wear
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What is wear in physics?
In physics, wear refers to the progressive removal or displacement of material from a solid surface as a result of mechanical action by another solid. It typically occurs when two surfaces slide against each other under load, leading to material loss or transfer.
There are four main types of wear:
* Adhesive wear arises from strong adhesive forces at the interface of two solids.
* Abrasive wear happens when a hard, rough surface slides over a softer one, creating grooves.
* Corrosive wear occurs when a gas or liquid chemically attacks a surface exposed by sliding.
* Surface-fatigue wear results from repeated high stress during rolling motion, causing subsurface cracks and particle separation.4 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What causes wear to happen between two surfaces?
Wear between two surfaces happens when material is removed from a solid surface due to mechanical actions from another solid. It's a progressive loss of material from the interaction of sliding surfaces under load.
There are four main types of wear:
* Adhesive wear This occurs due to strong adhesive forces at the interface of two materials. As surfaces slide, junctions form and break. Wear particles form if the junction breaks away from the original interface.
* Abrasive wear This happens when a hard, rough surface slides across a softer one, creating grooves. It can also be caused by loose particles between surfaces or particles embedded in a surface.
* Corrosive wear This occurs when a gas or liquid chemically attacks a surface exposed by sliding. The sliding action removes protective deposits, speeding up corrosion.
* Surface-fatigue wear This is caused by repeated high stress from rolling motions, leading to subsurface cracks and eventual separation of large particles.4 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What are the main types of wear?
Wear is the removal of material from a solid surface due to mechanical action by another solid. There are four main types of wear:
- Adhesive wear This arises from strong adhesive forces at the interface of two materials. During sliding, junctions form and break. If a junction breaks away from the original interface, it forms a wear particle. This type of wear is greater for unlubricated metal surfaces.
- Abrasive wear This occurs when a hard, rough surface slides over a softer one, creating grooves. It can also happen when loose, abrasive particles roll between surfaces or are embedded in one of the surfaces. To prevent this, eliminate the hard, rough constituent or make the surface harder.
- Corrosive wear This happens when a gas or liquid chemically attacks a surface exposed by sliding. The sliding action removes surface deposits that would otherwise protect against further corrosion.
- Surface-fatigue wear This is caused by repeated high stress from rolling motion, leading to subsurface cracks. As these cracks grow, large particles separate from the surface, resulting in pitting. This is common in rolling elements like bearings or gears.
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How does friction relate to wear?
Friction and wear are closely related, as friction is a significant factor in wear. Tribology is the study of friction, wear, and lubrication as they relate to the interaction of surfaces.
Wear is the removal of material from a solid surface due to mechanical action by another solid. Friction is the force resisting the motion of surfaces sliding against each other. The amount of friction is affected by the lubricant available to sliding surfaces.
Four basic types of wear exist: adhesive, abrasive, corrosive, and surface-fatigue. During sliding, adhesive wear happens when junctions form and break. Abrasive wear occurs when a hard, rough surface slides across a softer one. Corrosive wear results when a gas or liquid chemically attacks a surface. Surface-fatigue wear is produced by repeated high stress from rolling motion.
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What factors can increase or decrease the amount of wear on materials?
Wear, the removal of material from a solid surface, is influenced by several factors. Understanding these can help in extending the life of materials in various applications.
Factors that can increase wear:
* Hard, rough surfaces Abrasive wear happens when a hard, rough surface slides over a softer one, resulting in grooves on the softer material.
* Chemical attacks Corrosive wear occurs when gases or liquids chemically attack a surface, especially when sliding removes protective corrosion products, accelerating further corrosion.
* Repeated stress Surface-fatigue wear, common in rolling motions, leads to subsurface cracks and eventual separation of large particles from the surface.Factors that can decrease wear:
* Lubrication Applying proper lubricants can combat abrasion, corrosion, and solid-to-solid contact by providing a film that increases the distance between sliding surfaces.
* Material selection Using harder materials can prevent abrasive wear, as the surface to be protected becomes more resistant to abrasion.
* Managing heat Ceramics with low thermal expansion coefficients or high thermal conductivities can decrease thermal stress, which mitigates wear from heat generation.5 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How do scientists and engineers try to reduce wear in machines and tools?
