Study And Experiment On Ultraprecision Polishing Of Optical Crystal Materials

Optical crystal materials have found more and more important application in modern optics and electronics. Optical polishing is still one of the most common process for material surface. The method aims at removing the imperceptible roughness and improving the face shape accuracy. From the precision manufacturing technique,the quality and life of workpiece will be advanced. With the development of science,there are more and more requirements for polishing method,which urges scientists to prope into new manufacturing techniques.In this thesis,the background of the latest development in the field of ultraprecision polishing is reviewed. By analyzing and comparing the current ultraprecision machining techniques for optical material,the conclusion that the "contactless-polishing" and "green-polishing" will be the developmental aspects in the future is drawn.The polishing mechanism and the key technique for ultrasmooth surface are studied in this thesis. From the aspect of kinematics,two-kind models of relative movement between polishing film and workpiece are established and the best parameters for polishing are discussed. With the measure of pressure,rotate speed and polishing time,the variety of face accuracy is analyzed from using the different polishing film materials(non-slubed polishing cloth,pitch,copper,tin). The stress field of cutting zone is analyzed by the load-penetration law.The surface stress is calculated in terms of single-point cutting and loose-abrasive polishing,and the variety of pressure in polishing stress field is investigated. In polishing zone,cracks initiate in the region of maximum equivalent stress in the vicinity of the grain edge and then propagate in the direction coincides with minimum gradient of equivalent stress field. The larger the pressure,the deeper the cracks propagate.From the general analye of experiment, the effective parameters are achieved.The crystal of Nd:YAG is polished through these parameters and ultrasmooth surface with precision of nanometer level...