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 brittleductile 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 Ra 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 Ra 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.

Experimental Study on Variation of Surface Roughness and Q Factors of Fused Silica Cylindrical Resonators with Different Grinding Speeds

“…It is noted that the surface roughness of GR06 is about 0.11 μm larger than that of GR05 after the surface roughness is stable. The surface roughness difference between GR05 and GR06 can be attributed to a degradation in the dynamic balance performance of the grinding tools caused by the excessive grinding speed [34]. The surface roughness is measured by a Taylor Hobson profilometer, the assessment length is set to 3 mm, and the measurement position is the outer surface of the resonant shell.…”

“…Extensive studies have been focused on the analysis and prediction of the SSD for the grinding and polishing of fused silica material [29][30][31][32][33]. Zhong et al investigated the effect of grinding parameters on the surface/subsurface qualities of fused silica [34]. It is known that the characteristics of SSD change with grinding parameters; however, studies on the features of SSD that affect the mechanical Q factor of fused silica resonators are rarely seen.…”

Research on Subsurface Damage Measurement of Fused Silica in Ultra-Precision Grinding Based on Laser Damage Performance

“…The grinding experiment was conducted on the UPL-450 ultra-precision three-axis grinder developed by National University of Defense Technology [26], as shown in Figure 1. The ultra-precision grinder draws on the layout and structure of the ultra-precision lathe bed.…”

Rapid Detection and Elimination of Subsurface Mechanical Damage for Improving Laser-Induced Damage Performance of Fused Silica

“…Surface cracks are generally identified by macroscopic evaluations as scratches and digs in the subsurface layer and serve as reservoirs absorbing precursors that heat up and explode upon exposure to high-fluence laser light, particularly during nanosecond pulses at 351 nm [11][12][13][14][15]. To fabricate SSD-free fused silica optics, researchers have developed a range of posttreatment techniques, including magnetorheological fluid finishing (MRF), ion beam etching (IBE), reactive ion/ion-beam etching (RIE/RIBE), and HF-based wet etching [16,17]. Among the available techniques, the HF-based etching route (which typically involves optimized and deionized water cleaning and the HF/NH4F etching process under ultrasonic/megasonic conditions described as AMP or DCE previously [18]) has demonstrated high effectiveness in exposing SSD and increasing the laser damage resistance of fused silica optics.…”