Research On Effect Of Cutting Edge Microgeometry On GH4169 Machined Residual Stress

GH4169 superalloy is widely used in the manufacture of aero-engine turbine disks because of its excellent thermos-physical and mechanical properties.The turbine disk is one of typical component of aero-engine.It is subjected to high temperature,high pressure and severe alternating loads during service,which cause fatigue damage.Strengthen the machined surface integrity of turbine disks plays a leading role in improving its fatigue life.The cutting edge microgeometry have an important influence on surface integrity such as residual stress.Adopting reasonable cutting edge microgeometry parameters helps to improve the machined surface integrity.Based on the study of the effect of cutting edge microgeometry on the machined residual stress,reveal the influence mechanism of the cutting edge microgeometry paratmeters on machined residual stress;explain the mapping relationship between cutting edge microgeometry and machined surface residual stress;optimized the cutting edge microgeometry parameters to improve the machined surface residual stress distribution.Firstly,the simulation model of GH4169 superalloy orthogonal cutting was established based on the ALE method.The form factor K and the average roundness (?) were used to parameterize the honed cutting edge.The influence of cutting edge form factor K and the average roundness (?) of the honed cutting edge on the machined surface residual stress characteristics(surface residual stress ?s and maximum compressive residual stress ?c)were analyzed.It was found that increasing the average roundness (?) or introducing chamfer on honed edge will increase the surface residual stress ?s and the maximum compressive residual stress ?c.Keeping the average roundness (?) of honed cutting edge constant,the machined surface residual stress with different form factor K of 1,0.5,2 was compared.When the form factor K=1,the surface residual stress ?s and maximum compressive residual stress ?c are the smallest;when the form factor K=2,the surface residual stress ?s is largest;when the form factor K=0.5,the maximum compressive residual stress ?c is largest.The experiment results showed that the simulation value of machined surface residual stress is in good agreement with the experimental value.Then,based on the temperature distribution along the cutting depth and the ploughed depth,the mechanism of the cutting edge microgeometry on machined surface residual stress is analyzed.It was found that the friction between the cutting edge and the workpiece increases the machined surface temperature gradient,which causes the increase of machined surface tensile residual stress;the increase of material volume ironed by cutting edge increases the machined surface compressive residual stress.The value of the machined surface temperature has a high correlation with the value of surface residual stress and the ploughed depth has a high correlation with the maximum compressive residual stress.This indicates the dominant factor of surface residual stress generation and change is the thermal load and the dominant factor of maximum compressive residual stress generation and change is the force load.Finally,based on the finite element method,artificial neural network and multi-objective optimization algorithm,the GH4169 superalloy machined surface residual stress prediction and multi-objective optimization model was established.The input parameters of the model are the rake angle,the clearance angle,the form factor K and the average roundness (?) of cutting tool.The output parameters are the maximum compressive residual stress and surface residual stress.The GABP neural network after training was used as the objective function of the non-dominated sorting genetic algorithm NSGA-II,and the multi-objective optimization of the value of the machined surface residual stress was carried out.The Pareto optimal non-dominated solution sets were achieved after calculated,which provide guidance for the design and selection of cutting edge microgeometry parameters.