热老化对316LN不锈钢焊缝微观组织和冲击性能的影响

为研究核电站主管道316LN不锈钢焊缝的热老化,开展了316LN不锈钢在400℃下15000h的加速热老化实验。采用TEM和HREM研究热老化后焊缝微观组织演变,利用冲击实验测定不同热老化时间下焊缝夏比冲击性能;以夏比冲击功作为热老化脆化参量,通过拟合法获得了焊缝热老化脆化动力学公式,利用热老化动力学公式预测焊缝在实际运行温度下服役60年内的夏比冲击功变化。结果表明:经1000h热老化后焊缝中的铁素体已经发生了调幅分解,形成了富Fe的α相和富Cr的α′相,同时在铁素体内析出了G相;焊缝中铁素体调幅分解和G相析出导致焊缝冲击功随时间延长而不断下降;夏比冲击功预测结果显示在运行25年内冲击功下降较快,随后的运行过程中下降过程趋缓。     

Numerical studies on STFD-HAT sections under axial dynamic impact

A new type of spot-weld double-hat section with symmetrically distributed tilt flanges (STFD-HAT) is introduced in this paper to improve the crushing performance, especially crushing stability. LS-DYNA code has been employed here to analyze the effect of several parameters on the collapse modes of STFD-HAT sections under axial dynamic impact loading condition. Some variables, such as tilt angle, size of core cross-section and thickness of sheet shell, have been proved to be effective in controlling the collapse mode and crushing performance of STFD-HAT sections by analysis on energy absorption and RSS of result curves. Compared with traditional double-hat sections, the STFD-HAT sections with reasonable designed profiles can effectively improve the crushing resistances and stabilities, especially, the bending mode.     

一种叶片安装角可调的离心泵设计

将叶片设计成若干带有凸形槽的长方块和带有凹形槽的长方块凸凹相对镶嵌、依次连接组成可伸缩叶片,将叶片的两端轴固定在轮盘的内、外两边缘,将轮盘的内边缘做成可以转动的,通过转动内边缘(圆环)改变叶片在轮盘的长度,从而改变叶片的内、外安装角。     

Suitability of Printing Materials for Heat-Induced Inkless Eco-Printing

Pyrolysis volatiles and the environmental impact of printing paper, newspaper, and silk were investigated to identify suitable materials for heat-induced eco-printing (HIEP) using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Furthermore, the printing effects of simulated HIEP and the material microstructures were studied using scanning electron microscopy (SEM). The results indicated that the toxicity of pyrolysis volatiles is highest for newspaper, followed by silk and then printing paper, whereas environmental friendliness follows the opposite trend. A high concentration of lignin, the basic structural element of which is phenyl propane, and the presence of halogens in the newspaper led to the generation of more toxic substances during the pyrolysis process. The benzene compounds and heterocyclic compounds in silk also produced high levels of toxic substances. Based on these findings and the higher color permeability of newspaper, printing paper was the most suitable material for HIEP and newspaper was the least suitable. Additionally, silk may still be used in HIEP in small amounts for the production of art, name cards, and clothing tags.     

Accelerated growth of the sugarcane,sugar, and ethanol sectors in Brazil (2000–2008): Effects on municipal gross domestic product per capita in the south-central region

During the 2000–2008 period, there was a marked acceleration in the growth of the sugarcane, sugar, and ethanol sectors of Brazil, which are most active in the south-central region of the country. Therefore, the objective of this study was to evaluate the effects of those sectors on the municipal gross domestic product (GDP) per capita in the south-central region of Brazil during that period. To that end, we constructed a theoretical model, estimating its parameters with a generalized method of moments system estimator and using spatial dynamic panel data to estimate the direct (municipal) effects and indirect (regional) effects. The cumulative direct and indirect effects increased the real municipal GDP per capita by 1028 $ in the host municipalities and by 324 $ in each of their 15 closest neighboring municipalities. On the basis of our findings, we can infer that the effects of establishing a sugar mill or ethanol plant are most significant for the host municipality and persist for at least 10 years after operations begin. Our results also indicate that sugarcane production has a significant, positive impact on municipal GDP per capita, not only in the municipalities where that production takes place but also in neighboring municipalities.     

