MECHANICS AND MATERIALS IN FRETTING

Materials fail through overstressing and overstraining. Overstressing leads to crack initiation and later propagation which can cause failure. Overstraining leads to material transformation, for instance strain hardening, followed by changes in material properties such as toughness loss. This paper presents an overview of the work done in the last ten years on fretting, and illustrates these types of failure with respect to this particular form of damage. It divides the factors that govern overstressing and overstraining into three groups: the imposed conditions, the material properties and limits, and the material response. It places types of damage relative to each other on fretting maps. A flow chart starting from the imposed conditions and ending with failure, and showing all possible alternatives, is drawn. The chart is then discussed in the light of fretting wear and fretting fatigue tests. It is shown that it is common during one test to cover both overstressing and overstraining conditions which complicates the interpretation of data. Static fretting fatigue which avoids that complication is therefore recommended.