Fatigue endurance of aeronautical aluminum alloy 7075-T6, with artificial and induced pre-corrosionTuesday (26.05.2020) 12:10 - 12:30
Conventional and very high frequency fatigue tests were carried out on the AISI-SAE AA7075-T6 aluminum alloy, in order to evaluate the effect of artificial and induced pre-corrosion. Artificial pre-corrosion was obtained by two hemispherical pitting holes of 500 m of diameter at the specimen center, machined and oriented following the longitudinal or transverse direction of the testing specimen. Induced pre-corrosion was achieved using the
international norm ESA ECSS-Q-ST-70-37C of the European Space Agency. Specimens were tested under ultrasonic fatigue modality at frequency of 20 kHz, and under conventional fatigue modality at frequency of 20 Hz. The two applied load ratios were: R= -1 in ultrasonic fatigue tests and R=0.1 in conventional fatigue tests. Both testing devices used to perform the conventional and very high cycle fatigue tests were developed and constructed in our laboratories. The effects of artificial and induced pre-corrosion on fatigue endurance were addressed in the analysis of experimentally results, together with the surface roughness evolution before and after fatigue testing. Fatigue endurance was observed to decrease importantly with artificial and induced pre-corrosion. Finally, numerical investigations were carried out to assess the stress concentration associated with pre-corrosion pits, and the fracture surface of testing specimens were analyzed to identify the trends on cracks initiation and propagation.