Ultra-precision Grinding Mechanism Of AlON And Machining Process Of Its Conformal Dome

Conformal infrared dome is the core component of future precision-guided missile,and the excellent optical and mechanical properties of polycrystalline Al ON ceramics make it the preferred material for conformal infrared dome.Ultra-precision grinding technology is employed to machine large aperture and high steepness conformal dome with better surface accuracy.However,Al ON is prone to surface damage and subsurface crack during processing due to its high hardness and brittleness,which seriously affects the working performance of the workpiece and requires subsequent polishing.However,the low material removal rate of polishing will affect the processing efficiency,and its uncertain removal characteristics will also reduce the surface accuracy.Therefore,the quality of surface/subsurface obtained by ultra-precision grinding is the key factor affecting the duration of subsequent polishing and processing efficiency.The removal mode of hard and brittle materials in machining directly affects the surface quality of the workpiece,and the realization of ductile removal becomes the premise of obtaining surface with low-damage and high-quality.The mechanism research of the ultra-precision grinding on Al ON material is of great significance for realizing its ductile grinding,the high-quality surface and high-efficiency processing of Al ON conformal dome,as well as to promote the development of the manufacturing technology of infrared guided missile in China.In order to realize the plastic grinding of Al ON conformal dome surface with high efficiency and low damage,this paper studied the ultra-precision grinding mechanism of Al ON by a variety of experimental and detection methods.On this basis,the processing technology of ultra-precision grinding of Al ON conformal dome was determined,and finally the ultra-precision grinding manufacturing of Al ON conformal dome with high surface quality was achieved.The main content of the paper includes the following aspects:The Vickers indentation experiments of Al ON materials under different loads were carried out,and the variation rule of damage forms of Al ON materials under different quasi-static loads was studied,the surface damage mechanism of Al ON materials under different loads were revealed.Vickers indentation and etching experiments were carried out on Al ON materials under the same load,and the relationship between crack growth mode and microstructure of Al ON materials was established.The single-point diamond scratching experiment of Al ON material progressive depth was carried out,and the corresponding relationship between the scratching force and the material removal method was found.The influence of the cutting speed on the cutting force,the material removal method and the characteristics of subsurface damage were analyzed.The above research results provide theoretical basis for the material removal and crack growth characteristics of Al ON materials in the grinding process.The grinding experiments of Al ON under different diamond wheel parameters were carried out to study the influence of wheel parameters on grinding surface quality and wheel wear.The non-uniform characteristic of Al ON grinding surface morphology was found caused by different removal modes of Al ON grains.The difference of mechanical properties and machining properties between Al ON grains was studied by nano indentation experiment.The surface generation mechanism of Al ON materials in ultraprecision grinding process was revealed by combining the EBSD results and the ground surface morphology,and the influence of grain orientation on crack growth and brittle removal mode was analyzed.The results lay a foundation for studying the ductile machining mechanism of Al ON workpiece surface.The critical conditions of different material removal modes on Al ON workpiece were established.The ultra-precision grinding experiment of Al ON workpiece under different grinding depths was carried out,and the evolution of the ground surface characteristics with the reduction of the grinding depth was analyzed.Combined with the results of ?XRD experiment,the ductile machining mechanism of Al ON workpiece surface was revealed.Based on EBSD experimental results,the anisotropy between different crystal planes of Al ON was studied by nano indentation experiment,the critical cutting depth of Al ON workpiece surface ductile machining was determined,the ductile grinding of Al ON workpiece surface was realized,and the uniform and high-quality ground surface was obtained.The deformation of Al ON subsurface layer under the ductile grinding was characterized by TEM,and the subsurface deformation mechanism under Al ON ductile removal mode was proposed.This study provides technical support for the design of process parameters in the ultra-precision grinding of Al ON conformal dome.Ultra-precision grinding experiment was carried out to machine the Al ON conformal dome.According to the geometry of the conformal dome,the machining methods of inner and outside surface and the parameters of grinding wheel has been reasonably selected.The clamping devices used in grinding process were simulated by finite element method.The high-precision and low-stress clamping of the workpiece in the ultra-precision grinding process was realized to avoid the impact of fixture deformation on surface quality.Based on the ductile grinding mechanism of Al ON,the parameters of ultraprecision grinding for the dome were designed.According to the relationship between grinding marks and rotation speed,Matlab was used to optimize the grinding marks.Finally,the ultra-precision grinding of Al ON thin-wall dome with large diameter and high steepness was realized,and the changing trend and influencing factors of surface quality were analyzed.