Slip index: a new unified approach to fretting

A new similarity criterion, termed slip index, is introduced. This slip index replaces conventional fretting maps in determining the different fretting regimes as well as the transition from fretting to reciprocal sliding. The slip index is derived from a dimensional analysis of the parameters that govern sliding conditions and provides a unified approach to fretting that is valid for any particular system. The validity of this approach is verified by comparison of fretting data from different test rigs and on different scales. A more accurate definition of fretting is offered based on the present approach.