Parametric study of precision abrasive machining processes for ultra-precise finishing

Abstract

This thesis investigates the ultra-precision machining of brittle Bismuth Germanate (BGO) single crystals, a key material in Time-of-Flight Positron Emission Tomography (TOF-PET) detectors. Due to its hardness and low fracture toughness, BGO presents significant challenges during micromachining. A combined experimental and numerical approach was developed. Mechanically prepared BGO samples underwent polishing process, evaluating the effects of abrasive size, pressure, and speed on surface roughness and optical transmittance. A strong link was established between improved surface quality and enhanced light transmission. To model BGO’s cutting behavior, a finite element simulation using the Johnson-Holmquist II (JH-2) model was implemented and validated with micro-milling and drilling experiments. The study analyzed material removal mechanisms, cutting forces, and the brittle-to-ductile transition. The results offer clear guidelines for minimizing machining damage and improving BGO performance in TOF-PET systems. This work contributes to precision manufacturing of brittle materials and supports advancements in medical imaging technologies.