Theoretical modeling and experimental analysis of single-grain scratching mechanism of fused quartz glass

Surface and subsurface damage, including cracks, scratches, microcracks, and residual stress, is inevitable when fabricating fused quartz glass because of their high brittleness and low fracture toughness. Single-grain scratching mechanism of fused quartz glass is examined using smoothed particle hydrodynamics (SPH) to clarify the mechanisms of material removal and produce crack-free optical surfaces. Single diamond grain experiments were conducted to validate the proposed SPH model, which predicts the critical depth of approximately 0.20 μm for ductile–brittle transition in fused quartz glass. Both simulation and experimental results indicate that three removal regimes, namely, complete ductile, ductile–brittle transform, and complete brittle modes, are involved in the material removal process. SPH simulation helps identify the location of crack formation and morphology of crack propagation during scratching. Thus, the SPH model is used to simulate the single grain scratching process under different conditions. Simulation results reflect that changing the scratching speed will lead to a remarkably different mechanism of crack initiation and propagation compared with changing the scratching depth. Effects of scratching depth and speed on scratching force and residual stress are also discussed thoroughly in the simulation analysis.