Life And Reliability Analysis Of Aeroengine Turbine Discs

Turbine disc is a critical component used to install and fix blades on an aero engine to transmit power.It bears complex loads under high temperature,high pressure and high rotating speeds conditions,including not only the centrifugal force and thermal stress,also the blades are driven by gas.The complex loads such as centrifugal force generated by the operation will also act on the turbine disc through the connected tongue and groove.Researches on the reliability of engine turbine discs are still lacking,especially on the problems of solving multiple failures,uncertainties,and strength degradation during their operations.Therefore,with regard these uncertainties,strength degradation and fatigue damage accumulation,fatigue life prediction and reliability research are conducted to reduce the occurrence of destructive failures during the operation of aeroengines and establish an analysis suitable for more mechanical materials.The method has a very high significance in the application of R & D in engineering practice.In this thesis,based on the full study of the fatigue life prediction and reliability analysis methods of engine turbine discs,the following researches on some of the difficult problems are carried out:(1)Using Bayesian theory to quantify multi-sources uncertainties during fatigue life prediction of high-pressure turbine discs.Due to the material parameters and the model parameters in the use model,more uncertainties will be introduced.This paper uses Bayesian theory and the existing experimental data,simulation data and expert experience,quantified these uncertain factors in the life prediction process.(2)Establishment of damage accumulation model based on strength degradation.This paper discusses the strength degradation laws and fatigue damage accumulation models of 7070-T7451 aluminum alloy,No.45 steel,and 16 Mn steel.The life prediction results of the three models are compared and evaluated.On this basis,it is proposed to introduce fatigue damage parameter A and the fatigue damage index d improves the Corten-Dolan model and verifies the effectiveness of the newly proposed model based on the existing test data.(3)Stress information fusion in turbine disc life cycle based on fuzzy theory and hierarchical bayesian theory.In view of the small sample characteristics of high-pressure turbine disc life data of aero engine,based on the quantification of uncertainty in each stage by hierarchical bayesian theory,the stress information obtained from test and simulation is integrated by fuzzy theory to obtain the stress distribution of weak links in high-pressure turbine disc at maximum rotation speed.(4)Turbine disc reliability calculation based on structural feature quantities.Based on the quantification of the strength degradation law of the turbine disc and the fusion of various stress information,the reliability of the aero-engine turbine disc considering strength degradation and stress fusion under complex load is calculated by combining the stress-strength interference model.