Effect of Shot Peening and Anodizing on Fatigue Crack Growth of Aircraft Material Al 7050-T7651: An Advance Study

The rate of fatigue crack propagation of the 7050-T7651 aircraft material subjected to automatic shot peening machine and chromic acid anodizing (CAA) has been studied and compared with previous research results. Shot peening is a surface treatment by firing shot material so that the dimple is formed and residual stress occurs on the surface of the working specimen in order to increase resistance to fatigue failure. Al 7050-T7651 is made into specimens according to ASTM E647 standard treated with automatic shot peening machine (with steel shot material, 0.017 inch diameter, shot flow 30%, 3 bar pressure, Almen intensity 0.0082 A with 100 mm shooting range and 90° angle of shot) and CAA (operating standard) in surface treatment area of Indonesian Aerospace. The fatigue cracking test with a load of about 200 kg, with a stress ratio of R = 0.1. The results of the fatigue crack growth test resulted in the constant of Paris A=3.654 × 10-9 and n = 1.67, indicating that the automatic shot peening machine and chromic acid anodizing treatment decreased the fatigue life and increased the fatigue crack growth rate compared to the automatic shot peening machine, manual machine with or without CAA, and without treatment.