Papers by Author: Ai Bing Yu

Abstract: Grinding stability was analyzed concerned with contact deformation and contact stiffness of wheels. Elastic deformations of the grinding wheel were measured with inductance sensors. Dynamic grinding system model was set up. Relation between contact stiffness and chatter growing index was analyzed. Chatter suppression experiments with variable grinding speeds were carried out. When wheel is in contact with a workpiece, contact deformation can occur. The contact stiffness of grinding wheel is a variable. The relation between chatter growing index and contact stiffness is an increasing function. Chatter growing index can be decreased by lowering contact stiffness of wheel. The grinding system stability will be improved with variable grinding speed.

Abstract: The nickel coatings and electroplated diamond tools were fabricated with ultrasonic and without ultrasonic condition. Hardness and adhesive strength of nickel coatings were tested. Diamond grains on tool substrate were observed with microscope. Al2O3 ceramic was machined with fabricated electroplated diamond tools to compare material removal rate and grinding ratio. Experimental results show that high hardness can be obtained under the effect of ultrasonic during tool fabrication processes. Ultrasonic agitation can make grain dense and guarantee nice contact between substrate and coating. With ultrasonic power of 200W, nickel coating presents highest values of hardness and adhesive strength. High grain density of diamond tool can be obtained. During buildup processes, some buildup time is needed to obtain enough thickness of nickel coating before ultrasonic agitation is applied. Grinding ratios of diamond tool with ultrasonic during buildup processes were better than without ultrasonic. The diamond tool fabricated with ultrasonic agitation presents better cutting ability. During tool fabricating processes, the reasonable application of ultrasonic agitation is very important.

Abstract: Tool edge geometry has obvious influences on cutting tool behaviors. FEM modeling and simulation of orthogonal cutting process using uniform and variable edge cutting tools were studied with dynamics explicit ALE method. AISI 1045 steel was chosen for workpiece, and cemented carbide was chosen for cutting tool. Three sections of uniform and variable edges were chosen for analysis. Cutting forces and temperature distributions were calculated for uniform and variable edge carbide cutting tool. Simulation results show that variable edge cutting tool obtains small cutting forces. Ploughing force tends to reduce when variable edge cutting tool was used. Variable edge cutting tool reduces the heat generation and presents reasonable temperature distributions, which is beneficial to cutting life. The force and temperature distributions demonstrate the advantages of variable edge cutting tool.

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: 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.

Abstract: Coating quality and electroplating efficiency can be improved by application of ultrasonic agitation. The nickel coatings and electroplated diamond tools were fabricated. The effects of ultrasonic agitation on tool fabrication processes were analyzed. Cathode polarization curves and coating hardness were measured. Diamond grains on tool substrate were observed with microscope. Alumina grinding experiments were carried out and grinding ratios were calculated. Experimental results show that cathode polarization degree reduced during ultrasonic electroplating processes. Before diamond grain tack-on operation, ultrasonic agitation can make grain dense and guarantee nice contact between substrate and grains. High grain density of diamond tool can be obtained in tack-on operation after above ultrasonic agitation operation. Ultrasonic agitation is not suitable for the tack-on operation of diamond grains. During buildup processes, some buildup time is needed to obtain enough thickness of nickel coating before ultrasonic agitation is applied. The diamond tools fabricated with ultrasonic agitation present better cutting ability. During tool fabricating processes, the reasonable application of ultrasonic agitation is necessary.

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 systematic engineering theory and method, interpretative structural model of ceramic grindability system was set up. Property parameters, grinding parameters and grindability indexes were selected as system elements. The adjacency matrix between system elements was constructed. The reachability matrix was calculated according to adjacency matrix. By calculation of reachability matrix and classification, interpretative structural model of the ceramic grindability system was obtained. The system model could describe the relationship between the ceramic grindability and system elements. The grindability system model also provides a fundamental theoretical reference for the research on the grindability of ceramic materials. The weight of each influencing factor of ceramic grindability can be calculated by applying the system model. The grindability of ceramic materials can be evaluated objectively and comprehensively.

Abstract: The machinable fluorophlogopite was drilled with tungsten-cobalt carbide and high-speed steel drill bits, respectively. The wear widths of major flank were measured, and the wear characteristic of twist was analyzed during drilling fluorophlogopite ceramics.Drilling experiments were carried to consider influence factors of drill bit wear, such as tool materials, cooling condition, spindle speed and tool angles. Tool materials and cooling conditions are the major factors to affect wear of drill bits. High-speed steel drill bits are not suitable for drilling fluorophlogopite ceramics. Cooling condition affects wear remarkably. With the rising of spindle speed, the wear widths of major flank grows. But apex angle has little affects on the tool wear rate. Research results indicate that low tool wear can be obtain through optimizing tool material and machining parameters in drilling fluorophlogopite ceramics.