Research On Removal Model Optimization And Application In Magnetorheological Finishing(MRF) Of Fused Silica Based On The Integrated Stress Field

With the construction of laser nuclear fusion,laser weapons and other powerful laser devices developed by many powerful scientific and technological countries in succession,modern optical systems have increasingly higher demands on the caliber,number and quality of optical components.It is not only necessary to complete the processing of large-aperture optical elements in a short period of time,but also optical components need have high surface quality,which is a major challenge for the traditional optical processing field.Magnetorheological polishing(MRF)is an advanced flexible shear stress polishing technology.It is dominated by shear stress.Owing to that it does not introduce new surface or subsurface defects,and has a stable removal function during polishing and other unique advantages,it is widely used in the processing of optical components in ultra-precision optical systems.Fused silica has become an indispensable high-energy optical element in high-light optical systems due to its excellent properties,such as high laser damage threshold,good light transmission and high temperature resistance.Facing with the demand for ultra-precision manufacturing of larger quantities and larger-diameter fused silica optical elements,in view of the incomplete force field and the lack of theoretical guidance for the removal efficiency and surface quality optimization of the current MRF,this paper carried out the research on removal model optimization and application in Magnetorheological Finishing(MRF)of fused silica based on the integrated stress field.The specific research contents are as following points:(1)Study on the stress field distribution in the polished area.According to the characteristics of the magnetorheological polishing fluid,the process of magnetorheological polishing was simplified.A mathematical model that was used to describe the stress field distribution in the polishing region was constructed.The equation that was applied to analyze the stress field distribution in the polishing region was solved by using a numerical iterative method.(2)Study on optimization of magnetorheological polishing removal function model and prediction of removal efficiency.The pre-existing magnetorheological polishing material removal function models were optimized.The material removal mechanism in magnetorheological polishing was explored.The coupling relationship between pressure and shear stress during material removal was analyzed.The coordination and cooperation of pressure and shear stress were realized.The material removal function model was optimized to improve the prediction accuracy of material removal efficiency.On the base of above studies,the process parameters could be quickly screened to obtain the optimal parameters of magneto-rheological high-efficiency polishing,shorten the exploration time and improve the processing efficiency.All of these researches can provide theoretical support for high-efficiency material removal of fused silica.(3)Study on the prediction method of surface roughness of fused silica.Considering that while fused silica is polished with high efficiency,it is also necessary to control the surface quality of the workpiece to fulfill the actual application requirements,the research on the relationship between the peak pressure and shear stress in the magnetorheological polishing zone and the roughness of the workpiece surface after polishing were carried out.The internal relationship between peak pressure,shear stress and roughness was investigated.On the base of above studies,the prediction method of surface roughness of workpiece after polishing was established.All of these researches can lay theoretical foundation for obtaining high-quality fused silica surface.