Modeling And Simulation Of Superalloy With Pit Defects

Aeroengine turbine disk makes the main parts of the engine,its working environment is very bad,the rotating speed is about 10000-20000 rpm,the working temperature is often higher than 500 ℃ to 800-900 ℃,at the same time,it bears great stress,its stress value is often as high as more than 500 MPa.In this case,the fatigue life of the turbine disk will be greatly affected in the case of damage defects.Therefore,timely repair is needed after inspection.The study of the fatigue life with pit defects is helpful to improve the assessment process of the remaining life of the turbine disk,and to improve the economy and safety performance of the domestic engine in the future.In this paper,the stress concentration fatigue life of Inconel 718 with pit defect is studied.Through modeling and finite element analysis of the plate with pit defect,the plate with different size of pit and the plate with different thickness ratio of pit are analyzed,and a preliminary analysis and conclusion of the stress concentration of pit defect in a certain range are obtained.After that,for several actual defect fatigue tests,the fatigue analysis and data comparison are carried out under the same situation using the data obtained,and then the finite element analysis and Simulation of defects in various situations are carried out,and the main notch sensitivity factor and fatigue strength attenuation are obtained.The main results of this paper are as follows.The stress concentration is mainly from the bottom and both ends of the pit.In the case of the pit with a radius of 0.5-2mm,the stress concentration factor increases with the increase of the pit and the pit depth.When the ratio of pit radius to plate thickness is less than 15%,the stress concentration coefficient is basically the same.When the ratio is greater than 15%,it will rise slowly first,then suddenly and rapidly.Even small pits can cause great stress concentration when the thickness of the parts is small.When judging the damage,the size of the pits and the thickness of the parts at the defects should be considered comprehensively.For the cyclic eigenvalue R=-1,when the stress concentration factor is less than 3,the relationship between the fatigue stress concentration coefficient and the stress concentration coefficient is linear,which is about15% different from the authenticity data in the material manual.The introduction of Hyper Mesh for automatic modeling of pre-processing process,can greatly reduce the pre-processing time for the establishment and modification of repeated modeling grid,material attribute assignment,load situation and fatigue simulation parameters,etc.,and save a lot of time for the analysis of pit size defects.