Subsurface mechanical damage correlations after grinding of various optical materials

摘要

Loose abrasive grinding was performed on a wide range of optical workpiece materials [single crystals of Al_2O_3 (sapphire), SiC, Y_3Al_5O_(12) (YAG), CaF_2, and LiB_3O_5 (LBO); a SiO_2-Al_2O_3-P_2O_5-Li_2O glass-ceramic (Zerodur); and glasses of SiO_2:TiO_2 (ULE), SiO_2 (fused silica), and P_2O_5-Al_2O_3-K_2O-BaO (phosphate)]. Using the magneto rheological finishing (MRF) taper wedge technique (where a wedge was polished on each of the ground workpieces and the resulting samples were appropriately chemically etched), the subsurface mechanical damage (SSD) characteristics were measured. The SSD depth for most of the workpiece materials was found to scale as E_1~(1/2)/H_1, where E_1 is the elastic modulus and H_1 is the hardness of the workpiece. This material scaling is the same as that for the growth of lateral cracks, suggesting that lateral cracks are a dominant source for SSD rather than radial/median cracks, as previously proposed. Utilizing the SSD depth data from both this study and others, semiempirical relationships have been formulated, which allows for estimating the SSD depth as a function of workpiece material and important grinding parameters (such as abrasive size and applied pressure). ©2019 Society of Photo-Optical Instrumentation Engineers (SPIE) [DOI:10.1117/1.OE.58.9.092604]