Study On Vibration Characteristics Of BTA Deep Hole Drill Pipe Assembly And Design Of Shock Absorber

The deep hole drilling is an indispensable important component in the mechanical manufacturing industry. As the rapid development and progress of the aerospace, high-speed railway and heavy machinery etc. it makes the growing demand for deep hole drilling technology. However, because of the particularity of the deep hole drilling, its drill pipe is thin, long and in the hollow state when machining. There are the high-pressure cutting fluid round its outside and cutting fluid with chip carrying out through its inside. These make a serious shortage of rigid leading to the pipe vibration that will have obvious influence on machining precision and machining efficiency and tool wear etc.The paper makes a thorough analysis of the mechanical properties of drill pipe components and vibration characteristics in the process of BTA deep hole drilling system. It provides the theory basis for the study of vibration reduction measures and the design of the drill pipe shock absorber with radial additional force. It will have very important practical significance.First of all, this paper introduces the structure characteristics and working principle of the BTA deep hole drilling. According to the actual machining process, the orthogonal cutting model of BTA drill is established and the stress of BTA drill is analyzed based on the model. According to the principle of cutting and the theory of micro cutting tools, drilling mechanics model of BTA is established. The influence of feeding and cutting speed on axial force and torque of cutting tool is studied through simulation and experiment, that laid a theoretical foundation for analysis and study of drill pipe vibration characteristic. In the process of the deep hole processing, the vibration of the drill pipe includes horizontal vibration, vertical vibration, torsional vibration, at the same time, combined with the significant effect of the cutting fluid on the stability of the drill pipe. So this article made detailed discussion and analysis on vortex of the drill pipe components, torsion and transverse, longitudinal vibration respectively.(1)Based on considering the effect of cutting fluid on the drill pipe during the actual process of the deep hole machining, the reasons of the vortex generated by drill pipe was analyzed, and according to the Reynolds equation motion differential equation of drill pipe eddy is deduced to get the drill pipe eddy critical conditions of instability.(2) Considering cutting fluid, chip, the influence of drill pipe’s rotating on the torsional vibration of drill pipe, the movement model of drill pipe torsional vibration is established. Then according to elastic mechanics, material mechanics and fluid mechanics etc., oscillatory differential equation of the drill pipe torsional vibration is established to obtain inherent frequency of the drill pipe torsional vibration and vibration mode function through calculating.(3) The theoretical analysis and modeling is used on study the transverse and longitudinal vibration of drill pipe. Differential equation of the transverse and longitudinal vibration of drill pipe is established and inherent frequency of the transverse and longitudinal vibration of drill pipe and the corresponding vibration mode function obtain is obtained. Once again, based on the above theoretical analysis and the actual situation in the process of deep hole processing, the vibration active control technology is introduced to the deep hole processing system, and drill pipe system of the drill pipe shock absorber installed the radial additional force is studied. Inhibiting effect of the radial force drill pipe shock absorber on drill pipe eddy instability, torsional vibration, transverse vibration and longitudinal vibration is analyzed in theory. Then, the structure of drill pipe shock absorber and the active control system carried on the preliminary design, and a processing example is simulated and analyzed by using Simulink software to verify damping effect of the shock absorber. Results show that the damping effect of the drill pipe shock absorber with the radial additional force is obvious.