Mechanical performance of shear studs and application in steel-concrete composite beams

This work experimentally investigates the effects of shear stud characteristics on the interface slippage of steel-concrete composite push-out specimens. ABAQUS is used to establish a detailed 3D finite element(FE) model and analyze the behavior of push-out specimens. The modeling results are in good agreement with the experimental results. Based on parametrical analysis using the validated FE approaches, the effects of important design parameters, such as the diameter, number, length to diameter ratio, and yield strength of studs, concrete strength and steel transverse reinforcement ratio, on the load-slip relationship at the interface of composite beams are discussed. In addition, a simplified approach to model studs is developed using virtual springs with an equivalent stiffness. This approach is demonstrated to be able to predict the load-displacement response and ultimate bearing capacity of steel-concrete composite beams. The predicted results show satisfactory agreement with experimental results from the literature.

The Study of Force and the Mechanical Characteristic of Incremental Launching Construction Method on a Steel-Concrete Continuous Beam Bridge

The usage of steel-mixed composite beams is quite extensive today.During an event of constructing steel-mixed composite bridges,the incremental launching construction method is generally adopted.This paper mainly analyzes the force of incremental launching construction on a steel-concrete continuous beam bridge,the classification of incremental launching construction,the application of incremental launching construction in steel-mixed composite beams,the temporary facilities existing in incremental launching construction as well as their existing problems.Lastly,the analysis of the stress of composite beams in incremental launching construction is described by using the reference for the construction of mixed composite continuous beam bridges provided.

Bending Stiffness of Truss-Reinforced Steel-Concrete Composite Beams

This paper is concerned with a special steel-concrete composite beam in which the resisting system is a truss structure whose bottom chord is made of a steel plate supporting the precast floor system. This system works in two distinct phases with two different resisting mechanisms: during the construction phase, the truss structure bears the precast floor system and the resisting system is that of a simply supported steel truss;once the concrete has hardened, the truss structure becomes the reinforcing element of a steel-concrete composite beam, where it is also in a pre-stressed condition due to the loads carried before the hardening of concrete. Within this framework, the effects of the diagonal bars on the bending stiffness of this composite beam are investigated. First, a closed-form solution for the evaluation of the equivalent bending stiffness is derived. Subsequently, the influence of geometrical and mechanical characteristics of shear reinforcement is studied. Finally, results obtained from parametric and numerical analyses are discussed.

Experimental study on seismic behaviors of steel-concrete composite frames

Steel-concrete composite frames are seeing increased use in earthquake region because of their excellent structural characteristics, including high strength, stiffness, and good ductility. However, there exist gaps in the knowledge of seismic behavior and the design provisions for these structures. In order to better understand the seismic behaviors of composite frame systems, eight steel-concrete composite frames were designed. These composite frames were composed of steel-concrete composite beams and concrete filled steel tube columns. The axial compression ratio of column, slenderness ratio and linear stiffness ratio of beam to column were selected as main design parameters. The low reversed cyclic loading tests of composite frame system were carried out. Based on test results, the seismic behaviors of composite frames such as failure mode, hysteresis curve, strength degradation, rigidity degradation, ductility and energy dissipation were studied. Known from the test phenomenon, the main cause of damage is the out-of-plane deformation of steel beam and the yielding destruction of column heel. The hysteretic loops of composite frame appear a spindle shape and no obvious pinch phenomenon. The results demonstrate that this type of composite frame has favorable seismic behaviors. Furthermore, the effects of design parameters on seismic behaviors were also discussed. The results of the experiment show that the different design parameter has different influence rule on seismic behaviors of composite frame.

