Research on High Speed Microcutting of Engineering Ceramics

点击翻译按钮获取中文摘要

As engineering ceramics has been recently utilized for mechanical components, improvement of machining performance is increasingly required. This study proposes high speed microcutting by daiamond tool as an new machining technique which performs crack-free surface finishing, in order to prevent the deterioration of the machined component due to machining processes, and elucidates the fundamental mechanism of microcutting of engineering ceramics.An argorithm for the analysis of the microcutting mechanism is proposed by application of fracture mechanics. According to the argorithm, the mechanism of plastic flow type material removal which enables crack-free machining is theoretically investigated by analyses of nonlenear fracture mechanics parameter J-integral and the distribution of cutting temperature at high cutting speed. By using a developed high speed micromachining device, the microcutting tests are carried out for selected engineering ceramics. The behaviour of formation and propagation of crack in associtation with the material removal process is also elucidated by means of in-situ scanning electron microscope observation.Analytical results suggest that the plastic flow type removal takes place in case of micromachining of partiaaly stabilized <ZrO_2> and WC-Co, while brittle fracture type removal occurrs for SiC and <Al_2O_3> . Also it is sugggested that as the depth of cut decreases and the cutting speed increeases, the type of material removal tends to change from brittle fracture type to plastic flow type. From the experimental spect, these findings are sustained, so that high fracture toughness ceramics such as <ZrO_2> and WC-Co produces plastic folw type chip which is similar to metal cutting, and even low fracture toughness materials such as Si-crystal, glass and <Si_3N_4> at high cutting speeds.