Optimization Of Geometric Parameters Of TC4 Titanium Alloy Drilling Tool

Ti-6Al-4V(TC4)titanium alloys,the usage of which accounting for more than half of the total usage of titanium alloys,are widely used in aerospace,chemical and medical fields because of their excellent performance in strength,toughness,heat and corrosion resistance as well as in biocompatibility.Hole processing accounts for about one third of the annual machining volume,which is often required in the processing of TC4 titanium alloy.In the drilling process,the special properties of TC4 titanium alloy make the drill bit easy to wear and break for the large drilling force and torque,which not only reduces the processing efficiency but also scraps the workpiece,thus increasing the production cost.Therefore,when drilling TC4 titanium alloy,the geometric angle of the standard bit can no longer be fully adapted.It is necessary to optimize the geometric parameters of twist drill used for drilling TC4 titanium alloy due to the condition of the “material”,so as to reduce the drilling force,torque and residual stress in the process of TC4 processing,and improve the hole processing efficiency and surface quality.Based on the above problems,the following aspects are studied in this paper.(1)This paper first introduced the structure and main geometric parameters of the standard twist drill,and analyzed several common grinding methods of the twist drill.According to the flank grinding principle of conical twist drill,a threedimensional model of conical twist drill was established in the NX10.0 software.The cutting edge was discretized according to the drilling principle of the twist drill,thereby establishing a mathematical model of the drilling force and torque.(2)With the apex angle,helix angle and blade width of the twist drill as the experimental factors,an experimental scheme was designed by using the orthogonal regression design method.Using the NX10.0 software,the tool models of different apex angles,helix angles and blade widths in 15 sets of test schemes were established,and the three-dimensional drilling model of TC4 titanium alloy was established by ABAQUS finite element analysis software.Besides,15 different twist drill models were used to simulate the TC4 titanium alloy drilling,and the drilling force,the torque and the residual wall stress were also obtained under 15 different sets of tool geometric parameters.(3)Regression models between the drilling force,the torque,the residual wall stress and the experimental factors were established respectively in this study by adopting the multivariate nonlinear regression method.With the removal of the insignificant part of partial regression coefficient in the equation,the regression equations between the drilling force,the torque,the residual wall stress within the range of selected experimental factors and the apex angle,the helix angle and the blade width of the twist drill as the experimental factors were finally established,which were based on the significance test of the regression equation and the partial regression coefficient.(4)The basic principle and characteristics of particle swarm optimization(PSO)were introduced and the optimization process of PSO was realized through programming in MATLAB.Based on the established regression equations of the drilling force,the torque and the residual wall stress as the fitness function,PSO was used to optimize the minimum drilling force,the minimum torque and the minimum residual wall stress respectively,and the optimized tool geometric parameter combination was thus obtained.Then using the optimized tool geometric parameter,the drilling simulation model was established again to verify that the drilling force,torque and residual wall stress could be reduced after optimizing the tool geometry parameters.The optimization of geometric parameters of twist drill used in drilling for TC4 titanium alloy can effectively improve the efficiency and quality of TC4 drilling,and provide some reference for practical production.