A comprehensive finite element study of cold expanded insert installation for the corrosion repair of 7075-T6 aluminum alloy holes

This study numerically investigates a cold expansion (CE) based insert installation for repairing 7075-T6 aluminum holes. A 3D elasto-plastic finite element model combined with response surface methodology examines three factors: the CE%, insert thickness (IT), and edge margin ratio (EMR), and their effects on mandrel force, residual stresses, and crack initiation cycles. Compressive hoop residual stress near the bore deepens from CE = 1 %–3 % and then saturates, while tensile residual stress at the free edge increases with higher CE and lower EMR. Fatigue crack initiation shifts from the hole entry at CE = 1 % to the free edge at CE ≥ 3 % due to the free edge tension. The highest initiation cycles are achieved with the process condition at CE = 3 %, IT = 0.254 mm, and EMR = 1.7. These results provide the range of process variables required to repair corroded aluminum holes using cold-expanded inserts.