Cup wheel grinding-induced subsurface damage in optical glass BK7: An experimental, theoretical and numerical investigation

Subsurface damage (SSD) is a predominant type of damage in grinding process of optical materials with direct effect on the optical components performances. A series of cup wheel grinding trials were carried out on optical glass BK7 under different grinding parameters to evaluate their impacts on SSD and surface roughness. The SSD depths of ground specimens were measured by the wedge chemo-mechanical polishing (W-CMP) method. The modified model of Lambropoulos, proposed by Li, was applied considering the ductile regime effect. Besides, a three-dimensional model was established based on the coupled finite element method (FEM) and smoothed particle hydrodynamics (SPH) to simulate the grinding-induced SSD in optical glass BK7. The experimental results were compared with the theoretical model and simulations which showed a good agreement. Therefore, both the theoretical and simulation models could be used for fast and nondestructive evaluation of SSD. Also, a novel method was applied to calculate the crack length of a SEM micrograph through image processing technique.