Scientists and engineers combat wear in machines and tools through several methods:
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Lubrication Applying proper lubricants helps to minimize abrasion, corrosion, and solid-to-solid contact by introducing a film between sliding surfaces. This film increases the distance between surfaces, reducing damage from contaminants and surface irregularities. Lubricants also act as preservatives when machinery is idle and control corrosion during use by coating parts with a protective film that may neutralize corrosive materials.
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Surface Modification Techniques such as ultraviolet curing and ion implantation enhance wear resistance. Ultraviolet curing increases resistance to wear, hardness, and resistance to corrosive agents. Ion implantation embeds atomic species to modify surface characteristics, like implanting titanium in iron alloys to reduce wear on bearings and gears.
4 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
wear, the removal of material from a solid surface as a result of mechanical action exerted by another solid. Wear chiefly occurs as a progressive loss of material resulting from the mechanical interaction of two sliding surfaces under load. Wear is such a universal phenomenon that rarely do two solid bodies slide over each other or even touch each other without a measurable material transfer or material loss. Thus, coins become worn as a result of continued contact with fabrics and human fingers; pencils become worn after sliding over paper; and rails become worn as a result of the continued rolling of train wheels over them. Only living things (such as bone joints) are in some sense immune to the permanent damage caused by wear, since they have the property of regrowth and healing.
There are four basic types of wear: adhesive, abrasive, corrosive, and surface-fatigue.
The most common type, adhesive wear, arises from the strong adhesive forces that are generated at the interface of two solid materials. When solid surfaces are pressed together, intimate contact is made over a number of small patches or junctions. During sliding, these junctions continue to be made and broken, and, if a junction does not break along the original interface, a wear particle is formed. These particles eventually break away. Adhesive wear is undesirable for two reasons: first, the loss of material will eventually lead to a deterioration in the performance of the mechanism; and second, the formation of large wear particles in closely fitted sliding members may cause the mechanism to seize at an early stage in its productive life. Adhesive wear is many times greater for unlubricated than for effectively lubricated metal surfaces.
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Abrasive wear occurs when a hard, rough surface slides over a softer one, producing grooves on the latter. It also can be caused by loose, abrasive particles rolling between two soft sliding surfaces or by particles embedded in one of the opposing surfaces. Abrasive fragments borne by a stream of liquid or gas may wear down a surface if they strike the surface at high speeds. Since abrasive wear takes place when the abrading material is rough and harder than the surface to be abraded, it can be prevented either by eliminating the hard, rough constituent or by making the surface to be protected harder still.
Corrosive wear occurs whenever a gas or liquid chemically attacks a surface left exposed by the sliding process. Normally, when a surface corrodes, the products of corrosion (such as patina) tend to stay on the surface, thus slowing down further corrosion. But, if continuous sliding takes place, the sliding action removes the surface deposits that would otherwise protect against further corrosion, which thus takes place more rapidly. A surface that has experienced corrosive wear generally has a matte, relatively smooth appearance.
Surface-fatigue wear is produced by repeated high stress attendant on a rolling motion, such as that of metal wheels on tracks or a ball bearing rolling in a machine. The stress causes subsurface cracks to form in either the moving or the stationary component. As these cracks grow, large particles separate from the surface and pitting ensues. Surface-fatigue wear is the most common form of wear affecting rolling elements such as bearings or gears. For sliding surfaces, adhesive wear usually proceeds sufficiently rapidly that there is no time for surface-fatigue wear to occur.
Though the wear process is generally thought of as harmful, and in most practical situations is so, it has some practical uses as well. For example, many methods of producing a surface on a manufactured object depend on abrasive wear, among them filing, sanding, lapping, and polishing. Many writing instruments, principally the pencil, crayon, and chalk, depend for their effect on adhesive wear. Another use is seen in the wear of the incisor teeth of rodents. These teeth have a hard enamel covering along the outer curved surface but only soft dentine on the inner surface. Hence, abrasive and adhesive wear, which occurs more rapidly on the softer side, acts to maintain a sharp cutting edge on the teeth.
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