碳化硅反射镜坯体光学加工的残余应力测量与分析

测量并分析了碳化硅反射镜坯体光学加工的残余应力。采用X射线衍射法测定了磨削成形、研磨以及抛光过程引入的表面残余应力的性质和大小;采用逐层抛光法测定了在用120#粒度金刚石砂轮磨削时引入的残余应力层厚度。研究结果表明:在用120#金刚石砂轮磨削加工时沿磨削方向和垂直于磨削方向分别引入了残余拉应力和残余压应力,其大小分别为40MPa和70MPa,应力层深度约为60μm,大于裂纹层深度;在用W7金刚石微粉研磨时引入了残余压应力,在其作用范围内残余应力平均值为60～80MPa;在抛光时理论上会引入残余压应力。在此基础上提出了在碳化硅反射镜坯体的光学加工过程中,可以通过研磨消除磨削引入的裂纹层和残余应力层。

Measurement and analysis of residual stress in the body of silicon carbide mirror during optical fabrication

The residual stress in the body of a silicon carbide mirror introduced by optical fabrication is measured and ana- lyzed.The characteristics and magnitudes of surface residual stresses introduced by grinding,lapping and polishing are all mea- sured by the use of X-ray method,and the depth of residual stress layer in the grinding process by 120 # diamond wheel is mea- sured by polishing layer by layer.The results indicate that in the grinding process by a 120 # diamond grinding wheel residual tensile stress and residual compressive stress are introduced in the grinding direction and the vertical direction,and the magni- tudes are 40MPa and 70MPa respectivdy.The depth of residual stress layer introduced by grinding is 60μm,which is deeper than the depth of the crack layer.About 60～80MPa residual compressive stress in the several microns near the surface is intro- duced by lapping with W7 diamond particle.Polishing introduces residual compressive stress theoretically.Based on the research results,the conclusion is made that the crack layer and the residual stress layer can be removed by lapping during the optical fab- rication of the body of a silicon carbide reflecting mirror.