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.