Research On The Method Of A Standardized Fatigue Test Loading Sequence For Aircraft Cold Section Engine Discs

Aircraft engine disk is of fracture critical part and its safety and reliability is of significance to the safety and reliability of the entire engine and aircraft. Effectively evaluating the performance of disk materials, manufacturing processes, surface treatment methods, structural details of the design and development of reliable life prediction method are important for ensuring the safety and reliability of disks. It is well known that data and models that characterize the fatigue behavior of materials and structures under base-line constant amplitude loading may not be appropriate or sufficient to adequately assess their fatigue performance under irregular variable amplitude loading. From this point of view, fatigue testing should be carried out under a realistic, operational loading pattern. So developing a standardized fatigue test loading sequence for aircraft engine disks is valuable for evaluating the performance of disk materials, manufacturing processes, surface treatment methods, structural details of the design and development of reliable life prediction method.Study in this thesis is focused on the methods for generating a standardized fatigue test loading sequence for aircraft engine cold section discs. Three aspects of research have been accomplished as follow:(1) The development status of the standardized loading sequence is reviewed. It is realized that developing a standardized fatigue test loading sequence in China is of importance and necessary.(2)Through studying and analyzing the generating process for the standardized fatigue test loading sequence, it is concluded that quantitative analysis of aircraft engine's operational mission profiles is important for generating a standardized fatigue test loading for cold section disks. The analysis procedure mainly comprises: selection and standardization of representative operational mission profiles, statistical analysis with respect to mission type, structure and content. The generating procedure for a standardized loading sequence main comprises: determination of sequence length and mission mix, sequence generation for a mission profiles based on statistical analysis results of representative operational mission profiles, and generation of whole standardized loading spectrum for aircraft engine cold section disks.(3) Based on the generating methods for a standardized loading spectrum, quantitative analysis of aircraft engine's operational mission profiles in China is carried out. Several sequences have been generated based on different statistical analysis results of representative operational mission profiles with different omitting criterion for small cycles. Then based on the fatigue data of TC4 alloy, the fatigue life is predicted for these different sequences with different maximum stress. It is conclude that omitting small cycles with load range less than 3% of the max load have little influence to the fatigue damage of standardized loading spectrum..