实验室内海水电导率测量方法的改进

介绍了一种实验室内海水电导率测量的改进方式,用于电导率测量仪的校准过程。通过配备恒温副槽和封闭式水样控制装置,与高精度海水恒温槽、8400B实验室盐度计进行组合,实现在封闭的环境下实时测量海水的电导率比,以获取海水标准盐度值和标准电导率值。对比实验结果表明,改进后的测量方式无需人工取样和恒温静置,实现了封闭、实时、高效测量,与传统方法所测盐度相差不大于0.0003,满足8400B盐度计技术指标和实验室内盐度计校准的要求。     

各向异性磁电阻传感器高精度测试技术

针对各向异性磁电阻(AMR)传感器在受到强磁干扰后灵敏度下降问题和温漂问题,提出运用"复位/置位"脉冲对传感器进行高精度测量的技术.分析了各向异性磁电阻传感器工作原理和复位/置位结构;阐述了复位/置位测试方案和零点补偿方法;设计了相应的电路,并进行了一系列的实验验证.实验结果表明:采用基于"复位/置位"脉冲的AMR磁传感器高精度测试技术可以有效解决磁阻传感器受强磁干扰后灵敏度下降问题,并有效消除AMR传感器零点温度漂移影响,提高了传感器的测量精度.在高精度磁场测量领域具有参考意义.     

导电矩形板的磁弹塑性动力失稳特征研究

基于Maxwell电磁场方程及电-磁-力多场耦合理论,研究了矩形导电薄板在横向脉冲磁场及面内恒定磁场共同作用下的弹塑性动力响应及其动力失稳特征.采用有限元方法探讨了悬臂矩形薄板在外加磁场作用下的涡电流的分布特征,数值模拟了矩形导电薄板的振幅,频率随外加磁场幅值的变化情况,给出了磁弹塑性动力失稳的临界磁场值与金属薄板的电导率、板的长厚比以及磁脉冲参数τ之间的关系,展示了不同磁场下导电薄板结构塑性区域等,这些研究结果为工程实际中电磁成形工艺的改进以及导电结构的安全设计和可靠性评估提供依据和参考.     

悬臂梁式光纤声传感器研究

光纤声传感器种类很多，但大多着眼于水声，作水听器用。现在本文提出一种可用于空气声检测的悬臂梁式光纤声传感器。本文给出了该种传感器的实验装置，谐振频率，灵敏度的计算，同时给出了它们的实验值。用这种传感器在实验室内可测到最低声正为１×１０－４Ｐａ（１００Ｈｚ时）     

磁传感器在导航系统中的应用

介绍了一种基于磁传感器和加速度计,结构简单、低成本、高精度的方位传感器。该传感器利用当地的地磁场矢量和重力加速度矢量确定传感器在空间的姿态信息。分析了使传感器产生误差的各种因素,如温度影响、附近铁磁物体和噪声影响等,并给出了消除这些干扰因素影响的技术。实验研究表明,此传感器能够为移动机器人导航提供可靠的高精度姿态信息。     

恒温槽温度梯度实验研究

通过实验研究了侧搅拌式恒温水槽和恒温油槽100 mm以上的温度梯度.研究表明在50～200℃范围内恒温槽30～100mm上层温场温度梯度能够达到工作用玻璃液体温度计、工业铂电阻温度计等常规工业温度计规程规范要求.根据实验结果,置入深度对传感器的测量结果的影响取决于传感器材料的导热系数.导热系数越小,影响越小.对于相同材质的温度传感器,置入深度对传感器的测量结果的影响取决于深度直径比.根据实验结果可以推断,在校准置入深度较短温度传感器时,被校传感器的轴向传热是测量误差的主要来源,随着校准温度的提高,置入深度对测量结果的影响越来越大.     

