Papers by Author: Bao Guo Zhang

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: 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: An edge chipping experiment under static load is adopted to study the Kaiser Effect during the failure process for engineering ceramics. The mechanisms inducing Kaiser Effect are discussed. Some AE signals during the course of Kaiser Effect are analyzed. The results show that there’s obvious Kaiser Effect during the failure process of edge chipping; count, energy and amplitude can be well used to describe the Kaiser Effect. The surface metamorphic layer remained on the ceramic surface during the course of machining is the main factor for Kaiser Effect. Edge distance and mechanics characteristic are the important factors for Kaiser Effect. The study on Kaiser Effect of edge chipping has provided some guidance to prevent edge chipping of engineering ceramics.

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.

Abstract: Axial turning 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 (or toes) as the main cutting edge to remove materials and the abrasives in the inner surface of tool as a minor cutting edge to sharpen the processed surface. The cutting thickness and feed rate could be more than 3~5mm and 30mm/min respectively in a cutting, and realized high-efficient, low-cost processing of engineering ceramics. Processing mechanism analyses showed that both median/radial cracks and lateral cracks occurred in the part to be removed, and the intensity of the processed part had little destroyed, only needing adjust the axial force to control the length of transverse cracks.

Abstract: Micro-detonation arc machining (MDAM) is a newly proposed special machining technology for engineering ceramics. To study its working principle is of important significance. By means of high speed video and current signal acquisition system, the shape of micro-detonation arc is observed and the formation course of micro-detonation arc is analyzed. The generation process of ablation pits for Si3N4 and Al2O3 is observed by high speed video. Experimental results show that the generating process of micro-detonation arc can be divided into two phases: spark discharge and stable arc. The diameter of micro-detonation arc increases as working current growing. Si3N4 ceramics decompose and Al2O3 ceramics melts when it machined with MDAM. The materials are removed by synergistic effect of high temperature and intensive impact pressure of micro-detonation arc.

Abstract: Based on the calculation of energy density for several kinds of non-traditional machining process of engineering ceramics, the material removal mechanism for ceramics was studied. The studies revealed that the key reason for these technologies to machine ceramics effectively is high-energy-density. For Laser machining, EDM and plasma arc cutting, the material was removed by the high temperature ablation while the high density energy is applied to material surface. For high pressure abrasive water jet machining, the material was removed by erosion using the abrasive particles with high density energy. The ceramics was machined by micro-detonation arc under the synergy of ablation and erosion.

Abstract: Based on the comprehensive summary of latest research achievements of Laser and EDM technologies in home and abroad, the other advanced machining technologies is summarized briefly, such as Ultrasonic Wave, Microwave machining techniques and their composite machining technologies, as well as High-speed (Super High-speed) Grinding, ELID Grinding and Interface Thermal Chemistry Reaction Aided Machining technologies developed on the basis of traditional grinding technology. At last, it is forecasted that the necessary direction of advanced technologies used for ceramics is combinatorial machining technologies of two or more kinds of advanced technologies.