Fundamental And Application Research On The Deep Hool Gun-drilling Of Ti6Al4V Titanium Alloy

Deep-hole processing has a wide range of technical requirements in key national development industries such as aerospace,weapons and equipment,rail transit and so on.Especially for the deep hole processing requirements of titanium alloy materials,such as all kinds of door guide holes in C919 aircraft.At present,gun drilling is an important technology in deep-hole processing.The processed hole in gun drilling has the characteristics of small aperture and long depth.At the same time,the structure of gun drill is complex and its rigidity is relatively weak.During processing,there are many outstanding problems,such as low efficiency,poor quality,difficult chip removal and serious tool wear.The processing performance rates of titanium alloy leads to serious tool wear and hardening which brings new challenges to deep-hole gun drilling.In this paper,basic research on deep-hole gun drilling of Ti6Al4V titanium alloy has been carried out.The main work is as follows:1.Based on Oxley cutting model and Johnson-Cook flow stress model,this paper take Ti6Al4V titanium alloy as the research object and use the"micro element"method to establish the mechanical model of gun drilling,which include cutting parameters,tool geometric parameters and material mechanical properties.On the other hand,the drilling model considers the influence of process damping and verified by experiments.The model provide a theoretical basis for the prediction of drilling force,tool analysis and straightness error analysis.2.The main factors affecting the hole straightness deviation of deep-hole gun drilling,such as insufficient rigidity of tool rod,clearance of guide sleeve,clearance of intermediate support and drilling force and their mechanism of action are explored.Based on Euler-Bernoulli beam theory,a predictive hole straightness deviation model considering the effect of misalignments at three supports,varying support distances and thrust force was developed and experimentally validated.Based on theoretical analysis,methods for adjusting the amount of clearance in fixed supports are proposed and tested successfully for the straightness control.The model provides a theoretical basis for the hole straightness deviation prediction and process control.3.Through experiments,the effects of feed and cutting speed on drilling force and chip deformation are analyzed.The wear form and failure mechanism of tool in deep-hole gun drilling are revealed.The influence of tool wear and tool outer angle on drilling force and chip deformation are further studied.The research provides a basis for the analysis of the processing quality of gun drills and the optimization of the processing parameters.4.The processing quality of Ti6Al4V gun drilling is studied.The influence of feed rate and cutting speed on surface roughness and hole diameter deviation are analyzed.The optimum processing parameters on the gun drilling of Ti6Al4V titanium alloy are obtained.The influence of tool wear and the change of gun drill external angle on the processing quality are analyzed.The strategy of optimizing the outside angle of gun drill and the important reference standard of blunt grinding of gun drill VB_max are put forward.The research results provide a theoretical basis for C919Processing Technology Specification for Deep Hole Parts.5.Based on the research,all the door shaft parts of a C919 aircraft have been processed and successfully accepted.