Abstract: A manufacturing facility for manufacturing a fatigue life enhanced product from a plurality of workpiece parts. At least one fatigue enhancing operation is performed on a first workpiece at a first work station. At least one fatigue enhancing operation is performed on a second workpiece at a second work station. The first and second workpieces are transferred to a first assembly station, where the workpieces are joined to form a fatigue life enhanced product. Aerostructures manufactured according to the method may include components fabricated at different locations to have fatigue life enhancing properties, especially in bounding material adjacent to holes designed to accommodate fasteners. By use of this business method, the final assembly step can thus avoid the necessity to include the processing of holes to enhance fatigue life, since this step has been performed prior to bringing components into position to be joined in the final shape or assembly of the airframe.

Abstract: A method for cold working spot welded structures to improve fatigue life, and structures made by the method. Partially finished structures are provided assembled and joined by a spot weld nugget. Opposing indenters, or an indenter and a backing anvil, are used to squeeze the spot weld nugget to form one or two cold working dimples, respectively. Residual compressive stress is imparted in the workpiece, resulting in increased fatigue life.

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.