MICROSTRUCTURE-PROPERTY PREDICTIONS AND MULTISTAGE FATIGUE LIFE PREDICTION OF HOLE RESTORATION COUPONS USING AFSD

Military aircrafts operate frequently in a highly corrosive environment. Corrosion in aluminum aircraft structures with holes and adhesive-bonded lap joints promotes multi-site cracking, which can lead to failure of major aircraft components. To expedite and facilitate the corrosion repair process, an emerging solid-state process, additive friction stir deposition (i.e. AFSD) is applied for the hole restoration followed by the fatigue performance evaluation. Because of the friction stir induced material flow of the deposited and substrate materials, the resulting microstructure and its associated properties are position-dependent. The weak metallurgical bond at the bottom of the repaired hole coupon can promote a crack initiation under cyclic loading and the total life consists of crack initiation, short crack growth, and long crack propagation. This paper describes the use of a multiphysics modeling approach to characterize the process-driven properties evolution and to evaluate the effects of a kissing bond on the total life of hole restoration coupons.
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