Applied Mechanics and Materials Vols. 401-403

Abstract: The effect of yield strength and elastic modulus of matrix on shear stress in two phases of composite reinforced with W fiber under pulse loading was simulated by ANSYS software. The results show that the effect of mechanical properties of matrix on composite should be taken into consideration in designing composite. The matrix with high yield strength and low elastic modulus can reduce the shear stress in W fiber, and is beneficial to keeping the integrity of W fiber during penetration, thus resulting in the improvement of penetration capacity.

Abstract: Nanometer calcium and magnesium oxides were added into molten steel by the carrier method in the experiment. The experiment takes the X80 pipeline steel as the research object and analyses the effect of nanometer calcium and magnesium oxides addition on the inclusions in the cast microstructure of the X80 pipeline steel. The scanning electron microscope (SEM) was used to analyse the morphology and distribution of the inclusions in the cast microstructure of the X80 pipeline steel. The results reveal that there are a small amount of inclusions in the sample of no nanometer oxides addition. With the amount of the nanoMgO oxide addition rising, the number of the inclusions in the sample firstly increases and then decreases gradually. When adding 0.05 wt% nanoMgO or CaO oxides, the size of the inclusions is big and the aggregation phenomenon appears. When adding 0.02 wt% nanoMgO or CaO oxides, the number of the inclusions in the cast microstructure is the most, whose size is smaller, about 2~4 μm and the inclusions are the most uniformly distributed.

Abstract: The pipeline steel as an application in pipeline construction must have good comprehensive mechanical properties due to the harsh environment of the pipeline engineering. So this experiment takes the X80 pipeline steel as the research object, the thermal stability second phase particles which would not be dissolved or aggregated at high temperature will be expected by means of adding nanomagnesium oxide into the steel with the method of carrier dispersion addition. The effect of nanometer magnesium oxide addition on the cast microstructure of X80 pipeline steel was analysed. The results show that the cast microstructure is consist of the ferrite and a small amount bainite. And the bainite is distributed at the boundary of the ferrite grains. When adding 0.02 wt% nanometer magnesium oxides, the number of bainite increases significantly in the cast microstructure, which is mostly distributed at the boundary of the ferrite grains.

Abstract: In order to reach high electromagnetic wave absorption property, here we developed a cement composites building materials. Special-shaped structure surfaces have been designed to make the continuity change of impedance and increase the incident times for electromagnetic wave. Different ratio of flexible glass fiber were introduced to adjust the impedance matching characteristics of the composites and to attenuate the incident wave by scattering. As the concentration of 9% glass fiber and the surface of rectangle, the reflectivity reached the highest in the absorber with 20mm thickness. the lowest reflection loss of-15.8 dB was obtained at 8.9GHz, and the effective absorption bandwidth (less than-8 dB) reached 12 GHz in the frequency range of 1.7~18 GHz. The new material can be used for building indoor electromagnetic radiation protection.

Abstract: Through methods, such as microscope analysis, chemical analysis, hardness analysis, metallography examination etc, the causes resulting in reheater tube cracking of 300MW station boiler have been analyzed. The result indicates this reheater tube cracking is reheat crack. The higher sensitive temperature in operating, excessive welding residual stress are the primarily inducement of cracking. In welding repair, the measures , such as replacing the material ,lower welding heat input, preheat treatment and so on, were taken. The welding repair succeeded greatly.

Abstract: The ceramic material of lead zirconate titanate has positive piezoelectric effect; Its mechanical energy can be converted to electrical energy. Finite element model is established for piezoelectric ceramic material, in addition that the transition between force and electric is simulated numerically by the analysis function of force-electric coupling field of ANSYS. We obtain the relationship between output voltage and external force, besides the relationship between different heights and the output voltage within the piezoelectric model. It indicates that pressure is proportional to the output voltage value, and it verifies the correctness of theoretical analysis. These provide a reference for the project application of piezoelectric materials.

Abstract: A new method based on the application of fluorescence spectrophotometry, which applied to the direct determination of bisphenol A (BPA) in food packaging materials, has been developed. Experimental results reveal that the linear rangeis0.1-0.6mg.L^-1atλ_ex/λ_em =266/304nm (pH =8). The calculated standard working curve is y=424+1031x, and R²=0.9951.Both of the optimization process and the final results, including the analysis of real samples, are given and discussed..

Abstract: Amorphous hydrogenated silicon carbide (a-Si_1-xC_x:H) films were deposited by plasma enhanced chemical vapor deposition and subsequently annealed in N₂ atmosphere at 1100 °C. The effects of high temperature annealing on the film’s optical and structural properties were systematically analyzed. It was noted that after high temperature annealing, amount of Si-C bonds increased significantly and SiC nanocrystalline was formed on the surface of the film, which resulted in an increasing refractive index in wavelength range of visible light, a decreasing absorbance index (wavelength<433.5 nm) and an increasing optical bandgap of the film. The changes of the optical properties illustrated that the performance of Si-based solar cell with a-Si_1-xC_x:H window layer could be improved by high temperature annealing.

Abstract: TiC-TiB2 composite ceramics were successfully fabricated via planetary ball milling of 72 mass% Ti and 28 mass % B4C powders, followed by low temperature sintering process at 1200°C. The microstructure of the ball-milled powder mixtures and composite ceramics were characterized by Differential thermal analysis equipment (DTA), field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The results showed that the ball-milled powder mixtures (Ti and B4C powders) were completely transformed to TiC-TiB2 composite ceramics as the powders were milled for 60 h and sintered at 1200°C for 1 h. The formation mechanism of the TiC-TiB2 composite was discussed. The high energy ball milling and necessary sintering for the powder mixtures plays an important role in the formation of the composites.

Abstract: Contrast ballistic tests were carried out on 93W alloy and W fiber reinforced Zr-based bulk metallic glass composite. The influence of penetrator material on micro-hardness around target crater was studied using microstructure observation and micro-hardness test. The results show that adiabatic shear band appears in both targets after severe plastic deformation of impact. The effect of composite on micro-hardness of target is greater than that of W alloy, and the thickness with high micro-hardness around target crater formed by composite penetrator is 2.5 times than that by W alloy penetrator.