Investigation On Of The Dynamic Deformation Mechanism Of Titanium Alloy Under The High Speed Cutting

Titanium alloy with its special strength,stiffness,low thermal conductivity,high temperature resistance,strong corrosion resistance,has been widely used in the aerospace industry,machinery,and medical field,which requires much higher satisfaction on the structure and machining processing.For this alloy,the most difficult problem is that the difficulty of the machining process due to the large plastic deformation and the instability of the metal phase structure during the process of temperature changing.In order to solve the difficulties of titanium alloy in high speed machining,this paper will investigate the cutting dynamic deformation mechanism of titanium alloy from the following three aspects:(1)In order to reveal the deformation mechanism of material plastic flow which in different loading conditions,the effects of constitutive behavior and loading conditions on the plastic flow stability of Ti6Al4 V alloy are studied in this paper,and the general principles are put forward to predict the instability of materials.It is believed that the instability of materials is affected by strain rate sensitivity,strain hardening and thermal softening effect.It also clearly shows the contribution of loading stress,strain rate sensitivity and heat conduction to thermal softening.Under this condition,we can obtain the critical instability criteria which in different loading conditions and evaluate different instability behaviors,such as shear band instability and the necking.The analysis results reveal the pressure sensitivity of shear band instability and the transition conditions between different instability modes are given.(2)In the currently visible results of previous studies,most of researches mainly focus on the strain,strain rate and temperature for the factors affecting the dynamic stability,few considering the microcosmic structures of the material.In this paper,the microstructure characteristics of materialsare described,and the micro structure are added to the dynamic control equation as the variables of these functions.Based on the modified governing equations,analysis of perturbation solution for the dynamic equation,the results show that material instability occurs easily while the influence of the temperature of the workpiece is not consistent with the change of microstructure.(3)The spacecraft structure system of the mechanical structure and some precision machinery parts,are necessary for ultra precision machining and precision metal processing,therefore these parts material microstructure must be considered.In the material constitutive models,the relationship between polycrystalline metal,grain size and grain boundary is the key factor to analyze the processing performance and material flow stress.This paper pay attention to the casting workpiece internal defects of materials and introduce three kinds of internal defects which are possible existing in the metal materials.The simulation analysis on two kinds of internal defects in the cutting process are studied.During the cutting process of Ti6Al4 V,the chip morphology,flow stress,real stress and temperature of shear band are discussed.In ultra-precision machining and precision machining,because of the existence of internal defects in materials,cutting morphology has occurred a different forms,and the internal defects of materials has also changed the chip on the flow stress and shear zone temperature distribution.