Abstract
The severe shot peening process was applied to the notched specimens from an AW 7075 alloy with the aim to improve fatigue endurance in the very-high cycle fatigue region. To reveal the stress state in the notch vicinity, finite element analysis was performed, simulating the conditions of the used 20 kHz ultrasonic fatigue loading. Modified surface characteristics by the severe shot peening process were analyzed in terms of residual stress distribution measured by X-ray diffraction methods and near-surface microstructural observations by scanning electron microscopy. The applied severe shot peening increased the fatigue limit by 11%; however, the positive effect was recorded only for the loading amplitudes corresponding to the fatigue lifetimes in the range 107–109 cycles. At higher loading amplitudes, the fatigue properties tended to decrease, most likely due to accelerated fatigue crack initiation on the surface damage features created by the peening process and also by rapid residual stress relaxation.
Highlights
High strength aluminum alloys based on the Al-Zn system are one of the most widely spread materials for the high strength application in the aircraft industry, combining high strength-related properties with sufficient toughness and corrosion resistance
Kt = 1 + 2 r where t is the depth of the notch, and r is the radius in the notch root
From the results,the thelow lowinclination inclinationcharacter characterofofthe thefatigue fatiguecurves curvesisisclearly clearlyseen, seen,asasininthe thecase caseof ofthe thenot not results, 6 and 109 of loading cycles is less than peened specimens, the difference in the fatigue strengths for peened specimens, the difference in the fatigue strengths for 10 and 10 of loading cycles is less than
Summary
High strength aluminum alloys based on the Al-Zn system are one of the most widely spread materials for the high strength application in the aircraft industry, combining high strength-related properties with sufficient toughness and corrosion resistance. Numerous methods of strengthening of the surface and subsurface layers were introduced to improve fatigue properties, especially in the high cycle fatigue area [3,4,5,6]. One of the most widely used methods is shot peening, where the treated surface is impacted by shots with high kinetic energy, resulting in the deformation of the surface layer. The positive effect of the shot peening on the fatigue properties has been proved in numerous studies [3,7,8,9,10,11] for various materials. In the shot peening process, several factors are contributing to the final surface properties, which influence the final fatigue life of the treated material [12].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
