Development Of Novel Method And System For Two-Dimensional Vibration Assisted Polishing

Development of novel method and system for two-dimensionalvibration assisted polishingComponents and elements with smooth or ultra-smooth surfaces are increasingly demanded in various engineering fields,such as aerospace,national defense,biomedical engineering,scientific instruments and energy.To achieve the demanded components and elements with smooth or ultra-smooth surfaces,much research has been done in the international academia and industry,and some very valuable non-traditional polishing methods utilizing the external energy fields have been proposed,such as magnetic field-assisted polishing,ultrasonic vibration-assisted polishing,flow field-assisted polishing,and electric field-assisted polishing.Among these proposed non-traditional polishing methods utilizing the external energy fields,the two-axis ultrasonic vibration-assisted polishing method can actuate the polishing tool to move in a closed path at ultrasonic frequencies to help achieve higher polishing removal rate,which has great application potential in the polishing of components and elements with micro geometric characteristics.Nevertheless,in the existing two-axis ultrasonic vibration polishing methods,the two-axis ultrasonic vibrations are generated by the longitudinal vibration along the axis direction and the bending vibration along the transversal direction of the stepped transducer,and its performance is restricted by some disadvantages below.Firstly,because the vibration body mode is subject to the structural constraints,it is difficult to obtain the longitudinal and bending vibration frequencies with expected ratios,which results in that the resultant motional trajectories cannot meet expectations.Secondly,under the large demanded vibration amplitudes,some higher order vibration modes along the axial and the transverse directions are stimulated easily,between which there exist unavoidable couplings.Thirdly,the ultrasonic vibration working frequencies relate with the resonant modal frequencies,which cannot be adjusted according to the specific machining requirements easily.To solve the existing problems in the two-axis ultrasonic vibration-assisted polishing,the studies on the novel method and system for the two-dimensional vibration-assisted polishing are carried out in this paper.The studies in this paper mainly involve the following three aspects: the generation of the closed motion paths of the polishing tool driven by the two-dimensional vibrations;the development and the performance verification of the two new decoupled two-dimensional vibration polishing systems;the development of the characteristics of the polishing removal function and the influences of the two-dimensional vibration parameters and the polishing process parameters on polishing removal.(1)The following study carried out: the parameter conditions when the two-dimensional vibrations generate the expected closed motions,the influences of the vibration parameters on the shapes of the generated motion paths,and the generated polishing area when the polishing tool moves in a closed motion path.The study results show that the expected closed motional path with uniform distribution and dense crossed grids,can be obtained to improve texture feature of the machining surface,under the controlled vibration parameters.Actuated by these closed motion,the polishing action scope is approximate to be square;the smaller the polishing tool,the closer the polishing action scope;the approximate square action scope has greater favor in stitching of subaperture path than that of circle action scope;the simulation results of ploshing removal function show that the function form is a bowler hat.(2)On the basis of the principle utilizing two independent langevin vibrators to actuate the polishing tool to move in a closed path,a two-dimensional vibration-assisted polishing systems with ultrasonic frequency is developed;on the basis of the principle utilizing two piezoelectric actuators to actuate the non-resonant polishing tool to move in a closed path,a two-dimensional vibration-assisted polishing systems with intermediate and high frequencies is developed.The experimental test results show that the two new systems have small disturbances between the motions in the x and y directions;the new decoupled polishing systems can achieve the resonant frequency of 29.3 kHz in both x and y directions;the new decoupled non-resonant polishing systems can achieve the working bandwidth of 300 Hz in both x and y directions;the motion paths with different frequency ratios can be generated easily utilizing the decoupled non-resonant vibration polishing systems.(3)The polishing experiments are carried out using the two developed two-dimensional vibration-assisted polishing systems,the polishing forces are disturbed to some extent because of the unevenness of the workpiece surface profiles and the feed motion during the continuous feed motion process,the statistical means of which mainly depend on the preloads applied by the polishing tools;the polishing tool moves in a closed motion path,and the generated polishing removal functions show the Bowler Hat distribution.(4)The polishing experiments are carried out using the decoupled resonant two-dimensional vibration-assisted polishing systems,in which the polishing tool is actuated to move in a closed motion path,and the maximum removal depth per unit time is proportional to the contact pressure,and the vibration amplitude,and is inversely proportional to the feed speed;when the polishing tool is actuated to move in a motion path utilizing the decoupled non-resonant two-dimensional vibration polishing systems,the maximum polishing removal depth will increase with the increasing of the vibration frequency,the frequency ratio and the preload.The studies on the new method and the systems of the two-dimensional vibration-assisted polishing conducted in this paper lay the theoretical and experimental foundation for further realizing the efficient polishing of smooth and ultra-smooth surfaces of the components and elements with micro geometric characteristics.