13th International Conference on Fracture June 16–21, 2013, Beijing, China -7- In the same way, the S-N curve was fitted according to the fatigue life of retired aircraft. 3 0.2698 6.1298 10 × = SN （13） The specimen value of DFR was calculated based on the fatigue life corresponding with a group data from the table 1, the result was shown in Table 3. Table 3. Detail Fatigue Rating/MPa Stress/MPa Life/10,000 cycle DFR/MPa Accelerated 4a 310 12.004 15.187 11.860 13.580 214.1635 Accelerated 12a 310 11.613 12.616 12.454 13.286 210.8297 Accelerated 20a 310 12.280 12.642 10.654 11.802 209.8210 Retired specimen 320 7.025 5.501 5.969 7.906 187.5407 The DFR in Table 3 was fitted by the exponential form and the change rule of DFR along with the calendar year was gained. 0.0747 ( ) 207.937 8.479 e T DFR T σ − = + × （14） 4.2. The example Accoding to the actual service condition, the fatigue life was only consumed about 10% when the aircraft was retired. Aimed at the status of consumed life and combined the formula (8) with (12), the theoretical calendar life was calculated by the dynamic S-N curve as the shape parameters were same as the formula (13); The calendar life was calculated by using the DFR method according to the formula (14) as the DFR value was same as Table 3. Compared with the actual fatigue life of retired aircraft, the result was shown in Table 4. Table 4. Comparison of theoretical value and actual calendar life Theoretical value /a Actual calendar life /a Error /% Dynamic S-N curve method 23.17 25 -7.32 DFR method 26.009 25 4.04 The results gained from Table 4: the error was not large between the calendar life calculated by the two models and the actual life, the two models could be used to predict the rule of life deregulation for the fatigue critical component at the parking environment. 5. The result ⑴ The accelerated environment test for the 2A12-T4 aluminum alloy is carried out. though comparing the fatigue life after environment test with the fatigue life of retired aircraft, the rule
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