Advanced Materials Research Vols. 472-475

Abstract: As to the problem that the assembly cycle and costs of quayside container crane always exceeds 40% of the entire production cycle and costs, improving the assembly efficiency becomes an important link to enhance the competence of port machinery manufacturing enterprises. In the product assembling cycle, virtual assembly can help to improve assembly quality and reduce the cost. Based on the physical structure of 45t quayside container crane, 3D components model were developed, the assembly hierarchy and modeling process were provided. The simulation analysis of assembly sequence was taken based on the CATIA DMU platform and virtual assembly animation was generated. The assembly interference detection results were analyzed to verify the part assembling ability, the whole disassembly and assembly process was displayed, which can help the assembly workers making visual analysis of fitting operation rationality.

Abstract: Based on stream of variation theory, parametric state space model of multi-station assembly process was built up. For problems of system-level evaluation index, the sensitivity evaluation index, soundness index as three methods of assembly system performance evaluation, the comprehensive stability index was presented. Parametric state space model was as a tool and the comprehensive stability index was as evaluation index to optimize the assembly lines, reduce the geometric deviation of product, improve the quality of product. Experiment verified comprehensive stability index can accurately evaluate the performance of assembly systems, improve the efficiency of optimizing assembly lines.

Abstract: By sol-gel method, nitrogen-doped nano-TiO2 photocatalyst are prepared with a series of different calcining temperature and different doping amount, using tetrabutyl titanate as a titanium source and hydroxylamine hydrochloride as a nitrogen source. And more, the photocatalysts were characterized by X-ray diffraction(XRD), Transmission electron micrograph(TEM) to analyze the microstructure and performance. We ensured the optimal process to prepare nitrogen-doped nano-TiO2 for self-cleaning fabric. At last, we are carried out the test of self-cleaning effect.

Abstract: The three-dimensional flow field simulation of a centrifugal pump was presented by using commercial CFD code. In order to study the most suitable turbulence model, the three known turbulence models of Standard k-ε, RNG k-ε, Realizable k-ε were applied to simulate the flow field of the MJ125-100 centrifugal pump and predict the performance of the pump. The simulation results of head and efficiency were compared with available experimental data, and the comparison showed that the result of the numerical simulation by RNG k-ε model had the best agreement. Additionally, the effect of number of blades on the efficiency of pump was studied. The number of blades was changed from 4 to 7. The results showed that the impeller with 7 blades had the highest efficiency.

Abstract: The theoretical analysis of the effect of uniaxial stress on the magnetization of the system of noninteracting nanoparticles is done by an example of heterophase particles of maghemite, epitaxially coated with cobalt ferrite. It is shown that stretching leads to a decrease in the coercive force H_c, and compression leads to its growth. The residual saturation magnetization I_rs of nanoparticles does not change. With increasing of interfacial exchange interaction, coercive force varies nonmonotonically.

Abstract: Filled fracture is a fracture in which sands or other materials occupy some void spaces. This study uses well-controlled laboratory experiments to investigate mechanical behavior of fracture filled with variable medium by means of normal compression and lateral restraint. A large number of stress-strain data are obtained. The mechanical behavior of filled fracture with variable medium can be divided into three phases: rheological phase, compaction phase and linear elastic phase. At the beginning of the experiment, the filled fracture is in the ideal plastic flow state. The overall strength of filled fracture increase with finite deformation and normal stress increasing, and show linear elastic characters. Based on the experiment results and characteristics, the mechanical behavior model of fracture filled with variable medium is constructed, and also its mechanism is analyzed.

Abstract: In order to investigate material properties of silicon nitride ceramic, nanoindentation tests are carried out on Hot-press silicon nitride specimen. The micro-hardness and elastic modulus are obtained. simultaneously, load-displacement curve is acquired. The whole process is simulated in ansys. Through comparing, there are satisfactory consistency between experimental curve and simulation curve. In addition, simulation can also indicate the distribution of stress fields during loading and unloading process. Base on these informations, the mode of cracks development and mechanism of material removal can be known.

Abstract: In this work, crack initiation due to the pre-existence of an initial crack has been predicted according to the criterion of critical stress intensity factor and succeeding crack evolution and propagation are also been performed using molecular dynamic (MD) method in combination with finite element method (FEM). The modified embedded atom method potentials were employed to characterize the interaction among atoms in magnesium alloy in MD simulation. Finite element simulations have been first conducted to provide subsequent MD simulation with boundary conditions constrained at the atoms. The MD simulation shows that atoms around crack arrange disorderly, aggravate rapidly suggesting the onset of crack initiation and eventually results in the failure of alloy specimen. It helps to evaluate the value of critical stress intensity factor for a specific crack configuration, which provides an effective way to determine the stress intensity factor for the specified configuration.

Abstract: The concentration error of standard gas in different locations of calibration system will have different degrees of impact on accuracy of calibration results. Among them, concentration of standard gas in gas mantle that combine detection sensors and gas transmission pipelines show the greatest impact on calibration results. In order to realize monitoring and analysis of the overall calibration process, this paper simulated gas concentration change status during calibration process of indoor environmental monitor gas mantle by FLUENT software. Gas concentration change status and sensor measurement accuracy at situations of different size sensors placed in the same gas mantle at the same location and same sensor placed in the same gas mantle at different location were analysed. Simulation results show that to make gas most quickly and evenly filled gas mantle, gas mantle size should be slightly larger than sensor and sensor should be placed in the top of the mantle as far as possible. On this condition, it can ensure gas concentrations error range between sensor workface and the inlet are within ±2%, thereby ensuring the accuracy of calibration results.

Abstract: Phenyl isocyanate is used to react with 1,3-butanediol at different temperatures. Toluene is used as solvent and 1,4-diazabicyclo[2,2,2]octane is used as catalyst. In-situ FT-IR is used to monitor the reaction to work out rate constant, Arrhenius equation and Eyring equation. The urethane reaction has been found to be a second order reaction, and the rate constant seems different between initial stage and final stage. The activation energy (Ea), activation enthalpy (ΔH) and activation entropy (ΔS) for the urethane reaction of primary hydroxyl group are calculated out, which are 26.4 kJ•mol^-1, 23.6 kJ•mol^-1 and -186.6 J•mol^-1•k^-1, respectively. They are very useful to reveal the reaction mechanism.