Dual phase (DP) steels belong to the group of high-strength low-alloy (HSLA) steels. Our study focuses on the causes of crack formation of sheets, which are designed for deep drawing, of DP780-grade dual phase steel. Also, a series of heat treatment experiments were performed regarding the effect of intercritical annealing temperature on the structure and mechanical properties of the finished product (in this case a rolled sheet).

关键词：钢铁；双相钢；深冲；高强度低合金钢

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Starting about 1920 it becomes easier to track the growth of bearing materials technology. Until 1955, with few exceptions, comparatively little progress was made in this area. AISI 52100 and some carburizing grades (AISI 4320, AISI 9310) were adequate for most applications. The catalyst to quantum advances in high-performance rolling-element bearing steels was the advent of the aircraft gas turbine engine. With improved bearing manufacturing and steel processing together with advanced lubrication technology, the potential improvements in bearing life can be as much as 80 times that attainable in the late 1950s or as much as 400 times that attainable in 1940. This paper summarizes the chemical, metallurgical and physical aspects of bearing steels and their effect on rolling bearing life and reliability. The single most important variable that has significantly increased bearing life and reliability is vacuum processing of bearing steel. Differences between through hardened, case carburized and corrosion resistant steels are discussed. The interrelation of alloy elements and carbides and their effect on bearing life are presented. An equation relating bearing life, steel hardness and temperature is given. Life factors for various steels are suggested and discussed. A relation between compressive residual stress and bearing life is presented. The effects of retained austenite and grain size are discussed.

关键词：滚子轴承;残余应力；钢；硬度

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The bridge is a basic element of all surface transportation networks. In military theaters of operation, transportation routes that cross bridges are essential for deploying personnel, supplies, and heavy equipment, as well as for facilitating communications. It is essential that the structural capacity of each bridge along a military route be assessed in order to avoid overloading the bridge or unnecessarily hindering military operations by overestimating or underestimating its capacity. For reinforced concrete structures, information about the number, size, and orientation of steel reinforcement is necessary to make a strength assessment. Since reinforcement is not visible externally, making an accurate assessment without design drawings is extremely difficult. The objective of this project was to develop more reliable means of in-field capacity assessment of reinforced concrete bridges by making improved estimates of the level of longitudinal and shear reinforcement. The proposed assessment procedure is based on comparing measured structural response under controlled loading conditions to predicted structural response from analysis. This report presents results from a preliminary sensitivity study of the analytically predicted response of simply supported reinforced concrete T-beam girders that have varying levels of longitudinal and shear reinforcement.

关键词：钢铁；桥梁；结构完整性；容量（数量）；探测器;

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This project addressed the goal of National Strategy for Surface Transportation Research to improve highway structures by enhanced materials, in particular by design and implementation of new, drastically improved steels with respect to strength, low-temperature fracture toughness, weldability, and weatherability. The goal of the project was to develop, standardize and commercialize a family of low-cost, high-performance steels for infrastructure applications. As a result we developed steels with yield strength of 50 to 80 ksi, with Charpy absorbed fracture energy significantly exceeding requirements of bridge construction codes at temperatures down to -100DGF, steels that are easy to weld without pre-heat or post-heat, steels that exhibit best weathering performance among other commercially available steels. In addition these steels are easy to produce; production does not involve any heat treatment or thermo-mechanically controlled processing which is available only to several US Steel companies. The steels developed in this project were commercially produced in the form of plate and wide-flange I-beams. The steels were used for seismic retrofitting of one bridge (in 2000) and for construction of two new bridges (in 2006 and 2010).

关键词：钢材；成本；营销；桥梁；建筑

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The thermal performance Rov of Flat-Plate Closed-Loop Pulsating Heat Pipe(FCLPHP) are effected by several elements such as the heat load Q, the tilt angle θ and the filling ratio F, they are interacted each other.In order to predict the effect of Q and θ on the thermal performance at locations Q and θ other than the experimental data conditions, and to study the relationship among the Rov, Q and θ in the range of the experimental data, we need a fitted regression model to estimate the function relationship that describes the data.The postulated depends on the range of the regression variables encountered in the data.In this paper, a simple model was developed.Since the coefficients in the model have been estimated from the experimental data, studies were carried out on an experimental set-up.FC72 was employed as working fluid.Method of least squares was used for building the model.By using the model, effects of the beat load and the tilt angle on the thermal performance of FCLPHP were discussed.It was found that the tilt angle had minimum value in a certain heat load in the experimental range (θ=30°-70°), and it increases with the increase of heat load.A sensitivity analysis was done with the model.

