Effects of Shot-Peening and Stress Ratio on the Fatigue Crack Propagation of AL 7475-T7351 Specimens

Abstract

Featured Application: 7475-T7351 aluminum alloy are widely used for structural components in aerospace applications. Abstract: Shot peening is an attractive technique for fatigue enhanced performance of metallic components, because it increases fatigue crack initiation life prevention and retards early crack growth. Engineering design based on fatigue crack propagation predictions applying the principles of fracture mechanics is commonly used in aluminum structures for aerospace engineering. The main purpose of present work was to analyze the effect of shot peening on the fatigue crack propagation of the 7475 aluminum alloy, under both constant amplitude loading and periodical overload blocks. The tests were performed on 4 and 8 mm thickness specimens with stress ratios of 0.05 and 0.4. The analysis of the shot-peened surface showed a small increase of the micro-hardness values due to the plastic deformations imposed by shot peening. The surface peening beneficial effect on fatigue crack growth is very limited; its main effect is more noticeable near the threshold. The specimen's thickness only has marginal influence on the crack propagation, in opposite to the stress ratio. Periodic overload blocks of 300 cycles promotes a reduction of the fatigue crack growth rate for both intervals of 7500 and 15,000 cycles.

Subsurface fatigue crack tip strains in 7475‐T7351 aluminium alloy measured using stroboscopic neutron diffraction

“…Mean FCGRs measured from six specimens are plotted in Figure 8 with comparison to data from previous studies 42–47 . Although these data represent a range of different stress ratios, loading frequencies, specimen thicknesses, and orientations, the results agree well.…”

Surface, Subsurface and Tribological Properties of Ti6Al4V Alloy Shot Peened under Different Parameters

“…It is an effective surface treatment that improves the service life of components subjected to general fatigue as well as fretting fatigue by preventing crack initiation and propagation through improving the mechanical and physical properties [ 31 , 34 ]. Thus, the effects of shot peening in plain fatigue behavior have been previously investigated in detail [ 23 , 32 , 40 , 41 , 42 , 43 , 44 , 45 ]. By contrast, the modification of surface and subsurface properties such as surface roughness, morphology, topography, hardness, and the tribological behavior of shot peened materials has not yet been fully clarified [ 19 , 46 , 47 , 48 ].…”

Special Issue on “Mechanical Behaviour of Aluminium Alloys”

“…Ferreira et al [8] considered the effect of shot-peening and the stress ratio on fatigue crack propagation in aeronautical components made by the 7475-T7351 aluminum alloy, and Olvera et al [9] analysed the stability of peripheral milling in thin-walled parts made of 7075-T6 aluminium alloys based on an enhanced multistage homotopy perturbation method.…”