Research On The Influence Of Prestress Treatment On The Disk Fatigue Life

Modern aero-engines require more and more high thrust-weight ratio and long service life,which forces the engine turbine disk to develop towards high strength,long life,and low weight.The disk is a key part in aeroengine.Its failure directly affects safety and maintenance costs,and even endangers flight safety.The low cycle fatigue life can be improved by prestressing the wheel disc.The main research work carried out in this paper is as follows:(1)The design of prestressed center bore specimens and low-cycle fatigue tests were carried out.The basic mechanical properties of GH4169 material were obtained by measuring the stress-strain curve under RT,500? and 650? conditions.Stress state analysis and low cycle fatigue test were carried out under three temperature conditions,different pretensile and fatigue loads.The high temperature creep-fatigue test was also carried out.(2)The low cycle fatigue life of prestressed specimens was studied.The fatigue life of samples under different temperatures and various pretensile loads was calculated by local stress strain method and stress gradient method.The results show that the prestress has obvious benefit to improve the fatigue life of the sample,but the fatigue life of the sample decreases slightly when the prestress exceeds a certain threshold.The results of creep-fatigue life analysis show that the low cyclic fatigue life gain of prestressed specimens is reduced by high temperature creep effect.(3)The low cycle fatigue life of prestressed disk is studied.Under the consideration of average stress and residual compressive stress,the stress life method and stress gradient method are used to calculate the low cycle fatigue life of the disk.The creep deformation value of the disk was calculated,and the veracity of the calculated results was verified by the creep test of the disk.The results show that prestress treatment can significantly increase the low cycle fatigue life of the disk,but the effect of prestress fatigue life extension will be reduced due to the creep of the disk.