Ultrasonic testing and microscopic analysis on concrete under sulfate attack and cyclic environment

The damage process of concrete exposed to sodium sulfate attack and drying-wetting cycles was investigated. The water to binder（W/B） ratio and the concentration of sulfate solution were taken as variable parameters. Through the experiment, visual change, relative dynamic modulus of elasticity（RDME） and the surface damage layer thickness of concrete were measured.Furthermore, SEM and thermal analysis were used to investigate the changing of microstructure and corrosion products of concrete.The test results show that the ultrasonic velocity is related to the damage layer of concrete. It approves that an increase in damage layer thickness reduces the compactness and the ultrasonic velocity. The deterioration degree of concrete could be estimated effectively by measuring the surface damage layer and the RDME of concrete. It is also found that the content of gypsum in concrete is less than that of ettringite in test, and some gypsum is checked only after a certain corrosion extent. When the concrete is with high W/B ratio or exposed to high concentration of sulfate solution, the content of ettringite first increases and then decreases with corrosion time. However, the content of gypsum increases at a steady rate. The content of corrosion products does not correspond well with the observations of RDME change, and extensive amount of corrosion products can be formed before obvious damage occurs.     

生草覆盖条件下不同降雨强度对紫色土坡面侵蚀产沙的影响

造林种草,增加植被覆盖度是防止土壤侵蚀的重要措施.通过人工模拟降雨试验,探讨生草覆盖下紫色土坡面侵蚀产沙的动态变化.结果表明,有生草覆盖的坡面径流含沙量较裸地的径流含沙量更快达到稳定状态;坡面侵蚀产沙率随覆盖度增加呈指数型递减,且坡下种草的减沙效果最好;覆盖度与降雨强度对坡面侵蚀产沙量的影响存在对比消长关系,但生草覆盖度对产沙量的影响小于降雨强度的变化对产沙量的影响.     

含盐高湿环境对沥青混合料性能及内部形态的影响

为了深入研究含盐高湿环境对沥青混合料的侵蚀机理,促进临海地区沥青路面的建设。在5%、10%和15%的NaCl溶液中干湿循环沥青混合料以加速模拟含盐高湿环境的侵蚀,通过室内试验研究氯盐溶液对沥青混合料性能的影响,并采用CT扫描研究混合料内部微观结构的变化。结果表明:混合料的高温、低温、水稳及耐久性能均随NaCl溶液浓度的增加逐渐下降,尤其是水稳定性下降最严重,残留稳定度和冻融劈裂强度比无法满足规范要求;混合料的空隙率随干湿循环次数的增加逐渐增大,混合料内部析出氯盐晶体并不断膨胀,最终导致了沥青混合料性能劣化。     

冻融条件下板式天然橡胶支座力学性能试验研究

以宁夏六盘山东毛高速公路桥梁工程为依托,通过室内试验,将一批板式天然橡胶支座置于标准冻融试验箱中,控制一定的温度与湿度,分别进行25,50,75,100,150次冻融循环处理,模拟宁夏高原地区冬季冻融交替环境对天然橡胶支座的影响.试验得到了其极限抗压强度、极限抗剪强度、抗压弹性模量、抗剪弹性模量、竖向刚度及水平等效刚度等力学性能方面的变化,并采用最小二乘法建立天然橡胶支座的衰减模型,推导出了相应的拟合曲线及衰减函数.     

西北风沙地区输电导线侵蚀及起晕电压实验模拟研究

针对西北地区风沙侵蚀输电导线现象,研究了导线粗糙度与起晕电压关系,在闭式风道内模拟了输电导线在第一年服役内受强沙尘暴侵蚀过程,并做了侵蚀铝棒的对照实验。用光切显微镜测量了表面粗糙度,电晕笼测量系统测量了起晕电压,再对实验数据插值与拟合处理,分析认为,导线粗糙度随风沙侵蚀呈增大趋势,而起晕电压在试验前期升高,试验中期起伏变化,后期与粗糙度呈负相关关系,即导线起晕电压随着粗糙度增大而降低。     

Synergic Effect of Shot Blasting and Deposit RE on Corrosion Behavior of TP304H steel in SO2-O2 at 923K

The corrosion behavior of TP304H steel with combined treatment of shot blasting and electrophoresis deposited RE coating in 1%SO2 14%O2 85%Ar mixture gaseous has been studied at 923K for 150 hours. The results show that both RE coating and shot blasting can improve the corrosion resistance of TP304H steel, and combined treatment has the best effect. Combined treatment reduces 50% mass gain, enhances the continuous and compactness of scale and changes the scale phase forms from Fe2O3/Fe1-xS/Ni1-x/S to Cr2O3/FeCr2Sn/Ni3-xS2. The synergistic effects of combined treatment on corrosion resistance and the effect of shot blasting on corrosion kinetics are discussed. Shot blasting increases the outward diffusion and surface concentration of Cr, Ce coating promotes the selective oxidation of Cr.     

钢包渣线侵蚀原因分析与改进

针对方坯螺纹钢,通过将渣中FeO+MnO含量降低至2.5%,AlO含量控制在15%左右,LF精炼升温效率从1~2℃/min提升至4~5℃/min,钢包渣线残厚逐渐提高;将渣中MgO含量控制在10%~12%,渣线残厚得到进一步提高,有效降低了渣线侵蚀速率。     

钒及钒基合金金相试样的制备方法

介绍了一种钒及钒基合金金相试样的常规制样方法,即试样的机械磨光,机械化学抛光,化学侵蚀等技术和经验。     

纳米掺杂Ag（SnFe）O2电接触合金的研究

利用化学共沉淀、高能球磨技术及热压烧结等方法制备出纳米掺杂Ag（SnFe）O2触头合金，通过X射线衍射（XRD）、透射电镜（TEM）和冷场发射扫描电镜（FESEM）等对合金触头及其燃弧性能进行了分析。结果发现：Fe元素的加入，使Sn02纳米颗粒在550℃以下焙烧制粉和750℃以下块体烧结成型时都未明显长大，保持在20nm左右，制备的触头合金呈现纳米第二相弥散均匀分布在Ag基体中。在模拟电弧侵蚀试验中，该合金电弧阴极斑点铺展在较大区域，形成多点燃弧形貌，有效降低燃弧时间和电弧电流，分散电弧能量，使阴极斑点没有明显的液体喷溅、Ag的蒸发和第二相的分解，同时非晶的纳米第二相与Ag的润湿性更好，可进一步增加熔体粘度，提高耐电弧侵蚀性能。     

对称复合板冷轧过程的上限分析

采用Hill提出的速度场 ,计算了对称复合板冷轧变形过程的能量消耗 ,在此基础上对软复层对称复合板在不同参数组合下冷轧时所需的最小摩擦、最大允许的加工率、以及复合板与轧辊间的摩擦状态进行了计算和分析 ,给出了相关计算曲线。计算结果表明 ,当基体材料的相对强度和相对厚度较小时 ,复合板冷轧时的变形行为与单金属冷轧时类似 ,但当基体材料的相对强度和相对厚度较大时 ,接触表面容易产生粘着现象。