A study on the combined effect of notch and fretting on the fatigue life behaviour of Al 7075-T6

Abstract

In this study, an investigation was conducted on the fatigue performance of Al 7075-T6 plates in the presence of stress raisers (notch, fretting, and a combination of notch and fretting). Fretting situation was induced on the surface of the aluminium plate through steel contacting pads under two different clamping forces of 2kN and 5.6kN. The fatigue tests revealed a more dominant effect from stress concentrators originating from geometrical discontinuities such as the tested notch compared to the fretting wear conditions. Therefore, no noticeable differences were found between the fatigue lives of the notched specimens and the combined notch and fretting condition. A finite element stress analyses of the notched model under the contacting fretting pads agreed with the experimental results. The stress distribution at the clamped area introduced tensile stresses at the edge of the contact region, however, the stress at the notch tip was observed to be higher when an axial tensile load was applied to the end of the plate. Fractographic analyses confirmed the presence of cracks initiating from the fretting damaged surface for most of the combined notch and fretting fatigue test specimens particularly at the high cycle fatigue (HCF) zone.