Research And Application On Analysis Method For Burst Of Engine Disk

The burst speed of engine disk is an important content of modern aero-engine strength design.Modern engines have many geometric discontinuities,like mortises,vent holes and bolt holes,which make the distribution of stress and strain quite uneven and the stress state multiaxial.In addition,for high-strength alloy,the deformation and fracture behavior under complex stress state is more complicated.At present,the prediction of burst speed and burst type of disk is still hard in engineering.On the other hand,there are many disk-disk or disk-shaft connecting structures in an engine rotor,which influence the burst speed of disk,therefore,the engine design needs to consider and optimize the connecting structures to enhance the fracture margin of rotor.This article is the research on the above problems.Based on predecessor's work,the paper has studied the yield and fracture behaviors of disk alloy,burst prediction method validation and evaluation and the influence of rotor connecting structure through laboratory test,theoretical analysis and numerical simulation.The main work content is as follows:GH4169 alloy material pull-torsional coupling test was performed.The result showed that: Tresca yield criterion is more suitable for GH4169 than Von Mises and twin shear yield criterion,and Tresca yield criterion could predict the notched tensile ultimate strength and the tensile curve of GH4169 notched specimen more accurately.By finite element analysis method,the study of stress and strain characteristics was carried,then the notch failure mechanisms are summarized: The distribution of stress and strain is greatly influenced by notch type and notch size.The early failure of sharp notched specimens is caused by ductile fracture,instead of the brittle cleavage fracture.On the basis of equivalent plastic strain and stress triaxiality distribution and ductile failure theory,the fracture of GH4169 notch specimen can be reasonably explained.In order to verify the accuracy of method,GH4169 disk-bursting test was performed.Then,refer to notch specimens fracture mechanisms and the stress and strain characteristics,the failure mode of disk is analysis.An assessment for several mainstream method was conducted.The results proved that: The new method of this paper has high precision and on the basis of equivalent plastic strain and stress triaxiality distribution and ductile failure theory,the fracture of GH4169 disk can be reasonably explained.The average stress method and Hallinan method have low precision.Local stress-strain method has high precision,but the judgment of fracture mode is inaccuracy.Residual deformation method is same with the new method in this paper in principle,it also has high precision.Based on the method based on plastic instability criterion,the study of burst speed and fracture behaviors of different turbine rotor structure schemes was carried and the results proved that: the disk will be enhanced,if the shaft is joined.At the same time,the yield speed will decrease,the radial deformation will increase,and the join position will affect the disk.Considered from burst speed,demountable structure is suitable for small-bore disk and one-piece structure is suitable for big-bore disk.Considered from yield speed,demountable structure is superior to one-piece structure.Considered from radial deformation,one-piece structure is suitable for small-bore disk and demountable structure is suitable for big-bore disk.