To predict phase equilibria of advanced high strength steels accurately,a new multicomponent thermodynamic database (FEDA) encompassing Fe,C,Mn,Si,Al and Ni is created according to relevant literatures.This study applies Thermo-Calc software to estimate phase transformation temperatures and phase fractions in ferrite and austenite two-phase region of test steels.Simultaneously,experiments are carried out with dilatometer and the quantitative metallographic analysis technology.It is found that the FEDA database is appropriate for predicting A/temperature and phase fractions of Al-containing steels at low temperatures,while the TCFE6 database can be used to estimate A3 temperature.According to calculated phase fractions using FEDA database,a two-step heat treatment is made in order to achieve TRIP-aided steels.Samples annealed at 780℃ for 3 min and held at 420℃ for 5 min exhibit an optimum value of strength and ductility product up to 23690 MPa.％.

关键词：热力学参数；含Al的AHSS；相馏分；转变温度

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No abstract available.

关键词：大气；空气过滤器；空气污染

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Until recently, solvent-based forms of monomeric alkyl (isobutyl) trialkoxy silane, produced under various trade names, were exclusively used in the United Kingdom for concrete protection of transportation structures and other structures subject to surface salt contamination. Reflecting the move toward more sustainable construction and with increasing demand for less-hazardous materials, alternative protective treatments that are based on various aqueous formulations have emerged. These treatments include dual-purpose materials for protection and concrete coloration. At the same time, developments in nano-materials have resulted in the availability of a low-hazard pure silane that is neither water nor solvent based. This investigation evaluated the performance of this material and three water-based materials with respect to their resistance to water and salt solution absorption and chloride ion penetration. A comparative investigation assessed the possibility of using convenient concrete cubes rather than larger-scale slabs for chloride contamination testing by the salt-ponding method. The results of the study are particularly relevant to older reinforced concrete structures, which frequently suffer low concrete cover to their steel-reinforcing bars.

关键词：纳米；建筑；耐水性

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This report explores the characteristics, sources, and processes of submicrometer particles in northern California via integrated analyses of atmospheric observation data obtained during the Carbonaceous Aerosols and Radiative Effects Study (CARES) that took place in northern California in June 2010. We focus on reporting aerosol chemistry, physical properties, and diurnal and temporal variations at Cool (denoted as the T1 site of the project) at the foothills of the Sierra Nevada Mountains, where intense biogenic emissions are periodically mixed with urban outflow transported by daytime southwesterly winds from the Sacramento metropolitan area. During CARES, the average mass loading of submicrometer particles (PM1) was 3.0 ig m- 3, dominated by organics (80%) and sulfate (9.9%). The organic aerosol (OA) had a nominal formula of C1H1.38N0.004O0.44, thus an average organic mass-to-carbon (OM/OC) ratio of 1.70. Three OA types were identified by PMF analysis of the high resolution mass spectra: two different OOA components (90% of total organics) and a HOA (10%). The more oxidized MOOOA (O/C = 0.54) was identified as biogenically influenced SOA, while the less oxidized LOOOA (O/C = 0.42) corresponded to anthropogenically influenced SOA (e.g., from the Sacramento area). The HOA factor corresponded mainly to primary emissions from local traffic. On average, SOA (= MO-OOA + LO-OOA) accounted for 91% of the total OA mass and 72% of the PM1 mass observed at Cool. Twenty three periods of urban plumes from T0 (Sacramento) to T1 (Cool) were identified using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem).

关键词：大气；环境保护；有机气溶胶

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The paper is focused on issues related to the behavior of reinforced soil walls at working stress and near failure, and the prediction accuracy of internal stability working stress and limit equilibrium (LE) design methods. The paper identifies the key variables, principles and assumptions that affect the accuracy of these methods considering the full range of conditions from working stress to failure. The strain at peak strength of a granular soil wall backfill is identified as a key parameter for understanding the differences between working stress and LE design methods. Both geosynthetic and steel reinforced wall systems are examined using measured reinforcement strain and loads taken from full-scale walls under both working stress (operational) conditions and at incipient collapse (failure).

