Research On Nonlinear Dynamics Of A Vibration Impact Drilling System

Vibration impact is widely used in engineering,such as percussion drilling machinery,vibration shakeout machine,vibrating screen,etc.Vibration impact drilling machinery is more and more widely used in engineering geological drilling and well drilling in farmland.At present,scholars at home and abroad have done a lot of research on vibration impact systems,but there are few researches on considering drilling motion in vibration impact systems.Therefore,based on the consideration of these two movements and the working mechanism of drilling rock in engineering,this paper establishes a vibration and impact drilling system model and analyzes its dynamic characteristics.Firstly,considering the viscoelasticity and dry friction of rock during drilling,a kind of single-degree-of-freedom vibration impact drilling system is established,the motion process of the system is analyzed,and the motion differential equation of the system is obtained Through numerical simulation,it is found that the system changes from period-doubling bifurcation to chaotic motion under certain parameters.The results of the study show that the system has the maximum drilling speed in a single period of motion.The drilling speed of the system increases first and then decreases with the increase of excitation frequency.The drilling efficiency of the system is also related to the ratio of constant force to harmonic excitation amplitude.When the ratio of constant force to harmonic excitation amplitude is low,the system is prone to chaotic motion,and the drilling efficiency of the system is low at this time.When the constant force is about half of the harmonic excitation amplitude,the system can obtain the maximum drilling amount.When the ratio of the two approaches 1,the system's drilling efficiency seems to be zero.Secondly,a two-degree-of-freedom vibration impact drilling system model is established,and a detailed dynamic analysis of the system is carried out through numerical simulation.The motion characteristics of the system under different control parameters and the process of evolution to chaos are studied.For this system,the research shows that the excitation frequency has a great influence on the drilling amount of the system,and the system has a great drilling efficiency when the system is in a single period motion by selecting an appropriate excitation frequency,which should be paid attention to in practical engineering.When the system has high drilling efficiency,the ratio of constant force to harmonic excitation amplitude is slightly different from that of a single-degree-of-freedom system.This is because the additional degree of freedom results in the variation of drilling efficiency and control parameters of the system.Finally,based on the theory of vibration,a three degree of freedom vibration percussion drilling system model is simplified according to the experimental device.Through numerical simulation,bifurcation diagram of the system is obtained by taking the external excitation frequency,constant force and harmonic excitation amplitude as bifurcation parameters,and the system dynamics is analyzed in detail by combining time history diagram,phase diagram and Poincaré maps.It is found that the motion state of the high-dimensional system is very complex,and there are many paths leading to chaotic motion,such as period-doubling bifurcation,Hopf bifurcation,torus bifurcation,and radical bifurcation.The results of this paper can provide a useful scheme for optimal mechanical design and make current drilling systems achieve optimal efficiency.