ABSTRACT
Early research was focused on bearings that operate under steady conditions, such
as constant load and velocity. Since the traditional objectives of tribology were
prevention of wear and minimizing friction-energy losses in steady-speed
machinery, it is understandable that only a limited amount of research effort
was directed to time-variable velocity. However, steady friction is only one aspect
in a wider discipline of friction under time-variable conditions. Variable friction
under unsteady conditions is referred to as dynamic friction. There are many
applications involving dynamic friction, such as friction between the piston and
sleeve in engines where the sliding speed and load periodically vary with time.
