With the rapid development of agricultural technology, the number of agricultural vehicles has increased rapidly. However, during the use of agricultural vehicles, their technical conditions will gradually deteriorate with the increase of driving mileage, which will cause the operational, dynamic and economical performance of agricultural vehicles to deteriorate and even cause malfunctions. The main reason is wear and tear. The main wear patterns are friction wear, abrasive wear, grip wear, corrosion wear, fretting wear and so on. Wear is unavoidable. If you master the rules of wear, you can use effective measures to slow the rate of wear and extend the life of agricultural vehicles. The following analyzes the wear mechanism, hazards and preventive measures from these five aspects.
First, friction and wear What is friction and wear? There are many relatively moving parts on the agricultural vehicle, such as cylinders and pistons, crankshafts and bearings, etc. These relative moving surfaces generate friction due to contact and mutual pressure, and friction causes minute convexities on the surface of the components. The part wears off, and gradually changes the geometry, size and surface quality of the part. This is frictional wear.
The speed of wear depends mainly on the friction between the two moving surfaces. The higher the friction, the faster the wear, and the size of the friction depends on the vertical friction surface pressure and friction coefficient. The magnitude of the friction coefficient is related to the degree of lubrication: 1 If the two surfaces are not lubricated, dry friction will occur, and dry friction will inevitably produce wear, which is the root cause of friction and wear. 2 If the friction surface is completely separated by a certain thickness of the lubricating film, it is liquid friction. Since the two friction surfaces do not directly contact, the friction occurs between the lubricating oil molecules, so the friction coefficient is very low, and wear can be effectively reduced. 3 If the two friction surfaces are separated by a very thin oil film, it constitutes the boundary friction, the friction coefficient of the boundary friction is lower than the dry friction, can reduce the wear of the parts, and is suitable for the friction surface under normal temperature, low speed and light load working conditions. However, if the temperature rises and the lubricant is oxidized, the lubrication will fail. At this time, the boundary friction of the contact surface will be converted into dry friction, thereby increasing wear.
During the start-up process, the friction and wear of the engine is relatively large. According to the data, the amount of wear caused by the start-up is about 50 to 60% of the total wear. This is due to the fact that the lubricant cannot be promptly moved into the part to be lubricated during start-up. The lack of oil forms dry friction, resulting in severe wear. In order to reduce the wear at startup, the following points should be noted when starting up:
(1) Before cranking, it is best to crank the crankshaft by several tens of revolutions. This should be the case for agricultural vehicles that have been parked for a longer period of time, so that the lubricating oil flows to the lubricating surface to reduce wear.
(2) The engine should not be supplied with fuel before it is warmed up sufficiently to prevent the flushing cylinder from diluting the oil.
(3) When starting, the throttle should not be too large, so as to prevent the idling speed being too high, and the lubricating oil has not reached the lubrication area, which aggravates the wear of the engine.
Second, abrasive wear parts of the friction surface and abrasive friction, so that the particles of the material from the surface of the phenomenon of the phenomenon known as abrasive wear, it is the agricultural vehicle in use, the most common form of wear is a more harmful form of wear. It is a kind of wear form that the agricultural vehicle most often encounters in use. Abrasives are mainly derived from sand particles in the dust (its main components are silica and alumina), iron scraps after metal friction, incomplete combustion of carbon deposits, and impurities in the lubricating oil. Although these abrasives have a small particle size, they are numerous and extremely hard. They greatly exceed the hardness of metals. After entering the friction, these abrasives cut parts like many tiny knives and destroy the lubricant layer between the mating surface and the parts, resulting in the parts. Draw grooves on the surface. If the oil in the oil sump of the engine is used for a long time and it is not replaced in time, more and more impurities are contained in the oil. A large amount of abrasive enters the friction surface with the lubricant, causing increased wear and causing the oil temperature to rise. The lubricating oil becomes thinner, the oil pressure drops, and some parts become stuck.