Compounded Surface Modification of ZK60 Mg Alloy by High Current Pulsed Electron Beam+Micro-plasma Oxidation

In this study, compounded surface modification technology-high current pulsed electron beam （HCPEB） ＋ micro-plasma oxidation （MPO） was applied to treat ZK60 Mg alloys. The characteristics of the microstructure of ZK60 Mg alloy after single MPO and HCPEB＋MPO compounded treatment were investigated by SEM. The results showed that the density of the ceramic layer of HCPEB＋MPO-treated ZK60 Mg alloy was improved and defects were reduced compared to that under MPO treatment alone. Surface modified layer of ZK60 Mg alloys treated by HCPEB＋MPO was divided into three zones, namely the top loose ceramic zone, middle compact zone and inside HCPEB-induced melted zone. Corrosion resistance of ZK60 Mg alloy before and after the compounded surface modification was measured in a solution of 3.5% NaCl by potentiodynamic polarization curves. It was found that the corrosion current density of ZK60 Mg alloys could be reduced by about three orders of magnitude, from 311μA/cm^2 of the original sample to 0.2μA/cm^2 of the HCPEB＋MPO-treated sample. This indicates the great application potential of the HCPEB＋MPO compounded surface modification technology in improving the corrosion resistance of ZK60 Mg alloys in the future.

Growth of high quality InSb thin films on GaAs substrates by molecular beam epitaxy method with AlInSb/GaSb as compound buffer layers

A series of In Sb thin films were grown on Ga As substrates by molecular beam epitaxy(MBE).Ga Sb/Al In Sb is used as a compound buffer layer to release the strain caused by the lattice mismatch between the substrate and the epitaxial layer,so as to reduce the system defects.At the same time,the influence of different interface structures of Al In Sb on the surface morphology of buffer layer is explored.The propagation mechanism of defects with the growth of buffer layer is compared and analyzed.The relationship between the quality of In Sb thin films and the structure of buffer layer is summarized.Finally,the growth of high quality In Sb thin films is realized.

Cr/CrN Compound Films Prepared by Ion Beam Assisted Deposition for Improving the Performance of Bearing Steel

With the development of industry, much attention has been paid to lengthening the life span of bearings. As reported in this paper, we investigated the Cr/CrN compound films formed on the specimens of W9Cr4V2Mo bearing steel by ion beam assisted deposition for improving the performance of bearing steels. The Vicker＇s microhardness, pin-on-disc, electrochemical measurement, XRD and SEM tests were used to characterize and analyze the treated samples. All results indicated that the mechanical properties of the treated samples were good, with the microhardness greater than that of the uncoated specimen, and the wear resistance, the passivity and pitting corrosion resistance increased considerably, the films possessed alternate Cr and CrN compound phases and produced different effects on the improvement of the performance of W9Cr4V2Mo bearing steels with different composing phases.

DETERMINATION OF SPACE GROUP OF PrCo_(12)B_6 COMPOUND BY CONVERGENT BEAM ELECTRON DIFFRACTION

The space group of PrCo_(12)B_6,compound has been determined using the convergent beam elec- tron diffraction method.The space group is found to be R3m.

钼合金与低合金钢电子束焊接的力学性能研究

对TZM钼合金与30CrMnSi低合金高强钢进行电子束焊接试验,分析了焊接接头微观组织、界面结构以及接头力学性能。结果表明,束流偏向钢侧0.2 mm时,形成熔钎焊接头形式。在钼侧熔合线附近产生的界面区根据组织形貌与相组成划分为反应层Ⅰ与反应层Ⅱ,结合能谱、线扫描分析和XRD分析表明反应层Ⅰ由连续分布的Fe2Mo相构成,会显著影响接头力学性能。拉伸结果表明,断裂沿反应层Ⅰ位置处扩展,呈现出脆性断裂特征,极限拉伸强度为209 MPa。显微硬度结果显示,沿水平方向接头不同特征区域硬度值差异较大,存在针状马氏体的钢侧热影响区显微硬度值最高,达到687 HV。

Microstructure and corrosion resistance of a Mg2Sn-dispersed Mg alloy subjected to pulsed electron beam treatment

We report that the corrosion resistance of a Mg-Sn-based alloy with MgzSn precipitates can be considerably improved by surface modification using pulsed electron beam treatment.The alloy subjected to a pulse electron beam treatment showed a modified surface layer with a thickness of〜12 μm,appearing more resistant to corrosion attack than the bare surface of the alloy.In 0.6 M NaCl solution,the alloys with and without the surface modification exhibited average corrosion rates of 4.3 and 8.1 mm y^-1,respectively.The improved corrosion resistance was attributed to reduced cathodic activation,resulting from the surficial reduction of relatively noble Mg2Sn precipitates.