大截面矩形盾构推进对地表环境的影响评估

随着地下通车道成为缓解城市交通压力的有效途径,大断面矩形盾构在软土地区发展潜力巨大.以此为背景,介绍了矩形盾构的特点及适用范围,并通过有限元数值模拟,研究了大断面矩形盾构推进方式对地表环境的影响,为控制地表沉降、推进施工参数的合理取值,提供了理论依据.     

A high accurate static contact angle algorithm based on Hough transformation

The static contact angle for blurry drop images is more intricate to obtain. To improve the accuracy of the Hough transformation for the static contact angle calculation, the water drop images with different volumes are generated by the Laplace equation, and the influence of the volume on the accuracy of the Hough transformation is analyzed. The results reveal that the circle Hough transformation is particularly well suited to the cases with small drop volume. At the same time, the critical water drop volume value corresponding to a contact angle error of 3° is given, a modified Hough transformation algorithm in conjunction with the critical water drop volume is proposed, and at the same time, the accuracy of the static contact angle calculation for blurry water drop images is significantly improved. The proposed algorithm is a powerful approach to estimate the static contact angle for blurry water drop images.     

Microstructure and Properties of Hot Working Die Steel H13MOD

Compared with H13 steel, the influences of different heat treatment process on the microstructure and properties of the new type of hot working die steel H13MOD were studied. The results show that the complete austenitizing temperature of H13MOD is around 1030 °C and the quenching hardness achieves the maximum value at this temperature. While for H13, the complete austenitizing temperature is above 1100 °C and the quenching hardness rise constantly with the quenching temperature increasing. In quenching process, the undissolved MC carbides can prevent the coarsening of grain in both steels. With the rise of quenching temperature, when MC carbides dissolve completely, the grain grows quickly. The hardness and strength of H13MOD at higher tempering temperature (above 570 °C) are nearly the same as those of H13, but its toughness is higher than that of H13. Mo₂ C carbide is the main strengthening phase in H13MOD, which is attributed to the higher content of Mo. The quantity of VC eutectic carbides is reduced because of lower content of V in H13MOD, which plays an important role in enhancing the impact toughness of H13MOD. Under a certain strength condition, H13MOD steel can be used in the environment that higher toughness is required and the service life of die casting mold can be improved.     

Critical contact angle for coarse sphalerite flotation in a fluidised-bed separator vs. a mechanically agitated cell

This work investigates the critical contact angle for the flotation of coarse (850–1180 μm, 425–850 μm and 250–425 μm) sphalerite particles in an aerated fluidised-bed separator (HydroFloat) in comparison to a mechanically agitated flotation cell (Denver flotation cell). In this study, the surface chemistry (contact angles) of the sphalerite particles was controlled by varying collector (sodium isopropyl xanthate) addition rate and/or purging the slurry with either nitrogen (N₂) or oxygen (O₂) before flotation. The flotation performance varied in response to the change in contact angle in both the aerated fluidised-bed separator and the mechanically agitated cell. A critical contact angle threshold, below which flotation was not possible, was determined for each particle size fraction and flotation machine. The results indicate that the critical contact angle required to float coarse sphalerite particles in a mechanically agitated cell was higher than that in the fluidised-bed separator, and increased as the particle size increased. At the same particle size and similar contact angles, the recoveries obtained by the aerated fluidised-bed separator in most cases were significantly higher than those obtained with the mechanically agitated flotation cell.     

Triaxiality at crack tip for combined Lankford's coefficient and degree of anisotropy subjected to mixed-mode (I/II) fracture

Structural parts used in boilers, turbines, ships, and many household purposes are manufactured through sheet metal forming processes. During manufacturing, the micro structure of the material is deformed and micro cracks along with anisotropic properties get induced. Present research deals with a thin sheet metal plate containing a central crack subjected to mixed mode (I+II) loading. With special reference to Lankford's coefficient and degree of anisotropy, the effect of anisotropic triaxiality on crack initiation angle has been investigated. The result reveals the combinations of Lankford's coefficient and degree of anisotropy for which crack initiation angle do not change.