3.1 | CCF life
The valid CCF life results are listed in Figure 7(a). Among them,
thirteen CCF life results come from the untreated blades and the other
nine results come from the PSP treated blades. According to these test
data, the σH-N curves of untreated and PSP treated
blades are shown in Figure 7(b). There is a linear relationship between
CCF life and vibration stress amplitudes. Furthermore, the least squares
method is used to fit experimental data to get the fitting equations
listed in Figure 7(b). It indicates that there is one threshold
vibration stress with the value of 194.0MPa. When the vibration stresses
are lower than the threshold value, the PSP treatment has a positive
effect on the CCF life of blades. In contrast, the PSP treatment has a
negative effect on the CCF life while the vibration stresses are above
the threshold value.