| Engineering ceramics have excellent mechanical and physical properties and are widely used in defense,chemical,aviation and other industrial fields.After making and shaping,engineering ceramics often need the second time procession,such as drilling and milling,according to assembly requirements.However,the engineering ceramics are hard and brittle.It is a typical difficult to process material.At present,the main way to process holes is grind drilling by diamond tools.The processing quality is difficult to meet the requirements of use,and it is difficult to realize engineering and batch processing.In this paper,diamond tools made by composite process of sintering and brazing are used to test the low frequency axial vibratory drilling of engineering ceramics.First,on the basis of the analysis of the manufacturing process of diamond tools,in view of the processing characteristics of the engineering ceramic materials,the preparation of the composite diamond tool for composite process of sintering and brazing is determined.The structure of the tool is designed.The main body of the cutter is a thin-walled cylinder structure,and the working part is designed to form wavy teeth.On the basis of the analysis of the selection principle of diamond abrasives,tool matrix material and working layer material,the diamond abrasive particles are mixed with three kinds of granularity 70/80,80/100 and 100/120,and the 40 Cr steel as the matrix material is determined,and the specific formula of working layer material is determined.The preparation process of diamond tool for composite process of sintering and brazing is designed.Secondly,through the single factor test of the engineering ceramic drilling,the influence of the spindle speed,feed speed and vibration amplitude on the axial force,the width of the avalanche and the roughness of the hole wall in the drilling of the engineering ceramic is studied.The experimental results show that the low frequency axial vibratory drilling is obviously superior to the traditional drilling.Through orthogonal test,the processing parameters of the low frequency axial vibratory drilling of engineering ceramics were optimized with axial force as the goal.The axial force prediction model on the processing parameters of low frequency axial vibration hole of engineering ceramics based on the orthogonal test results is established,and the model is verified by the preliminary test.After that,the material removal mechanism of engineering ceramics was studied by analyzing the mechanics of indentation fracture of hard brittle materials and surface micromorphology of the hole wall of engineering ceramics.The results show that the brittle fracture and plastic forming of the material removal mechanism of the alumina engineering ceramics are obtained.The influence of feed speed,vibration effect and coolant on the surface morphology is studied.The experimental results show that,with the increase of feed speed,the plastic deformation ratio of alumina engineering ceramics is reduced;compared with the low frequency axial vibratory drilling of the engineering ceramic materials,the plastic removal marks are more in the surface morphology of the traditional drilling;under the same processing conditions,the plastic removal trace of the surface of the wall without coolant is obviously more than that with coolant.Finally,the wear tests of diamond tool for composite process of sintering and brazing were carried out.The results show that abrasive wear and working layer material wear are the main wear mechanisms of diamond tool for composite process of sintering and brazing,and abrasive wear is divided into three kinds of polishing,breakage and shedding,and working layer material wear is divided into two kinds of flow sand wear and fracture wear.Taking the total distance of the accumulative machining hole as the machining amount of the cutting tool,the wear conditions of the end and side of diamond tools after the different processing amount were analyzed respectively. |
PDF Full Text Request