The measure to reduce abrasive wear is mainly to prevent the abrasive from entering between the friction pairs. For the engine, abrasives come in the form of: metal wear debris and corrosion products resulting from wear on the surface of the parts, entering the compression system with the intake stroke, entering the fuel system with the lubricating oil, and not being cleared during machine assembly and maintenance Clean metal shavings, sand, etc. Therefore, the following points should be noted in use:
(1) Strengthen the maintenance of the filter device. Air filters, fuel filters, and oil filters, commonly known as "three filters," are barriers to contain impurities and reduce abrasive wear on the parts. They must be cleaned and replaced in strict accordance with the requirements specified in the maintenance. When the agricultural vehicle is working in a dusty area, the number of maintenance of the air filter should be increased. The paper filter elements of fuel and oil should be replaced in time to ensure a good filter function.
(2) Add oil and regular replacement. In addition to the leakage of engine oil in use, the engine shall be allowed to consume a small part of the amount, but it must not exceed 5g/ps?h. Therefore, check each time before starting and if necessary, make up for the scale of the dipstick. When the lubricating oil in the engine is diluted, deteriorated, and impurities increase, it should be replaced in time, and the lubricating oil and the filter element should be replaced at the same time. When adding new oil, pay attention to the cleanliness of the oil filler and oiler.
(3) When maintaining agricultural vehicles, choose clean and tidy environment, where there is little dust in the air and where there is no dust on the ground. Be sure to clean the parts before assembly and pay special attention to removing impurities from the oil passages and corners.
(4) Regularly inspect each joint surface, if the pipe joint is loose, remove the oil sludge on the machine, and keep the machine clean.
Third, grasping sticky wear Sticking wear is the most dangerous form of wear. It often occurs on mating surfaces that work under conditions of high speed, heavy load, and lack of oil. During the friction process of the mating parts, intermetallic adhesion occurs at some contact parts of the two contact surfaces, and the less strong metal parts are bonded to the surface of the other part. This phenomenon is called grip-adhesion wear. When the two friction surfaces are only contacted at some points, the pressure at the contact point will be large, plastic deformation will occur on the contact point surface, and the metal surface film will be broken, the pure metal of the two friction surfaces will directly contact, and the solid-phase welding will occur at the contact points. ??adhesion. When the friction surface is relatively slid, the adhesion point is sheared. When the shear strength of the adhesion point is greater than the strength or hardness of the friction surface material, the friction surface will be interlocked and the surface will be strongly worn, even the parts cannot slide relative to each other. Causes "killing."
Once the stick and wear occurs, the consequences of damage are also serious. For example, aluminum alloy pistons and cylinder liners in the engine cylinder cylinders due to improper assembly or use, the crankshaft and the bearing shell due to lack of oil to cause the shaft, will lead to parking overhaul. In order to reduce the occurrence of sticking and wear, attention should be paid in use:
(1) Control the load, travel speed, and operating temperature of agricultural vehicles. Overloading and overspeeding will overload the engine for a long time, leading to higher engine operating temperatures, lower lubricant viscosity, and poor lubricating performance. High temperatures can also result in excessive cooling water consumption. Normal working conditions help to reduce the adhesive scratches on the parts.
(2) Reasonable selection of lubricants and greases. For parts that work under severe conditions, choose lubricants with good quality and excellent anti-wear properties. Also check the pressure of oil during driving to ensure that the supply of lubricants cannot be interrupted. .
Fourth, corrosion wear If the friction surface exposed to corrosive gas or liquid environment, mutual movement, the friction surface and the corrosive medium chemical reaction or electrochemical reaction, the formation of new substances, these substances are rubbed off during the friction phenomenon Corrosion wear. That is, the corrosion process is accompanied by a corrosion process, and corrosion and wear occur simultaneously. Corrosion causes the material to degenerate and become brittle. The friction causes the corrosion layer to wear away quickly, exposing the surface of the new material, and the new surface is eroded. As a result, the surface is continuously corroded and worn, and the friction surface is damaged rapidly.
