Evaluation of subsurface damage and residual stress of glass ceramic under grinding process

The glass ceramic, ZERODUR®, has found broad applications such as mirror substrates and optomechanical structures, and is usually manufactured by grinding, lapping and polishing to achieve the final shape. As a brittle material, cracked layer (also called subsurface damage, SSD) or residual stresses are inevitable on the processed surface, which will reduce the mechanical strength as well as deteriorate the optical performance of the component. This research investigates the SSD and residual stress on ZERODUR® substrates after different grinding processes. Optical inspection, confocal microscopy and photoelasticity are utilized to analyze the SSD and residual stress on the surfaces. In addition, the surface finish (roughness) of the ZERODUR® surface under different grinding processes is also considered. The effects of different grinding parameters on the SSD and residual stress are evaluated, and the relationships among the grinding parameters, SSD and residual stress are discussed. The information of SSD and residual stress are essential for subsequent process such as polishing and acid etching. The experimental results are believed to be beneficial for optomechanical engineers and optical manufacturers.