Rotopeening Method

Author:  Harman et al.
Source:  US Patent 4,616,497
Doc ID:  1985097
Year of Publication:  1985
Abstract:  
A method of uniformly rotopeening the inside walls of metallic tubes to a desired final peening intensity by means ob at least one rotatable peening flapper is disclosed herein. The method generally comprises the step of simultaneously rotating and orbiting the flapper within the tube while maintaining a selected stand-off distance between the inner edge of the flapper and the inside wall of the tube, The angular speed of the flapper and the stand-off distance are selected so that the slope of the curve defined by peening intensity over time is substantially flat in the vicinity of the disired final peening intensity. The method is particularly useful in uniformly and accurately peening the inside walls of the heat exchange tubes anchored in the tubesheet of a nuclear steam generator in order to relieve tensile stresses in the walls of these tubes which might otehrwise lead to stress corrosion cracking in the tube walls.