Low temperature corrosion wear of diesel engine cylinders is a typical example. After combustion of diesel in the cylinder, the combustion products include carbon monoxide, carbon dioxide, nitrogen dioxide, steam, and a small amount of carbon dioxide and sulfur trioxide. When the engine is working at a low temperature, when the cylinder wall temperature is lower than 70°C, the water vapor is The cylinder wall condenses into water, and combines with the above gas cost-effective substances, corrodes the cylinder wall, causes corrosion wear, and greatly increases the wear rate of the cylinder wall. In order to prevent corrosion and wear, attention should be paid in use:
(1) Avoid the engine running at idle speed for a long time. When it takes a long time to stop, the engine should be turned off.
(2) In winter, warm-keeping measures can be adopted, and the warm-up time can be shortened. Before the engine is warmed up to 40°C, it can be restarted. In normal operation, the water temperature is maintained within the range of 70-90°C.
5. There is no macroscopic movement of fretting wear between the contact surfaces of the mating parts, but there are relative vibrations with small amplitude (less than 100 micrometers in amplitude) under external variable load. In this case, wear occurs between the surfaces. Fretting. Such as agricultural vehicles on the keys and bolts, high contact pressure on the mating surface of the micro convex part of the plastic deformation, and the occurrence of metal adhesion, in the external small amplitude of repeated vibration, the sticky point of the metal cut The metal particles that are cut off and cut off are not easily discharged in the static fit surface, thereby accelerating fretting wear. This not only loosens the connectors, but it can also cause stress concentration and lead to part breakage. Therefore, in use should pay attention to:
(1) Elastic spacers are used to eliminate or reduce the relative motion between the contact surfaces.
(2) The use of solid lubricants (such as MoS2) has a good effect on preventing fretting wear.
The above analysis of the common wear patterns of agricultural vehicles in use, in addition to fatigue and wear of parts, these wear will cause defects in the parts, resulting in reduced technical conditions and reduced service life. Although wear and tear are unavoidable, as long as we recognize its hazards and grasp its mechanism, we can reduce the speed of wear and prolong the service life of agricultural vehicles.
First, friction and wear What is friction and wear? There are many relatively moving parts on the agricultural vehicle, such as cylinders and pistons, crankshafts and bearings, etc. These relative moving surfaces generate friction due to contact and mutual pressure, and friction causes minute convexities on the surface of the components. The part wears off, and gradually changes the geometry, size and surface quality of the part. This is frictional wear.
The speed of wear depends mainly on the friction between the two moving surfaces. The higher the friction, the faster the wear, and the size of the friction depends on the vertical friction surface pressure and friction coefficient. The magnitude of the friction coefficient is related to the degree of lubrication: 1 If the two surfaces are not lubricated, dry friction will occur, and dry friction will inevitably produce wear, which is the root cause of friction and wear. 2 If the friction surface is completely separated by a certain thickness of the lubricating film, it is liquid friction. Since the two friction surfaces do not directly contact, the friction occurs between the lubricating oil molecules, so the friction coefficient is very low, and wear can be effectively reduced. 3 If the two friction surfaces are separated by a very thin oil film, it constitutes the boundary friction, the friction coefficient of the boundary friction is lower than the dry friction, can reduce the wear of the parts, and is suitable for the friction surface under normal temperature, low speed and light load working conditions. However, if the temperature rises and the lubricant is oxidized, the lubrication will fail. At this time, the boundary friction of the contact surface will be converted into dry friction, thereby increasing wear.
