Prediction of subsurface damage depth in rotary ultrasonic machining of glass BK7 with probability statistics

Subsurface damage (SSD) generated in rotary ultrasonic machining (RUM) process significantly deteriorates the technological and structural performance of the optical components. However, the invisibility of subsurface cracks underneath the machined surface makes it difficult to accurately and online evaluate the SSD depth. In the present research, incorporated with the probability statistics of the abrasive heights and the indentation fracture mechanics of the brittle material, a theoretical prediction model was established by investigating the inherent correlation between the measured cutting force of the diamond tool and the maximum depth of the subsurface cracks. Utilizing this predictive method, the SSD depth could be rapidly and precisely calculated through the mechanical properties of the material, the cutting force of the diamond tool, and the geometrical characteristics of the abrasives. To validate the feasibility of prediction technique, the experimental measurements of the maximum SSD depths were compared with the predicted results, revealing the acceptable consistency in their values.