Report On Shot Peening Coverage

Author:  Miller and Flyn
Source:  Buick Motor Div. GM, September, 1952
Doc ID:  1952004
Year of Publication:  1952
Abstract:  
The desired effect of a shot peening operation is primarily to increase the fatigue life of a part. The percentage increase in life due to peening is determined by comparing either the service life or test endurance life of a peened part to that of an unpeened part. As a rule, the need for peening is recognized in the designing or early testing stages. For some parts such as springs, peening has long been considered a requirement. Occasionally where new designs are involved, the need for peening becomes evident only after service failures have been encountered. Experimental shot peening is generally carried out in laboratory equipment or in suitable production machines under closely controlled conditions. When the peening operation is carried out in production, the process is controlled by inspecting for intensity and coverage. Intensity measurement can be accomplished satisfactorily with the Almen test strip. Coverage, on the other hand, is largely a matter of judgment on the part of the inspector. Laboratory methods have been developed for measuring coverage, but until now there is no standard method for its evaluation in the shop. The purpose of this paper is to review the subject of coverage and to evaluate some proposed methods for its measurement and control.