Papers by Author: Feng Xu

Abstract: Cubic Boron Nitride (cBN) has wide application prospect in the field of high performance cutting tool, for its outstanding mechanical properties. In this paper, the cBN coating was synthesized on cement carbide by chemical vapor deposition nanocrystalline diamond interlayer in radio frequency magnetron sputtering system. The SEM, FTIR and AFM were used to investigate the microstructure, purity and morphology of the cBN film. The research was carried out on the effect of the deposition parameters on the cBN content in the film. High temperature and high pressure locally in the substrate is an important factor of transformation of cubic phase BN from hexagonal phase BN. There is a narrow optimization parameters window in cBN synthesis by ion bombardment assist radio frequency magnetron sputtering method. The good quality of cBN film can be obtained by a combination of moderate substrate bias voltage and gas pressure, high substrate temperature and a certain N₂ partial pressure.

Abstract: Nanocrystalline diamond film was deposited on silicon by double bias hot filament chemical vapor deposition (HFCVD) system. The effect of substrate temperature on the microstructure and mechanical properties of the film were investigated systematically. More defects and non-diamond contents were found as the decrease of grain size, which cause the decrease of hardness and elastic modulus. It is shown that the proper substrate temperature is in the range of 720~760 . The excessively high substrate temperature leads to the °C dramatic increase of nondiamond content and the decrease of mechanical properties.

Abstract: In this paper, the study is carried out on the milling parameters optimization and cutting database development of radar key parts in electronics industry. The method is proposed in detail on parameters optimization. The material removal rate is chosen as optimization objective. The cutting constraints include machining tool power, tool life, surface quality, deformation and strength of milling cutter and the chatter stability. The genetic algorithm is selected as global optimal method. At last, it presents the solutions of cutting database based on Web, which include general structure, basic function and entity relationship data model.

Abstract: The analysis and identification of wear particles for machine condition monitoring is usually very time-consuming by experienced inspectors. In order to remedy the limitation, automation of the analysis procedure appears to be necessary. A novel weighted fuzzy c-means algorithm for wear particle classification is proposed in this paper. The algorithm uses the variation of the pixel intensities of a region to choose strong resembling area. Then, the spatial relationships of the membership function are constructed to regulate the pixel membership obtained from the FCM object function. Finally, wear debris are classified based on the fuzzy membership. The example shows that the method is briefly and effectively.

Abstract: Chemical vapor deposition nanocrystalline diamond (NCD) film has numerous unsurpassed properties, among them, bulk modulus, hardness; abrasion resistance and thermal conductivity are notable ones like polycrystalline CVD diamond film. The super mechanical properties have made NCD film to be an effective way to improve the resistance performance of the ceramic bearing and extended its life. The contact stress of bearing ball with NCD coating in elastic contact was analyzed. Factors such as substrate material, thickness of NCD coating, load and interlayer material which affect the shear stress distribution of NCD coating on bearing ball were investigated. The results show that substrate with low elastic modulus and heavy load will enlarge the difference of equivalent stress value at NCD/substrate interface. Thick film will make the stress distribution at the interface uniform. Soft interlayer should be inhibited to avoid extra stress in contact status.

Abstract: The performance of Atomic Force Microscope (AFM) is greatly determined by the quality of its probe. Nowadays, probes of diamond tips have become more and more popular than silicon ones, and have been widely used in industries. In this paper, research about the fabricating of nanocrystalline diamond (NCD) coated AFM probe has been done using Hot-Filament Chemical Vapour Deposition (HFCVD) technique. The results showed that NCD films have been grown on the probe. Problems about the growth of NCD on the tips have been discussed. The optimum parameters have also been proposed. This research can provide reference for the further experiments on the fabrication of NCD coated tips.

Abstract: The magnitude and the uniformity of the substrate temperature are the most important factors that affect the quality and the growth rate of diamond films deeply. In this paper, the model of the swing substrate temperature field is established according to the heat transfer theory in Miniature EACVD System, the effects of the hot-filament parameters and the substrate swing parameters on the magnitude and uniformity of the substrate temperature were discussed. The calculated results show that the hot-filament parameters have great influence on the magnitude of the substrate temperature , the results also show that the hot-filament number , the substrate swing angle and the distance between the hot-filament and the substrate affect the uniformity of the substrate temperature field deeply. All the results provide a basis for optimizing the parameters of deposition in Miniature EACVD System.

Abstract: At present, the lack of the optimal cutting parameters of high speed milling is the obstacle to its widely application. In this paper, the simplified and rapid optimization method is proposed on high speed milling alloy thin-walled workpiece. The normal selection method of cutting tools and cutting conditions is put forward as the precondition of parameter optimization. The acquirement method of optimal parameters is presented. The maximal critical axial depths of cut at the different cutting conditions are achieved according to chatter stability theory. The materials removal rate is selected as the optimal objective. The optimal parameters are filtrated up and validated according to the constraint conditions including machining tool, cutting tools, surface quality and precision of the parts.

Abstract: The thermal blockage and thermal round flow in HFCVD system for CVD diamond growth will lead to un-stability of product quality. Finite element method has been used to simulate the gas flow field around the cutting tool substrate within a HFCVD diamond reactor. Experiments have been done to prove the simulation results. Excellent agreement between simulation and experiment was obtained by depositing of CVD diamond coated cutting tool. The thermal blockage and thermal round flow in HFCVD system decrease by using a hollow substrate holder. High quality CVD diamond coating can be obtained using a hollow substrate holder.

Abstract: In this paper, by adopting an equivalent geometry model of the cutting layer, a three-dimensional (3D) finite element model was built to investigate the milling of Ti-6Al-4V. The chip separating process was simulated by Arbitrary Lagrangian-Eulerian (ALE) method and automatic re-meshing technology. The experiments of milling Ti-6Al-4V were carried out to verify finite element model of milling process. The comparisons of the predicted cutting forces and the measured forces showed reasonable agreement. Finally, the finite element model was used to predict the chip deformation and the three-dimensional distribution of cutting force, stress and temperature in milling Ti-6Al-4V.