Study On Ultrasonic Vibration And ELID Combined Grinding Mechanism Of Nano-ceramics And Its Surface Quality

Nano-ceramics materials have many advantages,such as high strength,high temperature resistance,wear resistance,chemical stability and so on,which has been applied in many fields such as aerospace,materials engineering and mechanical engineering.At the same time,nano-ceramics materials with the characteristics of high elastic modulus,low fracture toughness,is very difficult to carry out grinding efficiently and precisely,which has become the bottleneck of pervasive application.At present,ultrasonic vibration assisted grinding and ELID grinding were proven and widely used in the high efficiency mirror processing of nano-ceramics materials and other hard brittle materials.In this paper,nano-ceramics workpiece ultrasonic vibration grinding and ELID grinding were compounded;the correlation and stability of composite grinding manner were in-depth analyzed;complex grinding material removal mechanism,the surface forming mechanism,the variation of grinding force and surface quality were studied,so as to reveal the mechanism of high efficiency and ultra precision machining through ultrasonic vibration and ELID combined grinding the nano-ceramics materials,and to provide support for the high efficiency mirror machining theory and technology of hard brittle materials.The main research contents of this paper were as follows:First of all,an experimental platform of the ultrasonic vibration and ELID combined plane grinding nano-ceramics materials was built.Based on the mechanism of ultrasonic vibration assisted grinding and ELID grinding,the adopted experimental device of ultrasonic vibration grinding system developed by the research group and the additional planar ELID grinding on the precise surface grinder,the experimental platform of ultrasonic vibration and ELID combined plane grinding system was completed.According to the analysis of ultrasonic vibration and ELID combined grinding system from a viewpoint of the integral combination by the finite element method,the optimization design of acoustic system and the vibration performance test were completed.Secondly,the oxide film state of the ultrasonic vibration and ELID combined plane grinding nano-ceramics materials was studied.According to theories about electrochemical reaction principle,ultrasonic vibration assisted grinding geometry parameter analysis and single grain cutting path analysis,the generation and removal of oxide film and the dynamic equilibrium in the process of ultrasonic vibration and ELID combined grinding were analyzed,and a theoretical thickness model of the oxide film was established,and the simulation was carried out.The oxide film state can be effective controlled by means of signal representation.According to the characterization of signal change of the oxide film on the grinding force and current,this paper concluded that ultrasonic vibration of ELID grinding process has little effect on the formation of oxide film thickness and strength and both of them are weakly correlated.Next,the removal mechanism and surface forming mechanism of ultrasonic vibration and ELID combined plane grinding nano-ceramics materials were analyzed.Based on the plastic removal principle of diamond abrasive grain indentation,the critical cutting depth and critical condition of the critical cutting depth and the brittle plastic transition of ultrasonic vibration and ELID combined plane grinding nano-ceramics were analyzed.Based on the study of nano-ceramics using ultrasonic vibration grinding of single abrasive material volume removal,considering ELID grinding,a mathematical model of the removal rate of combined plane grinding materials was built;simulation prediction and experimental research were carried out.Compared with the ordinary ELID grinding,the material removal efficiency improved significantly.Ultrasonic vibration and ELID combined plane grinding nano-ceramics surface generating mechanisms were analyzed from the angle of the workpiece material particle trajectory and it was concluded that ultrasonic vibration and ELID combined plane grinding nano-ceramics materials can obtain better machining surface through the comparison test of ultrasonic ELID grinding with ordinary ELID grinding,.Then,grinding force characteristics of ultrasonic vibration and ELID combined plane grinding nano-ceramics was studied.According to the mathematical model of grinding force in common grinding,the grinding force of ultrasonic vibration and ELID combined grinding was analyzed from three aspects: cutting force,friction force and ultrasonic vibration impact force.Considering the effect of ultrasonic vibration and ELID grinding,a mathematical analysis model of the grinding force was established under the condition of ultrasonic vibration and ELID combined plane grinding nano-ceramics materials.The simulation prediction and experimental research were carried out.The compound action of ultrasonic vibration and ELID was helpful to improve the polishing properties of the oxide film,which can effectively reduce the grinding force.The unique characteristics of the grinding force were conducive to the realization of the grinding of hard and brittle materials containing nano-ceramics.Last,the research about the surface micro quality of ultrasonic vibration and ELID combined plane grinding nano-ceramics materials was conducted.According to the basic principle of electrical discharge machining,the metal bonded grinding wheel was precision dressed,the roundness error of the grinding wheel is reduced to about 3μm,which meets the requirement of ultrasonic vibration and ELID combined plane grinding nano-ceramics materials.The influence conditions of different grinding parameters,ultrasonic vibration parameters and ELID parameters on the surface roughness were discussed through the test of surface roughness of nano-ceramics materials by ultrasonic vibration and ELID combined grinding.By means of SEM,white light interferometer,the basic characteristics of surface morphology and surface damage of nano-ceramic material ultrasonic vibration and ELID combined grinding were analyzed.Experimental research shows that the ultrasonic vibration and ELID combined grinding process can obtain high quality machining surface,lower surface roughness value,more smooth and uniform surface morphology and less surface damage.Research shows that ultrasonic vibration and ELID combined plane grinding nano-ceramics works for the ultrasonic vibration precision grinding,and achieves the effect of the ELID ultraprecision mirror grinding with relatively stable,controllable oxidation state,which can realize high performance mirror grinding nano-ceramics materials and other hard and brittle materials.