恒温槽温度梯度实验研究

通过实验研究了侧搅拌式恒温水槽和恒温油槽100 mm以上的温度梯度。研究表明在50～200℃范围内恒温槽30～100 mm上层温场温度梯度能够达到工作用玻璃液体温度计、工业铂电阻温度计等常规工业温度计规程规范要求。根据实验结果,置入深度对传感器的测量结果的影响取决于传感器材料的导热系数。导热系数越小,影响越小。对于相同材质的温度传感器,置入深度对传感器的测量结果的影响取决于深度直径比。根据实验结果可以推断,在校准置入深度较短温度传感器时,被校传感器的轴向传热是测量误差的主要来源,随着校准温度的提高,置入深度对测量结果的影响越来越大。     

影响磁天平测量结果的因素

介绍了磁天平装置测量弱磁材料磁化率的工作原理和装置组成,对影响测量结果的各种因素进行仔细的分析和研究,主要是由于测量时因质量称重、磁场稳定性、样品形状、磁干扰等多种因素给磁化率测量结果带来影响。通过实验验证,提出解决测量误差的方法,以提高磁天平测量不确定度水平。     

力-磁-环境耦合作用下超磁致伸缩材料TbDyFe表面畴变的观察

就TbDyFe超磁致伸缩材料在应力、磁场和环境耦合作用下的表面畴变进行了研究。主要利用光学显微镜及其微分干涉相衬显微（Differential Interference Contrast，DIC）系统，并自行设计搭建了恒磁场试样台和环境试验箱，由此实现了对应力、磁场及环境作用下材料表面磁畴变化的原位跟踪研究。     

基于群延时分析的海水声速测量

在海水声速测量过程中,测量系统存在群延时,影响测量精度.建立声速直接测量系统信号传输模型,分析系统群延时及换能器群延时.建立声速直接测量系统并在恒温水槽中完成测量实验,所测量的声速值与某高精度声速仪测量声速值相差小于0.3 m/s,与经验公式计算声速值相差小于0.1 m/s.实验结果表明,系统群延时分析方法可用于声速测量.     

水中弹药的电磁感应测速方法研究

为解决现有的水下速度测试装置存在测试精度低和受水介质特性影响大的问题,设计了一种基于电磁感应原理的测速装置感应式线圈靶水下测速系统.针对水介质特性对测试系统的影响,对线圈靶进行了密封设计,对测试电路进行了抗干扰设计,并进行了水中弹药的速度测试实验.实验结果表明:测速系统受水介质特性干扰小,所测信号基本不含干扰信号,且对弹丸外弹道无影响;线圈靶与高速摄影的测速结果相比,测速精度高,相对偏差在5%以内,且可测速度范围宽,可广泛应用于水中弹药速度的测试.     

电磁搅拌法制备导电聚苯胺纳米线的电磁屏蔽性能研究

针对低频频段(<1.5GHz)的电磁屏蔽涂层,采用快速混合法制备出导电聚苯胺纳米线,使用透射电镜(TEM)对其形貌和尺度进行表征,研究了搅拌方式对聚苯胺/聚氨酯涂层的导电性能和电磁屏蔽性能的影响。研究表明,由于磁场的作用,采用电磁搅拌法可以缩短聚苯胺聚合反应时间,合成均一的导电聚苯胺纳米线,其渗滤阈值为33.3%,含量为33.3%的聚苯胺纳米线的聚苯胺/聚氨酯涂层的电磁屏蔽性能为32.2dB,优于含量为45%的机械搅拌法制备的聚苯胺粉体,这可能是由于线性结构的导电聚苯胺在基体中能够较容易形成三维导电网络结构所致。     

Effect of electromagnetic stirring on melt pool free surface dynamics during vacuum arc remelting

The deformation of the free surface of the liquid pool in the VAR process may play a key role in explaining the apparition of surface defects on the ingot skin. In the present study, the deformation of the surface induced by electromagnetic stirring is investigated, for a simplified geometry, using CFD-based simulations, combining models for the turbulent fluid flow, heat transfer, free surface movements and electromagnetic forces. Particular attention is given to the implementation of thermal and electrical boundary conditions at the moving free surface. Verification of the developed model is carried out by comparison with the dedicated code SOLAR. The free surface dynamics of a liquid zirconium pool is then quantitatively analysed for different stirring procedures, and the effects of the stirring parameters (magnetic induction, reversal time) are predicted and discussed. The obtained results provide some insights into mechanisms by which surface deformation may influence the ingot skin solidification, leading to poor ingot surface quality.     

