Bao Guo Zhang

Research on the Removal Mechanism of Engineering Ceramics Based on Energy Density

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.

Study on Axial Turning of Engineering Ceramics

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.

Research Progress of Advanced Machining Technologies for Engineering Ceramics

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.

Mechanism Analysis of High Efficiency Axial Turn-Grinding of Engineering Ceramics

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.

Energy Characteristics Analysis of Engineering Ceramics during the Process of Edge Chipping Based on AE

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.

A Study on Tribological Behavior of Engineering Ceramics - Representative Metals

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.

Experimental Research on the Relationship between Surface Polishing and Fracture Strength for Ground Ceramics

Fracture strength is one of the key mechanics performances for engineering ceramics products, greatly influenced by the microscopic topography and residual stress field of ground surface. In this work, several testing equipments, such as the metallurgical microscope, surface profiler and X ray residual stress tester were introduced to investigate the relationships between microscopic topography, surface roughness, residual stress and fracture strength of ground ceramics, after the surface grinding and mechanical polishing. The experimental results show that a smoother machined surface with low roughness and residual stress is obtained through polishing with absolute alcohol for 20 minutes; the fracture strength of Si3N4SiC and Al2O3 are increased by 6.64%8.18% and 6.58% respectively, comparing to the ceramics without polishing; the surface stress concentration and residual tensile stress of polished ceramics are both reduced after an appropriate time of polishing process, which causes a certain improvement of ground fracture strength.

Finite Element Simulation of Axial Creep-Feed Grinding Engineering Ceramics Based on ANSYS/LS-DYNA

Introducing the grinding mechanism of axial creep-feed grinding ceramics with a single diamond grain. Establishing the simulation model of a single grain grinding engineering ceramics by axial creep-feed grinding and analyzing the simulation results of the grinding force in the X,Y,Z axis. Finally, the impacts of the wheel speed, axial feed rate and workpiece speed upon grinding forces were discussed by simulating the single diamond abrasive grinding process under different grinding conditions.

Research on Predicting Model of Surface Roughness for Ground Engineering Ceramics

Grinding is the mostly leading machining technology for engineering ceramics. The quality of ground surface can be evaluated by various roughness parameters. And a textural analysis method based on Gray Level Co-occurrence Matrix was employed in researching the roughness of ground ceramics. The relationship between texture features and roughness was investigated through a series of surface images of engineering ceramics collected by a digital microscope. The sampling offset and total gray levels of surface images were determined firstly. Then 4 GLCMs were built up to calculate the average of texture features. And 6 parameters were fixed as main texture parameters. Furthermore, the multiple nonlinear regression theory was used to assess the relation between the texture features and roughness Ra. By statistic test and comparison, the deviation of calculated Ra and actual Ra is less than 0.25. It is shown that this relation is much satisfactory and the method may be suitable for quickly measuring the roughness of ground ceramics.

Investigation on Tool Wear about High Efficient Axial Turning-Grinding of Engineering Ceramics

Axial turning-grinding is a processing method to cut cylindrical workpiece or inner surface of hole 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. And the 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. Using the method, the ceramic sleeve of delivery valve precision coupling components in the engine is processed with high efficiency, and tool wear was researched with single factor test. The result indicated that the ratio of spindle speed and workpiece speed should be within a certain range in order to minimize tool wear, and tool wear increases with the increase of cutting depth, but not a linear relation.