| Turbine disk is one of the major and key parts of aviation, working in high temperature. In working condition, the turbine disk bears the coupling effects of centrifugal force, air power and heat stress. Multi-axial low cycle fatigue is the main failure mode of turbine disk. With the increase of engine thrust weight ratio, the intake and exhaust temperature of aircraft engine and speed of rotor system are also larger. The high thermal and mechanical load cause the increased stress and the local changes of turbine disk work in the plastic state. The traditional method based on S-N curves for the assessing of low-cycle fatigue that plastic changes is in dominated mode is failed.In this paper, the method that theory combined with experimental is used to research the low cycle fatigue life and reliability of turbine disk and shows the fatigue life based on SWT model. Because the speed, elastic modulus, Poisson's ratio are random variables, the fatigue life of turbine disk is scattered and the results of probability of fatigue life and reliability histogram curve have been obtained. Main tasks are as follows:1. Described the basic concepts, theories and three common methods of fatigue analysis. In order to lay the theoretical foundation of fatigue life analysis model, analyzed the advantages and disadvantages of each method.2. The three dimensional model of turbine disk have been established through the actual measurement, used the HYPERMESH to mesh grids and the MSC. PATRAN to analyze the modal, verified the accuracy of the finite element by comparison with the result of experiment. The elastic finite element analysis show that the local of turbine disk change into the plastic states. The stress cloud has been obtained by further elastic-plastic finite element analysis used multi-linear kinematic hardening model.3. The fatigue material parameters have been obtained by heteroscedastic linear regression treatment for the standard low-cycle test data. Considered the multi-axial stress effects on fatigue life, used the SWT model based on critical plane method to assess the low cycle fatigue life of turbine disk.4. In order to study the effect of material properties and speed's volatility on the fatigue life's distribution, established reliability analysis model used by Monte-Carlo method combined with the fatigue life modeling. A group of data were obtained by finite element simulation using central composite method and the distribution of fatigue damage and life were obtained by fitting the parameters of the data combined the SWT model Shows the relationship of the fatigue life and reliability. |
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