Friction and Lubrication
Webster defines friction as the ?rubbing of one body against another, resistance to relative motion between two bodies in contact.? Overcoming this resistance requires additional energy. Contact between the two moving surfaces generates heat and usually results in surface wear.
A simple example of friction is the heat generated when one rapidly rubs one?s hands together. Note that the faster and harder you rub, the more rapid and greater the heat that is generated.
Friction as a force of nature can be both beneficial and detrimental to our lives.
Friction can be beneficial in several ways. As we overcome this resistance to motion between two objects in contact, heat is generated.
This heat is what warms our hands or starts a fire. It is the principle behind the braking systems we find on our automobiles. Without friction, the simple task of walking would not be possible.
However, friction can also be our enemy. The heat generated as a result of friction can cause damage. Because contact is required to generate friction, wear in the areas of contact can occur.
This can also lead to damage and a significant reduction in the expected life of the two bodies in contact.
Friction and lubrication. The reduction of friction is the primary goal behind the purpose for lubrication. Though there are many ways to reduce friction, the most common method is through the use of a fluid or semi-fluid material.
When placed between two components in contact, these fluid materials will attempt to maintain a layer of separation. This occurs because such fluid materials are not readily compressible.
Though the separation may be only a few millionths of an inch, it is sufficient to not only minimize contact, but in many cases, eliminated it altogether.
The inherent ability of a oil to maintain an uninterrupted film and hence component separation is referred to as lubricity. Lubricity, sometimes referred to as film strength, varies dramatically from one fluid to another. Another way to minimize friction and wear is through the use of special chemical compounds. The main role of these compounds is to offer protection when the lubricating fluid cannot maintain component separation.
They may also be required to address areas of concern beyond the capabilities of the fluid itself. Examples of such areas are detergency, dispersantcy, corrosion control and acid neutralization. Chemical compounds placed in the lubricating fluid are generally referred to as additives.
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