Design of a d_(33)-mode piezocomposite electricity generating element and its application to bridge monitoring

The piezoelectric effect is used in sensing applications such as in force and displacement sensors.However,the brittleness and low performance of piezoceramic lead zirconate titanate(PZT) often impede its applicability in civil structures which are subjected to large loads.The concept of a piezocomposite electricity generating element(PCGE) has been proposed for improving the electricity generation performance and overcoming the brittleness of piezoceramic wafers.The post-curing residual stress in the PZT layer constitutes a main reason for the PCGE's enhanced performance,and the outer epoxy-based composites protect the brittle PZT layer.A d33-mode PCGE designed for bridge monitoring application was inserted in a bridge bearing to provide a permanent and simple weigh-in-motion system.The designed PCGEs were tested through a series of tests including fatigue and dynamic tests to verify their applicability for monitoring purposes in a bridge structure.A simple beam example was presented to show the applicability of the proposed bridge bearing equipped with the PCGE for adequately measuring the traffic loads.

A Novel Half-Bridge Power Supply for High Speed Drilling Electrical Discharge Machining

High Speed Drilling Electrical Discharge Machining (HSDEDM) uses controlled electric sparks to erode the metal in a work-piece. Through the years, HSDEDM process has widely been used in high speed drilling and in manufacturing large aspect ratio holes for hard-to-machine material. The power supplies of HSDEDM providing high power applica-tions can have different topologies. In this paper, a novel Pulsed-Width-Modulated (PWM) half-bridge HSDEDM power supply that achieves Zero-Voltage-Switching (ZVS) for switches and Zero-Current-Switching (ZCS) for the dis-charge gap has been developed. This power supply has excellent features that include minimal component count and inherent protection under short circuit conditions. This topology has an energy conservation feature and removes the need for output bulk capacitors and resistances. Energy used in the erosion process will be controlled by the switched IGBTs in the half-bridge network and be transferred to the gap between the tool and work-piece. The relative tool wear and machining speed of our proposed topology have been compared with that of a normal power supply with current limiting resistances.

CMC International Advertising & Exhibition Co.Ltd.-Bridging the Sino-foreign Mechanical and Electrical Trade

CMC International Advertising & Exhibition Co. Ltd.(CMC-IAE) is a specialized subsidiary of China National Machinery Import & Export Corporation (CMC) with corporate status. In the past 47 years, the company has played a positive role in the conveyance of information and development of China’s mechanical and electrical trade with other countries in the forms of specialized advertising and exhibitions, contributing greatly to the bridging of Sino-foreign mechanical and electrical trade and expansion of international economic and trade exchanges. CMC-IAE deals mainly in and acts as agent for the advertising business of both Chinese and foreign enterprises, and trading companies. It sponsors large-scale exhibitions and promotional activities both at home and abroad; undertaking to design and produce various advertisements,pamphlets and printing matters; engaging in

Characteristics of a plasma flow field produced by a metal array bridge foil explosion

To improve the energy utilization efficiency of metal bridge foil explosion, and increase the function range of plasmas, array bridge foil explosion experiments with different structures were performed. A Schlieren photographic measurement system with a double-pulse laser source was used to observe the flow field of a bridge foil explosion. The evolution laws of plasmas and shock waves generated by array bridge foil explosions of different structures were analyzed and compared. A multi-phase flow calculation model was established to simulate the electrical exploding process of a metal bridge foil. The plasma equation of state was determined by considering the effect of the changing number of particles and Coulomb interaction on the pressure and internal energy. The ionization degree of the plasma was calculated via the Saha-Eggert equation assuming conditions of local thermal equilibrium. The exploding process of array bridge foils was simulated, and the superposition processes of plasma beams were analyzed. The variation and distribution laws of the density, temperature, pressure, and other important parameters were obtained. The results show that the array bridge foil has a larger plasma jet diameter than the single bridge foil for an equal total area of the bridge foil. We also found that the temperature, pressure, and density of the plasma jet＇s center region sharply increase because of the superposition of plasma beams.