Theoretical Analysis and Numerical Simulation of the Feasibility of Inspecting Nonferromagnetic Conductors by an MFL Testing Apparatus

ABSTRACT

It has been widely accepted that the magnetic flux leakage (MFL) testing system can be applied only to the inspection of ferromagnetic materials. The possibility of using the MFL testing apparatus to inspect nonferromagnetic metals is discussed in this article. According to Faraday’s law of induction, eddy current rises in the conductor passing through the MFL magnetizer. The perturbation of eddy current and its corresponding magnetic field caused by defects are theoretically analyzed. Then, the finite element method is carried out to verify the theoretical analyses and extract the perturbed magnetic field signals. Furthermore, the influences of specimen conductivity and moving velocity on the detection signal amplitude are also simulated. The results show that the nonferromagnetic conductors are possible to be inspected by the MFL apparatus, and higher conductivity or inspection speed will facilitate the inspection.     

Liquid metal model experiments on casting and solidification processes

This paper is concerned with laboratory studies using liquid metals with T _melt ≤ 300°C to model the flow of metals in industrial processes. Considering three selected examples the main features of such cold models are described. In the first instance we examine an aluminium alloy investment casting process. The requirement of reducing high flow velocities was achieved by the application of a static magnetic field. Local velocity measurements as well as integrated flow rate determination were carried out using eutectic InGaSn (T _melt = 10°C). Secondly, model experiments were performed on the electromagnetic stirring of liquid metals in a cylindrical cavity. We applied a rotating magnetic field (RMF) and a travelling magnetic field and recorded flow maps by means of ultrasonic Doppler velocimetry. With the goal of an efficient 3D-mixing, measurements were made using a combination of both field types with promising results. Thirdly, we report on systematic studies of the effect of an RMF on the solidification of a PbSn alloy. Directional solidification experiments demonstrate the influence of the electromagnetically driven convection on the resulting microstructure.     

Study on Multiple Electromagnetic Continuous Casting of Aluminum Alloy

To obtain semi-solid Al alloy billet with high quality, an investigation was carried out by imposing a multiple magnetic field from the outside of a copper mold in the continuous casting. AISi6Mg2 alloy designed for semi-solid metal （SSM） processing was continuously cast through a submerged entry nozzle under various conditions. Effects of multiple magnetic field on meniscus motion, temperature distribution and billet quality were examined. The experimental results showed that meniscus disturbance caused by electromagnetic stirring could be controlled effectively and the surface quality of semi-solid AI alloy billet was improved greatly, and an uniformly fine, globular microstructure across the transverse section of the billet was achieved by optimizing the distribution of multiple magnetic field.     

Mathematical simulation of electromagnetic stirring of liquid steel in a DC arc furnace

Results are given of numerical simulation of electromagnetic stirring of metal melt in a dc arc furnace. The flow pattern and the transport of passive admixture in baths with one and two electrodes are studied. The mathematical model describes three-dimensional turbulent flow of electrically conducting liquid in the field of gravitational and electromagnetic forces. The parameters of turbulence are calculated in two approximations, namely, unsteady-state approximation by the large eddy simulation (LES) model and quasisteady-state approximation by the k-ε model.     

声级计抗电磁场辐射干扰试验研究

介绍了射频电磁场对声级计进行电磁辐射干扰的详细情况以及利用工频磁场测试装置进行声级计抗工频磁场干扰的研究设计     

磷化工艺对铁基软磁复合材料电磁性能的影响

研究了磷化工艺对铁基软磁复合材料电磁性能的影响。XRD、SEM、EDS分析和元素面分布结果表明,合适的磷化工艺能在铁粉表面生成1层很薄的非晶或纳米晶结构磷酸盐,并且包覆完整均匀。磁性能测量结果表明,室温条件下用0.01g/mL磷酸对铁粉进行磷化30min,所得到的磷化铁粉磁芯具有优异的综合电磁性能。随着磷酸浓度的增大,磷化时间的增长和磷化温度的提高,软磁复合材料磁芯的电阻率增大,中高频磁损耗不断降低,同时磁导率也有一定程度的降低。