Experimental Study on Surface Integrity and Subsurface Damage of Fused Silica in Ultra-Precision Grinding

Abstract To realize low-damage ultra-precision grinding on fused silica, the surface quality and subsurface damage (SSD) distribution with fine-grained grinding wheel under different depth-of-cut and cutting speed are experimentally studied. The material removal mechanism under different grinding parameters is revealed by calculating undeformed chip thickness and observed with the help of transmission electron microscopy. The results show that brittle-ductile surfaces and ductile-like surfaces are generated during grinding. With the decrease of depth-of-cut and the increase of wheel cutting speed, the ultra-precision grinding changes to ductile-regime grinding with plastic flow removal. Besides, the surface roughness (SR) and SSD depth are reduced. The fracture defects such as fractured pits and grinding streaks on brittle-ductile surface gradually decrease. Instead, a ductile-like surface covered with grinding streaks is found. On brittle-ductile surfaces, the nonlinear relationship SSD∝SR 4/3 is no longer proper under the influence of plastic flow. Using surface roughness R a to predict SSD depth is more accurate. When depth-of-cut is 1 µm, cutting speed is 23.4 m/s and the material removal mode is dominated by plastic flow removal, the surface R a is improved to 2.0 nm and there is no crack but only a 3.4 nm deep plastic flow layer in subsurface after grinding.