Papers by Author: Fang Guo

Abstract: The plastic deformation and brittle fracture damage remained within a certain depth of the abrasive surface of ceramic materials during axial creep feed grinding process, which included much information about damage mechanism and removal mechanism of ceramic materials. The surface morphology analysis showed that the brittle fracture was the main removal mode of grinding surface in addition to some micro-cracks in the affected layer, and cracks were not found in the matrix. Compared with general grinding, only the surface deterioration layer is thicker than general grinding surface, and there is no obvious damage to the workpiece

Abstract: Axial turning-grinding is a processing method to cut cylindrical workpiece or inner surface of hole along its axis, using the kinetic energy of high-speed rotation annularity tool, the abrasives in tool tip as the main cutting edge to remove materials and the abrasives in the outside surface of tool as a minor cutting edge to sharpen the processed surface. And the cutting thickness and feed rate could be more than 5~10mm and 200mm/min respectively in a cutting, realizing high-efficiency, low-cost processing of engineering ceramics. Using the method, the ceramic sleeve of delivery valve precision coupling components in the engine is processed with high efficiency, and tool wear was researched with single factor test. The result indicated that the ratio of spindle speed and workpiece speed should be within a certain range in order to minimize tool wear, and tool wear increases with the increase of cutting depth, but not a linear relation.

Abstract: Surface roughness is one of the key factors to evaluate the grinding quality for engineering ceramics. This study introduces a new method based on grayscale information of surface images, to assess and predict the roughness of ground ceramics rapidly and effectively. The investigation sets the functional parameters of digital acquisition device as Brightness 140, Contrast 42, Saturation 24 and Acutance 9. Afterwards, it selects the mean value and the mean square deviation to describe surface roughness, and some image processing techniques are adopted to reduce noises and enhance the images. Lastly, it gives the relation curves on R_a，R_z，R_y versus grayscale information, and concludes a direct proportion law between the grayscale information and ground surface roughness.

Abstract: Micro-detonation of striking arc machining (MDSAM) is a new machining technology for engineering ceramics rough machining. In the paper, the constituent part and principle of machine system are introduced. In addition, the characteristics of corresponding technology are summarized, and nozzle burning law of micro-detonation generator is also analyzed. Lastly, the reasonable machining quality and efficiency can be achieved by controlling nozzle diameter between 2.4 mm and 2.8 mm.

Abstract: In order to improve the performance of the engine oil pump, a growing number of engine designers are employing ceramic plunger matching parts instead of metal plunger matching parts due to its excellent properties. We compared the stress and deformation change of the metal and ceramic couplings by Finite Element Method (FEM), and the advantages of ceramic plunger matching parts were validated in this paper. After determining the machining technology of plunger and sleeve, the machining processes of difficult-machining positions such as inlet and outlet oil holes, spiral grooves and so on, were analyzed in detail. The results of measurement and test show that the ceramic plunger matching parts are fully suitable for the design and work requirements.

Abstract: The impact force of micro-detonation of striking arc machining is studied. The orthogonal experimental design and regression analysis method are employed to build the prediction model and the influencing laws of processing parameters on impact force are educed. Experimental results show that the impact force decreases with the increment of working current and increases with the growth of working pressure and nozzle diameter. The exponential type model is consistent with experiment results. The research can offer an important reference for the process control of micro-detonation of striking arc machining.

Abstract: The surface roughness and surface texture feature both are the key factors to evaluate the ground ceramics surface. The Gray Level Co-occurrence Matrix (GLCM) is introduced to extract and analyze the texture features of ground surface, in order to discover the relationship between texture features and roughness, and predict the roughness of ground ceramics according to the defined texture parameters. Four matrices about different sampling orientations are built up after the sampling offset and total gray levels are determined. By analyzing the correlation about every two features, Contrast, SS and ASM are selected to characterize the texture information of machined surface. Finally, the paper reveals the linear variation laws between R_a, R_y, S, t_p and above features. The grounding quality of ceramic products also can be roughly estimated on the ground of that.

Abstract: Axial turning-grinding is a high efficient and low cost method of processing engineering ceramics. During the research of its processing mechanism, by choosing diamond grits and alumina workpiece to creat model and using ls-dyna modeling software to simulate the stress changes and strain of the generation and development in the process of workpiece to study the mechanism of its processing, and analyzes the feasibility of this method combined with experimental results.

Abstract: Axial turn-grinding is a method to cut the cylindrical work piece along its axis, using the kinetic energy of high-speed rotation annularity tool, the abrasives in tool tip as the main cutting edge to remove materials and the abrasives in the inside or outside surface of tool as a minor cutting edge to sharpen the processed surface. Through analysis the simplified model, a slightly stress concentration was found at the junction surface of processed surface and machined surface, which had little damage to the workpiece because of happening in the part to be removed or precision machining allowance, and both cracks propagation caused by material rupture were effective removal after material removal mechanism analysis because the extension of the median/radial crack and lateral crack were both happening in the part to be removed.

Abstract: MDAM technology is a brand-new and low-cost machining technology. Based on the brief introduction of MDAM system, the generator structure and additional anode access method are in-depth studied. The results show that the cost of consumable parts can be reduced to a minimum of only 10.9% of the original design for optimized generator based on cost reduction, but have the problems of lifespan reduction and frequently replacement. Cost and efficiency are considered comprehensively in the design of final optimized generator, which not only extends the lifespan of consumable pieces about 4 times and improves machining efficiency, but also reduces the cost to only 36.4% of the original design. So it is adopted by the system. On the choice of additional anode access methods, through comprehensive comparison, the method of additional anode attaching with the nozzle directly is ascertained, which is simple and easy realized, and reduces the damage to the surface and sub-surface during the machining of ceramics and other brittle materials. The results lay a solid foundation for further technology promotion.