For the unexpected failure of hollow fan blade in the HCF test

vibration simulation and crack analysis was done. The results indicated that

the failure region was not the high stress region

and the crack initiates from crossing area of thin plate and thick plate in the suction side

which was caused by fatigue. The failure mechanism was that thin plate of local region distorted in the SPF process so that the thick and thin plates fret wore in the high cycle fatigue test

which induces the fatigue failure. Based on the fatigue analysis

improvement measure was made through both optimizing the parameters in the SPF process and adding CT inspection in the test process. Validation test showed that the improvement measure was effective

and the unexpected failure problem was solved successfully.