Optimization Design of Exploding Foil Bridge Shape

The exploding foil,which is a main influence factor of exploding foil initiator(EFI),was studied to improve the utilization rate of energy in EFI.The burst currents of three bridge foils with different shapes were measured,and the sensitivity of initiation charge made of HNS-IV was tested by slappers.The test results show that,for O-shaped bridge foil,the burst current density is maximal,and the initiating voltage at 50% of firing probability of HNS-IV is minimal.The O-shaped bridge foil can be used to improve the utilization rate of energy in EFI and reduce the firing energy.

Mechanical and electrical properties of Pd-Ru system doped with Zr, Mo, Y

The effect of Zr, Mo, Y dopant on mechanical and electrical properties of Pd-Ru binary alloy was investigated in this work. The alloys were prepared in a vacuum high-frequency melting furnace. X-ray diffraction and metallographic microscope were employed to detect the microstructures of alloys. Electric bridge and eddy current conductive instrument were employed to test the electrical resistivity, and the mechanical properties of alloys were tested by AG-X100KN-type tensile testing machine. The results show that adding rare metal elements into Pd-Ru system could refine the structure effectively and increase the melting point, density, tensile strength, and hardness of alloy, but the elongation and electrical conductivity of alloy decrease. © The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg 2012.

A New Structure of Multilevel Inverter with Reduced Number of Switches for Electric Vehicle Applications

Both Hybrid Electric Vehicles (HEVs) and Electric Vehicles (EVs) need a traction motor and a power in-verter to drive the traction motor. The requirements for the power inverter include high peak power, opti-mum consumption of energy, low output harmonics and inexpensive circuit. In this paper, a new structure of multilevel inverter with reduced number of switches is proposed for electric vehicle applications. It consists of an H-bridge and an inverter in each phase which produces multilevel voltage by switching the dc voltage sources in series. As the number of switches are reduced, both conduction and switching losses will be de-creased, which leads to increase the efficiency of converter. The size and power consumption of driving cir-cuits are also reduced. The proposed three phase inverter can produces more number of voltage levels in the same number of the voltage source and reduced number of switches compared to the conventional inverters. This structure minimizes the total harmonic distortion (THD) of the output voltage waveforms. The structure of proposed multilevel inverter, modulation method, switching losses, THD calculation and simulation re-sults with PSCAD/EMTDC software are shown in this paper.

A Qualitative Assessment of a Modified Multilevel Converter Topology M2LeC for Lightweight Low-Cost Electric Propulsion

A Cascade H Bridge (CHB) is evaluated for both electric vehicle motor traction control and off-vehicle charging against the Power ElectronicsUK Automotive Challenge for cost and mass for the year 2035. By combining the power electronics with batteries using low-voltage MOSFET transistors in a series cascade arrangement the cost and mass targets could be met 12 years earlier (in 2023 and 20 times lighter if an application specific integrated circuit (ASIC) is used. A 200 kW peak reference car was used to evaluate cost and mass benefits using four different topologies of power electronics. Vehicle installation is shown to be simplified as only passive cooling is required removing the need for liquid cooling systems and the arrangement is inherently safe;no high voltages are present when the vehicle is stationary. The inherently higher efficiency of CHB increases vehicle range. The converter with integrated batteries can also behave as an integrated on-board battery charger delivering additional off-vehicle benefits by removing the need for costly external chargers.

Study on the Temperature of the Bridge Wire in the Initiator Used in Nuclear Explosion Valve

This paper established the mathematical model of bridge wire temperature rise under direct current condition and gave the solution. It computed bridge wire temperature by using the thermal-electric coupling method provided by ANSYS-Workbench finite element analysis software. In the end, the temperature bridge wire applied to different electric current was measured by the infrared thermal imaging temperature measurement method. The result shows that the ANSYS simulation results are in agreement with the theoretical calculation and the experimental results. It is feasible to compute bridge wire temperature of initiator by using ANSYS-Workbench software, and it is an important method to analyze complex structure of pyrotechnics.

