Research On Methods Of Fatigue Life Prediction And Reliability Analysis For Key Components Of Aero-Engine Rotor

As the power source of an aircraft,the working reliability of the aero-engine directly affects the safety of the aircraft.With the continuous improvement of aero-engine performance,the engine rotor is developing to the trend of lighter structure,larger workload and higher temperature,so more related fatigue and reliability problems also emerge.For the fatigue and reliability of key components of aeroengine rotor,the fatigue life prediction of the disk,drum and spindle and the fatigue reliability evaluation method of the rotor blade system are systematically studied in this paper.The main contents of this paper are as follows:(1)Taking turbine aeroengine as an example,based on a specific type of aero-engine,the structure composition and stress characteristics of its rotor system are briefly introduced.The main force components of the engine rotor system are introduced and classified according to their stress states.On the premise of mechanical load(aerodynamic load and centrifugal load)considered only,the static force analysis of turbojet 7 engine rotor system is carried out by finite element software.Based on the results of finite element analysis,the theoretical analysis emphasis on fatigue reliability of aero-engine rotor system is put forward,which provides engineering basis for the research in following chapters.(2)In view of the shortcomings of the traditional stress field strength method,a new method for calculating the field strength of the dangerous parts of the compressor disk of an aeroengine is presented based on the original assumptions.The definition criterion of fatigue failure zone and function form of weight function were revised in the new method.The corresponding algorithm and model were also proposed,which fundamentally overcomes the difficulty of the traditional field strength method in the definition of the fatigue failure zone and makes the calculated field strength have an objective and accurate solution.Based on the basic structure of the dangerous part of the aeroengine compressor disk,the validity of the new model is verified qualitatively and quantitatively by the basic samples related to the dangerous parts of the disk.(3)Aiming at the multiaxial fatigue problems of thin-walled components represented by compressor drum,a multiaxial fatigue life prediction model considering additional hardening effect is proposed based on the traditional critical plane method.In the new model,in order to quantify the effect of material additional hardening behavior on fatigue life,a subcritical plane reflecting the direction of grain slip and deformation is defined according to the load variation path at the dangerous part of the component,and the corrected parameters related to material additional hardening behavior are calculated on this plane.In order to verify the prediction accuracy of the new model,the prediction accuracy of the new model is verified by eight kinds of metal materials for the test simulation sample of compressor drum—thin-walled tube specimen.(4)Aiming at the multiaxial fatigue problem of rotor spindle,a multiaxial fatigue life prediction model suitable for different stress states is proposed by means of finite element simulation software and basic theoretical mechanics formulas.Unlike the planar multiaxial fatigue life prediction model proposed above,the new model focuses on the particularity of additional hardening effect and fatigue damage mechanism at the notched three-dimensional stress location,which means the new model has a wider application background.Similarly,in order to verify the prediction accuracy of this model,based on the basic structure of the dangerous parts of the aero-engine rotor spindle,seven kinds of test specimens similar to their structures are used to simulate the test of the rotor spindle,and different multiaxial fatigue life models are used to analyze and compare the test data.(5)Aiming at the unconventional complex mechanical system,a new dynamic reliability modeling and analysis method is established to fully consider the inherent characteristics of the blade subsystem on the engine rotor.In the new model,the force state of the engine rotor blades is fully considers,and with the help of the theories of order statistics and stochastic process,the spatial characteristics between the blades are transformed into plane integral problems in time domain to solve them.In order to verify the validity of the new method,the reliability state of the blade system during a multiple cruising is analyzed by taking the cruise data of a certain type of aircraft as an example.The validation results show that the proposed method is more reasonable than the traditional method in solving the reliability problem of engine rotor blade system in multi-stage cruise,and,therefore,the results of the new method are closer to the engineering practice.