Heat Transfer in Thermally Enhanced Machining of Ceramics

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ABSTRACT CTS-9400654 Incropera The proposed study seeks to experimentally and theoretically delineate transport phenomena related to a processing technique which uses intense, localized sources of heat to augment conventional machining of ceramic materials. Specifically, thermally enhanced machining (TEM) processes will be studied for turning operations involving integration of a lathe with existing CO2 laser or plasma arc sources to machine cylindrical specimens of silicon nitride, zirconia and alumina-zirconia. Theoretical treatments of TEM processes will be used to delineate the role of pertinent physical mechanisms. Models will consider localized heating at and convection heat transfer from the workpiece surface, conduction within the workpiece, friction at the tool-chip interface, and/or plastic flow. Supporting experiments will also be performed to determine flow and convection heat transfer conditions at a simulated or actual workpiece surface. On-line monitoring will include sensing of workpiece and tool temperatures and cutting forces for a wide range of system operating parameters and heat source conditions. Off-line measurements will also be used to determine the residual stress, tool wear, microstructure and hardness distribution in the machined surface. The objective of the theoretical and experimental studies is to obtain an improved understanding of underlying physical mechanisms for TEM processes and to establish a range of suitable operating conditions.