High-speed imaging observation on molten bridges of AgNi10 electrical contact material

The electrical contact-high-speed imaging experimental system was developed to investigate the molten bridge phenomena of AgNi10 electrical contact material.The dimension of molten bridges was measured along with the measurement of waveforms in the contact voltage under the load of direct current(DC) 6 V(8-20 A)and breaking speed of 50.0 mm·s^(-1).A part of the observed results was presented as well as surface morphology of the contacts after electrical contact behavior,which shows some interesting and new phenomena.Molten bridges and arc could exist simultaneously.The stable molten bridge looks like cylindrical shape and then becomes needle tip at its rupture,the diameter and length of molten bridges both increase with the increase in current and the growth gradient of the diameter is larger than that of the length.The morphology and elemental distribution of the contact surface are changed by the behavior of electrical contact.

金属桥箔电爆炸驱动飞片过程数值模拟研究

为研究金属桥箔电爆炸等离子体驱动飞片全过程中飞片的性能特征和影响规律,建立了金属桥箔电爆炸驱动飞片全过程的多相流数值计算模型,并进行了数值模拟计算.计算中,利用了相变分数描述金属桥箔由固相到等离子体相的相态转变,采用了考虑粒子数目变化及粒子间库仑作用的高温高压等离子体状态方程描述电爆炸等离子体的形成和运动行为,采用了动网格模型描述飞片的运动.将计算结果与实验结果进行对比分析,计算得到的飞片速度值与实验值的误差小于5%,表明计算模型的准确性较好.基于该计算模型,对总面积相同的双体阵列桥箔和单体桥箔电爆炸等离子体驱动飞片过程进行了数值模拟,计算结果表明,由于阵列桥箔电爆炸过程中等离子体和冲击波的叠加汇聚作用,提高了能量转化效率,使得等离子体及冲击波流场对飞片的驱动力增加,从而提高了飞片的速度.等离子体流场对飞片表面的烧蚀厚度约为0.1μm,飞片的完整性较好.

不同电激励方式对桥带电点火器的性能影响

为解决恒流发火在多点点火时的电源功耗和线缆能量损耗等问题,提出了采用电容放电激励方式起爆桥带电点火器,开展电容放电激励下桥带换能元的伏安特性、能量转换特性研究,并对比电容放电及恒流两种激励方式下桥带换能元的作用特性及桥带电点火器的输出特性。研究表明:采用电容放电激励起爆桥带换能元时,电容容值和充电电压的增加对桥带换能元的放电电压和电流峰值、断桥时间、能量利用率影响较大,达到桥带起爆的有效能量均为0.17J;采用电容放电激励方式时,桥带出现电爆炸现象,而采用恒流激励时桥带出现电热现象,两种不同电激励下双桥之间能量加载互不干扰;相比电容放电激励方式,采用恒流激励起爆电点火器时的建压时间、峰值压力及峰值时间均较大。

组合赋权简化ELECTRE法优选桥梁加固方案

为了从众多初步可行的桥梁加固方案中选择最佳方案,研究了组合赋权简化ELECTRE法在桥梁加固方案优选中的应用问题。采用非线性规划方法将层次分析法确定的主观权重和熵值法确定的客观权重进行组合,既考虑了决策者的主观意向,又在一定程度上避免了主观随意性。首次以简化ELECTRE法对备选方案进行综合比选,给出了方案间按优劣程度的完全排序。与经典排序方法ELECTREⅡ相比,简化ELECTRE法排序过程的复杂性和繁琐性,计算效率提高且更便于程序化操作。不再需要设定主观参数,避免了很多主观不确定性因素,提高了分析结果的鲁棒性。算例分析表明选出的最优加固方案与实际采用的相同,并且方案优劣顺序与ELECTREⅡ法、TOPSIS方法的结果一致。

