Applied Mechanics and Materials Vols. 121-126

Abstract: Crystal transformation of dicalcium silicate (2CaO•SiO2, C2S) has influences on the microstructure, hydraulicity, and grindability of cement clinker. The transformation of β-C2S to γ-C2S can destroy the clinker nodule integrity by volume expansion due to the low density of the γ-phase. It can be used to pulverize cement clinkers for saving grinding energy, but the hydraulicity of γ-C2S is lower than β-C2S. Quantitative control of C2S crystal transformation could balance the energy saving and hydraulicity. The influences of sintering temperatures, cooling methods and chemical impurities on the transformation were investigated. The results show that the appropriate sintering temperature of γ-C2S was 1250～1500 °C, and the rate of cooling should not be higher than 500 °C/min to guarantee β-C2S transform to γ-C2S. Chemical impurities (Na2O, P2O5, B2O3, Cr2O3 and K2O) were stabilizers of β-C2S, which could prevent β-C2S transforming to γ-C2S. The stability effect was related to their concentrations. The characteristic concentrations of Na2O, P2O5, B2O3, Cr2O3 and K2O were approximately 1.2%, 0.3%, 0.3%, 1.0% and 1.5%, respectively. Above these concentrations, most of β-C2S could be stabilized rather than transforming to γ-C2S. In “transition zone”, C2S crystal transformation could be controlled quantitatively by adjusting the stabilizer concentration.

Abstract: Due to many of advantages such as lightweighted, high-bending mechanical characteristics, composite sandwich materials play an important role in today’s structural manufacturing industry. This study is to aim at the low-velocity impact responses of sandwich plates subjected to a rigid, spherical-shaped impactor. The sandwich made of PVC core material (two kinds of core with different densities) and FRP facesheets (three kinds of fibrous laminae) were investigated experimentally and numerically. Because the dynamic behaviors of specimens due to low velocity impact is nearly the same to those in static indentation, the impact failure analysis of sandwich material can be simulated statically. Beside the experiment, finite element method was employed to analyze the static failure behaviors of sandwich panels. With the maximum stress failure criterion as well as a modified stiffness degradation method coded in the finite element software, the initial failure and sequential progressive failure process can be analyzed effectively.

Abstract: The Au electrode plated nanostructure Pd was used to study the reaction mechanism of C.I. reactive blue 19 and reactive brilliant blue K-GR with atomic hydrogen in 0.2M H2SO4 solution by the electrochemical method. The nanostructured Pd/Au electrode showed the various forms of hydrogen. Through the result of cyclic voltammetry, Tafel curve and EIS, the protonation of dye molecule could accelerate the production of atomic hydrogen and the adsorption of dye on Pd/Au electrode. The decolorization efficiency using potentiostatic polarization at -0.18V was highest than that at other polarization potential because the proportion between adsorbed dye and adsorbed atomic hydrogen on electode was optimum.

Abstract: The FDM numerical simulation software View Cast system was employed to the counter-pressure casting of aluminum alloy large-scale thin-section casting. By analyzing the mold filling and solidification, the distribution of liquid fraction, temperature field were studied. The potential shrinkage defects were predicted to be formed at the top of the casting. A solution towards reducing such defects has been presented. The feeding capacity of the riser was improved. Analysis on the shrinkage proved that the improved riser is an effective method for reduction of defects.

Abstract: Parts precision is one of the key points in industrial application of rapid prototyping technology (RPT), and also the pivot of RPT research, but presently high precision is hard to achieve. This paper focuses the emphases on the principle of error analysis. Obtain chord errors corresponding to the number of triangles with pro/E software during the STL, and the formula for computing stair errors taking the quarter of sphere for an example during the slicing. In the end, propose the measures to improve the principled errors, viz. sloping slicing, adaptive slicing, direct slicing and so on, and further propose the theoretical range of adaptive slicing thickness.

Abstract: Al-Mn alloy coatings were electrodeposited on an iron substrate from AlCl3-NaCl-KCl low-temperature molten salts with anhydrous MnCl2 enhanced by the addition of NdCl3.The microstructure and properties of the Al-Mn alloy coatings were investigated, and scanning electron microscopy, X-ray diffraction, and polarization curves were used to determine the composition, surface morphology, phase structure, and corrosion resistance of the obtained deposits. The results show that the surface coatings were smooth, and that the crystallites were dense and uniform when 0.23 wt% NdCl3 was added to the molten salt. An amorphous mixture of Al and Al6Mn was obtained. NdCl3 enhanced the corrosion resistance and increased the hardness of the single amorphous phase alloys. The pitting potential of the coating was approximately −1.04V, and its hardness was 392 kgf/mm2.

Abstract: In this study, the elastic buckling behavior of general dome ends under presumed temperature distribution and external pressure was studied. The Finite Element Method (FEM) was used to predict the elastic buckling pressure behavior when the domes were subjected to various operating temperatures. The freedom of the edges of the dome ends was completely restricted to simulate clamped end conditions. The four-centered ellipse method was used to construct the geometry of the dome ends. The influence of geometrical parameters such as thickness, knuckle radius, and the ratio of minor axis to the major axis of dome ends and the effect of temperature on critical buckling pressure of hemispherical, ellipsoidal, and torispherical dome ends were studied. It has been found that the under thermal condition, the thickness and the shape of the domes have the most significant effect on the critical buckling pressure. Two models of torispherical and ellipsoidal dome ends are analyzed by using finite element analysis.

Abstract: In this paper, several types of sealing ceramic arc tube furnace and layout design of super purified glove box were introduced. The methods of injection of mercury and metal halide, electrode assembly and gas injection were put forward.

Abstract: The tensile strength of joints is one of the most important indexes which can affect joint quality. The effect of gluing length, specimen width and thickness of wood single lap joints on the maximum tensile load and tensile strength has been researched through the experiment method. The maximum tensile load increases with the increase of gluing length, specimen width and thickness, but the increase degrees are different; the tensile strength is consistent with the increase of gluing length, but does not change obviously with the increase of specimen width and even decreases with the increase of specimen thickness. The conclusions of this paper will have guiding significance for the design of wood single lap joints.

Abstract: Magnesium alloys were treated by micro-arc oxidation at a constant applied current density. The friction and wear properties were investigated by optical microscope and universal friction and wear tester in 3.5%NaCl solution. The result reveals that the film formed by micro-arc oxidation enhances the corrosion resistance of the magnesium alloys. The Ecorr of micro-arc oxidation film improved 94mV than the Ecorr of magnesium alloys matrix. Wear resistance of the film was weakened in 3.5%NaCl solution. The wear mechanism of film depends on the load. Abrasive wear was predominant at low load. Peeling wear was predominant at high load, which result from damage of the film adhesion.