Simulation And Experimental Verification Of Broaching Process Of Turbine Disk Mortise

The high-performance manufacturing of the core components of aviation engines(turbine discs)is the core demand of the 14 th Five Year Plan major project,and the broaching of turbine disk mortise is the key part of efficient shape control manufacturing of air engine.The service life of turbine disc under the complex alternating load of high temperature and high pressure is directly affected by the process quality.As the fir-tree shaped mortise profile around the turbine disc is extremely complex,as well as high machining accuracy and surface quality requirements,self-research of fir-tree turbine disc broach is obstructed.At present,the broaching mechanism of turbine disk mortise has not yet clarified,thus it is difficult to realize the high-performance design and manufacture of turbine disk mortise broach,for this reason,processing quality is difficult to control.Based on this,this paper will focus on the turbine disk of aeroengine,aiming to carry out research on turbine disk mortise broaching process.As is known to all,the metal cutting process is a typical thermal mechanical coupling process,accompanied by a very small area of high strain,high strain rate and high temperature gradient,the traditional analytical methods have difficult depicting and settling such problem,and only through the experiment method is time-consuming and expensive,and not enabling capturing the instantaneous alteration in the state of the cutting area,thus the finite element method play a role.In order to realize the "true" simulation of machining process and provide more accurate guidance,this paper attempts to build a high precision simulation model with finite element subroutine.The main work of this paper is as follows:(1)Owing to the tooth lift of fir-tree mortise broach is 0.04 mm,that is,the depth of broaching is 40 μm.In the same order as the size of teeth profile fillet,the strong size effect will be aroused by broaching process,and the conventional material constitutive model cannot accurately depict the broaching process.Therefore,this paper modifies the traditional J-C constitutive model based on the strain gradient theory,so as to obtain the dynamic rheological properties of the material surface layer of the workpiece.With the help of the VUMAT of ABAQUS,through the actual broaching test and comparing with the traditional JC constitutive cutting simulation model,it makes clear that the comprehensive simulation error of the modified constitutive model is about 10%,and the accuracy can be improved by more than 5%compared with the traditional constitutive model.(2)In the broaching simulation,the tool-chip friction model is also an important factor affecting the simulation accuracy.Therefore,based on the modified J-C constitutive model,this paper deeply explores the tool-chip contact mechanism.The thermal stress coupling in the cutting process not merely occurs in the first shear zone,but also has a significant impact on the tool-chip contact interface.Since the tool-chip contact area can be divided into the sticking area and the sliding area.The shear strength of the sticking area is affected by the material characteristics,whose properties are controlled by thermophysical properties and temperature related constitutive models.Therefore,based on the SCG constitutive model of nickel based materials and the VFRIC of ABAQUS,this paper establishes a thermo mechanical coupling time-varying stick-slip friction model in the tool-chip contact area.Compared with the traditional friction model,the comprehensive error of the cascade modified model is about 6-7%,that is,the friction model can improve the accuracy of the model by 4-5% on the basis of the first-level constitutive model,so as to complete the construction of the high-precision simulation model of the cascade modified material constitutive and chip friction.(3)On the basis of this accurate model,the progressive cutting load modeling and verification of the complex profile teeth are carried out,in this process,the finite element method acts as a bridge for load modeling,and the error of broaching load modeling is controlled within 10%,which manifests that the model can also accurately recurrent the chip formation process,and can provide ideas for load modeling of complex blades.The highprecision cascade modified simulation model is also applied to the three-dimensional finite element simulation of the single-tooth straight profile teeth in the leading part of turbine disc broaching and fine-finished single-tooth turbine disc broaching teeth with the similar profile.It shows that the average model error is less than 10% under two working conditions,indicating that the model can accurately depict the actual broaching,which shows the versatility and high accuracy of the cascade correction model.