There are several types of abnormal wear and tear that belong to the wear mechanism

There are four types of mechanical wear. Physical wear (also known as physical wear) The wear and tear generated by external forces in the use of equipment, such as wear and tear in normal use, accidental damage and damage, damage and residual delay in maintenance, etc., is called the first type of tangible wear; The wear and tear caused by the action of natural forces in the idle process, such as the decay, rust, aging, weathering and so on of the equipment caused by wind, sun and rain, is called the second type of tangible wear. Both of these types of physical wear and tear contribute to the technical obsolescence of the equipment.

In other words, the physical wear and tear of the equipment leads to the reduction of the performance and accuracy of the equipment, which increases the operating and maintenance costs of the equipment and is inefficient, reflecting the reduction of the use value of the equipment. The technical structure and performance of intangible wear (also known as mental wear and tear) equipment have not changed, but due to technological progress and the improvement of social labor productivity level, the reproduction value of similar equipment has decreased, resulting in the relative depreciation of the original equipment. This type of wear is called the first type of invisible wear.

The second kind of invisible wear is due to the progress of science and technology, and constantly innovating equipment with more perfect performance and higher efficiency, so that the original equipment is relatively old and backward, and its economic benefits are relatively reduced and depreciated. Both tangible and intangible wear and tear cause a depreciation of the original value of machinery and equipment, which is the same for both. The difference is that the equipment that suffers from physical wear, especially the equipment with serious physical wear, often fails to work before repair, and the maintenance cost will be very high in order to make the equipment work normally; However, even if the intangible wear and tear of equipment is very serious, the material content of its fixed assets may not be worn, and it can still be used, but whether it is economically cost-effective to continue to use it needs to be analyzed and studied.

Comprehensive wear and tear of equipment. Comprehensive wear and tear of equipment refers to the combined situation of damage and depreciation with both tangible wear and invisible wear. For any given piece of equipment, these two types of wear and tear must occur at the same time and affect each other at the same time.

Technological progress in some aspects may accelerate the speed of physical wear and tear of equipment, such as the development of high-strength, high-speed, and high-load technology, which improves the utilization rate of equipment, but inevitably aggravates the physical wear and tear of equipment. At the same time, technological progress in some aspects can provide new materials that are heat-resistant, wear-resistant, corrosion-resistant, vibration-resistant, and impact-resistant, so that the tangible wear of the equipment is slowed down, but due to the extension of the service life, its invisible wear is accelerated.

1. Early wear of the first part of the tire: the main reason is that the inflation is too large. Properly increasing the inflation capacity of tires can reduce the rolling resistance of tires and save fuel.

However, when the inflation is too large, it will not only affect the vibration damping performance of the tire, but also make the tire deformation too large, reduce the contact area with the ground, and the normal wear can only be borne by the tread ** part, forming early wear. If you choose wide tires on narrow rims, it will also cause some early wear. 2. Excessive wear on both sides of the tire:

The main reason is insufficient inflation, or long-term overloading. When the inflation capacity is small or the load is heavy, the contact surface between the tire and the ground is large, so that the two sides of the tire are in contact with the ground and cause early wear. 3. The amount of wear on one side of the tire is too large

The main reason is misalignment of the front wheels. Early wear is formed on the outside of the tire when the camber of the front wheel is too large, and early wear ...... is formed on the inside of the tire when the camber is too small or absent4. Jagged wear on the tire tread: the main reason is that the front wheel alignment is improperly adjusted or the position of the front suspension system is abnormal, the ball joint is loose, etc., which makes the normal rolling wheel slide or the wheel alignment changes continuously during driving, resulting in tire jagged wear.

5. Large wear of individual tires: abnormal suspension system of individual wheels, bending of supporting parts or unbalanced individual wheels will cause early wear of individual tires. When this happens, the positioning of the worn wheels, the operation of the independent suspension springs and shock absorbers should be checked, and the wheel rotation cycle should be shortened.

6. Tire bald wear: The reason for bald wear in individual parts of the tire is poor tire balance. When the unbalanced wheels rotate at high speed, the individual parts are subjected to large forces, the wear is accelerated, and the steering is not smooth, and the handling performance becomes poor.

If you notice a slight jolt in a particular speed direction while driving, you should balance the wheels to prevent bald wear.

For example, if a machine is damaged by use, it is the first type of physical wear.

