Effect of subsurface damage on indentation behavior of ground ULE™ glass

The subsurface damage in ground optical glasses was characterized using the ball-dimple technique. At the same lapping conditions, larger abrasive size introduced deeper subsurface damage, and the surface damage was proportional to the surface roughness. Surface degradation in the ground glasses due to the formation and propagation of the subsurface damage was evaluated using microindentation method. A two parameters empirical equation was used to describe the indentation behavior of the ground glasses. It was found that the nominal near-surface elastic constant decreases with the indentation load, suggesting the propagation and formation of surface cracks during the indentation.