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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.

This work lays great emphasis on studying the technique of the laser cutting the closed curve shape inside glass with laser induced thermal-crack propagation. The conventional LITP cutting is unable to complete a closed curve. The reason and the crack propagation behavior are studied by the extended finite element method (XFEM) analysis and experiments. In order to achieve the closed curve shape inside glass, the stress-release crack is proposed for the first time. The stressrelease crack-tip with 90° and 1.5mm is the suitable arrange. This paper indicates the experiment of the LITP cutting the closed outer curve shape with the stress-release crack. Optical microscope photographs of the crack surface are obtained to examine the cutting quality. This work provides a method to cut the closed curve shape inside glass with LITP successfully

Owing to the properties of high-transmittance, wear-resisting and lightweight brittle, glass plays an important role in various electronic equipment screens. The laser induced thermal-crack propagation (LITP) can separate the glass with the advantage of the high-quality, high-efficiency and high-strength. However, the deviation of the separation path (which means the material do not separate in the path of laser scanning) is one of the serious problems in asymmetric linear cutting glass with LITP. In this study, a dual laser beam revision the separation path technology (DLBRP) has been developed for the first time by skillfully arranging two defocused diode pump solid state laser (1064 nm). The principle of DLBRP is expounded. This paper studied several factors's effects on the cutting quality such as Master laser power (PM), scanning speed (VM) and laser spot diameter (DM).The smaller the Master laser spot diameter, the smaller deviation of the separation path. The effects of revision factors including Accompanying laser power (PA), Accompanying laser spot diameter on the material surface (DA) and the horizontal relative distance between the Master laser and Accompanying laser (∆X) were investigated. The optimum processing parameters were presented in this paper. The cambered separation path (which means the material gets separated in the arc way) in asymmetry linear cutting glass (which means the cutting path deviating from the symmetry axis of the material in a large scale, and the area of two separated parts is varied widely) could be revised into the straight one. A numerical simulation on the thermal stress and the dynamic propagation of crack in the DLBRP for asymmetric linear cutting glass with LITP was developed to analyze the revision mechanism, which is corresponding to the theoretical analysis and experimental results. The analysis of experimental results and numerical simulation results shows that the DLBRP technology can effectively revise the deviation of the separation path in asymmetry linear cutting glass with LITP. Besides, the clean surface without any pollution and surface damage can be achieved.

In laser-induced thermal-crack propagation, thermal stresses control the crack propagation mode and the quality of the crack surface. In this article, the 1064-nm semiconductor laser as a volumetric heat source is used for symmetry and asymmetry cutting glass. One of the problems in laser asymmetry linear cutting glass with laser-induced thermal-crack propagation is the quality of the crack surface which gets worse than that in symmetry cutting. This study lays great emphasis on analyzing the effect of the focus position and shear stresses on the crack sectional shape in semiconductor laser asymmetry linear cutting glass. This article indicates the volumetric heat flux formula, which simulates the temperature distribution from the material above or below the focal point. The heat source should be positioned above the focal point. Optical microscope photographs of the crack surface and sectional shape are obtained to examine the surface quality which is explained from the results of the stress fields using the extended finite element method simulation. In asymmetry cutting, shear stress is parallel to the crack surface and perpendicular to the cutting direction, which makes the crack surface smooth but uneven.

Laser induced thermal-crack propagation (LITP) makes the material to produce an uneven temperature field, maximum temperature can’t soften or melt the material, induces the thermal stress, then the crack separates along the cutting path. One of the problems in laser asymmetry cutting glass with LITP is the cutting deviation along scanning trajectory. This study lays great emphasis on considering the dynamic extension of crack to explain the reason of the cutting deviation in laser asymmetry cutting glass, includes asymmetric linear cutting and a quarter of a circular curve cutting. This paper indicates the experiments of semiconductor laser asymmetry cutting glass with LITP. Optical microscope photographs of the glass sheet are obtained to examine the cutting deviation. The extended finite element method (XFEM) is used to simulate the dynamic propagation of crack; the crack path does not have to be specified a priori. The cutting deviation mechanism and the crack propagation process are studied by the stress fields using finite element software ABAQUS. This work provides a theoretical basis to investigate the cutting deviation in laser asymmetry cutting glass. In semiconductor laser asymmetry cutting glass, the tensile stress is the basis of crack propagation, then the compressive stress not only makes the crack to extend stably, but also controls the direction of crack propagation.