Low Cycle Fatigue Life Analysis Of Inconel 718 Remanufactured Turbine Disc

Due to the high cost of aero-engine turbine disks and the low economic benefits of direct replacement,it is very urgent to remanufacture and repair failed turbine disks.Laser additive manufacturing technology is widely used in the field of turbine disk remanufacturing.The aim of remanufacturing is to ensure that remanufactured product have a longer working period.The working Environment of the remanufactured turbine disc is also harsh.Compared with new products,at the remanufactured turbine disks working time,the failure is mostly generated by the low cycle fatigue,their interactions damage,the insertion of particle from outside and have a strong impact on the aircraft turbine disk's life and durability.High pressure,high temperature,and the generated residual stress also affect the aircraft turbine disk.The fatigue life of turbine engine components can be reduced by 50% as a result of such damage.Therefore,this thesis mainly analyzes the performance of the thin-walled specimens of turbine disc materials produced by laser additive manufacturing technology.Hardness Measurement test,tensile test,and residual stress test have been conducted to analyze the influence of heat treatment on its physical and mechanical properties,and the strength analysis and stress strain analysis of the remanufactured turbine disk under working conditions are carried out by Finite Element Analysis.Based on the results,the low cycle fatigue life of the remanufactured turbine disk was predicted.This research is divided into two parts.Firstly,based on Experimental Analysis some specimens have been remanufactured by laser cladding at different process parameters.The material used for remanufacturing is Inconel 718 alloy as it has good tensile strength,hardness and corrosion properties.A suitable specimen has been selected by observing their microstructure for different kinds of tests.Hardness Measurement test,tensile test,and residual stress test have been conducted before and after the Heat-Treatment of the remanufactured specimen.Heat-Treatment's influences on the material properties of the remanufactured specimen by laser cladding.After heat-Treatment,the Mechanical properties of Inconel 718 alloy,such as tensile strength,material hardness,and residual stress,have greatly improved.Secondly,for simulation Analysis engine turbine disc of Inconel 718 alloy material have been designed and simulated by using Abaqus software.Establish a finite element model for turbine disk simulation,and different loads such as high pressure,high temperature and shrink fitted load have been applied on the turbine disc.After applying the load and boundary condition,1/41 th part of the turbine disk is analyzed and calculated,and the relationship between Stress,Strain,pressure,distance,and heat flux of the remanufactured disk have been calculated out.The dangerous points with the greatest stress are found,such as assembly holes and disc holes by finite element analysis.Then,the low cycle fatigue life has been calculated at critical points of the remanufactured turbine disk.Results show that disc bore having maximum stress have maximum chances of failure.Considering the number of dangerous points and the influence of the remanufacturing process on the low cycle fatigue life.At disc bore,low cycle fatigue life of the remanufactured turbine disk has been calculated out by modified morrow equation.