Applied Mechanics and Materials Vols. 84-85

Abstract: Material selection in mechanical products based on total life cycle design is a complicated work, which should be studied systematically. A material selection model of mechanical products based on total life cycle design was proposed. A set of candidate materials were screened out, and then assessed according to the technical, economic and environmental assessment index. The candidate materials were ranked by using by using Z-transformation method in each of the assessment index. Different weights were assigned to each of the three assessment indexes, and global assessment was carried out according to different strategies or requirements which pay more attention to technical, economic or environmental performance of the material product used. A case in selecting aircraft structure element material was studied. The analysis results showed that the method could rank the candidate materials and selected out the “optimized material”, and the influence of the subjectivity of designer was reduced. The method provides some practical values for preliminary material selection in the early design stage of the mechanical products based on life cycle design.

Abstract: Field-induced oxidation has become a promising process that is capable of directly producing high-resolution surface oxide patterns on variety materials. This report initiated the idea of the possibility of a controlled nanofabrication of SiO₂ on silicon wafer by utilizing a frozen humid air film. A low temperature (-70°C) operation of an atomic force microscope (AFM) was used to condense ambient humidity (40%) to perform a thin frozen water layer covering a silicon wafer surface. A scanning probe was contacted with the layer and a zero bias voltage was applied to the sample surface with the AFM probe tip connected to the reference -2.44V. The frozen water film acted both as an electrolyte to form silicon dioxide and as a resource of hydroxide. Using this technique (a) a consistency in height of 6 nm silicon dioxide patterns layer could be achieved showing that the effect of tip vibration could be reduced; (b) easy to remove frozen water by just operating the AFM to the ambient temperature; (c) it is possible to control thickness by making different humidity.

Abstract: The electrostatic charge accumulates on the surface of the aerial vehicle when flying. And the electrostatic discharge would impact the aerial vehicle and the airborne equipment enormously. In order to study the triboelectrifiction of the aerial vehicle skin material and space particle, the triboelectrifiction principle of the skin material is analyzed, and aerial vehicle skin material triboelectrifiction experimental platform has been designed. Lots of troubles are overcome like the relatively high speed of aerial vehicle and space particles, required high bleeder resistance for analog devices, and testing problem of friction potential. The rotary friction method, composite insulating layer, contact electrostatic potential test method are adopted for the experimental platform. And aerial vehicle skin material has been tested using the test platform. From the experimental results, the friction contact time, the separation process, and the contact area are analyzed. So the material electrostatic test platform can be used as material electrostatic charge experimental research equipment.

Abstract: Catalog is a celestial databank which records various parameters, such as location, motion, magnitude, and spectral type. UCAC2 (The Second U.S. Naval Observatory CCD Astrograph Catalog) is a high density, highly accurate, astrometric catalog of 48,330,571 stars. Currently the UCAC2 catalog can only be accessed by an index of ascension and declination. To facilitate the efficient multi-dimensional access to UCAC2, this paper proposed the detailed design and implementation of the multi-indexed catalog database. The newly established index system can provide efficient access in multiple entrance to the catalog.

Abstract: The Auto Rivet-Placing System was designed to replace the existing manual operation which was hard to ensure the precision and the inefficiencies caused by human fatigue. The paper analyzed the details of the whole system including the transmission, drive, and control of the mechanisms especially manipulator and plat. The model of manipulator and other mechanisms in the system were designed in the human-oriented modeling environment of Pro/E especially some important parts. The control system was at work with image positioning technology.

