Papers by Author: Xin Li Tian

Abstract: In order to obtain the optimal engineering ceramics-metals pair with the best tribological performance, the tribological orthogonal tests for engineering ceramics such as Si₃N₄, SiC, ZrO₂ and representative metals such as 45steel, CCr15 bearing steel, tin bronze QSn4-3 and tin-based babbit ZChSnSb8-4 with oil-less lubrication were carried out by using UMT-3 wear machine and SEM. Single factor analysis of load on friction and wear properties of Si₃N₄- babbit pair was performed. The results indicate that ceramic-metal pairs possess excellent tribological performance. Si₃N₄- babbit pair has the lowest friction coefficient and SiC-babbit pair is best in attrition. The friction coefficient varies sharply on low loads and the wear rate monotonous rises with the increase of load.

Abstract: To study the failure process of edge chipping for engineering ceramics, a method of energy analysis is used. Acoustic emission parameters such as energy, cumulative energy and amplitude collected in the experiment system are analyzed in this paper. The results show that energy and cumulative energy change little, amplitude changes among 40dB to 60dB before fracturing; the main reason for these is the micro-cracks propagation. While edge chipping engenders, energy, cumulative energy and amplitude would increase sharply and reach to the maximums; the main reason for these is the macro-cracks coming into being, and lots of energy release out. The change regulars of different parameters have reflected types of acoustic emission source. The method of energy could reveal the fracture mechanism of edge chipping for engineering ceramics well.

Abstract: A theoretical model of temperature for Al₂O₃ ceramics during micro-detonation of arc strike machining was established. Based on finite element theory, the temperature of Al₂O₃ ceramics during micro-detonation of arc strike machining was simulated with the aid of Ansys software, combined with the actual processing, the width and depth of cavity impacted by micro-detonation were calculated. The simulation results show that the highest temperature of Al₂O₃ ceramics is over 13435 °C in a given processing parameters, while the high-temperature zone is quite small. With the increase of pulse width and electricity, the temperature within the machined zone increases rapidly, but the outside area kept a low temperature; and with the increase of nozzle radius, the diameter to depth ratio of the distribution of temperature is increasing gradually. The data gained from the simulation is proved to be accordant with the data gained from experiments.

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 developments of edge chipping for engineering ceramics are analyzed. An edge chipping experiment under static load is adopted to study the fracture process of edge chipping. The results show that the fracture processes of edge chipping under different edge distances are similar, which can be divided into four stages based on load-displacement curve. There is obviously Kaiser Effect during the fracture processes of edge chipping. Counts, average frequency, RMS, duration, amplitude and inverse calculation can be used to describe the process of edge chipping for engineering ceramics. Amplitude, duration and average frequency become highly active on the eve of fracture, which can be regard as the omens of edge chipping and used to predict the fracture of edge chipping.

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: A theoretical model of heat transfer for Si3N4 ceramics during micro-detonation of arc strike machining was established. Based on finite element theory, the temperature of Si3N4 ceramics during micro-detonation of arc strike machining was simulated with the aid of COMSOL Multiphysics software, combined with the actual processing, the width and depth of crater impacted by micro-detonation were calculated. The simulation results show that the highest temperature of Si3N4 ceramics is over 12100 °C in a given processing parameters, while the high-temperature zone is quite small; the material removal rate with the increase of pulse width and electricity increases, with the increase of the nozzle radius first increases and then decreases; the diameter to depth ratio with the increase of pulse width and electricity decreases, with the increase of nozzle radius increases. The data gained from the simulation is proved to be accordant with the data gained from experiments.

Abstract: A series of experiment were performed to test the cleaning ability of different organic emulsion for Si₃N₄ ceramic grinding. The experiment results showed that the grinding fluid made by short chain organic substance and alkane will induces the jam of grinding wheels. At the same time, polar organic substance with long carbon chain can suppress wheel loading phenomenon. The main reason of the jam by alkane is the nonpolar oil film surface possesses the strong attraction to abrasive dust of Si₃N₄, which will lead to jam in the grinding process. The polar oil film relieves the aggregation of abrasive dust in the grinding area to some extant, which is beneficial to decrease jam. By analyzing the cleaning property by some types of polar organic substances, the paper discusses the relationships of molecular structure characters to their cleaning ability.