Research On Negative Pressure Cavitation Abrasive Water Jet Polishing

At present,the application of optical glass,silicon carbide,tungsten carbide and other hard brittle materials has become more and more widely used,and it's development direction is more likely to the high precision and miniaturization.The require of the surface quality and the removal efficiency is higher and higher.Due to the restriction of polishing tools,it is very hard to use the traditional method to polish the small,irregular workpiece.Therefore,the polishing of free-form surface and small special-shaped surface has become a new problem in the field of ultra precision machining.Based on this,a new method called the negative cavation abrasive water jet polishing has been proposed in order to realize the polishing to small irregular worepiece and improve the polishing efficiency.The principle and experiment of the negative cavation abrasive water jet polishing has been discussed,and the main research work has been carried out from the following aspects:(1)The removal mechanism of negative cavation abrasive water jet polishing is revealled from the abrasive water jet(AWJ)removal and the enhancement of negative pressure cavitation.Fluent Software has been used to simulate the flow field of vertical jet and inclined jet,and forecast the polishing shape based on the pressure field,velocity field,abrasive track and abrasive particle distribution of the jet.At last,the influence of different environmental negative pressure and inlet pressure to the cavitation bubble content is simulated.(2)The experimental platform is designed and built,and the stability of the platform has been tested.The selection of the abrasive in the polishing experiment has been introduced,and the influence of different hardness and particle size of the abrasive on the surface roughness after polishing has been analyzed.Several important parameters which influence the polishing of abrasive water jet were optimized by experiments,and some experiments on K9 glass has been carried out by using atmospheric pressure water jet polishing and negative pressure water jet polishing.The surface roughness can be up to llnm and 5nm after the polishing in atmospheric pressure and negative pressure.The surface roughness has been much lower after the polishing,and the grinding marks on the workpiece surface are removed very obvious.The experiment proves the feasibility of the device and the method.(3)Three kinds of polishing methods have been carried out on copper workpiece which has been polished by sandpeper.The results showed that the removal of abrasive jet is the main factor in the negative pressure cavitation abrasive water jet polishing,and negative pressure cavitation plays the role of assisted removal.Several important parameters affecting the removal rate and surface quality of negative pressure cavitation abrasive water jet were studied.Finally,the K9 glass was polished by negative pressure cavitation abrasive water jet,and the lowest surface roughness can be 2.5nm after polishing.