Abstract: Microstructure and the precipitated high temperature ferrite δ phase of an austenitic steel 10Cr18Ni9NbCu3BN tube was investigated. It reveals that segregation during solidification process results in the precipitation of high temperature ferrite. The calculated amount of δ phase was consistent with our XRD analysis. With decreasing solution treatment temperature, Nb-containing phase will be refined and the amount of δ phase as well as process-cost can be reduced. Because of the highest performance/cost ratio, austenitic super 304H steel is applied as pressure component under supercritical conditions. It was originally developed by Sumitomo Metal Industries, Ltd and Mitsubishi. Based on 304H, Super304H has lowered the upper limit of Mn, but added Nb, N and Cu. Elements Nb and N can form stable NbN,Nb(C,N)-phase, so as to refine the grain size and result in precipitation-hardening. Cu can form coherent segregation phase which also has the hardening effect, decreases the hardening rates in the cold-working process and improves the plastic formation of steel. In this kind of steel, the main strengthening phases are copper-rich phase, MCs. The alloying effect of elements Nb,N and Cu can increase allowable stress and service life of the steel under the working temperature[1]. In this paper, experimental and theoretical analysis was carried out in order to develop new 10Cr18Ni9NbCu3BN steel tube. In accordance with ASME code case 2328-1, the contents of steel 10Cr18Ni9NbCu3BN were listed as follows in Table 1.

Abstract: As to the production of degreasing unit, fully integrated with the equipment and technological features of the line, the approach for the setting of coiling tension was changed, which was mainly tabular method in the past. Under the new idea, the degreasing process was closely integrated with the bell-type annealing for the first time. Then, to minimize the severity of stick breaks was set as the objective function, and no loose coil and no heart-shaped coil is took as the constraint condition. On these bases, a new comprehensive optimization model for the setting of coiling tension in degreasing unit was put forward. The relation between coiling tension and coil radius was obtained, which was a quadratic curve. This simple and practical technology can make the distribution of internal stress of coil more reasonable, and reduce the incidence of stick breaks, loose coil and heart-shaped coil defects effectively and improve production efficiency, quality and the metal yield.

Abstract: The Pig is an important tool during the process of oil-gas pipeline’s production, replacement, daily operation and management. Its outer diameter is 2% to 5% larger than the inner diameter of pipelines. It stays a clamping state in the pipelines. The fluid pressure difference before and after the Pig push it from the beginning to the end of the pipelines in order to clear all kinds of impurities in the pipelines and detect the internal and external wall corrosion status of the pipelines or achieve other goals. But during the cleaning-up operation, it is difficult for the Pig to get in and out of the pipelines because of its heavy weight. So a Pig and Pigging ball handling trolley is designed in this paper to push and pull the Pig or Pigging ball to get in and out of the Pig launcher & receiver device. This handling trolley will mechanize the Pigging operations, reduce the labor intensity and improve the work efficiency.

Abstract: With the wide use of NC, higher accuracy in machining is increasingly required for premium mechanical components. However, machining accuracy is affected by many factors, especially by the way of the tool positioning and the geometry of the tool nose. This paper, based on the actual NC lathe tool and turning, generalized and abstracted the machining process by establishing the imaginary tool nose and the tool tip’s arc centre as the cutter-contact point, and analyzed systematically the influence of the factors, including the way of the tool positioning, the nose, and the tool tip’s arc radius, on the machining accuracy when machining transverse, cylindrical-surface, circular cone, quarter-circular and some surfaces can be expressed by formula etc.. Derived the error calculating formulas for turning in different surfaces. Put forward two error compensation methods, direct calculating method and enveloping method of error compensation. Experiments were carried out and results have shown that the two error compensation methods can considerably reduce the machining error in NC turning operations.

Abstract: The edger mill stand belonged to the oversized integrated-casted stand-type heavy parts, if it was machined on the planer milling and boring machine, above 90% of the milling and boring process could be completed by only clamping for two times, and more accurate values could be obtained. Improved and changed the numerically-controlled process of this part in the machining process, and all working procedures of the edger mill stand were machined on the numerically-controlled floor-type boring machine with the diameter of 260, thereby accumulating the experience of machining the stand parts with complex cavity sizes and further expanding the scope of numerically-controlled floor boring machine process. The improvement and implementation of NC process on this workrpiece is of important meaning of reference for the kind of parts.