Papers by Author: Jun Fei Yang

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: With reference to the principle that the strong detonation wave generates the transient dynamic high pressure, the small power pulse power supply and the electrode micro-detonation wave generator are developed. The engineering ceramic material machining with low cost is realized successfully with the devices. It is shown from the study results that there is a degenerative layer about 0.25~0.45mm thick, which is composed of amorphous phases and crystalloid Si and can be machined and removed with the ceramic tool after micro-detonation machining. There are obvious transverse cracks near the interface of the degenerative layer and the matrix, but the cracks along the depth direction are not found. The performance of the degenerative layer is roundly analyzed and its removing mechanism is primitively discussed.

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.

Abstract: This paper carries out grinding efficiency experiments on various formulas composed of long carbon chain alcohol and halogenated hydrocarbons with the first principle of grinding fluid as main evaluating index and finds via infrared spectrum testing that the conjugating ways of lubricating films between alcohol-type grinding fluid and ceramics is based on chemical adsorption or hydrogen bonding adsorption and generates alkoxy silane or polyalkoxy silane with perfect anti-friction action under the condition of grinding high temperature. With adding of halogenated hydrocarbons, it can further make grinding fluid with perfect extreme pressure property and improves grinding efficiency. Furthermore, this dissertation firstly introduces heat capacity as analysis means and discusses the influential factors on the removal rate of ceramics materials when using abovementioned grinding fluid. It is shown from the result that the material removal rate when silicon nitride ceramics grinding will increase with the augmentation of heat capacity.