Advanced Materials Research Vols. 335-336

Abstract: As a necessary component in pneumatic muscle, minimum switch and minimum mechanical hand, pen cylinder used as prime actuator possesses the characteristics of high speed actuation possible, easy installation, improved wear resistance and so on. The construction and working principle of the pen cylinder are introduced. Using 3-D stress field finite element analysis (FEA) method, the stress field distribution of pen cylinder with preload in mounting nut is analyzed. Simulation results are presented. The stress characteristics are compared between different preload in mounting nut and thickness of mounting bracket.

Abstract: A modified continuum model of electro-statically actuated micro-beam is presented based on the modified couple stress theory. The new model contains a material length scale parameter and can capture the size effect, unlike the classical Bernoulli-Euler beam theory. The governing equation of the micro-beam is derived based on the Hamilton’s principle, which accounts for the effects of the moderately large deflection, the residual stress and the fringing electrostatic field. The numerical analysis of mechanical characterization is performed by the Analog Equation Method (AEM). The effects of the couple stress on the static and dynamic responses, pull-in voltage and pull-in time are discussed.

Abstract: The numerical modeling and modal analysis had been investigated on vibration of magnesium alloy honeycomb panels. With a simplified model of honeycomb panel, imposing the boundary and initial conditions, the distribution of the natural frequency and inherent vibration mode of the honeycomb sample could be simulated by using Lanczos method, the summit amplitudes and the most dangerous points are found. The effective factors such as materials modulus, the density as well as the assembling all contribute to the analyzed results. The vibration modes and the basic vibration frequencies were analyzed. According to the analysis, the risk-reduction program is proposed.

Abstract: The microstructure and precipitates of the V-N microalloyed steels whose carbon content were respectively 0.27% and 0.35%, were investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM). It is shown that the microstructures of the test steels are all composed of ferrite and pearlite, the area percent of ferrite decreases from 49% to 40% and the grain size also descends from 8.96μm to 8.61μm with the increase of carbon content. TEM results show that the precipitates in two kinds of steels all include a large amount of 10~20nm dispersion distribution irregular flake VC, the part of fibrous VC that grows toward to intragranular ferrite along the grain boundary in the local area, and only a small amount of spherical VN or V (C, N). When the carbon content increases from 0.27% to 0.35%, the number of the spherical VN or V(C,N) increases obviously and the size of it varies from 20~100nm to 45~105nm, while the number of flake VC and fibrous VC decreases significantly and the length of fibrous VC shortens from several micrometers to nanometer size. Experimental results indicate that most of the spherical VN or V (C, N) firstly appear in austenite, then the flake VN and fibrous VN with precipitation strength effect emerge in ferrite during the following γ→α transformation and cooling process. The increase of carbon content can lead to the increase of driving force that VN or V (C, N) firstly appear in austenite, which results in the significant increase of ferrite nucleation rate and the refinement of microstructure.

Abstract: For providing basic data to the reliability evaluation of the carrying capacity of the overhead traveling crane’s structure, by using Visual C++6.0 development platform, Pro/Toolkit and the element birth and death technology, the parametric model of the overhead traveling crane’s structure and the automatic analysis of the structure finite element model have been achieved. The results from the analysis obtained maximum element stress from each load step, and then the failure paths of the structural element which undered static load were found, from which the failure order consistented with failure development law of the overhead traveling crane’s structure, this would provide a technical basis to the search of dynamic failure paths which undered dynamic load. Finally, engineering examples which verified the feasibility of this method were brought.

Abstract: The property of surface electron in undoped IIn_0.13Al_0.87N epilayers with different thicknesses has been investigated using x-ray photoemission spectroscopy (XPS) and micro-Raman scattering spectra. XPS has been used to determine the characteristic of the native oxide at the free surfaces of In_0.13Al_0.87N film. It is showed that the binding energy shift to higher with the thickness reduction from the Al 2p, N 1s, In 3d_5/2 spectra. While, there is more native oxide at the surface of In_0.13Al_0.87N film with the decrease of thickness. In addition, a broad peak in high energy region was only observed in the thinnest In0.13Al0.87N epilayer from micro-Raman results, and it may be relative to L+ coupled mode of In0.13Al0.87N.

