The paper presents changes of natural frequencies of industrial steel hall due to simplifications or changes of numerical model.Firstly,the natural frequencies were calculated for basic Variant A of the numerical model of the steel hall which consisted of the main frames,footings,roofpurlins and girts.In this Variant columns were fixed at bases,both purlins and girts were rigidlyconnected to main frames and designed as continuous beams.Then,in Variant B of the model columns were pinned at bases.Next,in Variant C different types of connections (semi-flexible joints)of roof purlins and girts with the main frame were implemented.Finally,in Variant D,soil-structure interaction was taken into consideration.The calculations of the dynamic characteristics of four abovementioned Variants of the numerical model of the hall showed that simplifications or changes of some details of the structure could result in significant errors in values of natural frequencies.

关键词：钢铁;固有频率;柔性接头;土结构相互作用

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A comprehensive modeling study has been carried out to evaluate the utility of multiple active neutron interrogation signatures for detecting shielded highly enriched uranium (HEU). The modeling effort focused on varying HEU masses from 1 kg to 20 kg; varying types of shields including cement, wood, polyethylene, aluminum, and steel; varying depths of the HEU in the shields, and varying engineered shields immediately surrounding the HEU including steel, lead, and cadmium. Neutron and gamma-ray signatures were the focus of the study and false negative detection probabilities versus measurement time were used as a performance metric. To facilitate comparisons among different approaches an automated method was developed to generate receiver operating characteristic (ROC) curves for different sets of model variables for multiple background count rate conditions. This paper summarizes results or the analysis, including laboratory benchmark comparisons between simulations and experiments.

关键词：钢铁；高浓缩铀；辐射探测器；伽玛射线

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The growing requirements of steel products qualities bring even tricky restrictions to the rolling process.With the fast response,reliable control and low maintenance requirements,the hydraulic automatic gauge control system has been widely applied to screw down the roller to maintain the precise rolling spaces for product quality control.Regarding to non-stopped heavy duties charged to the system,unavoidable faults and disfunctioas not only influence the product quality,but also bring underlying safety issues.The hydraulic cylinder is the executing component of the roller screw down and it has the dominant percentage of hydraulic components' faults.Working with unexpect loading is one of major impact factor that causes several chain-effects happened to the cylinder,as the classical diagnostic process is lack of cross-validating and time-consuming,the paper proposes the potentials of using acoustic emission to fill the dilemmas.The works include the data acquisition process to record the ultrasound acoustic signals from the hydraulic cylinder during it was loaded with 6 types of conditions,a modified image based acoustic emission approach constructed by using 8 significant waveform features was applied to generate visual effects and transform the cylinder acoustic emission signals under various loadings to a uniform format,the subtle differences among various Ioadings can be observed based on the pixel and intensity changes of the images.By applying the principal component analysis to project the acoustic emission image profiles onto the 3D plane,a clear trajectory can be observed with normal and overload conditions allocated upon the positive and negative sides of the axis.The result provided not only the potential of using acoustic emission for dynamic state identification of the subtle changes,but also opens up the possibility of preventive measures to the cylinder at risks in the future.

关键词：声发射；液压缸；自动厚度控制

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In construction stage, a large buffeting response would endanger construction safety and quality for a long span concrete-filled steel tube (CFST) arch bridge. Developing the study on buffeting security is indispensable to CFST arch bridge in construction stage. Combining random vibration analysis of structure with modern probability theory, taking an actual large span CFST arch bridge as example, dynamic reliability of buffeting responses research and analysis is developed, which is based on the buffeting analysis on time domain at the longest cantilever construction stage. The paper gives quantitative valuation on wind-vibration safety performance of the bridge in construction phase and offers a new thought and reference for homologous project.

