Advanced Materials Research Vol. 500

Abstract: The profile of a single-pass milling can be assumed as a cosine curve. Therefore, the maximal depth model for single-pass milling is established which indicates the quantitative relationship between the AWJ single-pass milling depth and the milling parameters. The depth model of milled surface, which shows the effect of water pressure, standoff distance, lateral spacing, abrasive flow rate and the properties of the material on the AWJ milling depth, is established based on the maximal depth model for single-pass milling. The derived model is assessed by AWJ milling experiments. The results show that the milling depth increases with an increase in water pressure and standoff distance, and decreases with an increase in lateral spacing and traverse speed. The theoretical milling depth predicted by the mathematical model is good agreement with the experimental result.

Abstract: Abrasive suspension jet is a new embranchment of abrasive jet. In the cutting process of this jet, the suspension concentration is constant, so the cutting quality is more stable. In this paper, a prediction model based on a back-propagation (BP) artificial neural network is presented for predicting the cutting depth generated by abrasive suspension jet. In the application of the BP neural network, the mean error of the output in the model training is 0.01, the relatively discrepancy is below 8.70%. The modeling method based on the BP neural network is much more convenient and exact compared with traditional methods, and can always achieve a much better prediction effect. It is verified with experiments to be reasonable and feasible, and it is the better foundation for the future study of abrasive suspension jet.

Abstract: Powder mixed near dry electrical discharge machining (PMND-EDM), which uses gas-liquid-powder mixture as three phase dielectric medium to remove materials, is proposed. Compared with dry EDM, much higher material removal rate (MRR) is achieved in PMND-EDM. The mechanism of PMND-EDM is analyzed and reasons for its MRR improvement are illustrated. Comparative experiment is done in compressed air and three phase dielectric medium, respectively. MRR is calculated. And discharge voltage waveforms are obtained by oscilloscope. It is shown that three phase dielectric medium can improve MRR effectively.

Abstract: In this paper an attempt has been made to investigate the performance of an electrode made through powder metallurgy (PM) of copper tungsten during electrical discharge machining (EDM). Experimental results are presented on electrical discharge machining of AISI D2 hardened steel in kerosene with a copper tungsten (Cu35% - W65%) tool electrode made through PM method with a constant duty factor of 80%. In term of high performance EDM process, higher peak current (>20A) and pulse duration (>400µs) with a high machining efficiency were used. Experimental results have shown that machining at a peak current of 40A and pulse duration of 400µs yields the highest material removal rate (MRR) whereas machining at a peak current of 20A and pulse duration of 400µs yields the lowest tool wear rate (TWR). The lowest surface roughness appears at the lowest material removal rate which is at a peak current of 20A and pulse duration of 600µs. The optimum machining performance can be performed by the combination of pulse duration and peak current at 600µs and 40A respectively.

Abstract: In order to investigate the influences of machining parameters on surface roughness in ultrasonic vibration mill-grinding, the motion of abrasive grain is analyzed. The analysis indicates that grain and workpiece separate periodically which are beneficial for coolant entering into grinding zone to reduce grinding temperature and grinding force and improve surface quality. Experiments are carried out and detected by SEM and roughmeter, the results indicate that influences of spindle rate, feeding speed, cutting depth and amplitude decrease in turn. Through regression analysis, an empirical formula is obtained. The experiments indicate that material removal mode dominates surface roughness.

Abstract: The technology of ultrasonic assisted machining has been successfully used in many machining processes recently. Conditioning in the CMP not only can extending the life of the polishing pad but also improve process stability. In this paper we develop a brand new conditioning process with ultrasonic assisted conditioning UAC head for chemical mechanical polishing CMP process. The slurry came from inside the polishing spindle and had an independent cyclic system. As a result, this UAC device can remove polishing debris 4-6 times faster than conventional conditioning process. This conditioning process may even use water instead of slurry to reduce the cost of consumables of CMP. Key word: Chemical mechanical polishing CMP, Ultrasonic assisted conditioning UAC, Polishing Pad

Abstract: With the development of economical society and the stone industry, the product of granite thin slab becomes a trend, and gets the welcome of people. The grinding technology influences the quality of granite thin slab. This paper first introduced the situation of the grinding technology of granite thin slab, analyzed the mechanism of the grinding process of granite thin slab and fractured problem by observing the fractured granite thin slab. Then, based on the Hoek-Brown criterion, we researched the fracture criterion and the critical thickness of granite thin slab when grinding. Finally, we set up the fracture criterion of the granite thin slab and built the mathematical model between the thickness of the granite thin slab and grinding process parameters. According to the thickness of the granite thin slab, grinding process parameters can be formulated, in order to ensure the granite thin slab no fractured.

Abstract: In the ultrasonic vibration assisted grinding and EDM, grinding and pulse discharge machining are favorable conditions for each other, can significantly improve the processing efficiency by adjusting the processing parameters, and get high-quality machined surface. The grinding force is an important parameter in characterizing the grinding process, which is the g the main object of study in grinding process. The interaction of ultrasonic vibration, grinding and EDM is investigated. From the view of material removal volume, the volume of removal by EMD is calculated. Then the volume by grinding is gotten. The grinding force model of combined machining is established. The influence machining parameters on grinding force is studied, which is helpful for the detection and control of grinding force.

Abstract: Grinding of metals is a complex material removal operation involving cutting, ploughing, and rubbing depending on the extent of interaction between the abrasive grains and the workmaterial under the conditions of grinding. In this investigation, various parameters of the process including the number of abrasive grains in actual contact, the number of actual cutting grains per unit area for a given depth of wheel indentation, the minimum diameter of the contacting and cutting grains, the probability of active contacting grains and cutting grains were determined analytically. The analytical work was proved to be practicable by the means of measuring grinding temperature. Research results enable the use of actual number of contacting and cutting grains in the grinding wheel for thermal distribution and wheel wear analyses and contribute to a better understanding on the mechanics of grinding.

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.