Peak contact pressure, cyclic stress amplitudes, contact semi-width and slip amplitude: relative effects on fretting fatigue life

Using Hertzian relationships and a finite element model of a cylinder-on-flat contact configuration, a set of critical fretting fatigue experiments have been conducted to determine the relative effects of six local mechanistic parameters on fretting fatigue life. The six parameters evaluated are: (i) the peak contact pressure, p0; (ii) the maximum local cyclic bulk stress range, ΔσL,max; (iii) the maximum, local cyclic shear stress, τL,max; (iv) the maximum, local cyclic shear stress range, ΔτL,max; (v) the maximum slip amplitude, δmax; and (vi) the contact semi-width, a. The findings are significant. Only the peak contact pressure and the local, maximum bulk stress range have direct effects on fretting fatigue life. The fretting fatigue life is found to have a previously unknown positive, exponential dependence on the peak contact pressure, which enables an elegant recovery of a standard (‘plain’) fatigue life equation. Additionally, interfacial shear tractions appear to have no effect on the life. Although some of the remaining four parameters can be correlated to fretting fatigue life, it is likely through their relationships to either the peak contact pressure or the local, maximum bulk stress range. These inter-relationships have been outlined for a cylinder-on-flat geometry and a general, physically based fretting fatigue life equation has been developed.