During the start-up process, the friction and wear of the engine is relatively large. According to the data, the amount of wear caused by the start-up is about 50 to 60% of the total wear. This is due to the fact that the lubricant cannot be promptly moved into the part to be lubricated during start-up. The lack of oil forms dry friction, resulting in severe wear. In order to reduce the wear at startup, the following points should be noted when starting up:
(1) Before cranking, it is best to crank the crankshaft by several tens of revolutions. This should be the case for agricultural vehicles that have been parked for a longer period of time, so that the lubricating oil flows to the lubricating surface to reduce wear.
(2) The engine should not be supplied with fuel before it is warmed up sufficiently to prevent the flushing cylinder from diluting the oil.
(3) When starting, the throttle should not be too large, so as to prevent the idling speed being too high, and the lubricating oil has not reached the lubrication area, which aggravates the wear of the engine.
Second, abrasive wear parts of the friction surface and abrasive friction, so that the particles of the material from the surface of the phenomenon of the phenomenon known as abrasive wear, it is the agricultural vehicle in use, the most common form of wear is a more harmful form of wear. It is a kind of wear form that the agricultural vehicle most often encounters in use. Abrasives are mainly derived from sand particles in the dust (its main components are silica and alumina), iron scraps after metal friction, incomplete combustion of carbon deposits, and impurities in the lubricating oil. Although these abrasives have a small particle size, they are numerous and extremely hard. They greatly exceed the hardness of metals. After entering the friction, these abrasives cut parts like many tiny knives and destroy the lubricant layer between the mating surface and the parts, resulting in the parts. Draw grooves on the surface. If the oil in the oil sump of the engine is used for a long time and it is not replaced in time, more and more impurities are contained in the oil. A large amount of abrasive enters the friction surface with the lubricant, causing increased wear and causing the oil temperature to rise. The lubricating oil becomes thinner, the oil pressure drops, and some parts become stuck.
The measure to reduce abrasive wear is mainly to prevent the abrasive from entering between the friction pairs. For the engine, abrasives come in the form of: metal wear debris and corrosion products resulting from wear on the surface of the parts, entering the compression system with the intake stroke, entering the fuel system with the lubricating oil, and not being cleared during machine assembly and maintenance Clean metal shavings, sand, etc. Therefore, the following points should be noted in use:
(1) Strengthen the maintenance of the filter device. Air filters, fuel filters, and oil filters, commonly known as "three filters," are barriers to contain impurities and reduce abrasive wear on the parts. They must be cleaned and replaced in strict accordance with the requirements specified in the maintenance. When the agricultural vehicle is working in a dusty area, the number of maintenance of the air filter should be increased. The paper filter elements of fuel and oil should be replaced in time to ensure a good filter function.
(2) Add oil and regular replacement. In addition to the leakage of engine oil in use, the engine shall be allowed to consume a small part of the amount, but it must not exceed 5g/ps?h. Therefore, check each time before starting and if necessary, make up for the scale of the dipstick. When the lubricating oil in the engine is diluted, deteriorated, and impurities increase, it should be replaced in time, and the lubricating oil and the filter element should be replaced at the same time. When adding new oil, pay attention to the cleanliness of the oil filler and oiler.
(3) When maintaining agricultural vehicles, choose clean and tidy environment, where there is little dust in the air and where there is no dust on the ground. Be sure to clean the parts before assembly and pay special attention to removing impurities from the oil passages and corners.
(4) Regularly inspect each joint surface, if the pipe joint is loose, remove the oil sludge on the machine, and keep the machine clean.
Third, grasping sticky wear Sticking wear is the most dangerous form of wear. It often occurs on mating surfaces that work under conditions of high speed, heavy load, and lack of oil. During the friction process of the mating parts, intermetallic adhesion occurs at some contact parts of the two contact surfaces, and the less strong metal parts are bonded to the surface of the other part. This phenomenon is called grip-adhesion wear. When the two friction surfaces are only contacted at some points, the pressure at the contact point will be large, plastic deformation will occur on the contact point surface, and the metal surface film will be broken, the pure metal of the two friction surfaces will directly contact, and the solid-phase welding will occur at the contact points. ??adhesion. When the friction surface is relatively slid, the adhesion point is sheared. When the shear strength of the adhesion point is greater than the strength or hardness of the friction surface material, the friction surface will be interlocked and the surface will be strongly worn, even the parts cannot slide relative to each other. Causes "killing."
