Method for Manufacturing Improved Fatigue Life Structures, and Structures Made Via the Method

Author:  Eric T. Easterbrook and Nils Juhlin
Source:  US Patent 7,131,310
Doc ID:  2006053
Year of Publication:  2006
Abstract:  
A method for cold working metal structures. A compound indenter is used to produce deformation in a workpiece to provide a selected beneficial residual stress profile, to provide improved fatigue life structures with minimal manufacturing steps. A compound indenter deforms a workpiece, resulting in dimples therein. A relatively uniform beneficial residual stress profile is provided at the surface and at the midplane of apertures in a workpiece, so as to improve overall fatigue life. A compound indenter tool having a first, elongate indenter with a shaped indenter surface portion, and a second shaped indenter surrounding the first indenter and forming an annular shoulder recessed from the surface portion of the first indenter, is used. Optionally, a foot having a bottom portion is used to confiningly surround an indenter during application of deforming force to the surface of a workpiece, to prevent deformation of adjacent workpiece surface