| Nickel-base alloy has excellent properties such as high strength,corrosion resistance and chemical stability,and widely used in industrial fields.However,it is a typical difficultto-machined material because of the problems such as large cutting force,high cutting temperature and serious tool wear.The ultrasonic vibration assisted drilling is an effective special machining method to solve the drilling problem of metal difficult-machining materials.The theory of ultrasonic vibration assisted drilling is studied in this paper,and then the simulation and experimental research on Inconel 718 nickel-base superalloy are carried out.The main work of this paper is as follows:(1)The theory of ultrasonic vibration assisted drilling and tool wear mechanism is studied.The basic theory of vibration drilling is described,and the displacement track and variable speed characteristics of cutting edge in ultrasonic vibration assisted drilling are studied,and the mathematical models of tool displacement function,velocity function and axial force were established,and the change of axial force and heat transfer of drilling temperature during ultrasonic vibration-assisted drilling were analyzed,and the heat transfer performance and temperature change law of cutting heat during ultrasonic vibration-assisted drilling were further summarized through experiments;the mechanism of tool wear during ultrasonic vibration assisted drilling is studied,and the reasons of improving tool wear by ultrasonic vibration assisted drilling are summarized through experiments.(2)The process of ultrasonic vibration assisted drilling and ordinary drilling of Inconel718 nickel-base superalloy was simulated by using finite element simulation software ABAQUS.Comparative simulation experiment were carried out and taking drilling axial force and drilling temperature as research indexes,and high-frequency vibration of 50 k Hz was used,according to the simulation results,the axial force and drilling temperature of ultrasonic vibration assisted drilling were reduced by 35.28% and 15.99% compared with ordinary drilling;the axial forces at different spindle speeds,amplitudes and feed speeds were simulated,and according to the simulation results,the axial force decreases with the increase of spindle speed,decreases with the increase of amplitude,and increases with the increase of feed speed.(3)The axial force of ultrasonic vibration assisted drilling of Inconel 718 nickel-based superalloy was studied using 50 k Hz high frequency vibration and verified with simulation.The axial force of Inconel 718 nickel-base superalloy drilling assisted by ultrasonic vibration was studied using 50 k Hz high frequency vibration and verified with simulation.Comparative experiment were carried out,and the experimental results show that the axial force of 50 k Hz ultrasonic vibration assisted drilling can be reduced by 26.19% compared with normal drilling;the axial forces at different spindle speeds,amplitudes and feed speeds were experimentally studied,and the results show that the axial force decreases with the increase of spindle speed,increases with the increase of feed speed,and decreases with the increase of amplitude;the orthogonal experiment was carried out,and the influence degree of axial force is as follows: feed speed,amplitude,spindle speed.(4)The tool wear of Inconel 718 nickel-base superalloy in ultrasonic vibration assisted drilling was compared with that of ordinary drilling.Using 50 k Hz high frequency vibration,taking the number of holes as a variable,the tool wear was studied from four aspects of tool microstructure,axial force,drilling temperature and surface roughness of hole wall;according to the tool microscopic morphology pictures,ultrasonic vibration assisted drilling can improve the wear of cutting edge and cutting surface;with the increase of drilling times,the ultrasonic vibration assisted drilling can slow down the rising speed of axial force,reduce the drilling temperature by 17.95%,and reduce the surface roughness by 17.63%.The conclusions from these four aspects indicate that the ultrasonic vibration assisted drilling can effectively reduce the tool wear and improve the tool life. |
PDF Full Text Request