Ductile or Partial Ductile Mode Machining of Brittle Materials

This paper reports ductile or partial ductile mode machining of silicon, glass and some advanced ceramics. Results are presented using scanning electron micrographs of the machined surfaces. Grinding and lapping operations using inexpensive machine tools could produce ductile streaks on surfaces of these brittle materials under good conditions. Manufacture of spherical glass lenses by the fracture mode or partial ductile mode grinding followed by partial ductile mode lapping and ductile mode polishing is fast and economical. Using partial ductile mode grinding and ductile mode polishing has also been very successful for manufacturing aspherical glass lenses. Reduced polishing time and improved surface quality are due to the presence of ductile streaks. Ground silicon, ZrO2 and Al2O3 also showed ductile streaks. Toroidal SiC surfaces ground with flat-face cup wheels indicated 100% ductile machining, and did not require polishing.