Production and Repair of Fastened Joints Incorporating Cold Expansion

Fastened joints are an integral part of aircraft design. Due to their complexity and function, they are also the primary source of structural fatigue problems. The incorporation of residual compressive stresses around a fastener hole greatly enhances the fatigue resistance and integrity of a fastened joint. This paper describes the split-sleeve cold expansion method to create residual compressive stresses which extend the fatigue life of holes in both new structure and field repairs. Data from test programs highlight process benefits and crack retardation effects for various specimen configurations. Other process features such as cold expansion to size are explained, along with the status of process automation.