Advanced Materials Research Vols. 652-654

Abstract: Based on experiment of sawing Wulian red granite with diamond circular saw, the relations between the cutting force with machining parameters are studied. Cutting speed, feed rate and cutting depth are considered as the process parameters. The cutting force in sawing granite operation are measured and the experimental results are then analyzed using response surface methodology. From the analysis, it is seen that the cutting force Fx , Fy and Fz are reduced with the increase of cutting speed and increased with the increase of feed rate and cutting depth, and the mathematical models of the cutting force are developed. By ANOVA for the cutting force models, It is concluded that the models are significant at 95% confidence level and the significant effects are the first-order of cutting speed, feed speed, cutting depth and the quadratic of cutting depth.

Abstract: The surface quality of graphite cannot be completely evaluated only by the roughness value Ra measured by profilometer. The surface damage ratio Sc is presented to give quantitative description of surface quality of graphite, which was calculated as the ratio of the projection area of fracture craters to the overall area of free surface. The machined surface was observed and taken photo by use of the stereo microscope with CCD image acquisition system. Matlab image processing tool was used to convert the color photo to binary image, in which fracture craters were shown as black pixels and the other surfaces as white pixels. The surface damage ratio is the result of the sum of black pixels divided by the overall pixels. Under the same conditions of high speed machining experiments for verification, the surface damage ratio was calculated in comparison with the Ra values measured by profilometer. The variation tendency of surface damage ratios exhibited good coherence to the measured roughness.

Abstract: This paper presents investigations on turning TC4 alloy with PVD TiAlN coated cemented carbide inserts. The turning test was conducted with variable cutting speeds ranging from 80 to 120 m/min. Wear surfaces of the cutting tools are analyzed to study the wear mechanism of PVD TiAlN coated cemented carbide tools in turning of titanium alloy TC4. Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer( EDS) analyses by wear maps indicated that the wear of coated cemented carbide tools was caused by adhesion, coating delamination and mechanical fatigue. The analysis of EDS indicated no oxidation wear generated during the machining. The excellent chemical stability and oxidation resistance performance of TiAlN coating made contribution to prevent oxidation wear.

Abstract: It is aimed at developing a new diamond wheel in order to overcome the shortages of traditional grinding wheel, such as the abrasive easily fall off the grinding wheel prematurely, high grinding temperature, random grits distribution and the loading problems become more severe in grinding process. And further study on the grinding temperature of the new diamond wheel prepared in comparison with traditional resin-bonded diamond grinding wheel in machining Al2O3 ceramic. The prepared new diamond wheel has many diamond fibers involved in grinding process which are artificially ordered, diamond grits are not easily fall off, and it has big chip-pocket space and heat dissipating capability. The experimental results indicated that the grinding temperature of the new diamond wheel in comparison with the conventional diamond wheel under the same conditions was decreased by 80°C-120°C.

Abstract: This paper is based on the experimental observation. The micro-topography characteristics of electrical discharge machining (EDM) surface were studied. The results show that the EDM surface is made up of three-dimensional craters and hard protrusions overlapped alternately which distribute randomly and non-directionally. The pulse energy has significant effect on the forming of EDM surface profiles, and peak current and pulse width are the main factors.

Abstract: The machine processing optimization model is one kind of typical restraint optimization model. This paper takes the lathe work as an example to study the construction way of optimization model construction under a series of constraint environments, and its goal is pursues the highest productivity and the lowest cost.

Abstract: Metal cutting indicates a specific category of processes in which unwanted material is removed from workpeice by single- or multi-point cutting tools for making products meeting prescribed specifications. Parameter optimization in metal cutting plays an important role in satisfying quality requirements of machined parts at low production cost or time. It requires optimal selection of cutting speed, feed rate, depth of cut, and the number of passes. A brief review of recent progress on the optimization of cutting parameters is introduced in the present work. Some new machining practices expending in recent years are involved including hard turning, dry cutting, high speed machining, machining of difficult-to-machine materials and composites. Modeling skills for creating optimization models and optimization techniques for solving optimal or near-optimal solutions are summarized and analyzed.

Abstract: Powder mixed near dry electrical discharge machining (PMND-EDM) is one of the novel EDM processes, which uses gas-liquid-powder mixture as the dielectric medium. The tool wear rate (TWR) in PMND-EDM is researched based on single factor experiments. Effects of process parameters, such as peak current, pulse on time, pulse off time, flow rate, powder concentration, tool rotational speed and air pressure, on TWR are found out. TWR increases with the increase of peak current. TWR decreases with increasing of pulse on time. TWR increases firstly and then decreases while pulse off time increases. Increase of flow rate results in the increase of TWR. With the increase of powder concentration, TWR increases firstly and then decreases. Existence of tool rotation facilities decrease of TWR, however, further increase of rotational speed leads to increase of TWR. Increase of air pressure leads to lower TWR.

Abstract: The most widely used Chemical Mechanical Polishing (CMP) process and most difficulty is the SiO2 dielectric CMP in ULSI. SiO2 cannot be removed by oxidation-reduction because Silicon is already quadrivalence. So we adopt water-solubility SiO2 growing directly from water which size can arrive 110~130nm to improve the polishing rate. The growth of silica sol is studied and the silica sol whose particle sizes can reach 120nm is gained.

Abstract: The vibration phenomenon appeared in orthogonal experiments of turn-milling machining of micro-miniature shafts. In order to study the causes and conditions of vibration, the vibration test experiment system was established and frequency spectrum analysis of acquisition data was done. The results show that its machining vibration is caused by the low-frequency flutter of the milling spindle. And the coupling relationship of the micro-miniature shaft and the turning spindle was discussed with FEM. The results show that the vibration of the micro-miniature shaft does not affect the vibration of the turning spindle, while the vibration of the turning spindle can cause the vibration of the micro-miniature in their low order vibration mode.