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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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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In August 2010, Midwest Roadside Safety Facility (MwRSF) developed and crash tested a low-cost, energy-absorbing bridge rail for the Manual for Assessing Safety Hardware (MASH) TL-3 applications. This low-cost bridge rail was designed to be compatible with the Midwest Guardrail System (MGS) such that an approach transition would not be required between the two barriers. It was desired that the system minimize bridge deck and rail costs. As part of this project, several concepts for an energy-absorbing bridge post were developed and tested. These concepts included strong-post systems designed with plastic hinges and weak-post systems designed to bend near the attachment to the bridge deck. The final post concept incorporated S3 OE 5.7 steel sections designed to yield at their bases. These posts were located on 6 ft-3 inches on center. A W-beam section was used as the rail element and was attached to the posts with a bolt designed to break during and impact event. Two full-scale crash tests were performed according to the TL-2 impact conditions provided in MASH. The new bridge rail system successfully met all the safety performance criteria for MASH TL-2. The Texas Type T631 Bridge Rail was developed as a low-cost, energy absorbing bridge rail system for TL-2 applications. Many of the features used for the system tested at Midwest Roadside Safety Facility for TL-3 were incorporated into the design developed for this project for MASH TL-2 application. The TxDOT Type T631 Bridge Rail designed and developed for this project was evaluated under MASH TL-2.

关键词：大桥护栏；碰撞测试；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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We consider a cutting problem, which have a practical application. In this problem, items are being cut from larger items, for example textile patterns from a panel of cloth. We deal steel tubes of given length, which have to be sawed from longer steel tubes. These longer steel tubes come with given costs and the sawing has to be planned such that the total costs are minimized.

关键词：切割的问题；一维；吉尔摩和戈莫里方法；钢铁

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Based on node test and finite element analysis results of four different structural form enhanced nodes,failure modes,hysteretic behavior,bearing capacity,ductility and energy dissipation capacity of nodes are analyzed comprehensively and comparatively for more in-depth exploration about the seismic performance of symmetric enhanced nodes.The results showed that all the symmetric enhanced nodes have full hysteretic curve and energy dissipation capacity.On the whole,The flange-plate reinforced node exhibit better seismic performance.

关键词：钢框架；加强节点；循环加载试验；有限元分析

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The discovery in the 1980's of local brittle zones (LBZ's) in and near the heat-affected zone (HAZ) of the fabrication welds in certain offshore platform steels caused great concern among the engineers and welding specialists of the period and led directly to the preparation and adoption of API RP2Z in May 1987 of Recommended Practice for Preproduction Qualification for Steel Plates for Offshore Structures. This recommended practice describes a procedure by which steel producers could prequalify their product in advance of purchase and delivery and thereby reduce the risk of steel plate being delivered to the jobsite which would exhibit weldability problems from the standpoint of low HAZ toughness or HAZ cracking problems when using typical and conventional welding procedures, i.e., the need for extensive fracture toughness testing by the fabricator on each weld procedure was eliminated in favor of a more sophisticated one-time test program in the laboratory of the producer. This recommended practice covers two areas: (1) testing weld HAZ for toughness using CTOD tests and (2) delayed cracking tests using the controlled thermal severity test (CTS) and Y-groove test. This RP was developed for use with API steel specifications 2H, 2Y, and 2W. Most of the effort has been toward the quantification of API 2Y and 2W steels in thicker sections s4" (100 mm). This program has been scientifically successful albeit with a significant penalty of time and cost to the steel producer. There has been sufficient standardization that various purchasers have and will accept the same qualification performed previously for another job. This, of course, is exactly what API standards are intended to accomplish. API RP2Z was revised in 1992 and is currently being reviewed for a second revision intended to reduce some of the conservatism built into the original document by our lack of full understanding of the embrittling mechanisms in the HAZ of welded structural steels but now strongly supported by a substantial data base of good material. The paper discusses some of the proposed changes and contains data on the currently achievable fracture toughness levels.

关键词：海洋平台；钢铁；断裂韧性

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Two kinds of welding methods,including SMAW and GTAW,were employed to connect 16MnR steel and 2205 steel.OM and TEM was used to observe the microstructure.EDX line scan was used to analyze elements in special areas of the joint.The results show that the degree of carbon migration in the side of 16MnRofthe seam welded by GTAW is larger than that by SMAW.Particle and chain-island are two maiin form of Fe3C in micro-area of carbon migration.The grain size of seam material in GTAW section is larger than that of SMAW and the content of austenitic of seam material in GTAW section is more than that of SMAW.The tongues in the side of 16MnR appear in both two seams welded by SMAW and GTAW and they are parts from base metal.

关键词：异种钢；焊接方法；热输入；微观结构

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