Advanced Materials Research Vols. 152-153

Abstract: Nylon 12 composite powder with low melting point prepared by the method of solvent settling out as the basis material is modified with basis material added by all kinds of filling. With the ortho-design experiment method, the sintering process of nylon composite powder is optimized for sintering density and mechanical property of prototype parts. On this basis, the effects of the sintering process parameters on the properties of the parts are analyzed. The result shows this method can make nylon composite power with high powder density, precision and mechanical properties.

Abstract: In-situ TiC particle reinforced iron based composite was further processed using quenching, and the effect of heating temperature of quenching for the properties of TiCp/Fe composite was investigated. The quenching phases of the composite are as same as that of the as-cast composite. Quenching can further improve wear resistance of TiCp/Fe, and the composite via quenching route is more suitable for the application of light load. When the optimum heating temperature of quenching of TiCp/Fe is equal to 780 °C, the microstructure of the steel matrix is fine martensite (M), as well as the composite has the highest hardness and wear resistance. The lower or higher heating temperatures of quenching process all result in the decrease of hardness of the steel matrix, which leads to the wear resistance being lower than the as-cast composite.

Abstract: Stating and analyzing the two existing microminiature manufacturing technology, an integrated innovation technology is proposed, based precision cutting technology and thin films technology, with other advanced technology such as precise measurement. The precise and miniaturized parts with three-dimensional complex structure can be manufactured by this technology. The technology not only improves the manufacturing accuracy and surface quality, but also implements batch production. The feasibility of new method is verified by the dimensional chain theory, and the challenge and development prospect is simply summarized.

Abstract: Kinematics and ground plane trajectory tracking motion plan of an unmanned bicycle were researched in this paper. For the unmanned bicycle controlled by a steering torque, a pedaling toque and a tilting torque, rigorous kinematics model was set up and discussed, and when the ground plane trajectories and the bicycle tilting angular trajectory were given, by use of Back-stepping design means, the steering angular velocity, the rear wheel rotation angular velocity and the other motion parameters trajectories of the unmanned bicycle were planned and discussed, the simulation results showed that the kinematics model built was accurate and rigorous, all above motion parameter plans were reasonable.

Abstract: On the fitting process simulation, the dangerous area related with buckling or tearing phenomena is identified with special colors and values, then deleting, cutting line designing, refitting and spreading processes are implemented to obtain a reasonable blank shape with dart feature. Moreover, a so called expanding surface method was presented in order to realize the fitting and spreading of free surface with hole feature. The above provided methods are realized through software codes and used in some cases effectively.

Abstract: The current research explores the effect of alternating magnetic field on corrosion rate and products compositions of 45 steel, by use of electrochemical test, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The calculated inhibition efficiency of the alternating magnetic field based on electrochemical corrosion rate is up to 16.66%. Electrochemical corrosion morphology and surface products were also discussed. The surface of specimen is uniform and compact in magnetized sea water relation to that in 3.5% NaCl solution and sea water. The corrosion products of 45 steel in sea water are FeCl2•4H2O, Fe(OH)3 and FeOOH. However, the corrosion products of 45 steel in magnetized sea water are FeOOH, Fe3O4 and FeCl3•6H2O chiefly.

Abstract: To predict the three-dimensional residual stress distribution of 7075 aluminum alloy thick plates, the quenching and pre-stretching process were simulated by using MARC finite element software. In order to simulate quickly according to different reality conditions, the parametric model was realized by using defining parameters and selecting objects by inputting coordinate value with the box mode. In the quenching process, a non-linear thermo-mechanical direct coupled analysis of the aluminum alloy thick plates was carried out, by taking into account of the temperature dependence of the thermo-physical properties. In the pre-stretching process, the clamp and release of the clamp of pre-stretch machine were simulated by using life and death element technology. The study demonstrates that the theoretical predictions agree well with the experimental values of residual stresses measured by the X-ray diffraction method. The simulation results provide the user a tool for analyzing and studying on quenching and pre-stretching technique using virtual reality method.

Abstract: An experiment was undertaken to investigate the effect of mineral admixtures, w/b, external chloride solution concentration, and carbonation on chloride binding capacity of cementitious paste. The test method was based on equilibrium method. Test results show that incorporating metakaolin, blastfurnace slag, steel slag, and flyash increases chloride binding capacities by 65.9%, 55.3%, 43.9%, and 26.8% respectively. Increasing external chloride concentration and w/c ratio can improve the chloride capacity of pure cement paste. Carbonation of cement paste will reduce the chloride capacity. Chloride binding do affect the durability of reinforced concrete in saline environment.

Abstract: Gearbox sliding bracket is an important component of Automobile Gearbox. Because it has many parts which have little difference in shape and size, it is very easy to make mistake in assembly parts of this component. Due to mass production, it is high time to develop an online inspection system for the aseembly quality. Analysis the assembly characteristic of the component, this paper develop an online inspection system which is mainly composed of a central control system(CCS) and a sensor. Under the command of the CCS, the sensor is able to automatically inspect the component’s parts of which are wrong assmbly, reverse assembly and missing assmbly. Also the sensor can send the inspection information to the CCS. Subsequently, the CCS judges the information and dispalys the judgment result in time. At the same time, through the network, it is able to send the assembly quality information to the enterprise quality management system, such as the eligible amount, the reject amount, the qualification rate. This online automatic inspection system has run in good condition since it was officially put into operation at 2007 and its accuracy comes up to 100%.

Abstract: Pd/C catalyst was used to eliminate chlorine compacted in shellac while it was being bleached with sodium hypochlorite in alkaline solution for the preparation of shellac with low chlorine content, a natural and biological product used in large scale in food industry and pharmaceutical fields. Experiments demonstrated that the Pd/C could catalyze dechlorination process effectively, which was affected by several factors such as reaction temperature, Pd/C ratio, and the induction of Pd/C catalyst, and that the dechlorination efficiency reached 88.2% under the optimal conditions of Pd/C loading ratio of 1.0% (mass), catalyst usage 12 g/L, H2 flowing rate 50 mL/min, and reaction temperature 90 for 120 min. Moreover, the mechanism of catalytic hydrogenation was elucidated through structure characterization of the final products using elementary analysis, and ultraviolet spectrophotometer. It was shown from the result of ultraviolet spectrophotometer that the wavelength of the maximum absorption of seedlac, the raw materials for obtaining shellac, was 235 nm. However, it was blue shifted to the same scope 220~225 nm when the shellac was dechlorinated by catalytic hydrogenation with Pd/C as the shellac without catalyzed. The big difference of wavelength of the maximum absorption between shellac and seedlac was due to that there was a lot of compacted chlorine in the shellac, while the little difference of wavelength of the maximum absorption between the shellac and the low chlorine shellac was due to that chlorine could not be eliminated completely. The results of elementary analysis showed that chlorine content in the final product was only 0.30% under the optimum conditions, compared to shellac it was just 1/9 of that of the product without declorination by catalytic hydrogenation. It was shown from the mechanism analysis that the dechlorination reaction took place mainly on the active surface sites of Pd/C, and chlorine ions compacted in the shellac was substituted by hydrogen ions.