13th International Conference on Fracture June 16–21, 2013, Beijing, China -5- 1 1 i 1 1 1 1 1 1 ( ) 1 ( ) n n n n i i i i i i i C N C S D N S α α − = = = = = = = = ∑ ∑ ∑ ∑ （4） Where, N0 is the initial life of component and N1 is the remaining life after parking for certain time, according to the formula (4), the formula (5) could be gotten: 0 1 1 0 0 1 0 1 n 1 1 1 1 ( ) ( ) n i i i i C N S C N S α α − = − = ⎧ ⎪ = ⎪ ⎨ ⎪ ⎪ = ⎩ ∑ ∑ （5） Where, S0 and S1 respectively is the loading level. And more: 1 0 0 1 1 0 1 1 i 1 1 1i 1 0 1 1 0 0 1 0 0 i 1 0i ( ) ( ) ( ) ( ) n i n i C N S C S C N C S C C S α α α α α α − = − = = = ⋅ = ∑ ∑ （6） Where, C0 andα0 respectively means the shape parameter of S-N curve for the intact component, C1 and α1 respectively is the shape parameter of S-N curve after parking for some time, other parameters are the same as above. Therefore, the model for the remaining life was set up for the component that had parked for different T years. ( 1) ( ) ( ) （ 1） (T 0,1,2, ) ( ) [ ] ( 1) T T N T N T C T C T α α + + = = …… + （7） The deregulation rule for fatigue life of component at different parking time was set up in the formula (7). The environment influence for the performance of fatigue critical component was only considered. After considering the condition of service, the formula (7) could be revised as followed: ( 1) ( ) [ ( ) ( )] （ 1） (T 0,1,2, ) ( ) [ ] ( 1) T T N T G T N T C T C T α α + − + = = …… + （8） Where, G(T) is the flight frequency for every year. Aiming at the current usgue situation of aircraft, the two-aparameter life prediction model could be set up based on the local environment and the test data, which considered the influence of environment for fatigue critical component. 3.2. The way of Detail Fatigue Rating The Detail Fatigue Rating (DFR) is usually used to analyze the fatigue quality for detail component. It is the inherent fatigue performance and is the measurement for component quality and ability of enduring repeating load. That is to say, the Detail Fatigue Rating (DFR) is the max stress at the constant loads for R=0.06, the cycles are for 105 cycles, the confidence level is 0.95 and the
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