Fatigue damage in copper polycrystals subjected to ultrahigh-cycle fatigue below the PSB threshold

Mechanical Properties of Copper Processed by Severe Plastic Deformation

“…32 can be considered to be nuclei of stage I cracks. Similar stage I cracks were observed by Weidner et al (2010) in CG copper (grain size 60 microns) subjected to ultrasonic cycling not only in the surface grains, but also in the bulk grains. Similarity of both observations indicates that the mechanism of crack initiation in CG and UFG Cu in gigacycle region might be very similar.…”

Development of Cyclic Slip Bands in Ufg Copper in Gigacycle Fatigue

“…Dislocation activity in near-by oriented grains leads to a slip of these highly localized regions and subsequently to the generation of surface relief and formation of cavities under the slip markings, which are sites of fatigue crack initiation. It is interesting that similar mechanism was described in CG copper in work [20], where the family of roughly parallel cracks under PSB surface markings was also observed and they were considered to be stage I shear cracks.…”

“…By contrast, fatigue properties in gigacycle region (alternatively called ultrahigh-cycle or very high cycle region) have been studied to substantially lesser extent, though fatigue failure of engineering components may appear after a number of cycles of 10 10 or even higher [15]. Recent studies [16][17][18][19][20] concerning gigacycle fatigue behaviour of CG metals and alloys distinguish two kinds of materials. The first one, called Type I, includes pure fcc materials like copper.…”

Mechanisms of strain localization, crack initiation and fracture of polycrystalline copper in the VHCF regime

“…7.5x10 -5 and 8.7x10 -4 ) >9@. After this, the tests were conducted with the same ramp loading procedure at several specified total strain amplitudes 'H tot /2 partly up to 1.7x10 11 cycles. In order to remove the damping heat, the specimens were cooled with compressed air, and pulse-pause sequences were performed.…”

“…For the VHCF failures in high-strength steels inclusions have been identified as internal crack initiation sites [1][2][3], whereas PSB intensification, leading to intrusions and micro-cracks are regarded as surface fatigue crack initiation places in single-phase ductile materials [4][5][6]. Their role for crack initiation in the VHCF regime has been discussed by Mughrabi [4], and since a few years [7] extensive investigations on the formation, extension and intensification of slip bands have been performed with the ultrasonic fatigue technique up to ~2x10 11 cycles in order to study the role of PSBs for fatigue failure. Different testing techniques were applied to study the development of slip bands into persistent slip bands.…”