The Research Of The Anisotropic Gatigue Behavior Of Aircraft Aluminium Alloy 7475 Plate

Aiming to understand the anisotropic fatigue behavior of aircraft aluminum alloy plate, the high frequency bending fatigue test was performed in this thesis, the results show that after the rolling process, Al7475-T3 formed a pancake structure and the resistance to fatigue damage has been improved. The specimens taken from the 3 Plan(S-T,S-L,T-L) show the highest fatigue strength reach to 200MPa in the room temperature bending fatigue test, except the performance of Plan T-L is isotropic, the other two Plans S-T and S-L both show us anisotropic. After the fatigue test , the specimen that has the best performance in the plan T-L was chosen to have shot peening with two different types ,in order to study the effect of shot peening parameters on the fatigue strength. The results show us that it is uncertain the shot peening process will improve the fatigue strength, because during that process, the introduce of the residual compressive stress will definitely enhance the fatigue strength ,on the other side, shot peening will destroy the specimen surface which will probably become the resource where the mico-cracks will originate. Based on the weakest link theory, using the probabilistic fatigue criterion, the simulation of the anisotropic fatigue is applied to analyzing the possibility of the nucleation of micro-cracks in the aluminum plate, but the result of the simulation is far from the that of the actual situation; integrating the consideration for both the effective slip length of the grains and the size of inclusions that both affect the fatigue strength into the model, the Kitagawa curve is in good agreement with the actual situation.