Fundamental Mechanical Aspects of Boundary Lubrication 400129
FROM the physico-chemical side, boundary lubrication already has been investigated fairly thoroughly. However, it is a great handicap in the intelligent selection of lubricants and materials that the physico-chemical results cannot be exploited to the full without knowing the fundamental mechanical aspects; therefore, data on this missing link are discussed first.
Starting from the thesis that pressure and temperature in the region of contact between the rubbing surfaces are the basic mechanical factors, it is shown that four main types of boundary lubrication should be distinguished:
Low-Pressure and Temperature Boundary Lubrication, briefly, Mild Boundary Lubrication.
High-Temperature Boundary Lubrication.
High-Pressure Boundary Lubrication.
High-Pressure and Temperature Boundary Lubrication, briefly, Extreme Boundary Lubrication.
Up to now Type 4 has been called “Extreme Pressure Lubrication” but, logically, the term now proposed should be adopted, as in this region of boundary lubrication it is more the extreme temperatures (for example, temperature flashes on gear teeth), than the extreme pressures that are decisive. Moreover, confusion with the High-Pressure Boundary Lubrication (Type 3) then can be avoided.
Phenomena, characteristic for each of the four main types of boundary lubrication are discussed.
Frictional (that is, tangential) vibrations of rubbing surfaces are referred to in the Appendix.