Study of Fatigue Damage in Shot Peened Aluminium Alloys using Acoustic Emmission and Macro/Microscopic X-Ray Diffraction Inve

Author:  Bonnafe, Maeder, Bathias, Compiegne
Source:  Conf Proc: ICSP-3, (p.485-498)
Doc ID:  1987092
Year of Publication:  1987
Abstract:  
Aeronautic industry needs to use materials which combine lightness and high mechanical characteristics, under static solicitations as well as under dynamic ones. In this last case, the study of fatigue behaviour of the material becomes very important. High strength aluminium alloys such as 2024 and 7054 are a good choice and for that are usually used in such cases. Moreover, these alloys are often shot peened to improve their fatigue strength. The recording of acoustic emission allows to detect the three stages of damage growth: plastic deformation of the surface, microcracks formation and macrocracking. The experiment pointed to the conclusion that the damage leading to crack initiation occurs in the following manner: cyclic cold working of the surface together with a rapid evolution of residual stresses, stabilisation of these stresses and a plastic deformation of the surface layers, appearance of the first microcracks without any change in the residual stresses and then, the ascendency of one or two macrocracks together with complete relaxation of the macrostresses in the close neighbourhood of this macrocrack.