Peter B. Senholzi Manager, Applications Engineering Mechanical Technology Incorporated In most discussions concerning tribology, authors felt compelled to introduce the topic by first defining the term. In this discussion, however, the term will not be defined until after the circumstances that spawned its existence have been summarized. This discussion will revolve around two facets of mechanical system design, that of structural integrity and wear integrity. In the not too distant past, the evolutionary process of machine design had in most cases attained a stage of development where the structural integrity of a system was ensured. Simply stated, this means that the machine components would not "break. " However, at this development phase, little emphasis was placed on component wear integrity. This meant that although machinery components would not break, they would be subject to high wear/wear-out rates. Frequent component replacements were used in order to compensate for this situation. A "throw away" philosophy was thus adopted. This philosophy, however, resulted in many undesirable secondary effects. Mechanical systems were characterized by expensive logistics, costly maintenance, limited availability, limited lives, and substantial energy consumption. This energy consumption resulted from primary effects of high equipment frictional levels {causing the high wear rate) and such secondary effects as spare parts production and transportation. As a result of these factors, the "throw-away" philosophy was a very vulnerable luxury. During the last fifteen or so years, environmental factors with respect to mechanical system operation have changed 2 drastically.