A stress gradient approach for fretting fatigue assessment of metallic structural components

In the present paper, the fretting fatigue life assessment of metallic structural components under cylindricalcontacts is performed by applying a critical plane-based multiaxial fatigue criterion. Such a criterionis formulated by using the so-called critical point method: a material point located at a certaindistance from the hot-spot on the contact surface is assumed to be the critical point where to performthe above assessment. The above distance, function of the material properties, is measured along threealternative paths (a normal path, an inclined path and a principal stress oriented path) and, using suchthree different paths to determine the critical point location, the effectiveness of the criterion is evaluatedby means of experimental data related to aluminium alloy specimens under cylindrical contacts. Further,in order to improve the accuracy of the critical plane-based criterion in terms of fretting fatigue lifetimeevaluation, a new approach involving a critical distance also function of the stress gradient in the contactzone is proposed and experimentally validated.