Tribology

You wasted in the teeth of a gear due to friction.

Friction.

tribology (from the Greek τρίβω tríbō, "to rub or brush") is the science that studies friction, wear and lubrication that They take place during contact between solid moving surfaces. The term has been used universally since the end of the 20th century.

Understanding tribology requires knowledge of physics, chemistry, and materials technology. The tasks of the tribologist (tribologist) are to reduce friction and wear by lubricating contact surfaces in order to conserve and reduce energy, achieve faster and more precise movements, increase productivity and reduce maintenance.

History

Tribological experiments suggested by Leonardo da Vinci

Early history

Despite the relatively recent name of the field of tribology, quantitative studies of friction date back to 1493, when Leonardo da Vinci first noted the two "laws" fundamentals of friction. According to Leonardo, the frictional resistance was the same for two different objects of the same weight but that the contact was of different widths and lengths. He also observed that the force required to overcome friction doubled when the weight was doubled. However, Leonardo's findings remained unpublished in his notebooks.

The two 'laws' The fundamentals of friction were first published in 1699 by Guillaume Amontons, with whose name they are now generally associated. They claim that:

• the friction force that acts between two sliding surfaces is proportional to the load that presses the surfaces together;
• the friction force is independent of the apparent area of contact between the two surfaces.

Although not universally applied, these simple statements hold true for a surprisingly wide variety of systems. These laws were developed in 1785 by Charles-Augustin de Coulomb, who noted that the force of static friction can depend on contact time and that sliding (kinetic) friction can depend on sliding velocity, normal force, and contact. area.

In 1798, Charles Hatchett and Henry Cavendish carried out the first reliable test for fretting wear. In a study commissioned by the UK Privy Council, they used a simple reciprocating machine to assess the rate of gold coin wear. They found that coins with sand between them wore more rapidly than self-paired coins. In 1860, Theodor Reye proposed Reye's hypothesis. In 1953, John Frederick Archard developed Archard's equation describing slip wear. and is based on the theory of contact with asperities.

Other pioneers of tribology research included Australian physicist Frank Philip Bowden and British physicist David Tabor, both of the Cavendish Laboratory at Cambridge University. Together they wrote the fundamental textbook The Friction and Lubrication of Solids (Part I originally published in 1950 and Part II in 1964). Michael J. Neale was another leader in the field in the mid to late 20th century century. He specialized in solving machine design problems by applying his knowledge of tribology. Neale was respected as an educator with a gift for integrating theoretical work with his own practical experience to produce easy-to-understand design guides. The Tribology Handbook, which he first edited in 1973 and updated in 1995, is still in use around the world and forms the basis of numerous training courses for engineering designers.

Duncan Dowson reviewed the history of tribology in his 1997 book History of Tribology (2nd Edition). This work covers developments from prehistoric times to early civilizations (Mesopotamia, ancient Egypt) and highlights key developments up to the end of the 20th century.

The Jost Report

The term "tribology" came into wide use after The Jost Report, published in 1966. The report highlighted the enormous cost of friction, wear and corrosion to the economy British (1.1–1.4% of GDP). As a result, the UK government established several national centers to address tribological issues. Since then, the term has spread throughout the international community, with many specialists now identifying themselves as "tribologists".

Tribology as a science

Tribology is defined as the science and technology of the interaction between surfaces in relative motion and involves the study of friction, wear and lubrication.

Before the birth of tribology as a science, the term “lubrication” or lubrication engineering was thought of. The reduction of friction and wear had not been generalized as daily practices. With tribology as a science, friction and its associated effects, such as wear, were studied, trying to prevent them with better designs and lubrication practices. It takes into account, among other aspects of industrial machinery, the following:

• the design,
• surface materials in contact,
• the lube application system,
• the surrounding medium,
• operating conditions.

Applications

Tribology is present in practically all moving parts such as:

Tribology helps to solve problems in machinery, equipment and industrial processes such as:

Fundamentals of Tribology

Tribology focuses on the study of three phenomena:

1. The friction between two moving bodies
2. Wearing as a natural effect of this phenomenon
3. Lubrication as a means to reduce wear.

Friction

Friction is defined as the resistance to movement during sliding or rolling that a solid body experiences when moving over another with which it is in contact. This resistance to movement depends on the characteristics of the surfaces. One theory explains the resistance by the interaction between contact points and the penetration of the asperities. The friction depends on

• (i) The molecular interaction (adhesion) of the surfaces
• (ii) Mechanical interaction between the parties.

The force of resistance that acts in a direction opposite to the direction of motion is known as the force of friction. There are two main types of friction: static friction and dynamic friction. Friction is not a property of the material, it is an integral response of the system.

There are three laws of friction:

1. The friction force is proportional to the normal load.
2. The friction force is independent of the apparent contact area between the sliding surfaces.
3. The friction force is independent at the sliding speed.

Wear

Wear is surface damage by removal of material from one or both solid surfaces in relative motion. It is a process in which the superficial layers of a solid are broken or detached from the surface. Like friction, wear is not just a property of the material, it is an integral response of the system. System analysis has shown that 75% of mechanical failures are due to wear on rubbing surfaces. It is easily deduced that to increase the useful life of a piece of equipment, wear must be reduced to the minimum possible.

• You wear out from fatigue: it arises from concentration of tensions greater than the material can endure. Includes dislocations, cavity formation and cracks.
• Abrasive waste: is the damage by the action of solid particles present in the area of friction.
• It is worn by erosion: it is produced by a current of abrasive particles, very common in gas turbines, exhaust pipes and engines.
• Disposed by corrosion: originated by the influence of the environment, mainly moisture, followed by the removal by abrasion, fatigue or erosion, of the formed compound layer. To this group is corrosion wear, caused mainly by the action of atmospheric oxygen (dioxygen) or dissolved in the lubricant, on the surfaces in motion.
• Degaste by frost: here the four forms of wear are combined; in this case the moving bodies have movements of oscillation of a width less than 100 μm. It is usually given in assembled systems.
• Discharged by slip: also known as wear by adhesion, is the process by which material is transferred from one to another surface during its relative movement as a result of cold welding due to the large pressures existing between roughnesses; in some cases part of the untapped material returns to its original surface or is released in the form of chips or rebates. There are tests of this type in which a bolt machine or disc dial is used.
• Get lost. Fretting: it is the wear produced by the vibrations induced by a fluid at its pace by a conduction.
• Disadvantage of impact: are the deformations produced by blows and that produce an erosion in the material.

Lubrication

Curva de Stribeck.

Sliding between solid surfaces is generally characterized by a high coefficient of friction and high wear due to the specific properties of the surfaces. Lubrication consists of the introduction of an intermediate layer of a foreign material between the moving surfaces. These intermediate materials are called lubricants and their function is to reduce friction and wear. The term lubricant is very general, and can be in any material state: liquid, solid, gaseous, and even semi-solid or pasty.