关键词：钢铁;钢管混凝土管;拱桥;施工阶段

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Fracture toughness and fatigue properties of pipeline steels play a critical role in developing advanced high-pressure hydrogen infrastructure for alternative fuel pipelines program. The reliability of structure components, particularly resistance to damage and failure in the intended service environment, is highly dependent on the selected materials. An effective surveillance program is also necessary to monitor the material degradation during the course of service. Steels have been proven to be desirable for hydrogen infrastructure. However, hydrogen embrittlement is an important factor that limits steel performance under high-pressure hydrogen conditions. In order to reach the above goal, we have proposed an innovative technology, based on spiral notch torsion test (SNTT) methodology, to effectively investigate the material performance of X52 pipeline steel. The SNTT approach was successfully demonstrated and extended to X52 steels during the performance period. In addition to single notch front geometry, the crack growth behavior of the SNTT process has been effectively established using an integrated experimental, numerical and analytical approach. The results indicate that the proposed protocol not only provides significant advance in understanding the compliance evolution of the SNTT specimen, but also can be readily utilized to assist future development of hydrogen infrastructures. In FY2011, an extensive study was performed to characterize the fracture toughness degradation of AISI 4340 high-strength steel exposed to high-pressure hydrogen using in situ spiral notch torsion tests. This effort included equipment setup and calibration, sample design and fabrication, finite element simulation of the specimen fracture, and fractographic characterization using advanced microscopic techniques. The detailed description of the results is summarized in by Wang (Wang 2011).

关键词：管道；钢；断裂强度；缺口冲击试验

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Continuous cooling transformation (CCT) curves of deformed austenite (A) of Nb-Ti microalloying high strength steel were measured using Gleeble-3800 thermo-mechanical simulator,and corresponding transformation and structure were analyzed,and the effects of cooling rate on the tested steel's mechanical property were studied.The resultes showed that the Ar3 transformation point decreased with increasing cooling rate after hot-rolling.The morphology of ferrite (F) grains changed from polygonal to lath,and the pearlite (P) colonies became more fine with increasing cooling rate.The quantity of ferrite and pearlite decreased,and the quantity of bainite (B) and martensite (M) increased.Then the hardness of Nb-Ti micro-alloyed steel is increased along with the increasing cooling rate,which may owing to the reasons that the hardness of ferrite and pearlite is far smaller than that of bainite and martensite,and the grain refinement causes the hardness increasing.

关键词：钢铁；铌钛微合金化钢；CCT曲线；相变

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The Commission instituted these reviews on June 3, 2013 (78 FR 33108,) and determined on September 6, 2013 that it would conduct expedited reviews (78 FR 59371, September 26, 2013).

关键词：钢铁；进口；碳素钢；钢管；焊件

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关键词：钢铁；换热器；不锈钢；显微组织；液态金属

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The goal of the proposed project is to further develop and market advanced 70-ksi-yield strength super-tough steel (designated as NUCu60ST in the text) for use in tank cars transporting cryogenic liquids, like chlorine, for example. Fracture of these tanks resulted in a number of industrial accidents. One in 2005 in Graniteville, South Carolina led to nine deaths and at least 250 injuries. This is a joint project with Union Tank Car Company (UTLX). Developed and investigated at Northwestern University by prior funding from ITI and CCITT, the super-tough cyrogenic steel was included into the 'Next-Generation Rail Tank Car Project', an innovative joint initiative of the three companies (Dow, Union Pacific and UTLX), Association of American Railroads (AAR), and US and Canada Departments of Transportation focused on the design and implementation of a next-generation rail tank car with enhanced ability to safely transport hazardous chemicals.

关键词：钢;坦克车;危险品运输;低温;氯

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The field emission characteristics of niobium electrodes were compared to those of stainless steel electrodes using a DC high voltage field emission test apparatus. A total of eight electrodes were evaluated: two 304 stainless steel electrodes polished to mirror-like finish with diamond grit and six niobium electrodes (two single-crystal, two large-grain, and two fine-grain) that were chemically polished using a buffered-chemical acid solution. Upon the first application of high voltage, the best large-grain and single-crystal niobium electrodes performed better than the best stainless steel electrodes, exhibiting less field emission at comparable voltage and field strength. In all cases, field emission from electrodes (stainless steel and/or niobium) could be significantly reduced and sometimes completely eliminated, by introducing krypton gas into the vacuum chamber while the electrode was biased at high voltage. Of all the electrodes tested, a large-grain niobium electrode performed the best, exhibiting no measurable field emission (> 10 pA) at 225 kV with 20 mm cathode/anode gap, corresponding to a field strength of 18:7 MV/m.

关键词：光电子;直流;电势;电极;铌

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