Research On Analysis Method For FGH96 Disc’s LCF Life And Burst Speed Considering Surface Machining Status

Aero-engine disc is the main load-bearing part.Low cycle fatigue can cause crack and disc’s bursting.Insufficent general strength can also cause disc’s bursting.LCF failure and burst failure are main failure mode.Machinery injuries exist on disc’s surface actually.The disc’s LCF crack and bursting originate from machinery injuries of disc’s surface.When machinery injuries’ tolerance is different,the disc’s LCF life and burst speed can be different.In order to predict disc’s LCF life and burst speed accurately,analysis methods of considering surface machining status and demonstration test must be researched on LCF life and burst speed.The main research content includes following several parts:(1)The first part is about analysis method of the low cycle fatigue life for disc considering surface machining status.Based on analysis for low cycle fatigue fracture mechanism,the energy expression of the low cycle fatigue fracture is studied;based on a time loading fatigue fracture mechanism,the energy expression of a time loading is studied.The low cycle fatigue life prediction model based on energy method for disc considering surface machining status is established.Using this model to analyze the low cycle fatigue life of a FGH96 disc,the results show that the low cycle fatigue life for disc considering surface machining status is 30% lower than that without considering surface machining status.Low cycle fatigue life test of the FGH96 simulation disc is completed at the vertical wheel spin tester.By means of fracture analysis,the low cycle fatigue life of the simulation disc are given.Comparing the experimental results with the predicted life,it can be found that the degree of predicting life decentralization is big and the predicting life is dangerous without considering surface machining status;the degree of predicting life decentralization is small with considering surface machining status.(2)The second part is about an analysis method of the burst speed for disc considering surface machining status.The burst speed method and application scope of disc without considering surface machining status is introduced.The criteria and application scope of notch crack initiation are described.FGH96 turbine disc’s burst speed are analyzed by the two methods.Analysis result show the turbine disc’s radial burst can happen firstly considering surface machining status,but the turbine disc’s circle burst can happen without considering surface machining status firstly.The burst speed test is completed at the vertical wheel spin tester and the burst speed is given.By means of fracture analysis,it can be found that burst originate from machinery injuries.Comparing experimental results with the predicted burst speed,it can be found that the predicting burst speed is dangerous without considering surface machining status,and the predicting burst speed of disc considering surface machining status is agreed well with test results when the ratio between the micro hole depth and the semimajor(b/a)is 0.5.Analysis method considering surface machining status on LCF life is based on fracture mechanism and energy.The method can express the relationship between LCF life and surface machining status well.In case of finite material property,the method is convenient in using and has good application in engineer and analysis result using it is credible.It can provide a kind of convient method for analyzing surface machining status’ effect to LCF life in engineer nowadays.It can also provide a kind of reference and foundation for subsequent development in this aspect.Analysis result considering surface machining status and test result of burst speed shows prediction result based on frequently used average stress in engineer is dangerous in case of without considering surface machining status.The analysis method on burst speed adopted in this paper can provide a kind of use of reference for other disc’s burst speed analysis.