Investigations of microstructures and properties in electron beam welded joints of TiAl to TC4

The normally centered electron beam and non-centered electron beam welding of TiAl to TC4 was investigated in order to analyze the electron beam weldability between TiAl/TC4 dissimilar materials. Macroscopic cold crack easily occurred near TiAl substrate in the joints. The optimal tensile strength was related to the welding heat input. The weld structures were composed of bulky columnar grains and equiaxed grains. The isolated phases consisted of large quantities of α2 -Ti3Al phase, small quantity of B2 phase, γ-TiAl phase and YAl2 phase. Insufficient melting of the base metal occurred in the weld when the beam position leaned to the TC4 side. The tensile strength could be improved when the deflection was limited in the optimum range. Otherwise, non-fusion zone was easily generated in the weld, which led to the low tensile strength.

Experimental study on interaction mechanism of small H-beams and a soil-cement retaining wall

Small H-beams such as the No.14–20 I-steel can be inserted into soil-cement retaining walls to form small H-beam soil-cement compound walls, functioning both as a retaining wall and a cutoff wall for braced structure excavations. Being different from the mixed soil-cement wall (SMW), the interaction between soil-cement and small H-steel is very good. We have carried out a series of bending experiments on small H-beams in soil-cement model compound beams to study the mechanism of interactions. The results show that the interaction between H-beams and soil-cement is very good, whether the H-beam is single or double. Joint forms of double H-beams at one end have little effect on both the contribution coefficient and on ultimate deflection before cracking. But after cracking, the joint forms greatly affect the contribution coefficient. We conclude that the rigid joint girder for double H-beams is a better choice in practice.

不同剂量辐照对鸡胸肉挥发性化合物的影响

为探究电子束辐照对鸡胸肉异味产生的影响,对不同剂量辐照鸡胸肉中的挥发性化合物进行检测和分析。用固相微萃取-气相色谱-质谱联用法(solid phase microextraction-gas chromatography-mass spectrometry,SPME-GC-MS)对不同剂量辐照鸡胸肉中的挥发性化合物进行分析,对辐照鸡胸肉进行感官评价实验,结合挥发性化合物含量进行偏最小二乘回归分析(partial least squares regression,PLSR)。检测到了18种香气活力值(odor activity value,OAV)大于1的挥发性化合物,其中2 kGy剂量辐照对鸡胸肉中挥发性化合物影响最明显。确定了对鸡胸肉果香、霉香、油脂、鸡肉味、油漆味有重要贡献的特征化合物。感官评价得分结合挥发性化合物的OAV表明反-2-辛烯醛、1-辛烯-3-醇、壬醛、3-羟基-2-丁酮可能是辐照鸡胸肉产生辐照异味的特征化合物。实验结果为电子束辐照食品中异味的检测及掩盖提供理论依据,推动电子束辐照保鲜技术在其他食品中的应用。

铁磁性加载复合管壳电子注聚焦性能的研究

大功率行波管通常利用复合管壳提升高频系统的集成度和散热特性。宽带行波管采用复合管壳高频制造工艺时,由于加载翼片含有铁磁性材料(纯铁)使得聚焦系统的横向磁场分量变大,径向和角向磁场分量呈非均匀性,电子注聚焦困难。本文研究了周期永磁聚焦系统横向磁场产生的原因并建立理论模型,并对磁场分量和其对电子注形态的影响进行了仿真,仿真结果与理论计算结果一致。根据横向磁场分布模型对加载翼片的形状和数量进行优化仿真,结果表明9片齿形加载翼片方案可在保持慢波电路参数的同时,降低聚焦系统的横向磁场分量,改善电子注聚焦效果。

