Research On Fatigue Life Prediction And Reliability Assessment Of The Turbine Disk On Aero Engine

Turbine disk is the key component of aero-engine.It withstands the complex load of high temperature and high speed in extreme environment.Its main function is to install and fix the turbine blades and fulfill the task of power transmission.The load on the turbine disk is mainly the temperature load and the centrifugal load,apart from that,the centrifugal load and the aerodynamic load of the blade which is conveyed by the dowel connection.With the continuous improvement of the aero-engine thrust-weight ratio,the momentum of the aero-engine is increasing,and the centrifugal load and the temperature load borne by the turbine disk are also increasing,and the centrifugal load and the internal stress of the turbine disk is increased obviously.The failure modes of the turbine disk are low cycle fatigue,rapture fatigue,vibration cracking and excessive deformation failure.The fatigue failure caused by repeated load and the low fatigue failure caused by creep damage under high temperature deformation are the main failure modes.In this paper,the finite element method is used to calculate the strength and stress analysis of turbine disk under the three kinds of loads of centrifugal load,temperature load and centrifugal load caused by blade.Based on the results of strength stress analysis,low cycle fatigue life of the disk is calculated and the running reliability of the disk is analyzed.First of all,this paper build the finite element model of the impellor based on the characteristic of the turbine disk structure,and the material property of GH4133 B is given;then the load and boundary conditions are given for the 3D model of the turbine disk,finally Abaqus software is used to simulate the stress and strain distribution result of the turbine disk under the maximum speed and the idling rotation speed.Secondly,low cycle fatigue life prediction is conducted,the stress concentration factor is determined,and the Goodman method is used to convert the non-symmetrical cycle load to the symmetrical cycle load,and finally use the S-N curve method of the nominal stress method to predict the fatigue life of the turbine.In addition,the material fatigue performance parameter and the local stress and strain distribution result obtained by the last chapter is used,and the life prediction gained from modified Morrow formula and modified Manson-Coffin formula is presented.The life prediction results obtained from three models are contrasted and analyzed.Finally,the influence of dangerous parts number on turbine disk fatigue life is considered,and the fatigue life prediction result of turbine disk is modified.Based on the fatigue life prediction result,the fatigue life probability distribution of the GH4133 B specimen with logarithmic normal distribution is calculated by using the fatigue test data of the material specimen.Using the distribution relationship between the parts and material specimen to fit the low cycle fatigue life probability distribution.Furthermore,the fatigue reliability model under the certain constant amplitude is obtained from the fatigue life probability density function at a given stress level.Based on the full probability formula,the stress-intensity interference model is rewritten and the conditional fatigue reliability is introduced.Under the condition of the probability distribution of fatigue strength without given life,the fatigue reliability analysis of the aero-engine turbine disk under uncertain load is deduced.