ABSTRACT
The hydrodynamic theory of lubrication, as launched by Osborne Reynolds in 1886 and subsequently expanded upon by a succession of analysts, provides a fairly solid foundation for a description of a wide variety of tribological devices and processes. Evidence has accumulated that the foregoing postulates can be violated and yet a bearing or seal can survive and continue operating in a manner no worse than with an optimum design. These contradictions occur in the area of parallel surface bearings; in flat face seals; in centrally pivoted pads; in boundary lubrication where, over large portions, there is contact between the surfaces; and in a number of other tribological processes. This chapter provides phenomenological evidence of these departures from basic theory. Another family of phenomenological observations will later be shown as being related to those present in parallel surface operation. This refers to what is, in the literature, often called “third body” or wear debris lubrication.