电动机械提梁机在钢-混组合箱梁预制桥面板安装中的应用

以甘肃省兰州市某公路工程建设项目桥梁工程上部结构施工为例,对双向六车道一级公路桥梁上部为宽幅钢波纹腹板-混凝土组合箱梁双钢梁的箱间预制桥面板安装施工工况进行分析,主要包括工艺原理、施工准备、测量放样、预制桥面板运输、电动机械提梁机起吊、预制桥面板安装架设等内容。针对该种施工条件,通过专门设计制作的轮胎式电动机械提梁机,将预制桥面板快速安装至钢波纹腹板-混凝土组合箱梁双钢箱梁箱之间预定位置上。这提高了施工安全性和稳定性,加快了施工进度和生产效率,减少了燃油消耗和车辆尾气的排放,对减少施工成本、提升安全环保文明施工水平具有良好的效用。

燃气电厂主接线优化方案探讨

电气主接线是发电厂电气设计的首要部分,也是构成电力系统的重要环节。本文分析大中型火力发电厂不同的接线型式,通过断路器检修、单一回路故障以及一回路故障另一断路器拒动几种工况的分析,对比不同主接线型式的可靠性;通过分析主接线调度、检修及扩建时的差异,对比不同型式主接线的灵活性;通过设备选型及数量、占地面积情况,对比不同主接线型式的经济性。通过对主接线可靠性、灵活性和经济性的比选,为同类型发电厂主接线设计提供思路及参考。

基于PLC控制的桥式起重机电气设计

随着工业领域的不断发展,桥式起重机在物流、建筑和制造业等领域的使用率逐渐增加。为提高桥式起重机的自动化水平和工作效率,将PLC控制融入桥式起重机的电气设计中,重点研究系统程序设计,并验证该设计程序。结果表明,该程序具有良好的控制精准性与使用安全性,可为相关人员或研究提供参考。

关于《交通建筑电气设计规范》3.4.4条的争议及改进建议

飞机中频电源、地面空调设备功率很大,其负荷计算的准确性对于变压器设备选型和供电方案的确定都有很大的影响。目前大部分支线机场只在近机位廊桥设置桥载设备,总设备数量为5台以下,这种情况下《交通建筑电气设计规范》3.4.4条中的需要系数不能直接使用。本文对于规范的该条文提出自己的理解看法,解释原因,并提出新的计算方法,供大家参考、讨论。

电气系统对岸桥远程操作安全性的保障研究

深入探讨了岸桥电气系统远程操作的安全性问题,包括远程操作的定义、挑战和解决方案。针对安全保障的要求,详细分析了电气系统在远程操作中的安全措施和风险评估策略。通过技术更新、培训优化等手段,提出了提升岸桥远程操作安全性的实用建议。这些成果对于确保港口运营的安全性和可靠性具有指导意义。

无人驾驶牵引负荷车的研制及试验验证

针对目前牵引负荷车存在的传动部件多、传动效率低、需要专业技术人员驾驶、手动调节加载载荷等问题,基于重型电驱加载桥、点对点无线传输、惯导定位等技术,研发了一台具有无人驾驶、自动调节加载载荷、数据无线传输等功能的新一代牵引负荷车,为非道路车辆牵引性能测试提供了一种全新的测试思路及试验方法。通过采用同一台被试车辆,在相同环境下,进行标准负荷车、牵引负荷车的牵引试验验证,结果显示,研发的新一代牵引负荷车满足牵引试验要求。

综合物探方法在城市道路典型障碍物定位研究中的应用

在城市主干道路改扩建工程中,为准确测定地下原水箱涵及其附属隐伏护管桥的空间位置,保障高架桥梁桩基的准确设计及顺利施工,采用高密度电法、地震面波法、探地雷达法、GEM-2多频电磁法等几种常用工程物探方法,旨在对比方法有效性,总结技术要点,为城市道路典型障碍物定位研究积累技术资料及工程经验。地下原水箱涵道及其附属隐伏护管桥为钢筋混凝土,具有特殊的工程结构,与地层具有明显的物性差异,这里利用GEM-2多频电磁法清晰地准确地探测到了护管桥的平面边界,高密度电法、地震面波法较为有效地圈定了护管桥及原水箱涵的空间位置,探地雷达法清晰地探测到了护管桥区域,并且精细地刻画了原水箱涵及护管桥的空间关系,这些成果为类似城市道路工程问题的地球物理勘察提供了实践依据及解决方案。