Stresswave, Inc.

Nils Juhlin

Eric T Easterbrook

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.

Method for manufacturing improved fatigue life structures, and structures made via the method

A compound indenter for metal coldwork, and a method of employing such tooling. The compound indenter tool is used to produce deformation in a workpiece structure, to provide a selected beneficial residual stress profile in the workpiece, in order to provide high fatigue life structures in a minimum number of manufacturing steps. Preferably, action of a compound indenter causes deformation of the workpiece, causing dimples in the workpiece. By optimized use of the method, a relatively uniform beneficial residual stress profile is provided at both the surface and at the midplane apertures in a workpiece, so as to improve overall fatigue life. An improved, compound indenter tool profile shape is described, 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. Additionally, a foot having a bottom portion can be used to confiningly surround the second indenter during application of force to the surface of a workpiece, to prevent surface deformation.

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Bothell, WA, United States of America

Nils Juhlin