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Each type of soil on which the machine is operated has a different abrasiveness. This is caused by the mixing of different soil types and structures. The structure of the soil is determined by the ratio of particles of different sizes and hardness.
Abrasiveness levels:
In fact, moisture increases the abrasiveness of the soil and acts as a grinding component, especially if it also leads to the formation of liquid sludge. For example, dry clean quartz sand may have an abrasiveness that is only 1/10 of the abrasiveness of saturated wet quartz sand slurry, and only 1/2 of the abrasiveness of the same sand in a wet state. This is because moisture affects the rate at which particles are transported (replaced) and adhered to a wearing metal surface. Moisture can also contribute to soil compaction. In addition, water itself increases the corrosion of the undercarriage parts, causing rust on steel parts, as well as increasing the corrosive effect of many other chemical elements and compounds contained in the soil.
On the other hand, water in large quantities can wash away abrasive particles and chemical elements and soften materials adhering to the parts of the undercarriage, thereby facilitating their removal.
Ground pressure can be described as the degree of penetration of the track shoe lug into the ground. Ground pressure is mainly determined by the curb weight of the machine. The ground load can be increased by reducing the speed of the machine or by using the narrowest shoes. The influence of soil on the wear of the components of the undercarriage systems can be classified as follows:
Ground pressure coefficient:
The results of ground pressure are reflected in the resource of the units of the machine's undercarriage system. Typical problems include the appearance of cracks, breakage, deformation of the shoes, increased wear and tear of links, and a reduced resource of the bushing-pin hinge.
Generally, machines with 1-lug shoes are more sensitive to high pressure coefficient soils than 2- and 3-lug shoes and shallow grousers.
Sticky materials are any materials that adhere to or wrap around moving parts in undercarriage assemblies. This has the following consequences:
Incorrect engagement of parts of interacting units, which in turn causes excessive tension of the tracks, increased load on the parts of the units of the undercarriage system, slipping and stopping of the track and support rollers and, accordingly, a sharp increase in the level of their wear. A typical example is the lack of adhesion between the drive wheel teeth and track bushings due to material adhering to the cavities between the teeth or in the space between the shoe and the bushing, the chain will suddenly break off the tips of the teeth (click), as a result of which the bushings or chain pins can break down. Excessive soil compaction can impede the rotation of the support and track rollers, in which case the track links are forced to slide along their treadmills, resulting in easily recognizable cut marks.
Wear is accelerated due to the introduction of small abrasive particles into the seal material, as well as on the surface of track parts, support and support rollers, and idler wheels. As a result, the parts of the undercarriage assemblies will constantly undergo mutual grinding all the time while they are in contact with these abrasive particles. Adhered materials are divided into recoverable and non-recoverable. The former include materials that, as a rule, when wet, can be removed from the space between the parts. Materials in the second category cannot be retrieved without modifying the standard undercarriage design.
By definition, the "sticking" effect cannot be controlled, but it can be minimized, for this it is recommended:
The chemical composition of the soil can be both natural and artificial. Chemicals such as salts, sulfur, organic elements and acids found in metal ores, fertilizers, chemical waste, landfills, and plant juices can contribute to the development of corrosion, as can soils with naturally high acid and salt content. All of these substances corrode steel parts and corrode rubber seals (some petroleum products can also attack rubber and plastic seals, causing them to swell and fail). Exposure to chemicals can lead to accelerated wear of materials, the appearance and development of a large number of cracks, loss of liquid lubricant and breakage of bushings and chain links.
It should also be noted that hardened steel may be more susceptible to the action of certain chemical elements than steel without heat treatment (hydrogen or sulfide brittleness develops depending on the acting elements, microcracks appear along the grain boundaries of the metal, further developing into cracks leading to the breakdown of the part when applying loads).
Suspension components are adversely affected by both ambient and material temperatures. This is especially evident when working in extreme conditions.
Too high temperature can reduce the hardness of the hardened steel, its strength and resistance to wear. Under these conditions, the seals can soften and fail. Situations like this are typical for machines operating in metallurgical plants.
At temperatures below 0 ° C, the soil freezes, which changes the pressure on the ground. Frozen soil enhances the adhesion effect of materials for which this may not be typical under normal conditions. Very low temperatures, close to -40 ° C, can increase the brittleness of the steel (loss of flexibility and shock resistance). Rubber rings and plastic seals can also become stiff, causing the components to lose lubricant.
At low temperatures, liquid lubricant can stop flowing from the pins into the bushings, thus depriving the track joints of lubrication, the same can happen in rollers and idler wheels, which leads to increased wear of the plain bearings and their failure. In this case, the machine should be put into operation gradually to allow the parts to "warm up" and thereby minimize the risk of failure.
The relief of the terrain on which the work is carried out has a different effect on the units of the machine's undercarriage system, since a change in the terrain leads to a change in the center of gravity of the machine. Slope work.
When properly operated (from top to bottom), the weight of the machine propels it forward, causing high wear on the front rollers. However, due to the undercarriage design, slope work reduces wear on the drive wheel and track bushings.
This situation is most favorable.
When working uphill, the weight is shifted to the rear, which causes more wear on the rear rollers and increases wear on the front sides of the drive wheel teeth and track bushings when driving straight ahead. This situation is worse than working on a slope, but much better than when working across a slope. Work on an inclined surface.
When working with a side tilt, the center of gravity shifts to the side of the tilt. Work with lateral tilt leads to increased wear of the lateral running surface of the links, the sides of the rollers and the idler wheel, the ends of the bushings and the edges of the shoes in the direction of the tilt.
Working in these conditions places the greatest stress on the components closer to the center line of the machine.
Wear increases on the inner surfaces of the treadmills of the links, rollers and idler wheel rim and shoe ends. In severe conditions, wear on the inner mating surface of the track bushing and the drive wheel teeth also increases.
Increases the load on external components. This results in increased wear on the outside of the treadmills of links, rollers, idler rim and shoe ends.
In severe conditions, wear on the outer contact surface of the hub and the drive wheel teeth increases.
Under these conditions, the weight of the machine is shifted forward, which leads to accelerated wear of the front rollers and idler wheels compared to the rear rollers.
When digging or filling a bucket, the weight of the machine is shifted to the rear rollers, while the front rollers are the most loaded during transport. This results in more wear on the rear and front rollers than on the rollers located in the middle of the track.
During such work, the weight of the machine is shifted backward, which leads to accelerated wear of the rear rollers. In severe conditions, wear on the drive wheels and track bushings increases.
The shift in weight from one side to the other affects the wear on the outer parts of the components. In some ways, this effect is similar to working on concave surfaces, although the wear is less due to static.
101 Traktorostroiteley Avenue, Cheboksary, 428028, Chuvash Republic, Russia
