ABSTRACT
The friction force generated when two bodies rub against each other can be drastically decreased, and the subsequent wear almost entirely eliminated, if a lubricant is interposed between the surfaces in contact. Lubricants are generally considered to be oils, particularly petroleum oils because we have so much experience with them. However, almost any material can be a lubricant. As da Vinci observed 400 years ago, “All things and anything whatsoever, however thin it be, which is interposed in the middle between objects that rub together lighten the difficulty of this friction.” Nevertheless, in this chapter lubrication with fluids, in particular incompressible fluids, is the only type of lubrication that will be discussed.
