Aluminum slurry coatings to replace cadmium for aeronautic applications

Cadmium has been widely used as a coating to provide protection against galvanic corrosion for steels and for its natural lubricity on threaded applications. However, it is a toxic metal and a known carcinogenic agent, which is plated from an aqueous bath containing cyanide salts. For these reasons, the use of cadmium has been banned in Europe for most industrial applications. However, the aerospace industry is still exempt due to the stringent technical and safety requirements associated with aeronautical applications, as an acceptable replacement is yet to be found. Al slurry coatings have been developed as an alternative to replace cadmium coatings. The coatings were deposited on AISI 4340 steel and have been characterized by optical and electron microscopy. Testing included salt fog corrosion exposure, fluid corrosion exposure (immersion), humidity resistance, coating-substrate and paint-coating adhesion, electric conductivity, galvanic corrosion, embrittlement and fatigue. The results indicated that Al slurry coatings are an excellent alternative for Cd replacement

Experimental and numerical investigation of footing behaviour on multi-layered rubber-reinforced soil

This paper describes the beneficial effects of multiple layers of rubber–sand mixture (RSM). The plate load tests, using circular plate of 300 mm diameter, were performed at an outdoor test pit, dug in natural ground with dimensions of 2000 × 2000 mm in plan and 720 mm in depth to facilitate realistic test conditions. The rubber used in the RSM layers was granulated rubber, produced from waste tires. The optimum thickness of the RSM layer was determined to be approximately 0.4 times the footing diameter. By increasing the number of RSM layers, the bearing capacity of the foundation can be increased and the footing settlement reduced. The influence of the number of RSM layers on bearing capacity and settlement become almost insignificant beyond three layers of RSM, particularly at low settlement ratios. At a ratio of settlement to plate diameter of 4%, the values of bearing pressure for the installation with one, two, three and four layers of RSM were about 1.26, 1.47, 1.52 and 1.54 times greater, respectively, than that for the unreinforced installation. Layers of the RSM reduced the vertical stress transferred through the foundation depth by distributing the load over a wider area. For example, at an applied footing pressure of 560 kPa, the transferred pressure at a depth of 570 mm was about 58, 45 and 35% for one, two and three layers of RSM, respectively, compared to the transferred stress in the unreinforced bed. By numerical analysis, it was found that the presence of soil-rubber layers resulted in expansion of passive zones in the foundation due to the effectiveness of the confinement provided by the rubber inclusions, and this tends to make the bed deflect less. On the basis of this study, the concept of using multiple RSM layers has not only been shown to improve the performance of foundations under heavy loading, but also, the environmental impacts of waste tires are attenuated by re-using their rubber as part of a composite soil material in civil engineering works

Effects of Redispersible Polymer Powder on Mechanical and Durability Properties of Preplaced Aggregate Concrete with Recycled Railway Ballast

The rapid-hardening method employing the injection of calcium sulfoaluminate (CSA) cement mortar into voids between preplaced ballast aggregates has recently emerged as a promising approach for the renovation of existing ballasted railway tracks to concrete tracks. This method typically involves the use of a redispersible polymer powder to enhance the durability of the resulting recycled aggregate concrete. However, the effects of the amount of polymer on the mechanical and durability properties of recycled ballast aggregate concrete were not clearly understood. In addition, the effects of the cleanness condition of ballast aggregates were never examined. This study aimed at investigating these two aspects through compression and flexure tests, shrinkage tests, freezing-thawing resistance tests, and optical microscopy. The results revealed that an increase in the amount of polymer generally decreased the compressive strength at the curing age of 28 days. However, the use of a higher polymer ratio enhanced the modulus of rupture, freezing-thawing resistance, and shrinkage resistance, likely because it improved the microstructure of the interfacial transition zones between recycled ballast aggregates and injected mortar. In addition, a higher cleanness level of ballast aggregates generally improved the mechanical and durability qualities of concrete

Mechanical performance and capillary water absorption of sewage sludge ash concrete (SSAC)

