Research On Particle Damping And Magnetorheological Compound Damping Boring Tool

In the field of Cutting,The cutting vibration of tool seriously affects the surface quality of the machined parts,restricts the improvement of processing efficiency.Especially for precision holes and deep holes boring,because of its processing needs of the boring tool with large aspect ratio,the damping effect of boring tool must be better,but ordinary boring tools often can not meet the design requirements of processing quality of workpiece hole,so,the technique of chatter suppression of large diameter ratio boring knife has become an important research topic.In this paper,aiming at the phenomenon of cutting chatter of large diameter ratio boring knife,the particle damping technology and magnetorheological damping technology were commonly used in large diameter boring knife,the particle damping and magnetorheological compound damping boring tool was designed.Not only can vibration energy be consumed by the collision and friction through the particles,particles and the boring bar wall,producing damping effect,but also the natural frequency of composite damping boring tool can be changed through the characteristics of magnetorheological fluids damping and real-time control to avoid the occurrence of resonance and achieve the purpose of vibration.The main contents and conclusions of this paper are as follows:1.The background and significance of the subject was elaborated,the developments of damping boring tool was introduced in detail,the working mechanism and the research status at home and abroad of particle damping and magnetorheological damping technology were emphatically introduced,the main research contents of this paper were put forward.2.The properties of particles were studied,the mechanical model of damping particles was established according to the principle of discrete element method and contact mechanics,the calculating method of the total contact force,total torque and energy dissipation of the particle damping system was provided.3.The dynamic model of the particle damping boring tool was established,under different filling particle parameters the hammering and boring experiments were performed for particle damping boring tool to test the feasibility of particle damping in damping boring tool and the performance of boring tool,the results show: the smaller diameter and greater density the filled particles has,the better damping effect boring tool produces,the best damping effect occurs at the filling ratio of 70%,the highest damping ratio of boring tool reaches to 4.38% and the minimum Ra value of surface roughness of workpiece is 1.392?m after boring,which has been reduced by 50.09% compared with the solid one,particle damping boring tool has good cutting performance.The orthogonal test method was introduced,the main and primary factors which had an influence on cutting performances of particle damping boring tool was determined,the effects of the experiment factors on cutting properties of particle damping boring tool was found,and an optimization scheme for further design was obtained.4.The rheological mechanism of magnetorheological fluids was described;the classification and principle of the working mode of magnetorheological fluids were introduced in detail.According to the four dynamic models of magnetorheological fluids damping,a modified Bingham model was created,Not only did the model fully embody the damping characteristics of magnetorheological fluids,but also had the advantages of simpleness and practicability of Bingham model.A simplified flow model of magnetorheological fluids was established;accordingly,the damping force of magnetorheological fluids was calculated.5.The structure,assembling method and working principle of particle damping and magnetorheological compound damping boring tool were introduced.The boring bar consisted of three sections which used the butt welding process to connect,and its materials was identified,according to the principle of material mechanics combined with estimated method the sizes of boring bar were determined.The materials of the magnetorheological damping system was identified,considering the restriction of structure sizes,the length of magnetorheological damping system and the height of boring bar shoulder were set.According to theories,the three main structural parameters of magnetorheological damping system were selected,and three sets of values of each structural parameter was selected as the levels of the next orthogonal test,the current density and model of the excitation coil are determined by the manual and GB,and according to Ampere loop theorem the turns of excitation coil were calculated.L9(34)orthogonal test table was designed,the magnetic induction intensity of the damping channel obtained by ANSYS two-dimensional static magnetic field analysis was taken as the evaluation index,the sizes of magnetorheological damping system were determined by range analysis,finally,the particle damping and magnetorheological compound damping boring tool was completely designed.6.The first four natural frequencies and vibration model of the composite damping boring bar were researched by ANSYS modal analysis,the results show: when the excitation coil current increases from 0A to 2A,the natural frequencies of composite damping boring bar improve,the first-order natural frequency increases from 450.69 Hz to 505.81 Hz,the relative displacement of each vibration model reduces,the composite damping boring bar has good dynamic controllability and vibration suppression performance.The response of the first-order natural frequency of a node at the front end of the outer circle of composite damping boring bar was studied by harmonic response analysis,the result shows: when the excitation coil current increases from 0A to 2A,the response amplitude of the first-order natural frequency of the node is obviously reduced,0A the response amplitude is 3.436?m,while 2A it is only 0.908?m,which further describes the good dynamic controllability and vibration suppression performance of the composite damping boring bar,the particle damping and magnetorheological compound damping boring tool achieves the design purpose.