Once the stick and wear occurs, the consequences of damage are also serious. For example, aluminum alloy pistons and cylinder liners in the engine cylinder cylinders due to improper assembly or use, the crankshaft and the bearing shell due to lack of oil to cause the shaft, will lead to parking overhaul. In order to reduce the occurrence of sticking and wear, attention should be paid in use:
(1) Control the load, travel speed, and operating temperature of agricultural vehicles. Overloading and overspeeding will overload the engine for a long time, leading to higher engine operating temperatures, lower lubricant viscosity, and poor lubricating performance. High temperatures can also result in excessive cooling water consumption. Normal working conditions help to reduce the adhesive scratches on the parts.
(2) Reasonable selection of lubricants and greases. For parts that work under severe conditions, choose lubricants with good quality and excellent anti-wear properties. Also check the pressure of oil during driving to ensure that the supply of lubricants cannot be interrupted. .
Fourth, corrosion wear If the friction surface exposed to corrosive gas or liquid environment, mutual movement, the friction surface and the corrosive medium chemical reaction or electrochemical reaction, the formation of new substances, these substances are rubbed off during the friction phenomenon Corrosion wear. That is, the corrosion process is accompanied by a corrosion process, and corrosion and wear occur simultaneously. Corrosion causes the material to degenerate and become brittle. The friction causes the corrosion layer to wear away quickly, exposing the surface of the new material, and the new surface is eroded. As a result, the surface is continuously corroded and worn, and the friction surface is damaged rapidly.
Low temperature corrosion wear of diesel engine cylinders is a typical example. After combustion of diesel in the cylinder, the combustion products include carbon monoxide, carbon dioxide, nitrogen dioxide, steam, and a small amount of carbon dioxide and sulfur trioxide. When the engine is working at a low temperature, when the cylinder wall temperature is lower than 70°C, the water vapor is The cylinder wall condenses into water, and combines with the above gas cost-effective substances, corrodes the cylinder wall, causes corrosion wear, and greatly increases the wear rate of the cylinder wall. In order to prevent corrosion and wear, attention should be paid in use:
(1) Avoid the engine running at idle speed for a long time. When it takes a long time to stop, the engine should be turned off.
(2) In winter, warm-keeping measures can be adopted, and the warm-up time can be shortened. Before the engine is warmed up to 40°C, it can be restarted. In normal operation, the water temperature is maintained within the range of 70-90°C.
5. There is no macroscopic movement of fretting wear between the contact surfaces of the mating parts, but there are relative vibrations with small amplitude (less than 100 micrometers in amplitude) under external variable load. In this case, wear occurs between the surfaces. Fretting. Such as agricultural vehicles on the keys and bolts, high contact pressure on the mating surface of the micro convex part of the plastic deformation, and the occurrence of metal adhesion, in the external small amplitude of repeated vibration, the sticky point of the metal cut The metal particles that are cut off and cut off are not easily discharged in the static fit surface, thereby accelerating fretting wear. This not only loosens the connectors, but it can also cause stress concentration and lead to part breakage. Therefore, in use should pay attention to:
(1) Elastic spacers are used to eliminate or reduce the relative motion between the contact surfaces.
(2) The use of solid lubricants (such as MoS2) has a good effect on preventing fretting wear.
The above analysis of the common wear patterns of agricultural vehicles in use, in addition to fatigue and wear of parts, these wear will cause defects in the parts, resulting in reduced technical conditions and reduced service life. Although wear and tear are unavoidable, as long as we recognize its hazards and grasp its mechanism, we can reduce the speed of wear and prolong the service life of agricultural vehicles.
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