methods and or processes which may include installing structural assemblies into the opening of a structural workpiece have also not necessarily been shown or described in detail to avoid unnecessarily obscuring descriptions of the embodiments of the invention it is appreciated and understood that the process of installing structural assemblies into the opening of the structural workpiece may or may not result in the creation of an annular zone of residual compressive stresses in the structural workpiece and or other associated structure in the following description and for purposes of brevity reference may be made to cold expansion or radial expansion of various components this reference is not intended to limit or otherwise narrow the scope of the disclosure the process of radial expansion is to be broadly interpreted as any process that radially expands at least some of the material of a component either directly or indirectly e g radially expanding a washer into another member the radial expansion may be done for a number of purposes or combination of purposes such as retarding the initiation and growth of a fatigue crack achieving a fatigue benefit in the structural workpiece mechanically capturing a component retaining a component against the structural workpiece or some combination thereof it is further understood that radially expanding one component in the structural workpiece may or may not induce beneficial compressive residual stresses and may or may not produce fatigue enhancing benefits in other outlying or nested components unless the context requires otherwise throughout the specification and claims which follow the word u201c comprise u201d and variations thereof such as u201c comprises u201d and u201c comprising.