基于复合梁结构的压电-电磁能量收集器研究

能量收集器是解决复杂环境下为无线传感器网络节点供能问题的有效方法之一。针对传统收集器的共振频率高、频带窄等缺陷,设计了一种基于复合梁结构的压电-电磁式能量收集器,并进行了动力学分析与实验研究。首先对该结构进行理论模型建模,建立动力学方程,验证了其结构合理性。之后将该结构与其他传统压电结构进行对比研究,分析了收集器的动力学特性以及发电性能,优化结构参数,并进行了实验验证。研究发现通过复合梁与电磁单元的引入,收集器的工作频带得到了拓宽,改善了其发电性能,有效地使得该结构的一阶与二阶共振频率靠近。实验结果表明:负载电阻为10 kΩ、磁铁线圈间距为7 mm时,该复合梁压电电磁结构收集器具有最优的输出特性,其最大输出功率为20.17 mW,有效工作带宽约为13.40 Hz。

等离子体技术在金属冶炼还原提纯中的应用

总结了活泼金属的熔炼提纯方法,概述了等离子束熔炼炉的基本形式和国内外现状,介绍了等离子束冷床与感应冷坩埚复合熔炼技术和感应冷坩埚连铸技术,提出了磁搅拌冷床技术,介绍了等离子体技术在金属冶炼还原提纯中的应用,展望了等离子体技术的未来应用方向。

基于旋转双棱镜的光束复合跟踪控制技术

提出一种基于旋转双棱镜的光束复合跟踪技术,用于取代传统伺服转台实现精密的光学跟踪。首先,建立双棱镜的光束偏转模型,详细推导光束偏转矢量与双棱镜转角间的转换关系,并对跟踪过程中的棱镜旋转非线性问题进行了分析。提出基于快速反射镜进行光轴修正的双棱镜光束复合跟踪方法,通过建立偏转光轴与光学基台间的扰动耦合关系,实现了对双棱镜转速的实时补偿,并改进棱镜控制器以提高光束控制性能。搭建实验系统,对旋转双棱镜复合跟踪技术进行验证。在动态跟踪实验中,采用改进控制器的双棱镜的控制精度明显提高,相较于比例-积分-微分控制器和线性自抗扰控制器,所提出的改进控制器使棱镜的控制精度分别提高58.33%和32.81%,并使跟踪误差由改进前的49.03μrad和38.88μrad降低为31.15μrad。开启视轴补偿后跟踪性能进一步提高,总跟踪误差降至7.49μrad,跟踪精度提高4.16倍。实验结果表明,光束复合控制能有效提高双棱镜的跟踪精度,验证了所提方法的有效性。

Optimizing depth of field in 3D light-field display by analyzing and controlling light-beam divergence angle

A concept of divergence angle of light beams(DALB)is proposed to analyze the depth of field(DOF)of a 3D light-field display system.The mathematical model between DOF and DALB is established,and the conclusion that DOF and DALB are inversely proportional is drawn.To reduce DALB and generate clear depth perception,a triple composite aspheric lens structure with a viewing angle of 100°is designed and experimentally demonstrated.The DALB-constrained 3D light-field display system significantly improves the clarity of 3D images and also performs well in imaging at a 3D scene with a DOF over 30 cm.

氯化锂-紫外-离子束复合诱变红霉素高产菌株研究

以红霉素生产菌红色链霉菌为研究对象,探讨了氯化锂、紫外、离子束3种不同诱变方式对红色链霉菌的影响,根据后代的存活率和突变率选定合适的诱变条件:氯化锂的最优诱变浓度1.2%,紫外的最优诱变时间120s,离子束的最优诱变注量200×1014 cm-2,然后将3种方式结合起来进行复合诱变。经复合诱变后筛选获得高产突变株E0317-1-7-26,该菌株摇瓶效价达7 126μg/mL,较出发菌株E03提高了20.3%;经多次传代分离实验表明,该突变株遗传稳定性较好。

高斯光束经复合光学系统的聚焦特性

讨论了高斯光束经由凹透镜 ,子系统和凸透镜构成的复合光学系统的聚焦特性 ,利用矩阵光学方法 ,推导出了高斯光束经复合光学系统聚焦后束腰宽度和像距的计算公式。计算例表明 ,选择适当参数的复合光学系统 ,既可以获得较小的束腰宽度 ,又可以获得较长的像距。