Hak Gu Lee

Micro-drilling of alumina green bodies with diamond grit abrasive micro-drills

Since ceramic plates containing many micro-holes are used for MCPs (Micro-channel plates) for electron amplification, catalytic converters, filters, electrical insulators and thermal conductors in integrated circuits, the efficient drilling of micro-holes in ceramic plates is important for productivity and cost. Since ceramics have poor machinability due to their low thermal conductivity, high hardness and high brittleness, in this work, alumina green bodies rather than sintered alumina were drilled to manufacture ceramic MCPs, followed by sintering the machined green bodies. Alumina green bodies were drilled with electro-deposited diamond grit WC micro-drills, and the cutting force with respect to drilling time was measured to determine a suitable micro-drilling condition. From the measurement of the micro-drill tip wear during micro-drilling of alumina green bodies, a model for the cutting force during micro-drilling was constructed.

Tribological Characteristics of Carbon/Epoxy Composites With Respect to Surface Groove Dimensions

Grooves on the surface of carbon/epoxy composite bearings yield good tribological characteristics because wear debris generated on the sliding surface are removed efficiently through the grooves. However, the surface grooves increase normal and shear stresses in composite bearings, consequently, excessive area of the grooves increases wear of the carbon/epoxy composite bearings, which necessitates the optimum selection of groove dimensions on the surface of composite bearings. In this work, the friction and wear characteristics of carbon/epoxy composites with micro-grooves were investigated by dry sliding test with respect to groove width and ridge width. Through comparison between the flat surface and the grooved surface, proper widths of the groove and ridge of carbon/epoxy composite bearings were determined.Copyright