Ferritic stainless steels are promising candidates for IT-SOFC interconnect applications due to their low cost and resistance to oxidation at SOFC operating temperatures. However, steel candidates face several challenges, including long term oxidation under interconnect exposure conditions, which can lead to increased electrical resistance, surface instability, and poisoning of cathodes due to volatilization of Cr. To potentially extend interconnect lifetime and improve performance, a variety of surface treatments were performed on AISI 441 ferritic stainless steel coupons prior to application of a protective spinel coating. The coated coupons were then subjected to oxidation testing at 800 and 850 degrees C in air, and electrical testing at 800 deg C in air. While all of the surface-treatments resulted in improved surface stability (i.e., increased spallation resistance) compared to untreated AISI 441, the greatest degree of improvement (through 20,000 hours of testing at 800 deg C and 14,000 hours of testing at 850 deg C) was achieved by surface blasting.

关键词：合金；尖晶石；不锈钢；表面处理；涂料

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The research under this project focused on a theoretical and computational modeling of dislocation dynamics of mesoscale deformation of metal single crystals. Specifically, the work aimed to implement a continuum statistical theory of dislocations to understand strain hardening and cell structure formation under monotonic loading. These aspects of crystal deformation are manifestations of the evolution of the underlying dislocation system under mechanical loading. The project had three research tasks: 1) Investigating the statistical characteristics of dislocation systems in deformed crystals. 2) Formulating kinetic equations of dislocations and coupling these kinetics equations and crystal mechanics. 3) Computational solution of coupled crystal mechanics and dislocation kinetics.

关键词：金属；统计力学；耦合；晶体；变形

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Using a 1984 benchmark experiment, MCNP6 replicated the neutron flux and neutron protection factor (NPF) measurements of an iron box, which simulated a basic military vehicle, resulting in less than 5% difference from the published results. Additionally, the neutron flux spectrum of a 239 PuBe source was characterized using a Bonner Sphere Spectrometer (BSS) and the solution unfolded using the Maximum Entropy Deconvolution (MAXED) program, producing a X2/df of 0.97. Utilizing a steel box provided by the DTRA, measurements of neutron flux from a D-D neutron accelerator were recorded via BSS inside and outside of the box. Both flux spectra were unfolded through MAXED using MCNP6 computations as a priori, which resulted in X2/df values of 0.86 and 0.91, respectively. NPF assessments of the steel box were then conducted using experimental and MCNP6 flux spectra for the box, as well as H*(10) scaling, with final results differing by less than 1%. MAXED software was leveraged for all flux spectrum unfolding, incorporating updated BSS response functions generated within this research from MCNP6. This experiment and its conclusions strongly support the verification and validation of MCNP6 for modeling NPF assessments of military vehicles.

关键词：中子通量；中子保护因子；中子能谱；钢铁

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Although steel orthotropic deck is currently the most widely adopted solution for long-span bridges, the poor adhesion to the upper asphalt layers still represents a serious problem without a clear solution. In recent decades many techniques that involve the use of special bituminous bonding coats, reinforced asphalt membranes, net-reinforced steel deck surfaces, or epoxy asphalt binders have been applied, with varying results, to improve the level of adhesion of the asphalt pavement to the steel surface. In this experimental study, two such techniques were adopted to investigate the shear resistance of steel-asphalt pavement systems. The first technique used epoxy asphalt both as a bonding coat and as a binder of the upper asphalt layer, while the second technique involved the use of a reinforced asphalt membrane that was applied on the steel deck before overlaying with conventional hot-mix asphalt (HMA). The Ancona Shear Testing Research and Analysis shear test device was used to evaluate the shear resistance of different types of HMA-steel interfaces and to investigate the effects of temperature and normal stress. The results have been compared with the shear properties of bitumen-coated interfaces, studied in previous research. The results showed that epoxy asphalt guaranteed high performance regardless of the test temperature. However, the shear resistance of the system with the asphalt membrane was lower than with the epoxy asphalt, although it was higher than the resistance of bitumen-coated interfaces at high temperatures.

关键词：正交异性钢桥；钢铁；沥青膜

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Improved software interoperability is key to realizing more fully the potential benefits of integrated and accelerated project delivery in a way that also somehow ensures product quality. The increasing appeal of three-dimensional (3-D) building information modeling (BIM) notions applied to bridges [known as bridge information modeling (BrIM)] motivates the need for principled prescriptions of associated electronic data exchanges between various project stakeholders and the various software applications that they use. Such data exchanges must be sufficiently precise to facilitate detailing for fabrication and construction while being sufficiently concise to facilitate parametric modeling and thereby avoid needless data duplication. The highway geometry to which bridges must conform distinguishes BrIM from the building column grid orientation of BIM at the outset of the bridge life cycle. In contrast to the overdefined highway geometry in the LandXML data exchange standard, a 3-D control curve is defined, presented, illustrated, and recommended as the basis for parametric data exchange suitable through the life cycle of steel Ⅰ-girder bridges on (straight and) curved alignments. This 3-D control curve combines in a single curve the traditional horizontal control line and profile grade line that bridge structural engineers receive from highway designers to define bridge geometry. Data exchanges associated with three distinct stages in the life cycle of a steel bridge are defined and illustrated: analysis and design, detailing for fabrication, and erection and construction. The data exchange based on a 3-D control curve provides the data integrity required through the life cycle of a steel bridge.

