| With the advantages of reliable chip breaking,smooth chip discharging,small drilling force,high machining precision and long tool life,the technology of deep hole vibration drilling on staggered teeth BTA has been widely used in the field of deep hole processing.However,because of the complexity of the mechanism of deep hole vibration drilling and the variety of processing conditions,the tool system is affected by various complex environment in the process of actual drilling,which leads to the very complex movement track of the tool center,and thus affecting the quality of the hole processing.Therefore,how to accurately control the size of chip and drilling force and predict the radial vibration of the tool system has become a hot and key problem in the machining of vibratory deep holes.Based on the deep hole processing of the third generation nuclear AP1000 steam generator tube plate,the numerical simulation and experimental research on the mechanism of chip breaking for vibration drilling,drilling force model and radial vibration characteristics of the tool system are carried out in this paper.It provides a reference for the control of the machining quality and the optimization of the process parameters for the BTA deep hole vibration drilling.The working principle of BTA axial vibration drilling is analyzed and the mathematical model of motion trajectory for BTA tool is established.Through the study of the mechanism of chip breaking for vibration drilling and the influence of process parameters on the chip shape,the conditions of chip breaking,the area diagram of chip breaking and the changing law of dynamic cutting thickness are obtained.According to the mechanism of chip breaking for vibration drilling,a mathematical model of theoretical chip length is established,and the effect of the ratio for frequency to speed on chip shape is studied.By analyzing the change law of the actual cutting angle at any point on the main cutting edge of the cutter in the vibration drilling process,the mathematical model of the dynamic cutting angle of the vibration drilling is established.The influence of drilling parameters on the dynamic cutting angle is discussed under the condition of vibration drilling.The force analysis of the cutter teeth in the drilling process is carried out.Based on the orthogonal shear force element model,the mathematical model of the drilling force for the BTA deep hole vibration drilling is established,and the influence of the drilling parameters on the drilling torque and the axial force is discussed.The cutting tool system is simplified and the extrusion of the guide bar is ignored.Only considering the influence of radial vibration of auxiliary cutting edge on the machining quality of holes,the radial dynamic model of the tool system is established,and the radial dynamic characteristics of the tool system are studied.On the premise of guaranteeing the precision of the solution of the dynamic equation of the tool system,the cutting process is discrete to a number of tiny cutting units while the adjacent cutting units meet the continuous condition of the state equation.Then using the difference equation to solve the method,the numerical solution of the radial vibration displacement of the cutting tool in deep hole drilling is given.The influence of drilling parameters on the dynamic characteristics and stability of the tool system is studied.It is revealed that the flutter of the tool system is one of the main cause for the deterioration of the machining quality in the BTA deep hole drilling,and the formation of the flutter is influenced by the cutting parameters.It is proved that the vibration drilling has the effect of restraining the flutter.The BTA deep hole vibration drilling platform was built,and the experimental research on drilling force,the effect of chip breaking,radial vibration characteristics of tool system and the quality of hole machining was completed.The experimental results show that the minimum point of drilling force appears when the ratio for frequency to speed is close to the integer,and the maximum point appears when i is close to 0.5.The vibration drilling reduces the radial vibration of the tool system and improves the stability of the drilling system.Compared with the conventional drilling,the roundness,the surface roughness and the micro morphology of the hole are improved obviously.The experimental results verify the correctness and effectiveness of the theoretical analysis. |
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