AN EVALUATION OF THE EFFECT OF SHOT PEENING ON THE FATIGUE CRACK GROWTH IN ALUMINUM ALLOY 2024 - T3
Douglas Henrique da Silva Costa1; Marcelo Augusto Santos Torres2; Carlos Antonio Reis Pereira Baptista3
1 IAE/DCTA - Institute of Aeronautics and Space, Aeronautical Systems Division, São Paulo, Brazil; 2 FEG/UNESP - College of Engineering Campus Guaratinguetá, Departament Mechanical, São Paulo, Brazil; 3 EEL/USP - School of Engineering of Lorena, Departament Materials, São Paulo, Brazil
doi:10.20906/CPS/COB-2015-1461
Resumo
The shot peening is a process that induces compressive residual stresses on the surface of a component and may improve the fatigue strength. However, studies of its effect on a pre-existent crack are scarce. This paper studies the effect of the shot peening process in the propagation rate of a fatigue crack in the high strength aluminum alloy 2024-T3. Compact Tension (CT) specimens were initially cracked by fatigue with two crack sizes and then shot peened on both sides behind the crack tip. After peening, the tests were resumed under the same conditions. Tests were carried out under constant amplitude at two load ratios. The results showed that, for stage II cracks, the shot peening process has greater influence on the growth rate at the lower load ratio. For cracks approaching stage I of propagation, the shot peening process induced a delay in their growth for all studied conditions. The retardation on fatigue crack propagation occurred only when the plastic deformation and compressive residual stresses induced on the surface by the shot peening process was able to affect the crack closure and therefore the effective stress intensity factor, ΔKeff.
Palavras-chave: Shot peening; fatigue crack propagation; 2024 - T3 aluminum alloy