Disposal of sewage sludge from waste water treatment plants is a serious environmental problem of increasing magnitude. Waste water treatment generates as much as 70 g of dry solids per capita per day. Although one of the disposal solutions for this waste is through incineration, still almost 30% of sludge solids remain as ash. This paper presents results related to reuse of sewage sludge ash in concrete. The sludge was characterised for chemical composition (X-ray flourescence analysis), crystalline phases (X-ray diffraction analysis) and pozzolanic activity. The effects of incineration on crystal phases of the dry sludge were investigated. Two water/cement (W/C) ratios (0.55 and 0.45) and three sludge ash percentages (5%,10% and 20%) per cement mass were used as filler. The mechanical performance of sewage sludge ash concrete (SSAC) at different curing ages (3, 7, 28 and 90 days) was assessed by means of mechanical tests and capillary water absorption. Results show that sewage sludge ash leads to a reduction in density and mechanical strength and to an increase in capillary water absorption. Results also show that SSAC with 20% of sewage sludge ash and W/C=0.45 has a 28 day compressive strength of almost 30 MPa. SSAC with a sludge ash contents of 5% and 10% has the same capillary water absorption coefficient as the control concrete; as for the concrete mixtures with 20% sludge ash content, the capillary water absorption is higher but in line with C20/25 strength class concretes performance

Gait and Force Analysis of Provoked Pig Gait on Clean and Fouled Concrete Surfaces

Gait and force analysis have proven to be useful methods in linking claw injuries to surface material conditions. To determine the relationship between claw disorder and floor properties such as friction and surface abrasiveness, the factors controlling gait must be characterised. The effects of fouled concrete floor conditions on the gait of 10 pigs walking in a curve, using kinematics and kinetics to record gait parameters and slip frequency are described and compared with clean conditions. Pigs adapted to fouled floor conditions by reducing their walking speed and stride length, using a higher number of 3-foot support phases and by lowering diagonality. This adaption produced lower vertical forces, a twofold reduction in propulsion and outward stabilisation force and a threefold increase in braking force, without reducing the peak utilised coefficient of friction (UCOF). The UCOF values for both limbs of the curve walking pigs exceeded the recorded dynamic coefficient of friction and the corresponding UCOF values for pigs walking a straight line in fouled floor condition. As UCOF increased and available friction from the fouled floor surface decreased, this resulted in higher forward and backward slip frequency in both limbs for pigs walking in a curve. Pigs provoked to walk in a curve can adapt to fouled floor condition, but if the floor is heavily fouled this adaption is not sufficient to ensure safe walking

Determination of water content in clay and organic soil using microwave oven

The article deals with the techniques of soil water content determination using microwave radiation. Its practical application would allow solving the problems of resource efficiency in geotechnical survey due to reduction of energy and resource intensity of laboratory analysis as well as its acceleration by means of decreasing labour intensity and, as a result, cost reduction. The article presents a detail analysis of approaches to soil water content determination and soil drying, considers its features and application. The study in soil of different composition, typical for Western Siberia including organic and organic-mineral ones, is a peculiarity of the given article, which makes it rather topical. The article compares and analyzes the results of the investigation into soil water content, which are obtained via conventional techniques and the original one developed by the authors, consisting in microwave drying. The authors also give recommendation on microwave technique application to dry soil

The High Voltage Feedthroughs for the ATLAS Liquid Argon Calorimeters

The purpose, design specifications, construction techniques, and testing methods are described for the high voltage feedthrough ports and filters of the ATLAS Liquid Argon calorimeters. These feedthroughs carry about 5000 high voltage wires from a room-temperature environment (300 K) through the cryostat walls to the calorimeters cells (89 K) while maintaining the electrical and cryogenic integrity of the system. The feedthrough wiring and filters operate at a maximum high voltage of 2.5 kV without danger of degradation by corona discharges or radiation at the Large Hadron Collider

Residual stress measurement round robin on an electron beam welded joint between austenitic stainless steel 316L(N) and ferritic steel P91

This paper is a research output of DMW-Creep project which is part of a national UK programme through the RCUK Energy programme and India's Department of Atomic Energy. The research is focussed on understanding the characteristics of welded joints between austenitic stainless steel and ferritic steel that are widely used in many nuclear power generating plants and petrochemical industries as well as conventional coal and gas-fired power systems. The members of the DMW-Creep project have under- taken parallel round robin activities measuring the residual stresses generated by a dissimilar metal weld (DMW) between AISI 316L(N) austenitic stainless steel and P91 ferritic-martensitic steel. Electron beam (EB) welding was employed to produce a single bead weld on a plate specimen and an additional smoothing pass (known cosmetic pass) was then introduced using a defocused beam. The welding re- sidual stresses have been measured by five experimental methods including (I) neutron diffraction (ND), (II) X-Ray diffraction (XRD), (III) contour method (CM), (IV) incremental deep hole drilling (iDHD) and (V) incremental centre hole drilling (iCHD). The round robin measurements of weld residual stresses are compared in order to characterise surface and sub-surface residual stresses comprehensively