Wear is a complicated area, where there seems to be few predictive relations. Most of the design criteria seem to be “rules of thumb”. In order for these rules to be applicable, they are limited to certain special areas of wear. Thus, wear is usually divided into some subareas.
- There are many different kinds of wear mechanisms
- We have to analyse these wear mechanisms using mechanics, thermodynamics, etc. Tribology is a multi-disciplinary subject
Definition: Wear; damage to a surface that generally involves progressive loss of material and is due to relative motion between that surface and a contacting substance or substances.
There are generally 12 Types of Metallic of Metallic Wear:
Wear is the result of erosion, abrasion, Wear is the result of erosion, abrasion, impact, metal-to-metal contact, oxidation and corrosion or a oxidation, and corrosion, or a combination of these.
Generally, removal of surface film material due to adhesion and subsequent loosening due to adhesion and subsequent loosening during relative motion. Mild Adhesion transfer and loosening of surface films only transfer and loosening of surface films only.
Cold welding of metal surfaces due to intimate metal to metal contact.
When two surfaces are brought together under load when two surfaces are brought together under load, asperities of the two surfaces adhere to each other. The conditions at the interface of these junctions are similar to those of a cold weld. A strong bond is formed but without much inter-diffusion of atoms and recrystallization would occur in a hot weld.
Abrasion is the wearing of surfaces by rubbing, Abrasion is the wearing of surfaces by rubbing, grinding, or other types of friction. It usually occurs due to metal-to metal contact. It is a scraping, grinding wear that rubs away metal surfaces and can be caused by the scouring action of sand, gravel, slag, earth, and other gritty material.
Cutting of materials by hard particles in a high velocity fluid impinging on a surface velocity fluid impinging on a surface. This type of wear results from sharp particles This type of wear results from sharp particles impinging on a surface such as the cutting of materials by hard particles in a high velocity fluid materials by hard particles in a high velocity fluid impinging on a surface. This action is very much like that of sandblasting.
Continuous removal of surface films by very fine abrasives. Polishing wear is characterized by very Polishing wear is characterized by very shiny, very smooth, mirror like metal surfaces. Fine abrasives wear away the surfaces. Fine abrasives wear away the surface films as they form and reform.
Metal removed by cracking and pitting, due to cyclic elastic stress during rolling and sliding cyclic elastic stress during rolling and sliding. This type of wear is produced when repeated sliding or rolling occurs over a track. The most common example is the action of a ball or roller common example is the action of a ball or roller bearing race. As the rolling element passes over a given spot on the raceway it is stressed as the a given spot on the raceway, it is stressed as the load is applied and released.
Corrosion wear is the gradual deterioration of Corrosion wear is the gradual deterioration of unprotected metal surfaces, caused by the effects of the atmosphere, acids, gases, alkalies, etc. This type of wear creates pits and perforations and may eventually dissolve metal parts.
Wear between two solid surfaces experiencing oscillatory relative motion of low amplitude. Fretting wear occurs where there is oscillatory motion with a small displacement (1 micron) of motion with a small displacement ( ~ 1 micron) of the contacting surfaces under load. Small wear particles are formed through the mechanism of particles are formed through the mechanism of adhesive wear.
Localized wear spots made by rolling elements on raceways due to limited rolling/repeated impact raceways due to limited rolling/repeated impact. Localized wear spots formed by rolling elements on raceways due to limited rolling/repeated impact. False Brinelling is typically characterized by indentations on the Brinelling is typically characterized by indentations on the inner or outer raceway of a rolling element bearing. The indentation corresponded to the position of the rolling elements.
Dissolution of a metal in an electrically conducive liquid by low amperage currents.
Removal of metal by high amperage electrical discharge or spark between two surfaces.
Removal of metal by vapour cavity implosion in a cavitating liquid. Cavitation happens, for example, in high-pressure pumps adjacent to the intake ports and on the blades of a ship’s propellers When a sudden blades of a ship’s propellers. When a sudden local reduction in fluid pressure occurs, a vapour cavity is formed. When the vapour cavity later cavity is formed. When the vapour cavity later collapses near a solid surface it produces a mechanical shock.