Effects Of Shot Peening On Fatigue-damaged High Strength Aluminum Alloy-appl.of Rejuvenation On Fatigue-damaged Components

Author:  Oshida, Yoshiki and Daly, James
Source:  Conf Proc: ICSP-4, (p.317-326)
Doc ID:  1990030
Year of Publication:  1990
Abstract:  
It is well established that the shot peening can prolong the fatigue lives and enhance the fatigue strengths as well. Many components and equipment operating currently were not shot peened at their initial installation. If the x-ray fatigue damage assessment method (previously reported by Y.O.) is applied to such components, one can estimate extent they are fatigue damaged. Extending the remaining fatigue lives of these existing components will be one of the most interesting demands among industry engineers. Therefore, it is the objective of the present study (i) to find effects of shot peening on fatigue damaged high strength aluminum alloy for rejuvenating fatigue-damaged materials, and (ii) to study the rejuvenating mechanisms by x-ray diffraction parameters including dislocation densities through the diffraction line analyses and residual stress development. Rejuvenating factor, newly proposed in this study, can be defined as N(sp)(f)/N(up)(f) where N(sp)(f) is the number of cycles-to-failure of shot-peened pre-fatigued condition and N(up)(f) is N(f) of un-peened non-damaged condition of the material. It was found that the remaining fatigue life can be prolonged to N(sp)(f) [N(f) of shot-peened but un-fatigued condition] if 50% or less of the N(up)(f) has been consumed during the previous fatigue stressing of un-peened condition. Descriptors: A1 7050-T7651, Pre-fatigue stressing; Four-point reversed bending fatigue test, Shot-peening; Rejuvenating factor; Residual stress; Surface and interior dislocation densities; Dislocation density ratio