Experimental Study On Ultrasonic Vibration-assisted Grinding Of Sapphire

Sapphire has been widely used in national defense,aerospace and civilian areas due to its excellent mechanical,physical and optical properties.The high efficiency and precision processing for sapphire is required in these areas.As the single crystal sapphire is a hard and brittle material,it is hard to obtain good surface quality by grinding the surface of sapphire.A mass of research results have shown that ultrasonic vibration-assisted grinding which is compared with ordinary grinding can not only improve the efficiency of grinding processing,but also improve the surface quality of the workpiece.So the project put forward the experimental study on ultrasonic vibration-assisted grinding of sapphire to reveal the mechanism of ultrasonic vibration-assisted grinding of sapphire.This paper introduces a ultrasonic vibration-assisted grinding experimental study of sapphire material with precise grinding machine and compares the differences of processing effect between three ultrasonic vibration directions and on-off ultrasonic vibration.In order to analyze the effect of different direction ultrasonic vibration-assisted grinding about sapphire,we carry out some researches in the following aspects: kinematics characteristics of single grain in ultrasonic vibration-assisted grinding processing;grinding characteristics;surface topography with SEM and surface defect characteristics with LSM.The main results are as follows:(1)Simulate and model the trajectory of abrasive particles which are applied with ultrasonic vibration.And analyze the interaction process between the abrasive particles and the workpiece.When the workpiece is loaded with axial ultrasonic vibration,the length of the motion trail about single grain is longer than common,the average area of debris is smaller than common,the grinding width is bigger than common;when the workpiece is loaded with radial ultrasonic vibration,the particles will separate from the workpiece sometimes,the number of effective particles on the surface of grinding wheel will reduce;when the workpiece is loaded with tangential ultrasonic vibration,the grinding wheel will iron repeatedly on the surface of workpiece,and the particles will separate from the workpiece as well.(2)Increasing ultrasonic vibration amplitude can reduce the grinding force.Compare grinding force in ultrasonic assisted grinding: the grinding force of radial ultrasonic vibration is smallest,the grinding force of axial ultrasonic vibration is second,and the grinding force of tangential ultrasonic vibration is smaller than common,in terms of grinding force ratio and specific grinding energy,both of them have been reduced.(3)Calculate the expression formula of surface roughness,and measured the surface roughness after grinding,the surface roughness of radial ultrasonic vibration is bigger than common,however,the surface roughness of axial ultrasonic vibration and tangential ultrasonic vibration is smaller than common,meanwhile,in the direction of grinding,the surface roughness of axial ultrasonic vibration is bigger than the surface roughness of tangential ultrasonic vibration,and in the direction which is perpendicular to grinding direction,the surface roughness of axial ultrasonic vibration is smaller than the surface roughness of tangential ultrasonic vibration.(4)Compare the surface topography and measure the surface defect characteristics,the surface of ultrasonic vibration-assisted grinding contains more micro fractured areas,and the number of big grooves is reduced;The size of the depth of the surface groove is:the depth of common grinding is 12.83?m,the depth of axial ultrasonic vibration grinding is 9.27?m,the depth of tangential ultrasonic vibration is 10.31?m,and the depth of radial ultrasonic vibration is 13.65?m.(5)Three different directions of ultrasonic assisted grinding improve the machinability of sapphire,axial and tangential ultrasonic grinding increases the surface quality,however the radial ultrasonic grinding makes the surface quality worse.