Papers by Author: Xi Peng Xu

Abstract: The topography of a grinding wheel can be obtained quickly and exactly through applying the computer vision method to detect the wheel topography. However, the application of computer vision in detecting wheel topography is restricted due to the contradiction between vision field and resolution while using traditional computer vision detecting method. In the present paper, the 3D topography of a diamond grinding wheel was reconstructed by combining image mosaic technique, corner detection algorithm, image matching algorithm and image fusion algorithm. The image mosaic technique was found to be effective in solving the contradiction between visual field and resolution and rapidly obtain high resolution image of the wheel topography in a wider range of vision field, thereby providing a valuable reference for quantitative evaluation of the performance of grinding wheels.

Abstract: In the present study, sawing forces of Al2O3 ceramic and wear of metal-bonded diamond cut-off wheel were examined by counting the statistical data of diamond wear and analyzing the force signals under different sawing conditions. The experimental results demonstrated that normal grinding force reduced with the increasing of sawing speed, and rose with the increasing of workpiece feed rate and grinding depth. In all of the variables, sawing depth made the greatest effects on normal grinding froce. The percentage of whole crystal or pull-out crystal decreased and fractured crystal increased as the sawing depth increased or the sawing speed decreased. Among machining factors, sawing speed was the greatest effectors on the wear of diamond cut-off wheel.

Abstract: The surface roughness and surface morphology of silicon wafers polished by three different polishing methods were analyzed in this paper. A polishing pad was prepared by means of sol-gel technology as semi-fixed abrasive tool. An electroplated polishing pad was chosen as fixed abrasive tool. And a polishing cloth was chosen as free abrasive tool. The results showed that the surface of silicon wafer polished by the sol-gel polishing pad was superior to the other two. It was easy to get mirror effect with few scratches while the free abrasive and fixed abrasive got lots of scratches on 23silicon wafers. The surface roughness of silicon wafer polished by the sol-gel polishing pad reached 1.41nm measured by atomic force microscope (AFM).

Abstract: An experimental investigation is reported on the temperatures and energy partitions involved in the grinding of cemented carbide (YT30) with a vacuum brazed diamond wheel. The grinding temperature at the wheel-workpiece interface was measured using a pair of grindable foil thermocouples and the energy partition to the workpiece was evaluated by matching the analytical temperatures to the measured results. Effects of the various grinding conditions, including wheel velocity, feed rate and depth of cut, on the temperatures and the energy partition were investigated. It was determined that the wheel velocity was the most significant factor in governing the temperature relative to the depth of cut and feed rate. The maximum temperature rise at the contact zone was below 25°C in the present study. Microscopic examination of the ground surfaces and the ground detritus revealed that brittle fracture was the dominant material-removal mode. This may be one of the reasons for the low grinding temperature in grinding YT30 with a vacuum brazed diamond wheel. The energy partition values to the workpiece obtained under different grinding conditions varied from 3.3% to 20% for dry grinding YT30.

Abstract: The effects of the machining parameters on the relative position of the resultant force were analyzed in circular sawing of granite with a diamond segmented blade. The horizontal and vertical force components and the power were measured. Calculated tangential and normal force components were subsequently used to calculate the relative position of resultant force besides the horizontal and vertical force components. It was found that the value of the relative position of resultant force in down sawing is less than that in up sawing. The shift of sawing swarf has heavy influence on the relative position of resultant force.

Abstract: Fixed-abrasive wire saw, with its ability to cut hard brittle material, such as silicon ingots, crystals and quartz, has emerged as a leading technology for production in semiconductor and photovoltaic industry. There are some defects in conventional fixed-abrasive wire saw such as significant low holding abrasive ability, low machining efficiency, high running costs, etc. A new fixed-abrasive wire, namely brazed diamond wires have been developed to overcome these problems. In this paper, brazed diamond wire were carried out to braze two different size diamond grits onto two different thin steel wires by using a nickel-based powder as brazing alloy. The mechanical properties of brazed diamond wire were evaluated by tensile and breaking twist experiment. The experimental results showed that the heating in the brazing process has litter influence on the wire mechanical properties. The addition of brazed alloy and diamond grits sharply decreased the wire mechanical properties significantly, both in the tensile strength and breaking twist angle. Bigger diamond grit would make the accumulation of brazed alloy which leaded to the deterioration of diameter consistency of wires.

Abstract: An attempt was taken to simulate the bending strength of diamond impregnated segments in three point bending tests by using a discrete element method (DEM). The influences of main bond matrix components (Fe and Cu), the porosity in the matrix, the coefficient of friction among the matrix particles, and the connection strength between abrasive particles and matrix particles on the bending strength were investigated through simulation. It is found that the bending strength increases with the proportion of Fe but decreases with the increase of porosity. An increase in both the friction coefficient of the matrix particles and the bonding strength between the diamond grains and metal matrix particles can also lead to the increase of bending strength.

Abstract: The sawing characteristics of a diamond circular blade with grits set in ordered distribution were investigated in comparison with a conventional blade on which grits are of random distribution. The two blades were tested under the same sawing conditions. Forces and power were monitored during sawing. The results indicate that the changing tendency of sawing forces and power versus sawing parameters are basically same for the two blades. However, the setting of grits in ordered distribution leads to lower sawing forces as well as force ratio, and can reduce nearly one third energy consumption.

Abstract: Ultrasonic machining has been proven to be a promising machining method on hard and brittle materials. However, due to the absence of high power ultrasonic machine tools, reported studies on ultrasonic machining were mainly concerned of relatively small hole drilling of the given materials. In the present work, with the development of the higher power Rotary Ultrasonic Machine Tool, two kinds of ultrasonic face machining with free abrasives, namely, Non-rotating Ultrasonic Machining with Free Abrasives (NRUSM) and Rotary Ultrasonic Machining with Free Abrasives (RUSM) are designed and comparatively conducted for the red granite, which is a typical hard-to-machine natural material. The effects of static force, spindle speed and amplitude of ultrasonic vibration on the performance of the machining are evaluated in terms of the material removal rate and surface quality. Experimental results indicate that ultrasonic machining is effective for face milling of the stone material with the designed machine tool. Furthermore, machining performances in RUSM are superior to those in NRUSM.

Abstract: The effects of the geometric parameters of a sawblade on the sawing fluctuated temperatures were analyzed based on a fluctuated temperature model advanced in my recent paper. The results show that the sawing temperatures are fluctuated only near the workpiece surface in the sawing zone, the blade segment ratio, the number of segments and the contact angle have great influence on the sawing temperatures, which has the guiding significance for optimal design of the sawblade structure.