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There has been a flurry of actlvity lately to revlse the specifications that control the processlnq of parts subject to fatigue and corrosion fatigue failures. Our aginq Commercial, Mllitary and Civll airplane fleets, coupled wlth the costs of replacement, have caused great pressures to extend component operating life. Stress cycling of both englne and airframe hardware often is sufficient to cause fatigue damage. Shot peening has been proven to increase the ability of these parts to withstand significant increases in stress cycling. Other factors (corrosion, fretting and foreign object damage, to name a few) cause stress concentrations which are often initiation points for fatigue damage. Shot peening is used to encapsulate those stress concentrations in layers of residual compression thereby offsetting the conditions for fatigue damage.

Search peening can be defined as the use of controlled shot peening as a tool to expose subsurface corrosion. The stretching of the surface coupled with the compressive stress induced by the multiple impacts of the shot help to delaminate hidden layers, as is found in exfoliation corrosion. Recently, Boeing Airplane Company's Defense and Space Group, in association with the United States Air Force, funded a study to determine the application of using shot peening to identify exfoliation corrosion. Metal Improvement Company and British Airways have also developed a method to determine the extent of corrosion so that the removal of damage can be accomplished with a high degree of accuracy. This certifiable controlled process, “search peening,” allows a minimal amount of metal removal, so that engineers have the maximum acceptable material to work with, enabling them to keep tolerances within safe limits.