Abstract
A ceramic cutter is subjected by a thermal cycle at each revolution, the cycle consisting of heating (machining) and cooling (idling) processes.This report deals with temperature and thermal stress distribution in ceramic cutter when machining and depth of thermal cracks. The results revealed are as follows.(1) Heat conduction from the tool surface toward the tool interior may be considered as that of semi-infinite body if limited to an infinitesimal period of time.Thermal region effected by the heating process (time is 0.024 s) ranges to the depth of within 5-6μ under the tool surface provided that thermal conductivity of sintered alumina (k) is 7. 2 kcal/m.h.°C and cutting temperature (θw) applied to the tool surface 1000°C.(2) The time dependence of temperature distribution at the cooling process (time is 0.12 s) has been calculated by Schmid's method with h=400kcal/m2.h.°C of heat transfer coefficient of the tool surface. It is, then, evident that the heat accumulated in the tool is conducted into the interior while a part escapes to the atomosphere andconsequently the thermal effect region at the cooling process extends deeper than at the heating process.(3) During cooling process there exists no thermal tensile fracture in the tool surface. Thermal cracks are caused by thermal shearing stress due to thermal compression, being generated during heating process and progressing during cooling process.
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