Because of the decline of the market, the machine is worthless, which is the first invisible wear.

As a result of technological advancements, machines have been eliminated and are no longer valuable, which is the second type of invisible wear.

Equipment can wear and tear during use or idleness, and there are two forms of wear: visible wear and invisible wear. Physical wear, also known as physical wear, refers to the physical wear or loss of equipment that occurs during the use or idle process.

Types of tangible wear:

Tangible wear can be divided into the first type of tangible wear and the second type of tangible wear.

The first type of physical wear is that the parts and components will be rubbed, vibrated and fatigued during the operation of the equipment, resulting in physical wear and tear of the equipment.

It can be divided into three stages: the first stage is the "initial wear" stage in which there is more wear and tear of machinery and equipment after new or major repairs; The second stage is the "normal wear" phase in which the amount of wear and tear occurs; The third stage is the "severe wear" stage, where the amount of wear increases rapidly.

The second kind of tangible wear is that the equipment is oxidized, rusted, corroded, and naturally lost accuracy and working ability due to the action of natural forces during the idle process.

The consequences of physical wear and tear of equipment: in terms of technology, the use value of the equipment is reduced, and in serious cases, the equipment can even be completely lost; The economic aspect reduces part of the original value of the equipment, or even depreciates it completely.

Answer: a

2021 2020 Textbook 54 2019 Textbook P53

Tangible wear (also known as material wear) 1. In the process of use, the wear, deformation and damage of the entity under the action of external force are called the first kind of tangible wear, and the degree of wear is related to the strength of the posture rock and the length of use. 2. The physical wear and tear of the equipment caused by the action of natural forces in the idle process, such as rust and corrosion of metal parts, aging of rubber parts, etc., is called the second kind of tangible wear, which is related to the length of idle time and the environment. The above two kinds of tangible wear and tear cause the performance and accuracy of the equipment to decrease, so that the operating cost and maintenance cost of the equipment increase, and the efficiency is low, reflecting the reduction of the use value of the equipment.

Answer]: a, b, c

The factors that affect the change in the amount of assets and the amount of value are:

The market price is infiltrated and marked.

Physical devaluation:

a.Meaning: It refers to the fact that after the asset is put into use, during its service life, due to the use of wear and tear and the action of natural forces, it will be lost in material form, and its physical properties will continue to decline, and its value will gradually decrease.

Physical depreciation can also be referred to as physical or tangible wear and tear of an asset.

b.Generally speaking, this is caused by two reasons:

First, due to the wear and tear of the asset in the process of production and use, the greater the intensity of the asset's use, the longer it lasts, and the heavier the material wear. Typically, the wear and tear of an asset is directly proportional to the intensity of use and the duration of use.

The second is the loss caused by the action of natural forces during the service life of the asset, such as the rust of metal tools, the decay of wooden equipment, the weathering of masonry, etc., all of which belong to the physical wear and tear of assets. In the practice of asset valuation, this physical depreciation is the most common consideration when evaluating a piece of equipment or property.

Answer]: A The second type of physical wear refers to the physical wear and tear caused by the action of natural forces in the idle process of the equipment; Item B is the invisible wear, and the height C and D items are the first tangible wear and tear.

The generation mechanism and influencing factors of the form of wear are as follows:

First, the generation mechanism of the form of wear.

1. Abrasive wear is caused by the erosion of particles or foreign matter, resulting in surface wear.

2. Adhesive wear is the wear caused by the local metal adhesion of the contact surface of the friction pair during sliding friction and the destruction of the adhesive in the subsequent relative sliding.

3. Erosion wear refers to a kind of wear phenomenon in which the surface of the material is damaged when it is impacted by small and loose flowing particles.

4. Fatigue wear is caused by local cracks under repeated loads, which evolve into tiny cracks and eventually lead to wear.

5. Corrosion and wear are caused by the corrosive action of metal structures on the surface of dendrites or holes.

6. Fretting wear refers to a composite type of wear caused by small amplitude vibration between the metal surfaces that are pressed against each other.

Second, the main factors affecting wear and tear.

1. Characteristics of abrasives.

The hardness, grain size and shape of the abrasive have a significant impact on wear. Experimental stool dismantling showed that the higher the grinding hardness, the greater the wear. If the scale of the abrasive particles is generally 20 to 200 m, the wear rate of the data will be added with the addition of the wear scale, but with the addition of the grinding scale to a certain critical value, the virtual jujube wear rate of the data will actually remain unchanged.

