Jian Quan Wang

Investigation on Axial Turning-Grinding of Engineering Ceramics

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.

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.

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.

The Morphology Analysis of Axial Creep-Feed Grinding about Engineering Ceramics with a Small Grinding Wheel

The plastic deformation and brittle fracture damage remained within a certain depth of the abrasive surface of ceramic materials during axial creep feed grinding process, which included much information about damage mechanism and removal mechanism of ceramic materials. The surface morphology analysis showed that the brittle fracture was the main removal mode of grinding surface in addition to some micro-cracks in the affected layer, and cracks were not found in the matrix. Compared with general grinding, only the surface deterioration layer is thicker than general grinding surface, and there is no obvious damage to the workpiece

Study on Ground Surface Roughness of Engineering Ceramics Based on Grayscale Information

Surface roughness is one of the key factors to evaluate the grinding quality for engineering ceramics. This study introduces a new method based on grayscale information of surface images, to assess and predict the roughness of ground ceramics rapidly and effectively. The investigation sets the functional parameters of digital acquisition device as Brightness 140, Contrast 42, Saturation 24 and Acutance 9. Afterwards, it selects the mean value and the mean square deviation to describe surface roughness, and some image processing techniques are adopted to reduce noises and enhance the images. Lastly, it gives the relation curves on Ra，Rz，Ry versus grayscale information, and concludes a direct proportion law between the grayscale information and ground surface roughness.

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.

Numerical Simulation of Temperature for Al2O3 Ceramics during Micro-Detonation of Arc Strike Machining

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.

Study on the Relationship between Surface Roughness and Texture Features of Engineering Ceramics

The surface roughness and surface texture feature both are the key factors to evaluate the ground ceramics surface. The Gray Level Co-occurrence Matrix (GLCM) is introduced to extract and analyze the texture features of ground surface, in order to discover the relationship between texture features and roughness, and predict the roughness of ground ceramics according to the defined texture parameters. Four matrices about different sampling orientations are built up after the sampling offset and total gray levels are determined. By analyzing the correlation about every two features, Contrast, SS and ASM are selected to characterize the texture information of machined surface. Finally, the paper reveals the linear variation laws between Ra, Ry, S, tp and above features. The grounding quality of ceramic products also can be roughly estimated on the ground of that.