3.2 | Experiments results

The distribution of stress amplitude \(\sigma_{a}\) and experimental fatigue life\(N_{f}\) is portrayed in Fig. 3. If a specimen exceeds \(10^{9}\)cycles, it was defined as “run out”.
Fatigue life mainly concentrates on the HCF regime\(10^{4}<N_{f}<10^{6}\). The transition between high cycle fatigue and very high cycle (VHCF) fatigue is shown as a broken line. Although the loading level begins to decrease, fatigue life will not be reduced readily. Only under fatigue strength, fatigue life can reach to VHCF immediately. Therefore, it can be deduced that the existence of micro scratches significantly reduced fatigue life, which means that TC17 possesses a high sensitivity to micro scratches in this experiment.
That is to say, it is indeed a potential danger for TC17 blade to continue service under the harsh service environment once the part with accidental micro scratches. Fatigue life of the rough blade can be significantly reduced, even cannot satisfy a whole service cycle because of the scratches. Consequently, a model to estimate the fatigue life of TC17 blade with micro scratches can be quite necessary to guarantee service safety.