RUNNING-IN - ART OR ENGINEERING

Running-in is an initial surface and subsurface conditioning process that often occurs when sliding or rolling contact is established between two solid bodies. This article first addresses and defines the nature of running-in as it relates to steady-state sliding conditions. Running in procedures are not always given the type of systematic analysis that goes into other forms of friction and wear testing, but are often developed by trial and error. Studies of running-in are relatively rare in the literature of tribology, and they often appear with only passing mention. The concept of a running-in (break-in) map is explored. Examples of the analysis of friction traces show how they can be used systematically to study the running-in process. Running-in is found to be a property not only of the materials in contact, but also of the system in which they reside.