ppt -friction wear lubrication and many releated to the tribology.pptx

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1. FRICTION- ORIGIN The concept of friction has been observed and understood intuitively by humans for thousands of years, long before it was formally studied and named. However, the formal study of friction as a scientific phenomenon began during the Scientific Revolution in the 17th century . One of the earliest recorded investigations into the nature of friction was conducted by Leonardo da Vinci (1452–1519 ), the Italian polymath, who studied the effects of friction on various surfaces and objects . He made numerous observations and sketches detailing the behavior of friction, though his work remained largely unpublished during his lifetime . In the 17th century, Galileo Galilei (1564–1642), the Italian physicist, and mathematician, made significant contributions to the understanding of friction. He formulated the principle of inertia , which states that an object will remain at rest or continue in uniform motion unless acted upon by an external force. Galileo also recognized that friction is influenced by the nature of the surfaces in contact and the normal force pressing them together.

2. The English physicist Sir Isaac Newton (1642–1727) furthered the study of friction in his famous work "Mathematical Principles of Natural Philosophy" (1687)- commonly known as the Principia. He described friction as a force that opposes the relative motion of two surfaces in contact. Newton formulated empirical laws of friction, which laid the foundation for modern friction theories. Since then , scientists and engineers have continued to study friction, leading to a deeper understanding of its underlying mechanisms and practical applications in various fields, including physics, engineering, materials science, and tribology (the study of friction, wear, and lubrication). The understanding of friction as a force that opposes motion gradually developed over time, with contributions from various scientists and scholars . Today , friction is a fundamental concept in understanding the behavior of objects in motion and plays a crucial role in the design and operation of machinery and everyday objects.

3. The term "friction" itself is derived from the Latin word "frictio," which means " to rub ."

4. FRICTION THEORIES Friction is a force that resists the relative motion or tendency of motion between two surfaces in contact. Over the years, several theories have been proposed to explain the nature and behavior of friction. Classical Theory of Friction This theory was developed by Leonardo da Vinci and further elaborated by Charles- Augustin de Coulomb in the 18th century. It states that friction arises due to irregularities or asperities on the surfaces of materials coming into contact. The resistance to motion is proportional to the force pressing the surfaces together.

5. Amontons' Laws: Guillaume Amontons formulated two empirical laws related to friction : The force of friction is directly proportional to the applied load. The force of friction is independent of the apparent area of contact. Coulomb's Law of Friction: Named after Charles-Augustin de Coulomb, this law states that the force of friction between two surfaces is directly proportional to the normal force pressing the surfaces together and is independent of the area of contact. It can be expressed as Ff ​= μN where Ff ​ is the force of friction, μ is the coefficient of friction, and N is the normal force .

6. Tribological Theory This theory is based on the understanding of the complex interactions between surfaces at the micro and nanoscale, taking into account factors such as adhesion, surface roughness, lubrication, and wear. Elastohydrodynamic Lubrication (EHL ) This theory deals with the behavior of lubricated surfaces under high pressure and shear conditions. It considers the deformation of the contacting surfaces and the formation of a lubricant film between them. Boundary Lubrication This theory focuses on the lubrication regime where the contacting surfaces are not completely separated by a lubricant film, and friction occurs due to direct contact between surface asperities . Various mechanisms, such as adsorption of lubricant molecules and surface-active additives , contribute to reducing friction and wear.

7. Mixed Lubrication : In many practical scenarios, lubrication conditions lie between boundary and hydrodynamic lubrication. Mixed lubrication theory addresses these situations, considering both direct contact between asperities and the presence of a thin lubricant film.