关键词：钢铁；脉动热管；热性能；整体热阻

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Multi-layered plates consisting of DH-36 steel coated by a thick layer of polyurea, for increased blast and impact protection, are of increasing importance to the Department of Defense. A hybrid approach of experiments and simulation was performed to characterize fracture and plasticity of DH-36 Navy steel, which is the first step in creating an accurate model of the composite material. The performance limit to this material during an impact is ductile fracture. The prediction follows that the onset of fracture occurs when a certain critical value of plastic strain is reached. This value is highly dependent on the state of stress. Seven different types of tests were performed, including tensile tests on dog-bone and notched specimens and punch indentation tests on circular blanks. Also, tensile and shear tests were performed on butterfly specimens using the dual actuator loading frame. Fracture surface strains were measured using digital image correlation. Local fracture strains were obtained by using an inverse engineering method of matching measured displacement to fracture with computer simulations. The results are used to calibrate the Modified Mohr Coulomb fracture model which is expressed by the stress state invariants of Lode angle and triaxiality.

关键词：钢铁;断裂（力学）;钢;海军;塑料涂料

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This article presents a new type of stress assessment method for double-layered pressure vessel. Due to its robust strength, a steel-concrete composite pipe is generally installed in poor burial conditions. However, it is difficult to directly define the stress state on pipe sections. For the convenient stress estimation of pipes encased in non-circular concrete, this article suggests a Stress Index (SI), a function of the interface pressure and changed diameter, based on the interface pressure. The ovalization characteristics of plain pipes and of pipes encased by circular and rectangular concrete are examined. The resultant stresses are replaced by the non-dimensional ratio of diameter change; thus, the stress index has the advantage of application for stress assessment irrespective of pipe characteristics.

关键词：钢铁；压力管道；压力指数；压力评估；界面压力

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The construction industry has historically made use of four materials: stone, timber, concrete, and steel. In recent years, civil engineers have been seeking alternative materials to steel and concrete that may be less vulnerable to environmental damage. Rising public concern about traffic delays experienced during construction have increasingly influenced civil engineers to seek materials and methods that allow more rapid construction. At the same time, costs must be competitive with traditional materials because of reduced public sector resources to maintain transportation infrastructure. Fiber-reinforced polymer (FRP) composites have emerged as an attractive potential alternative. Inspections of sign structures by the Florida Department of Transportation (FDOT) have revealed the occurrence of premature corrosion of galvanized steel structural members. As a result, FDOT engineers are also seeking alternative materials that may be employed in these structures.

关键词：建筑材料；石材；木材；混凝土；钢材

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The paper presents experimental data generated for calibrating finite element models to predict the performance of reinforced concrete panels with a wide range of construction details under blast loading. The specimens were 1.2 m square panels constructed using Normal Weight Concrete (NWC) or Fiber Reinforced Concrete (FRC). FRC consisted of macro-synthetic fibers dispersed in NWC. Five types of panels were tested: NWC panels with steel bars; FRC panels without additional reinforcement; FRC panels with steel bars; NWC panels with glass fiber reinforced polymer (GFRP) bars; and NWC panels reinforced with steel bars and external GFRP laminates on both faces. Each panel type was constructed with three thicknesses: 152 mm, 254 mm, and 356 mm. FRC panels with steel bars had the best performance for new construction. NWC panels reinforced with steel bars and external GFRP laminates on both faces had the best performance for strengthening or rehabilitation of existing structures. The performance of NWC panels with GFRP bars was strongly influenced by the bar spacing. The behavior of the panels is classified in terms of damage using immediate occupancy, life safety, and near collapse performance levels. Preliminary dynamic simulations are compared to the experimental results.

关键词：钢铁；混凝土；纤维；玻璃纤维；性能

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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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