Theoretical model and digital extraction of subsurface damage in ground fused silica

Based on the fracture mechanics and grinding kinematics, a theoretical model is developed to determine various subsurface damage (SSD) parameters and roughness Rz of the ground brittle material with consideration of the material removal mode and spring back. Based on the image processing, a digital method is proposed to extract various SSD parameters from the cross-section micrograph of the ground sample. To verify the model and method, many fused silica samples are ground under different processing parameters, and their SSD depth and roughness Rz are measured. The research results show the average SSD depth (SSD_a) can be expressed as SSD_a = χ₁Rz^4/3 + χ₂Rz (χ₁ and χ₂ are coefficients). The SSD_a is closer to half of the maximum SSD depth (SSD_m) as the wheel speed decreases or the grinding depth, feed speed, or abrasive diameter increases. The SSD length or density basically increases linearly with the increase of the SSD_m. The digital method is reliable with a largest relative error of 6.65% in SSD depth, extraction speed of about 1.63s per micrograph, and good robustness to the micrograph size and small-scale residue interference. The research will contribute to the evaluation of SSDs and the optimization of the grinding process of fused silica.