Analysis Of Stick-slip Vibration Of BTA Deep Hole Drilling System And Optimization Of Drill Pipe Structure Parameters

Taking BTA deep hole drilling system as the research object,the workpiece has serious quality defects in roundness error and surface quality at the middle and late stage of processing,which is manifested as multi-lobe periodic vibration pattern.A theoretical model is established to analyze and compare the vibration characteristics of drilling system with or without stick-slip vibration.This paper presents an optimization scheme for the structural parameters of drill pipe and the supporting position interval,and illustrates the effect of vibration suppression before and after optimization by combining the vibration characteristics of drill pipe and experimental data.The stick-slip vibration characteristics and vibration suppression methods of drilling system are studied in this paper.Specifically,it can be divided into the following points:(1)The vibration characteristics of drilling system are analyzed from friction model and self-excited vibration theory,and the basic assumptions of the correlation analysis are proposed;the simplified mass torsion model and subdivision unit torsion model of drilling system were established on the basis of dynamic analysis,including differential equation model and motion state space representation.(2)Based on the established torsion analysis model of the drilling system,combined with the main factors that affect the stick-slip vibration in the system,the motion differential equation of the drilling system is established and solved.Substituting the actual physical parameters of the on-site drill pipe system into the mechanical model for solving,and study on the stick-slip vibration response characteristics of the drilling system and the system energy transfer mechanism accompanied by the stick-slip vibration phenomenon.(3)Contrast the response curve of drilling system when feeding to different machining positions,the drill pipe vibration type,drill bit frequency domain response behavior and experimental test signals when the drilling system feeds to the depth of 300 mm and 900 mm in the direction of the workpiece to be processed were studied respectively;It is found that when the stick-slip vibration occurs in the drilling system,the workpiece also has emerged with periodic flap-shaped vibration patterns.(4)The vibration characteristics of the drilling system were tested with the acceleration sensor and relevant experimental instruments.By comparing the simulated modal results,the measured points of the acceleration sensor are iterated repeatedly.In order to ensure the authenticity of experimental results and simulation results,the test results and simulation model have undergone multiple calibrations.(5)The equivalent stiffness and working stability of the drill pipe are analyzed when the structural parameters of the drill pipe wall thickness and the inner diameter of the drill pipe are changed under the condition of ensuring the minimum chip removal space.By discretization analysis method,the optimization interval of support position of drill pipe before and after machining is solved.By comparing the results of the numerical analysis of the natural mode and the harmonic response of the drilling system before and after optimization,the conclusion shows that the use of the optimized support interval can increase the robustness and stability of the drilling system.At the same time,the vibration signal measured by the experiment also proves that the optimized support interval can obviously reduce the excessive vibration behavior of the drill pipe in the machining process.