关键词：三维参数；钢铁；曲线钢桥

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Fine balance between active galvanic and passive barrier corrosion protection by zinc-rich hybrid paints is explored depending on the absolute and relative amounts of the electrically semi-conducting particles, viz. polypyrrole (PPy) modified alumina hydrate and multi-walled carbon nanotubes (MWCNTs) and the zinc pigments. The former was varied between 3.21 and 1.75 wt.%, the latter was altered from 70 to 80 wt.% in the primers. The coating with less zinc indicated firm and stable barrier nature in a 254 h immersion test whereas the primer with greater zinc content afforded superior galvanic corrosion prevention in salt-mist test over 142 days. Different nature of the coatings are expounded on the basis of structure and 3D arrangement of the nano-size inhibitor particles in the epoxy vehicle besides interpreted considering varied grain contents caused changing electrical percolation and electrolytic conductivity of the primers.

关键词：聚吡咯修饰碳纳米管；低碳钢；富锌涂料混合

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Fluidized bed reactor chemical vapor deposition (FBR-CVD) has been used to enrich the surface of oxygen free high conductivity (OFHC) copper with titanium, silicon and aluminum. This technique enables the production of coherent and adherent intermetallic surface layers of uniform thickness and high hardness. The characterization of the coatings was performed using backscatter scanning electron microscopy (BS-SEM), X-ray diffraction (XRD), glow discharge optical emission spectroscopy (GDOES) and micro-hardness. The tribological properties of the coatings in dry sliding contact with steel were evaluated by pin-on-disc wear testing.

关键词：铜；磨损；摩擦系数；钢铁

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The French five-point bending (5PB) test provides a laboratory-scale test that allows studying the fatigue resistance of surfacing systems on orthotropic steel deck (OSD) bridges. The surfacing structure for OSD bridges in the Netherlands is mostly a multilayer system: top porous asphalt (PA) layer, guss asphalt (GA) layer, steel deck, and two membrane layers. In this paper, an analytical solution for the 5PB test setup is presented first. To understand better the influence of geometrical, mechanical, and structural parameters on the performance of the typical multilayer surfacing system of OSD bridges in the Netherlands, the 5PB test specimens with five structural layers have been investigated. The parametric study was performed at the numerical platform CAPA-3D, which was developed at the Section of Structural Mechanics of the Delft University of Technology. The thicknesses of the top PA layer, middle GA layer, and the steel plate were varied. The influences of the mechanical properties of both top and bottom membrane layers were studied. The sensitivities of those influence factors were evaluated by examination of the maximum tensile stress at the top surface of the PA layers and the strain distributions through the entire thickness of the specimen at two cross sections.

关键词：五点弯曲；钢铁；抗疲劳性

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Gas carburizing is a widely used heat treatment process in which carbon is transferred into steel. The hardening reliability involves an active control of mass transfer during the process and this is why understanding diffusion in solids is so essential to model the process. The currently used models are often based on the simplest, one-dimensional form of the diffusion equation in which diffusivity depends on composition. The objective of this work is to develop a model of carbon diffusion in multicomponent alloy subjected to pulse carburizing. The model is based on the Darken method (bi-velocity method) in which the diffusion velocity depends on the diffusion potential gradient and is independent of the choice of the reference frame while the drift velocity is common for the carbon and steel components. Our model allows predicting the kinetics of carbon transfer at various treatment conditions and is applied to the pulse carburizing process at constant temperature. The process is carried out by repeating consecutively a carburization stage, when the carburizing gas is supplied into a carburizing chamber, and a diffusion stage at vacuum conditions, when the carburizing gas is exhausted and only the diffusion of carbon takes place. The numerical calculations are made for varying carburization and diffusion periods and are confirmed by the experimental results. On the basis of the series of computer experiments some findings that are important in designing the carburizing technology are formulated.

关键词：脉冲渗碳；扩散；双速度法

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A data base of 84 pile load tests was developed for steel pipe piles, driven in clay (small amounts of sand near the surface for a few tests), where there was sufficient data to estimate effective overburden pressures with reasonable accuracy, where soil strengths were well defined, and where a load-settlement curve was available for the load test. Measured pile capacities were compared with values predicted using five methods that have been, are being, or potentially may be used in engineering practice. The two lambda methods had the least scatter but tended to overpredict capacities by about 20%. The current API method had slightly more scatter but overpredicted capacities by only about 13% on the average. The two alpha methods had the largest scatter and the greatest differences between measured and predicted capacities.

关键词：荷载试验；钢铁；负载沉降曲线

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