A simple method for predicting the machinability in microwave cutting ceramics with microwave-induced thermal-crack propagation

Abstract

Microwave-induced thermal-crack propagation (MITP) is an advanced processing technology for cutting ceramics introduced recently. However, due to the lack of methods to predict its machinability, its application has been limited. In order to evaluate the machinability of this method for different ceramic materials, in this paper, a simple method is presented to predict the machinability in microwave cutting ceramics. Firstly, the processing difficulty of microwave cutting ceramics using MITP is analyzed based on the fracture mechanics, and the concept of crack initiation factor is proposed. An experimental work demonstrates that crack initiation factor is effective to predict the machinability. However, the crack initiation factor is closely related to many process parameters in MITP, so its prediction process is complicated. To find a practical and straightforward method, the ceramic heated by the static point heat source is analyzed, and the crack initiation factor is simplified as the crack factor which is only related to the physical parameters of the material in this model. The theoretical calculation shows that there is a positive correlation between the crack factor and the crack initiation factor, so the machinability in MITP can be predicted by this simplified factor. By establishing a link with the processing parameters, the crack factor can be used to pre-select the processing parameters. The simulation results show that the crack factor can also be used to predict the relative magnitude of temperature gradient and maximum thermal stress of different ceramics under the same processing conditions. This study provides a simple and effective method for predicting the machinability of ceramics using MITP.