Laser welding and post weld laser treatment of modified 9Cr-1MoVNb steels (Grade P91) were performed in this preliminary study to investigate the feasibility of using laser welding process as a potential alternative to arc welding methods for solving the Type IV cracking problem in P91 steel welds. The mechanical and metallurgical testing of the pulsed Nd:YAG laser-welded samples shows the following conclusions: (1) both bead-on-plate and circumferential butt welds made by a pulsed Nd:YAG laser show good welds that are free of microcracks and porosity. The narrow heat affected zone has a homogeneous grain structure without conventional soft hardness zone where the Type IV cracking occurs in conventional arc welds. (2) The laser weld tests also show that the same laser welder has the potential to be used as a multi-function tool for weld surface remelting, glazing or post weld tempering to reduce the weld surface defects and to increase the cracking resistance and toughness of the welds. (3) The Vicker hardness of laser welds in the weld and heat affected zone was 420-500 HV with peak hardness in the HAZ compared to 240 HV of base metal. Post weld laser treatment was able to slightly reduce the peak hardness and smooth the hardness profile, but failed to bring the hardness down to below 300 HV due to insufficient time at temperature and too fast cooling rate after the time. Though optimal hardness of weld made by laser is to be determined for best weld strength, methods to achieve the post weld laser treatment temperature, time at the temperature and slow cooling rate need to be developed. (4) Mechanical testing of the laser weld and post weld laser treated samples need to be performed to evaluate the effects of laser post treatments such as surface remelting, glazing, re-hardening, or tempering on the strength of the welds.

关键词：电弧焊接；激光焊接；钢；焊接接头

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In 2005 Focus: HOPE began working on a Technical Area Task to investigate advanced manufacturing in the area of Direct Deposition of Metal (DDM) for the Tank and Automotive Command (TACOM). In 2006, the scope was expanded to include basic research areas of Direct Deposition of Metal applicable to repairing military equipment and Focus: HOPE demonstrated the feasibility of conducting repairs on military equipment using Direct Deposition of Metal (Work Directive WD-FH-0001). The study also demonstrated that there could be a potential cost saving by repairing parts using DDM over purchasing new replacement parts. The overall project was extended in 2010 to provide additional time to conduct additional certification testing of repaired components and demonstrate the effectiveness of the parts repaired using Direct Deposition of Metal. For the present project, extensive studies were conducted on the metallurgical properties and bonding between the newly deposited metal and the parent metal substrate. The findings, results and conclusions of this process certification testing are provided in this report.

关键词：金属；军钢铁；弯曲；腐蚀；沉积零件

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Among underground coal miners, hearing loss remains one of the most common occupational illnesses. To address this problem, the U.S. National Institute for Occupational Safety and Health Office of Mine Safety and Health Research (NIOSH OMSHR) conducts research to reduce the noise emission of underground coal mining equipment, an example of which is the roof bolting machine. Field studies show that, on average, drilling noise is the loudest noise that roof bolting machine operators would be exposed to, and it contributes significantly to the operators noise exposure. OMSHR has determined that the drill steel and chuck radiate a significant amount of noise during drilling. OMSHR and the Corry Rubber Corporation (CRC) have developed a bit isolator that breaks the steel-to-steel link between the drill bit and drill steel and a chuck isolator that breaks the mechanical connection between the drill steel and the chuck. This effectively reduces the noise radiated by the drill steel and chuck and in turn reduces the noise exposure of roof bolter operators. This paper documents the evolution of the bit isolator and chuck isolator. Laboratory testing confirms that production bit and chuck isolators reduce the A-weighted sound level generated during drilling by 3.7 to 6.6 dB.

关键词：钢铁;煤炭开采;听力损失;演习;屋顶螺栓

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The primary objective of the research project was to investigate alternatives to open grid steel decks. Three alternative deck systems, including aluminum deck, ultra-high performance concrete (UHPC) high-strength steel (HSS) deck, and UHPC-fiber reinforced polymer (FRP) tube deck, were developed and studied in the first phase of the research project. The UHPC-HSS deck showed a great potential to serve as a viable alternative. However, more studies were needed on its components and system design before it was deemed ready to be implemented. Accordingly, this phase of the project covered all the studies needed for the design and implementation of the UHPC-HSS deck system. Also, suitability of an FRP bridge deck system as an alternative to open grid steel decks was evaluated. The UHPC-HSS deck was experimentally investigated at both the component and system levels. Studies included the deck-to-girder connection test for shear and uplift forces, deck-to-deck connection test, multi-unit specimen tests to determine the lateral distribution of live loads, full-scale test for fatigue loading and residual strength, and pullout and beam tests to evaluate the development length. The deck-to-girder and the deck-to-deck connections both proved to be adequate for the loading conditions expected from the HS20 truck and wind forces. Tests for the live load distribution showed that most of the load is taken by the ribs under or immediately next to the load. The deck panels and connections successfully endured two million cycles of repeated loading and had a residual strength beyond their target design load. It was shown that the development length of HSS rebars in UHPC can be reasonably predicted by ACI 408R-03. The dowel action of longitudinal steel reinforcement in UHPC and the uniaxial fatigue behavior of UHPC specimens were also evaluated through both experimental and analytical studies. It was shown that the dowel action would contribute considerably to the shear resistance in reinforced UHPC structures. In another part of the research, an FRP deck system was tested under static and fatigue loading. The FRP deck withstood two million cycles of AASHTO-specified repeated loading with no sign of damage or failure, while its deflection under service load significantly exceeded the deflection limit suggested by AASHTO LRFD.

关键词：钢铁；钢格甲板；可移动的桥梁；轻型甲板；电梯桥梁

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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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关键词：钢铁；钢管；防腐；排水

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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：钢铁；工作压力；极限平衡；钢筋

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In the present study,the failure of basic redundant steel structural systems is investigated.By considering that each member of the system has brittle,semi-brittle,or perfectly plastic properties,the statistical behavior of perfectly brittle systems,semi-brittle systems,perfectly plastic and combination systems are evaluated,and the effects of the coefficient of variation (CoV) of members on the systems are investigated.Uncorrelated strengths with the same mean are considered for the system elements.By using the Monte Carlo simulation (MCS) method,maximum strength,yield strength and residual strength of the redundant steel structural systems are evaluated.The CoV of member strength is an essential parameter for statistical assessment of steel structural systems.In this study,the strength is defined random variable a selected normal distribution represents the random variable,for the member strength.The deformation capacity of the member is strongly depends to the characteristics of member strength,but the post failure factor has deterministic values,only for the combination system.The post failure factor is a random variable that represents the uncertainty,uniform distribution is selected to represents random variable,in combination system post failure factor.

关键词：钢铁;单调荷载;强度;变形

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The paper is focused on key points and lessons learned from LRFD calibration of simple limit state functions for the internal stability of metallic reinforced soil walls. The example used in the paper is the ultimate pullout limit state for ribbed steel strip reinforced mechanical stabilized earth (MSE) walls and a single load due to soil self-weight plus a permanent surcharge load. The paper demonstrates how load and resistance measurements from instrumented walls and physical pullout tests can be used to generate bias values. Bias statistics are then used to: a) improve the accuracy of underlying deterministic models used to compute nominal load and resistance values; b) remove hidden dependencies; c) select load factors; and, d) calculate resistance factors to meet an acceptable probability of failure. While the paper is focused on the pullout limit state example, the model fitting approach and LRFD calibration methodology is applicable to a wide range of other soil-structure limit state design problems in geotechnical engineering.

关键词：钢铁；极限状态；金属；附加载荷

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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：钢铁；钢框架；增强节点；循环载荷试验

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