关键词：工作压力；加筋土墙；钢铁

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Directly-generated compressive residual stress has become a widely used surface modification technique. Intentional residual stress in solid materials can be produced by different surface compression methods. It is well known how residual stress field is influenced by the parameters of the shoot peening but only few articles address the phenomenon about the evolution of the stress during the operation of the machine component. The literature on residual stress decrease caused by fatigue load is scarce and the kinetics of this mechanism is not yet investigated. The present work reports on the examination of the effect of the fatigue load on compressive residual stress strengthened specimens. Investigations have been conducted at three stress levels. Residual stress data have been measured by X ray diffraction method before fatigue load and measurements have been repeated after defined fatigue cycles.

关键词：残余应力；X射线衍射；疲劳

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Small batches of two oxide powders falling in the particle size range of about 30-230 μm were received from industrial sources and were electroless nickel (EN) coated in order to prepare properly modified reinforcing particles for further laboratory experiments with the Laser Melt Injection (LMI) technique to produce particle reinforced steel composite surface layers. The partially calcined alumina (Al2O3) as well as the hydrothermally recycled crystalline iron(Ⅲ) oxide precipitate were characterized first to check their exact size ranges, specific surface areas and major chemical contaminants so that the best possible EN plating technique would be selected and applied. It was revealed soon that the sensitization and activation pre-treatment steps could not be omitted and after their proper adjustment, also the composition and pH of a relatively commonly used hypophosphite reducing type bath had to be modified to the given purpose. Eventually a slightly alkaline EN bath was successfully prepared with which both industrial oxide powders surface could be nickel coated soundly, which final result was demonstrated also by several metallographic testing techniques showing the microstructure of the quite evenly and fully coated oxide particles.

关键词：化学镀镍；氧化铝粉；氧化铁粉末

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High hard armor steels are used on many tactical vehicles, such as the Stryker and the mine-resistant, ambush-protected vehicle. Although they provide good protection against armor-piercing threats, these steels corrode rapidly without the use of a good corrosion protective coating. Corrosion on military ground vehicles increases the infrared signal from the vehicle that the topcoat camouflage usually inhibits, making the vehicle more vulnerable to detection by the enemy. Stryker vehicles are prohibited from using hex-chrome and are currently coated without any pretreatment or conversion coating. The products demonstrated here will satisfy the hexavalent chrome prohibition while minimizing environmental impact and worker safety. This demonstration plan is designed to generate the data necessary for authorization and implementation decisions by appropriate authorities within the U.S. Department of Defense.

关键词：护甲；腐蚀；六价铬；高硬度装甲腐蚀

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The structural reliability analysis is the widely accepted method for bridge safety assessment. Identification the subset of significant failure modes is the most important part of system reliability estimation. In this paper, a stage critical strength branch and bound algorithm is proposed for the failure mode identification of bridge systems. The innovative method is implemented in the combination with the finite element package ANSYS and the MATLAB procedure. The suggest method is applied to a concrete filled steel tubular (CFST) arch bridges. The results reveal various combinations of the failure modes in significantly reduced time and efforts in comparison to the previous permutation method. Additionally, the suggested method can be used for the verification of the system reliability with more specific predictions of the failure mode.

关键词：拱桥；故障模式；识别策略；交通负荷

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In recent decades, bridge fires have become a major concern in the U.S. Fire hazard in bridges can result in significant economic and public losses. New construction of bridges often use Weathering Steel (also known as Corten Steel), which has a corrosion-retarding effect since the steel forms a protective rust layer on its surface under the influence of the weather. To date, no information exists on the high temperature mechanical properties of weathering steel. The objective of this work is to develop a database of mechanical properties of A588 weathering steel that has been exposed to high temperatures. These properties include the residual (after heating and cooling) stress-strain, fracture toughness, and surface hardness. The parameters that are investigated include temperature (800 degrees F, 1000 degrees F, 1200 degrees F, and 1500 degrees F), cooling methods (in air (CIA), and in water (CIW), representing fire-fighting effects), and material. Experiments are also done in a steady-state elevated temperature condition. A comparison is made between A588 weathering steel, used widely for bridges, and another material whose chemical composition and mechanical properties allows it to be classified by ASTM as both an older weathering steel (A242), a steel commonly used in building construction (A992), and also a non-weathering steel used for bridges (A709 Grade 50).

关键词：桥梁（构）筑物；化学成分；腐蚀；钢铁

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