Abstract: In order to investigate the bending performance of Continuous casting 945 steel sandwich board in cross plate, it is carried out the bending performance numerical simulation for Continuous casting 945steel ,find the largest stress zone in bottom plate when it is at the end of the Elastic stage; Find the most adverse regional、limit bearing capacity、stress-strain relationship and stress three-dimensions degree in the ultimate state. The most unfavorable area of board appeared in middle core board and mid-span junction of sandwich board. When applied 10mm and 90mm displacement, the most adverse regional appeared yield and destruction at first time. According to the stress three -dimensional degree can draw that tension board’s destruction form is stretch destroy in the most adverse regional. When applied limit displacement 90mm, the reaction force is 763.4KN in mid-span. The analysis results note that the most unfavorable area of continuous casting 945 steel sandwich board and destruction form, it has some practical significance for future sandwich board test.

Abstract: Fused quartz granules (d₅₀=19 μm) were used as raw material, and Gd₂O₃-Nd₂O₃ (1:1, in mass) was used as additive with dosages of 1% (in mass, similarly hereinafter), 2% and 3%. Fused quartz ceramic materials were fabricated in reduction atmosphere at 1300 °C, 1350 °C and 1400 °C for 1 h. The apparent porosity, bending strength and thermal expansion ratios of the samples were examined and the samples were further analysed by means of XRD and SEM. The results showed that the sample sintered at each temperature with 3% Gd₂O₃-Nd₂O₃ had the lowest apparent porosity, the highest bending strength and more compact microstructure. This indicated that 3% Gd₂O₃-Nd₂O₃ was helpful to sintering of fused quartz ceramic materials. The results of XRD and thermal expansion ratio analysis showed that 3% Gd₂O₃-Nd₂O₃ compound additive had better effect on inhibiting crystallization of the samples sintered at 1300 °C and 1350 °C, but had a little effect on inhibiting crystallization of the sample sintered at 1400 °C.

Abstract: Mn_(1-X)S:A_X/ZnS (A: Er, Dy) nanocrystals were synthesized by chemical precipitation method. X-ray diffraction analysis show that Mn_(1-X)S:A_X/ZnS nanocrystals were zincblende structure. The high-resolution transmission electron microscope images indicated that Mn_(1-X)S:A_X/ZnS nanocrystals show a spherical shape, and their average grain size is about 4 nm. Photoluminescence spectra of Mn_(1-X)S:A_X/ZnS nanocrystals revealed that there existed several major emission bands, ～417 nm, ~509 nm, ~580 nm, ~617nm and ~680 nm. Mn_(1-X)S:A_X/ZnS nanocrystals exhibited enhanced luminescence properties compared with the pure Mn_(1-X)S:A_X nanocrystals. The enhanced photoluminescence properties of Mn_(1-X)S:A_X/ZnS nanocrystals should be attributed to the effective suppression of nonradiative recombination by the surface-passivation layer.

Abstract: Flaky and porous rod-like MgO powders were prepared by molten salt synthesis with MgCl₂, CaCO₃, NaNO₃ and KNO₃ as raw materials. TG-DSC, XRD and SEM were used to investigate the reacion process and characterize the resulting products. The results indicated that Ca²⁺ was displaced by Mg²⁺ and dolomites were formed and finally converted into magnesium carbonates during the molten salt synthesis. Fibrous Mg(OH)₂ formed in PEG solution and flaky Mg(OH)₂ formed in EDTA-PEG solution illustrated that EDTA and PEG molecules could define the growth direction of Mg(OH)₂. The porous rod-like MgO powders with 20-80 nm in diameter and 40-100 in length-to-width ratio were obtained by the decomposition of fibrous Mg(OH)₂ at 600 °C, while the flaky MgO powders were prepared by the decomposition of flaky Mg(OH)₂ at 600 °C. Flaky MgO powders were platelike, with 30-50 nm in thickness, 200-500 nm in diameter, and up to 1.0 µm² in a single slice surface area.