Study On Mechanism And Technology Of Zirconia Ceramics With Longitudinal-Torsional Conposite Vibration Ultrasonic Grinding Machining

As one kind of hard and brittle materials,ceramic materials have the advantages of high strength and hardness,good resistance to high temperature,high pressure and corrosion,and good biological properties,so ceramic materials are widely used as the key precision parts in the fields of precision instruments,military industry,aerospace,medical equipment,computer engineering.etc.As to methons of ceramic materials machining,such as wire cutting,electrolytic or grinding machining in industrial production at present,they are easy to produce concentrated heat in the process of machining,resulting in thermal stress and thermal cracks.Then the machining quality is poor and the efficiency is low.Therefore,according to the process characteristics of ultrasonic vibration machining in the hard brittle ceramic engineering,it’s first to analyze the practical significance of ultrasonic machining hard brittle ceramic material with choosing zirconia ceramic material as the research object,,and then summary the ceramic materials processing theory and technology in the actual processing process based on indentation fracture mechanical to analyse crushing removal mechanism in longitudinal-torsional compound ultrasonic vibration machining on ceramic material,then build the test platform to analyse the material removal mechanism by surface morphology changes and the changes of the machining process physical grinding force in the processing to combine the theory.The main research methods and conclusions are as follows:1.Firstly,by summing up the theoretical basis,the advantages and disadvantages of the existing machining methods of ceramic materials,it is concluded that the composite ultrasonic vibration has some advantages on the machining of ceramic materials.The researchs and applications of composite vibration ultrasonic machining on hard and brittle materials are summarized and the advantages of longitudinal-torsional composite vibration ultrasonic machining on ceramic materials are determined.2.The relative motion form and machining process between tool and materials in the process of longitudinal-torsional composite vibration ultrasonic machining are modeled and analyzed.Different vibration output modes produce the micro contact-separation between tool abrasive particles and materials surface.The friction force between chip outflow and abrasive particles has reverse effect.Combined with the contrast test,it is proved that the unique motion form can effectively keep the sharpness of the grinding edge to reduce tool wear,and the material can be removed evenly,which leads to the formation of better surface quality.3.Based on the theory of indentation fracture mechanics of ceramic materials and the effect of applied ultrasonic vibration,a model of elastic-plastic stress field in the contact region during single abrasive particle indentation is established.By analyzing the nucleation and growth of the crack group and the process of interlacing spreading in the process of abrasive indentation,the critical cutting depth formula for the brittle plastic transition of the material in the process of machining is obtained.It is found that the nucleation and growth of cracks are directly related to the size of the applied load.The applied ultrasonic vibration machining is beneficial to the expansion of the plastic processing area of the material.Transverse crack and radial crack can promote the material fragmentation removal,improve the material removal rate,can also guarantee the quality of the machined surface;4.The grinding force model in ultrasonic machining process of longitudinal-torsional composite vibration is established.A platform to test force measurement is set up.Through the comparative analysis of grinding force test,it is found that ultrasonic vibration machining has the characteristics of reducing grinding force,smoothing machining process,lowing force and uniforming force.Furthermore,the variation of grinding force with ultrasonic vibration energy,spindle speed,feed speed and grinding depth is analyzed.5.Single factor measurement in longitudinal-torsional composite vibration ultrasonic grinding procesing is carried out with choosing the engineering of zirconia ceramic material as the experimental object,to analyse the parameters’ influence(ultrasonic vibration energy,spindle speed,feed speed and grinding depth)on surface quality to find that the surface roughness value decreases with the increase of ultrasonic vibration energy and spindle speed,while the grinding depth and feed speed increase,the surface roughness value increases.On the basis of the influence law of single factor parameters,the level of important machining parameters is selected to carry out orthogonal experiments.The experimental results show that the degree of influence of ultrasonic vibration energy,spindle speed,feed speed of grinding depth on surface roughness decrease in sequence,and the best processing parameters of ultrasonic vibration is that the ultrasonic vibration energy values 34 V,the grinding depth values 9 μm,the feed speed values 15mm/min and the spindle speed values 24000r/min.