Cold Expansion of Elongated Hole: A Realistic Finite Element Simulation

Abstract

Elongated holes are found in many aerospace structural components and are prone to fatigue failure due to the stress concentration effect at the edge of the hole. Different approaches like shape reworking, shape optimization, and cold expansion combined with interference fitting are currently used as a repair/life extension option, to overcome fatigue cracking problems around elongated holes. In practice, these approaches lead to either addition of material or modification of geometry. A novel and economical method derived from renowned hole cold expansion process is proposed in the literature to enhance the fatigue life of elongated hole without adding material and modifying hole geometries. Benefit of implementing proposed novel cold expansion method for elongated hole is investigated in this work through a simplified three-dimensional nonlinear Finite Element simulation. Distributions of induced beneficial residual stress around and along the thickness direction of elongated hole are predicted from the FE simulation. The results indicate introduction of significant beneficial residual stresses throughout the thickness surface of elongated hole. These beneficial residual stresses are responsible for fatigue life extension and can be further used to quantify the achieved fatigue life enhancement.