Papers by Author: Fang Guo

Abstract: Tool edge radius has obvious influences on micro-cutting process. It considers the ratio of the cutting edge radius and the uncut chip thickness as the relative tool sharpness (RST). FEM simulations of orthogonal cutting processes were studied with dynamics explicit ALE method. AISI 1045 steel was chosen for workpiece, and cemented carbide was chosen for cutting tool. Sixteen cutting edges with different RTS values were chosen for analysis. Cutting forces and temperature distributions were calculated for carbide cutting tools with these RTS values. Cutting edge with a small RTS obtains large cutting forces. Ploughing force tend to sharply increase when the RTS of the cutting edge is small. Cutting edge with a reasonable RTS reduces the heat generation and presents reasonable temperature distributions, which is beneficial to cutting life. The force and temperature distributions demonstrate that there is a reasonable RTS range for the cutting edge.

Abstract: Axial turning-grinding is a processing method to cut the cylindrical workpiece 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. Comparing with concentric axial turning-grinding, eccentric axial turning-grinding has higher efficiency. The result indicated that 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. According to axial force, chips’ shape and damage degree of surface to be processed, obtaining the proper feed rate range. Removal 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 axial force to control the length of transverse cracks.

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: This study selected three types of organic substance as the main components of high-efficient organic grinding liquid for grinding ceramics with silicon. The grinding efficiency test was conducted on the basis of self-developed grinding mechanism and the findings indicated that the grinding performance of all these three types of grinding liquid were better than average grinding liquid. With Si3N4 Ceramics as the representative test material, the grinding efficiency can be increased at least 1.37 times and more than twice with the grinding fluid prepared with oleic acid or oleic alcohol. The analysis of liquid-solid interface with the help of infrared spectrum showed that there existed abnormal vibration peaks in the liquid-solid interface between Si3N4 ceramics and grinding liquid with (organic substances)–OOH and －OH under normal temperature, which resulted from the adsorption effect of hydrogen bond generated between organic molecule and Si3N4 ceramics. Under high grinding temperature, the friction chemical reaction took place as the result of the absorption effect and the resultant could not only reduce the surface hardness, but also improve the lubricating effect, thus improving the grinding efficiency and surface quality.