Corrosion measurements of steel reinforcement in concrete exposed to a tropical marine atmosphere

As part of a broad research program, reinforced concrete cylinders of different qualities were exposed to the marine atmosphere of North Peninsula of Yucatán. The cylinders were electrochemically monitored over a period of 56 months. The time for the onset of active corrosion was shorter for rebars in concretes with a high water-to-cement (w/c) ratio compared to that for rebars in low w/c ratio concrete. Results also indicate, as expected, that for equal periods of exposure, nominal corrosion current density (i_corr) values were generally higher for rebar in concrete with higher w/c ratio than those for rebar in low w/c ratio concrete. Analysis of the observed impedance spectra in terms of a modified Randles circuit (in which the ideal capacitor is replaced by a constant phase element (CPE)) appeared to be a reasonable approximation.     

Preparation of Rayon Fiber-Reinforced Polypropylene Composites by Extrusion Techniques

Hybrid composites from rayon fibers (～2–5 cm size) and polypropylene (PP) were fabricated by using an extruder. Fibre content of the composite was varied from 5–30% by weight and physico-mechanical properties of the composites were measured. Surface morphology as observed by SEM showed good interface adhesion between rayon and PP matrix. Furthermore inclusion of rayon (up to 15% fiber inclusion) in the composite increased tensile, bending and hardness properties. As the fiber content in the composite increased more than 15%, physico-mechanical properties decreased due to the decrease of fiber matrix adhesion. The change of tensile properties due to environmental aging was carried out by keeping the composite under soil for 1 month and tensile properties were measured periodically. The aging result suggests that composites retained about 75% of its original tensile and bending strength even after 1 month soil burial. The modified fibers were also used for the study. As such the fibers were treated with vinyl-trimethyoxysilane and methanol solution and irradiated under UV before being used with PP in extruder. The results showed retardation of the physico-mechanical properties for composites obtained from irradiated rayon fibers than the composites fabricated from non irradiated rayon fibers.     

Microstructure and mechanical properties of SiC platelet reinforced BaOAl2O32SiO2 (BAS) composites

BaOAl₂O₃2SiO₂ (BAS) glass–ceramic powders were prepared by sol–gel technique. SiC platelet reinforced BAS glass–ceramic matrix composites with high density and uniform microstructure were fabricated by hot-pressing. The effect of additional crystalline seeds on hexagonal to monoclinic phase transformation of Barium aluminosilicate was studied. The effects of SiC platelet content on the microstructure and mechanical properties of the composites were also investigated. The results showed that the flexural strength and fracture toughness of the BAS glass–ceramic matrix composites can be effectively improved by the addition of silicon carbide platelets. The main toughening mechanism was crack deflection, platelets' pull-out and bridging. The increased value of flexural strength is contributed to the load transition from the matrix to SiC platelets.     

轴承钢丸直径配比对强化研磨内圈沟道面硬度及形貌的影响

为研究强化研磨加工过程中轴承钢丸在不同直径的组合配比条件下对轴承内圈沟道面硬度的影响,通过理论与试验结合研究分析了钢丸法向碰撞内圈表面的过程,同时采用了扫描电子显微镜(SEM)观察内圈沟道面形貌的变化,并通过激光共聚焦显微镜与洛氏硬度计检测了其加工前后的表面粗糙度与硬度。研究结果表明:在试验所设定的工艺参数条件下,使用直径为2、3 mm的钢丸组合配可大大提高沟道面硬度,强化效果最佳,更能保证强化研磨加工质量。     

钢骨架塑料复合管的研究进展及对策

介绍了钢骨架塑料复合管的分类、结构、特性及成型,综述了国内外发展研究状况,指出了钢骨架塑料复合管面临的问题,结合实践提出了相应的解决对策。     

基于PLC的轴承强化研磨机控制系统设计

针对第一代强化研磨设备安全性能较差、加工效率较低、自动化程度不高等问题,设计基于S7-200smart PLC的轴承强化研磨机控制系统。该系统由输入层、CPU处理层和动作执行层组成,可实现复杂环境下的可靠控制,满足了轴承强化研磨机的功能要求,易于操作、界面友好、效果良好,为轴承套圈沟道强化加工提供了较好的解决方案。     

钒氮微合金钢生产热轧Ⅲ级钢筋

向20MnSi钢中添加钒氮合金以替代钒铁生产HRB400钢筋的试验中,分析了氮对HRB400钢筋力学性能的影响。结果表明,在钢中碳当量、钒含量基本一致的情况下,向钢中添加氮可促进细小V(C、N)化物析出,获得更高的强度,且性能稳定,组织更细。用钒氮合金替代钒铁,可节约钒29％,降低成本。     

影响增强聚丙烯雾化测试结果的因素

雾化重量法是衡量汽车内饰材料挥发物中的有害成分对人体健康的影响程度的测试.因此,为了合理控制挥发性物质的产生,降低车内环境污染,对用于汽车内饰的材料进行雾化测试是十分必要的.通过控制变量研究样品状态、加工工艺、测试温度、测试时间、平衡时间对雾化重量法进行测试,分别测试了内饰材料增强聚丙烯系列的长玻璃纤维增强材料和短玻璃...     

Drilling of Multi-Layer Composite Materials consisting of Carbon Fiber Reinforced Plastics (CFRP), Titanium and Aluminum Alloys

In this paper results are presented concerning the realization of economical drilling processes of multi-layer materials. Different carbide drill designs with improved geometries and coatings were investigated and compared by characterizing the cutting forces, tool wear, hole quality, and chip formation. Investigations have shown that dry machining of titanium workpiece layers leads to increased tool wear, chip formation problems, and surface damage in the aluminum and CFRP-layers. Consequently, the drilling experiments were carried out with minimum quantity lubrication (MQL) using different cutting fluids and supply strategies. The investigations were mainly focused on the development of the optimum drilling condition with respect to tool shape, tool material, and machining parameters. Another objective of the investigations was to analyze surface defects of the hole and the resulting diameter tolerances due to the high mechanical and thermal loads when machining titanium.     

Prevention of steel corrosion in concrete exposed to seawater with submerged sacrificial anodes

This paper presents the results of a study of the effectiveness of submerged sacrificial anodes in preventing the onset of pitting corrosion in the emerged part of marine piles. Experimental tests were carried out on reinforced concrete columns with steel embedded both in chloride free concrete and chloride contaminated concrete in order to compare the effects of sacrificial anodes on passive steel and on corroding steel. Results have shown, at least under the present testing conditions, that sacrificial anodes may be more effective in preventing corrosion initiation (i.e. in providing cathodic prevention) than in controlling ongoing pitting corrosion (i.e. in guaranteeing cathodic protection). Monitoring criteria for this type of prevention are also discussed.