Key Engineering Materials Vols. 315-316

Abstract: This paper presents an approach to fabricate nanoscale gratings by direct imprint on silicon substrate. Imprint conditions that affect the transcription accuracy, such as imprint temperature and pressure, are discussed, and the profile of the imprinted 80nm width gratings with a 250 nm pitch is checked by SEM. High fidelity and fine uniformity demonstrate that nanoimprint is an economical and efficient method to fabricate nanoscale gratings.

Abstract: Fused-taper fiber coupler is usually fabricated by using a microburner. The coupler’s excess loss and performance repeatability are unstable. To simulate the fabrication process and to find solution to the performance questions, A viscoelastic rheological model of fused biconical taper process is presented by using generalized Maxwell model to simulate the viscoelastic characteristic of fused fiberglass, and the rheological numerical analysis under the non-isothermal condition is carried out with ANSYS software. The effect of technical parameters such as drawing speed and fused temperature on the fabrication process is studied. Drawing speed is in direct proportion to the maximum stress, and fused temperature affect extremely the fabrication process. The fluctuation of fused temperature by 5
can lead to the change of maximum stress by 30%. It is found by experiments that the flame temperature fluctuates in the range of 5-30
, while the drawing speed is rather stable. It can be reached a conclusion that it is the fluctuation of fused temperature that induces the poor performance repeatability and unstable excess loss.

Abstract: To meet the high speed and high precision requirements of machining freeform workpieces, a 4-DOF parallel kinematic platform with the configuration of 4 actuated legs plus a passive leg is proposed in this paper. Inverse kinematics and the calibration algorithm are developed, and virtual prototype modeling and kinematic simulation using MSC/ADAMS are carried out. The simulation results exhibit that the proposed structure is capable of implementing the high-precision machining requirements of freeform parts.

Abstract: The externally pressurized gas journal-thrust bearing with slot restrictors is investigated by the finite element technique. A consistent transform principle is proposed in this paper to simplify the analysis of Reynolds equation for journal and thrust bearing. The second-order partial differential equation, Reynolds equation, is reduced by one-order with weighted residual method in the discretization procedure, which releases the requirement of continuity degree of the interpolation function while finite element method is adopted. The static characteristics of externally journal-thrust gas bearing are analyzed. Factors that influence the radial and axial bearing capacity are discussed. The interactional rules that exist between the journal bearing part and thrust bearing part are discovered. Predicted characteristics are in good agreement with experimental results.

Abstract: This paper describes a micro-target semiautomatic assembly system used in ICF. In the system two halves of a cylindrical gold hohlraum (1.6 mm long by 0.8 mm in diameter) and a microsphere capsule (about 0.2 mm in diameter) are assembled. CCD cameras are applied to monitor the process of closed loop assembly.

Abstract: Nanocrystalline diamond film with smooth surface and uniform grains was deposited successfully on Co-cemented carbide using the bias-enhanced hot filament chemical vapor deposition (HFCVD). The surface morphology and chemical quality of film were estimated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman spectroscopy. Comparative experiments of tribological and wear performances of conventional and nanocrystalline diamond films were carried out by pin-on-disc tester. The research results show that nanocrystalline diamond film with good tribological performance and high quality can be deposited by regulating the deposition parameters on Co-cemented carbide. The film not only has high adhesive strength but also has smooth surface, low surface roughness, low friction coefficient. The work done in this paper provide the wide application of diamond on complex shape tools, drawing dies and other wear resistant device with experimental reference.

Abstract: In order to achieve the smooth surface of diamond, several kinds of mixture oxidizing agents have been used to polish the single crystal diamond by a designed polishing apparatus. The existing of graphite and amorphous carbon has been found in the surface of diamond after polishing. The mechanochemical actions of oxidizing agents and the polishing iron plate have been proved. The mixture of oxidizing agents can decrease the polishing temperature so that the super-smooth surface of single crystal diamond can be achieved at lower temperature. The method provided is benefit not only to simplify polishing device and control the polishing process, but also to improve the removal rate and surface roughness.

Abstract: This paper focuses on developing an empirical model for the prediction of milling forces in high-speed end milling of P20 die-mold steel. The spindle speed, feed rate, axial and radial depth of cut are considered as the affecting factors. The data for establishing the model are derived from high-speed end milling experiments conducted on a 5 axis machining center according to the principles of DOE (design of experiments) method. The influences of milling parameters on milling forces are investigated by analyzing the experimental curves. Consequently, multiple-regression analysis is applied in developing the empirical model. Furthermore, the significances of the regression equation and regression coefficients are statistically tested in this paper to validate the model.

Abstract: In order to optimize static performance of a new orifices compensated externally pressurized gas spherical bearing, the paper presents a theoretical study using finite element method (FEM). Galerkin weighted residual method is applied to reduce the order of derivatives of the transformed Reynolds equation. On the basis of theoretical analysis, the influence of supplying pressure and geometrical parameters to radial load carrying capacity and stiffness was analyzed. As a result, the reasonable range of the bearing’s parameters was proposed.

Abstract: Recognizing and evaluating the development level of a country’s precise finishing industry, is the prerequisite to the country’s decision-making on the development planning and guiding policies in this industry. This paper presents a Fuzzy Analytical Hierarchy Process (FAHP) Model on the base of “Expert Knowledge”. This model combines the advantages of Fuzzy Evaluation Method and Analytical Hierarchy Process (AHP), and can give relatively reliable evaluation results with incomplete information of the evaluation criteria. The application of the FAHP Model provide reliable comprehensive evaluation data.