Surface and subsurface damage in Zerodur® glass ceramic during ultrasonic assisted grinding

The material removal process in grinding and lapping of brittle materials leads to different kinds of defects such as microcracks, fractures, scratches, and deformed areas which can exist under the finished surface in the layer called subsurface damage (SSD). In this work, experiments were carried out to study the impact of the ultrasonic assistance during grinding machining of the Zerodur® glass ceramic. The effect of the process parameters on the surface formation and the subsurface damage was investigated. The SSD depth was measured using the dimple method in combination with the use of the optical microscopy for the morphological study of the SSD, while the surface roughness was measured using the mechanical profilometer. The experimental results showed that the SSD depth generated within the ultrasonic assisted grinding is about 35 % less than that of the conventional grinding process. On the other hand, the surface quality obtained by the conventional grinding was superior to that of ultrasonic assisted grinding. To validate the experimental results, the SSD values measured by the dimple method are compared with the values obtained in both the experiments and other theoretical previous studies. It was concluded that machining of the Zerodur® glass ceramic with ultrasonic assistance is more suitable than that with the conventional grinding. This study provides valuable insights into the material removal mechanism and the dependence of surface and subsurface integrities on grinding mode with/without ultrasonic assistance.