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Many aerospace components undergo a finishing process during their manufacture. Such finishing processes include chromium, nickel, zinc and cadmium plating on steels; anodize on aluminum alloys; and various coatings on titanium and nickel base alloys. Certain of these finishing processes result in loss of fatigue strength of the part in question. Loss of fatigue strength caused by chromium and nickel plating amounting to 60% has been measured. Shot peening is frequently used on fatigue critical parts to regain fatigue properties which may have been lost due to a particular finishing operation. Shot peening is a process which bombards the surface of a part with small spherical balls. The cold working effect of the peening balls leaves the surface of the part in a state of residual compressive stress. The beneficial compressive stresses induced by shot peening are effective in increasing fatigue properties of the component.

Advances in chemistry and parts design have extended the useful life of many engine, structural and landing gear components. Sufficient data has been collected and sunmarized to estimate length of service periods between inspection and overhaul, and even the number of times that components can be reconditioned and reused. Shot-peening has become an important element in obtaining improvements in fatigue life and as a preparatory process for many coatings. The purpose of this paper is to discuss typical applications of shot-peening used in the overhaul process. we will also identify process controls necessary to retain or restore the shot-peening benefit designed into parts by the original manufacturer.