Papers by Author: M. Wang

Abstract: In order to provide effective guarantee for the prediction of residual stress and deformation after welding process of large-sized aluminum alloy structures, temperature field and thermal efficiency during double-sided multi-layer TIG welding of aluminum alloy was studied. By integratedly considering temperature-depended material properties, convection, radiation, filling rate of solders, et al, numerical analysis about the form of molten pool and temperature field was given. Element birth and death technique was taken during the simulation. Double-sided multi-layer TIG welding experiment was carried out and sample of cross section of weld seam after welding was prepared. By trying different thermal efficiency for calculation, simulation result consistent with experimental result was obtained finally, making the present thermal efficiency as the aim result for study. Confirmation was given by comparing temperature value from experiment with simulation one.

Abstract: The crater diameter and depth of the surface machined by electrical discharge machining (EDM) were used to evaluate indexes for EDMed surface. The influence of discharge parameters selected on the crater diameter and depth in mirror-like surface EDM process was investigated, and the optimization scheme was obtained. An L16 (44×23) Taguchi standard orthogonal array was chosen for the design of experiments. Experimental results indicate that peak current and open discharge voltage have more influence on the crater diameter and depth in comparison with pulse off-time and pulse duration. Also the results confirm that the crater depth is about 10 to 20 percent of its diameter while the near-mirror EDM conducted in the NAK80 steel with fine discharge parameters.

Abstract: The cutting force in manufacture process was observed with Kistler dynamometer. A special clamp was designed to simulate the real condition of blade cutting. Series of experiments were done. Cutting force reflected structure of the blade and movement of machine. Cutting force was changed with feed speed varied and the rotation of axis B & C. Resultant cutting force was uniform in back and basin of blade and increased with cutting speed went up. Resultant force was waved in edge of blade. Back and basin forces were lager than edge force in X direction. Force X invoked vibration.

Abstract: Boron-doped micro-nanocrystalline diamond coating may be successfully prepared on Mo substrate with DC arc plasmas jet deposition device. Along with the increase of doped-boron concentration in the film, two-point resistance measurement indicates that film resistance presents exponential decrease; Raman spectrum test shows that, the characteristic peak value of diamond 1332cm-1 in the spectrum moves toward low frequency, the semi-height width of diamond peak, peak D and peak G, etc. in the spectrum is expanded, and the component of non-diamond bonds such as sp2, etc. in the film is increased; SEM and AFM observation shows that, increasing the doped-boron concentration could further subdivide the crystal grains in the film, and is beneficial for the growth of nano- or ultra-nano-crystalline diamond film; film annealing test shows that, micro-nanocrystalline diamond film with higher doped-boron concentration has better thermal stability than the micro-nanocrystalline diamond film without doped boron.

Abstract: Chemical vapor deposited (CVD) diamond film has a series of outstanding properties. However, it can not be easily machined by conventional technologies available currently for its high hardness and stability. Laser processing diamond film method can be an efficient way to process diamond film because of its high energy density. The mechanisms of laser processing diamond film are thermal oxidation, graphitization and evaporative ablation of graphite. Temperature distribution is of great importance to understand these complex phenomena taking place during the process because different temperatures lead to different physical and chemical changes of diamond. In this paper, the finite element method (FEM) software ANSYS is applied to calculate the temperature distribution. The relation between etching depth and laser machining parameters (laser power and scanning speed) is presented. The proper parameter ranges of laser power and scanning speed for a certain etching depth is also investigated with this method.

Abstract: Diamond film was deposited on spherical molybdenum substrate by DC arc plasma CVD method. Diamond film morphology, purities and orientation evolution, obtained from atomic force microscopy, scanning electron microscopy, Raman spectroscopy, X ray diffraction respectively, has showed that grains on the growth surface are compact, continuous and uniform. Characteristic diamond (111), (220), (311) peaks were found and (111) facets were predominant. It revealed that diamond film was polycrystalline texture characteristic. There is a typical diamond Raman spectrum peaks at 1332.0 cm-1, and not graphite and amorphous carbon characteristic peak. High purity diamond film was deposited. When methane concentration was increased, diamond film has more local clusters and vacancy defects such as voids, graphite inclusion, and hydrogen cluster. Therefore, some important parameters such as methane concentration and substrate temperature should be optimized in depositing diamond film.

Abstract: Based on the traditional HFCVD system, a new set of miniature HFCVD diamond film-deposition system with a swingabe substrate platform has been designed. Simulations of the substrate temperature field have been done respectively when the platform is still, rotating continuously, or swinging. The results suggest that when the swing angle is bigger than 100, uniform temperature field close to that achieved through continuous rotation can be got. So, in this paper, the crank-rocker mechanism has been used to produce a swingable substrate platform, which simplifies the traditional structure. And satisfactory temperature field can be achieved. It meets the requirements of the miniaturization design.

Abstract: According to dyeing and printing wastewater of high chroma and difficult decomposition, a new ultrasonic focalize decomposition method is provide, which can decompose those are difficult to do. In this article, Dynamic adding-pressure dissolving-air, ultrasonic focalize and flocculate floating-air are assembled to advance the treatment effect. Through the research, the dynamic models of adding pressure and dissolving air and flocculate floating-air are constructed. Based on the theory research, a experiment device is designed. The effect and influence factors are discussed, which provides a new way to process dyeing and printing wastewater of high chroma and difficult decomposition.

Abstract: Although research on various diamond polishing techniques has been carried for years, some issues still need to be examined in order to facilitate application on large areas in a cost-efficient manner. A compositive technique for machining efficiently thick diamond films prepared by DC plasma arc jet is reported in the present paper. A two-stage polishing was applied on thick polycrystalline diamond films, by employing first electro-discharge machining (EDM) for rough polishing and subsequently mechanical polishing for finishing operations. Experimental results obtained clearly indicate the applicability of the proposed two-stage technique for fabricating transparent diamond films that can be used for the production of X-ray windows. Appropriate etching with EDM is an effective pretreatment method for enhancing the efficiency of rough polishing process in mechanical polishing of thick diamond film. The machined surfaces of diamond films are studied by Scanning Electron Microscope (SEM) and Raman Scattering Spectroscopy (Raman).

Abstract: Cryogenic polishing single silicon wafer with nano-sized CeO2 abrasives can be known as cryogenic fixed abrasives CMP (CFA-CMP). The abrasive slurry was made of nano-sized CeO2 particles dispersed in de-ionized water with a surfactant and the polishing slurry froze to form cryogenic polishing pad. Then the polishing tests of the blanket silicon wafers in the presence of the cryogenic polishing pad containing the nano-particulates were carried out. The morphologies and surfaces roughness of the polished silicon wafers were observed and examined on an atomic force microscope (AFM). The results show that a super smooth surface with roughness of 0. 293 nm is obtained within 5000 nm× 5000 nm and the removal of material is dominated by plastic flowage.