Change or change very slowly; Under the same conditions, multi-angle abrasive grains wear four times more than round spherical abrasive grains. Comparatively speaking, the shape of the abrasive grain has a greater influence on the hard data, but less on the coarse brittleness data.

2. The nature of the target.

The hardness, resistance and elastic modulus of the target are decisive factors in confirming whether the data is wear-resistant. In general, the higher the hardness of the target, the better the resistance, the higher the elastic modulus, and the better the performance of the material. However, the suitability of the target's hardness, resistance and elastic modulus for specific working conditions does not depend entirely on the target itself, but largely on changes in the external environment, which is also the center of gasoline and gasoline.

Anti-wear. The significant difference in corrosion properties between plastic materials and brittle materials depends on their corrosion mechanisms. For resistant materials such as metals, micro-cutting is the main mechanism of corrosion. It is used for crack propagation and interspersed brittle fracture of brittle materials such as ceramics, which is the main mechanism of corrosion.

3. Incidence velocity.

Experiments have shown that velocity has a great influence on wear, and the amount of wear is proportional to the cubic of velocity.

4. Angle of incidence.

When the angle of incidence is very low, the kinetic energy component of the incident particles in the direction of the vertical material surface is not enough to cause serious damage to the material, the brittle material reflects the superiority of high hardness, showing a lower erosion rate than ductile material.

This is also the reason why the wear of pipes such as elbows, tees, reducers, distributors is more serious than that of straight pipes, and in systems where materials are transported with pipes, the erosion wear at the elbow is about 50 times more serious than the wear of the straight pipe part. The influence of the angle of incidence is related to the type of target, and the plastic material is very damaged when it is impacted at an angle of 20°-30°. Whereas, brittle materials are very damaging when impacted vertically.

Summary. The main forms of wear are as follows:1

Adhesive wear: On the contact surface, the surface of two objects is rubbed due to relative motion, resulting in an increase in surface roughness and an increase in local temperature. When the temperature rises to a certain level, the surface of the object will melt or soften, causing adhesion between the two surfaces.

In this case, when the two surfaces are separated, it can cause local tearing or peeling of the material. 2.Fatigue wear:

Under cyclic loading, small plastic deformation and crack propagation will occur inside the material, which will eventually lead to material failure. This form of wear usually occurs under conditions such as high-frequency vibration, rotation, rolling, etc. 3.

Abrasive abrasion: When hard particles (e.g., sand, dust) enter the contact surface between machine parts, they can scratch the surface of the material during movement, resulting in surface wear. 4.

Corrosion and wear: due to the presence of acid, alkali, salts and other corrosive substances in the medium, the surface of the material is chemically reacted, resulting in surface wear.

What are the main types of wear? What are the characteristics of its generation mechanism and development process?

The main forms of wear are as follows:1Adhesion wear:

On the contact surface, friction occurs between the surfaces of two objects due to relative motion, resulting in an increase in surface roughness and an increase in local temperature. When the temperature rises to a certain level, the surface of the object will melt or soften the premature bending, resulting in adhesion between the two surfaces. In this case, when the two surfaces are separated, it can cause local material to tear or peel.

2.Fatigue wear: Under the action of cyclic load, small plastic deformation and crack propagation will occur inside the material, which will eventually lead to the return and failure of the material.

This form of wear usually occurs under conditions such as high-frequency vibration, rotation, rolling, etc. 3.Abrasive wear:

When hard particles (e.g., sand, dust) enter the contact surface between machine parts, they scratch the surface of the material during movement, causing surface wear. 4.Corrosion wear:

Due to the presence of corrosive substances such as acids, alkalis, and salts in the medium, chemical reactions occur on the surface of the material, resulting in surface wear.

The generation mechanism and development process of the above wear forms have different characteristics. Adhesive wear is mainly due to the adhesion of the surface of the object due to friction and local temperature increase; Fatigue wear is due to the small plastic deformation and crack propagation inside the material under cyclic load, resulting in material failure. Abrasive grinding damage is caused by hard particles scratching the surface of the material; Corrosion and wear pins are caused by the presence of corrosive substances in the medium, resulting in chemical reactions on the surface of the material. In practice, there are often multiple forms of wear at the same time.