Design Simulation of the Low Fatigue Life of a Fan Blisk Using the Simulating Specimen Approach

The development of blisk structure has made the low cycle fatigue (LCF) life test more expensive for the critical components. This paper aims at design several simulating specimen to simulate the working condition and stress distribution of a high-loaded fan blisk. The finite element analysis was performed to confirm the constraining locations of the fan blisk. Afterwards, the LCF life of the blisk was calculated according to Mason-coffin equation and the total damage methods with the predicted maximum allowable LCF life reaching 158352 cycles. Meanwhile, the crack propagation simulation was carried out to figure out the propagation cycle life of the critical locations. The predicted cycle life of the fan blisk is about 4276 and 3991 cycles using the semi-elliptical crack and the 1/4 surface corner cracks. Then, by optimizing the three critical parameters with regard to the stress gradient of the specimen, the optimum simulating specimen were confirmed and tested in the thermo-mechanical fatigue test rig. Results comparisons show that the LCF life of the designed simulating specimen is approximate 153339 cycles, which is content with the calculation. The simulating specimen approach proves to be a reliable and accurate way to validate the cycle life of the engine critical components.