Key Engineering Materials Vols. 315-316

Abstract: The existent studies on milling dynamics of the thin-walled structure components are reviewed first, then a kind of FEM simplified model analyzing the milling dynamics of the thin-walled structure components is proposed. Based on the proposed model, some simulations have been done under different cutting parameters and different machining conditions. At last, the simulation results are analyzed and discussed.

Abstract: High quality diamond film wafers with different thickness are prepared by high power DC arc plasma jet CVD (DCPJ CVD) method using a CH4/Ar/H2 gas mixture. The effects of methane concentration on the growth of carbon balls in anode nozzle and arc stability are studied with theoretical analysis and experimental investigation. The results indicate that different sizes of carbon balls may rapidly grow in the anode nozzle with methane concentration higher than 2 Vol-%, symmetry and uniformity of the rotating arc are strongly affected with the occurrence of carbon balls, which will result in non-uniform deposition of diamond films over a large substrate area. The methane concentration should be controlled at a low level to keep diamond film wafers growth stable. Characterization by X-ray diffraction, Raman spectroscopy and SEM analysis are also carried out.

Abstract: Two-Axle Bending Technique with Elastic Roller (TABTER) is a kind of advanced manufacturing method for bending tubular parts, specially suiting for the difficult-to-work metal materials with high specific strength, and it can obtain a finer forming accuracy. Now the technique has been applied to bend split-sleeve and missile body cylinder successfully. In existed theories, the forming precision of the parts is controlled by adjusting the feed distance between the two axles. But because of the aging problem of the elastic roller and other uncertain factors, the feed force may be different even using the same feed, thus the forming precision cannot be ensured. To solve this problem, the forming theory by controlling the feed force between the two axles is proposed. Then the NC model of forming the non-circular cross-section tubular parts based on the theory is built. At last, the NC prototype machine is developed and some experiments are carried out on the machine.

Abstract: In order to machine the complex free surface, in this paper, NC interpolation of any complex surface is realized used the recursive reconstruction algorithm. The interpolating errors of this algorithm are controllable, and its applicability is relatively wide. Then, these NC codes of the complex human’s free surface are obtained with data exchange of the manufacturing module in the software UG, and machining simulation is obtained used NC codes. Finally, these NC codes are entered into the NC micro-machine tool, which is controlled by the PMAC and developed by ourselves, and the experimental research of the human’s free surface has been finished on this machine tool. The experimental results show that the NC interpolation accuracy of this recursive reconstruction algorithm is very high, and the machining simulation and machining experiments of the complex human’s surface are completely consistent. The study result shows that the complex surface molding is smooth and continuous, and the machined surface is satisfactory.

Abstract: An improved arc welding method was developed to fabricate carbon nanotube probe under direct view of optical microscope. The new fabrication method here needs not coat silicon probe in advance with metal film, which greatly reduces the fabrication’s difficulty. An easy method for shortening the nanotube probe was also developed. The improved fabrication method here is simple and reliable. The fabricated carbon nanotube probe showed good properties of higher length-to-diameter aspect ratio, better wear characteristics than silicon probe.

Abstract: Atom Force Microscopy (AFM) can be employed to create surfaces in Si substrate with recessed features. The resulting patterns can serve as masters to make the required elastomeric stamps for soft lithography. Morphology analysis of patterned features on Si substrate and polydimethylsiloxane (PDMS) stamp by AFM imaging confirms that pattern can be successfully transferred from Si substrates to PDMS stamps. It is shown that this method for creating masters can be performed with an AFM, making this method particularly straightforward, economical and accessible to a large technical community that are provided with AFM for measurement.

Abstract: In order to investigate nanoindentation data of polymer film-substrate systems and to learn more about the mechanical properties of polymer film-substrate systems, SEBS (styreneethylene/ butylene-styrene) triblock copolymer thin film on different substrate systems have been tested with a systematic variation in penetration depth and substrate characteristics. Nanoindentation experiments were performed using a Hysitron TriboIndenter with a Berkvoich tip. The resulting data were analyzed in terms of load-displacement curves and various comparative parameters, such as hardness and Young’s modulus. The results obtained by the Oliver and Pharr method show how the composite hardness and Young’s modulus are different for different substrates and different penetration depth.

Abstract: Submicron-sized top layer was synthesized on an austenitic stainless steel sample by adopting laser shock processing (LSP). The substructures were characterized and examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), moreover, the mechanism of ultra-refinement laser-induced was analyzed. It showed that a refined top surface with average subgrains size of 0.5(m was synthesized by the model of single laser loading, black paint as absorption coating and the peak pressure induced by LSP approximating twice of the dynamic yield strength of target. It indicated that thermoplastic destabilization had happened in heavily localized regions imposed by LSP. Streak-like subgrains were oriented perpendicular to shock wave (Gaussian profile) vector. In order to accommodate plastic strain, streak-like subgrains experienced necking, breaking up and dynamic rotational recrystallization, as a result, the submicron grains were formed on the surface of sample.

Abstract: The lubrication properties of the slurry between the silicon wafer and the pad in chemical mechanical polishing (CMP) are critical to the planarity of the silicon wafer. The effects of porous pad and suspending abrasives on the slurry film beneath the wafer become more prominent as the size of the silicon wafer becomes bigger. In order to explore the effects of porous pad and suspending abrasives on the lubrication properties of the slurry, a three-dimensional lubrication model based on the micropolar fluid theory and Darcy’s law is developed. The effects of the nanometer abrasives and the porosity of the pad on the lubrication of the slurry film between the silicon wafer and the pad are discussed.

Abstract: Ripples in the area of femtosecond laser irradiated discrete points and continuous lines were studied. The characteristics of interference-induced ripples (LSFL) in the area irradiated by single shot were investigated by AFM. During single point irradiation, morphology of the irradiated area changed with energy deposition. Morphologies of the irradiated continuous lines with and without ablated groove inside were both investigated. The intensity of interfered light waves varied in different positions of each energy stripes. Thus the characteristics of ripples in the irradiated area varied with different positions. Ripples much larger than LSFL were found perpendicular to laser polarization.