline structure of the "Baleby layer" discovered by G.T. Beilby in
1921. Such a layer arises during the polishing of metals and the grinding of friction pairs,
possessing higher hardness, chemical stability, and adsorption properties compared to the base
metal. This "Baleby layer" is much harder than the base metal and has a much smoother friction
surface, which in turn creates a larger contact surface. The increase in the contact surface ensures
uniform load distribution across the surface and prevents local pressure increases and reduces
wear.
At the initial stage of the grinding process, the surface of the metal
the growing ends of the roughness are partially cut, then the microscopic sharp edges on the
crystal surface are smoothed and transformed into an amorphous surface. In this case, the sharp
edges in them fill the depressions in the roughness due to plastic deformation and shear.
The quality of the friction surface depends not only on their geometric position and physical-
mechanical properties, but also on a number of factors that have not yet been fully studied
(chemical, electrical, diffusion, etc.).
Table 1
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Passenger car engine braking stand hardening modes
No. Hardeningstage
Number of crankshaft
revolutions per minute
Load,
%
duration of hardening,
min.
1. Cold
640-670
-
20.
740-770
-
15.
2. At idle
21.00
-
10.
3. Under load
3100
15.
10.
3,300
30.
15.
3,400
45.
15.
3,500
60.
15.
4,000
105.
5.
Total
-
-
95.
Note.
With cold grindinglthe number of revolutions per minute corresponds to the gear ratio of the
brake stand's gearbox.
As can be seen from the table 1, spolishing is the most accurate processing method. In this case,
the surface accuracy is of the 5th quality and higher. When machining cylindrical surfaces, it is
possible to achieve an accuracy of 1 μm in diameter. This machining method provides surface
roughness equal to 1.25 μm.
When repairing internal combustion engines, grinding and honing operations are used for final
machining of the working surfaces of parts. Then these parts are assembled into a joint with a
roughness of 0.68-1.0 μm. These roughnesses are cut and plastically deformed during the
grinding process. This, in turn, reduces the quality of engine repair and, as a result, leads to a
reduction in the inter-repair life of the internal combustion engine.
Conclusion.
1.
In the process of machining the crankshaft of an internal combustion engine with a belt
and sandpaper , the geometric shape and surface parameters of the parts change, i.e., they wear
out due to uneven grinding. This type of friction affects both the part and the tool. The wear
resistance of part surfaces depends on their hardness during the period of friction.
2.
The wear process depends on the cutting angle of the tool: the concentration of
abrasive particles, their shape, hardness, dynamic strength, as well as the physical and
mechanical properties of the wear materials affect the wear intensity.
References
1. Nasirov I.Z., Kasimov I.S. Teshaboev U.M. Results of a comparative test of car engine
crankshaft grinding methods. // Innovation in the modern education system: a collection of
scientific works of the International scientific conference (25th March, 2021) – Washington,
USA: "CESS", 2021. Part 4, Issue 1– p. pp. 318-322.
2. Kosimov I.S. Improving the efficiency of lapping engine parts using a rotary brush. //
Universum: Technical sciences: electronic scientific journal. -2020. No. 12 (81). P. 45-48s.
3. Nasirov I.Z., I. Kasimov. Choosing Method of Grinding Crankshaft Neck. // Eastern
European Scientific Journal DOI 10.12851/EESJ201905. Dusseldorf – Germany:
www.auris-verlag.de. 2019. pp. 60-62.
4. Karimkhodjaev N., Kosimov I.S., Almataev T.O. Preparing the design of a tractor engine for
various purposes. // Far Eastern Research Institute of Engineering and Technology Journal.
2021. Vol. 25. No. 5, pp. 174-178.
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5. Degtyarev A.I., Khanov A.M. Friction and wear of machine parts. / Study guide. Perm State
Technical University. Perm. 2003. - 335 p.
