Issue 37

J. Vázquez et alii, Frattura ed Integrità Strutturale, 37 (2016) 38-45; DOI: 10.3221/IGF-ESIS.37.06 39 E XPERIMENTAL RESULTS he fretting fatigue tests analysed are better described elsewhere [[18]]. The material is Al 7075-T651. The setup is shown in Fig. 1. The rectangular cross section of the specimens were 7x10 mm, where the contact is produced at the 7 mm side. The specimens were photographed after failure with the optical microscope, SEM and confocal microscope with the objective of finding the crack initiation points and study the crack at the early stage. In a fretting fatigue test of this type, forces are applied on both sides of the specimen, therefore, there are two contact zones (one of them shown in Fig. 1). But final failure is due mainly to only one of them because usually cracks do not initiate exactly at the same time on both sides. Nevertheless, since the stress concentration in fretting is high, the initiation is fast and after fracture small cracks are always found growing from the other contact zone. These cracks are the ones analysed here. This paper shows the results obtained on a specimen with the following loads: N = 5800 N, Q = 850 N and σ = 50 MPa. The number of cycles to failure was 676704. Figure 1 : Experimental setup in the fretting fatigue tests. Figure 2 : Fretting scar and the fracture surface. T 7 mm