单摆式电涡流TMD装置优化设计与模型试验研究

为实现单摆式电涡流TMD构造与磁路优化设计,探讨了TMD装置整体构造,综合理论分析、模型试验与三维电磁场有限元仿真,研究了TMD质量块与板式电涡流阻尼器(PECD)二者之间的磁场吸引力作用对TMD振动频率的影响程度,以及磁路布置对PECD等效阻尼系数的影响规律。结果表明:PECD宜安装在TMD运动质量块的底面;磁场吸引力作用将增大TMD振动频率,TMD初步设计宜适当调整初始摆长以避免TMD失谐;通过尽可能减小磁场间隙、适当加厚导磁钢板、优化铜板厚度等方法均可提升PECD耗能效果;沿TMD运动方向,相邻永磁体磁极宜交错布置,通过有限元仿真确定最优间距;沿垂直于TMD运动方向,相邻永磁体磁极宜同向布置,且间距越小越好。     

新型装配式竖向电涡流TMD试验研究

针对城市大跨度钢结构人行天桥的减振需求,研制了一种结构紧凑、装配简单的新型装配式竖向永磁式电涡流TMD样机,综合TMD样机阻尼参数测试与电涡流阻尼磁场有限元分析结果提出了电涡流阻尼的初步设计方法与磁路优化布置。结果表明:新型TMD具有优良的阻尼特性、耐久性,且易于装配,工程应用可行性强。研究得到了用于竖向TMD的电涡流阻尼磁路优选构造:导体铜板两侧的矩形永磁铁宜采用同侧极性相同、不同侧极性相反的布置方式;永磁铁宜以水平单排布置为主,间距控制在永磁铁边长的一半以内;永磁铁必须安装2排或多排时,上下2排间距不宜小于永磁铁边长。     

基于微型永电磁式涡流阻尼TMD的人行桥模型减振试验研究

针对现有结构模型减振实验用调谐质量阻尼器(Tuned Mass Damper,TMD)难以实现TMD刚度与阻尼参数完全分离、阻尼参数试验过程中无法保持恒定且难以调整问题,研制微型永磁式电涡流阻尼TMD。其性能试验与分析结果表明,微型TMD采用电涡流阻尼装置既能确保刚度与阻尼参数的有效分离,亦能实现阻尼参数稳定、简单易调。通过某大跨度人行桥模型一阶横向振动模态自由振动减振实验识别获得结构模态阻尼比及强迫振动减振实验识别获得结构模态阻尼比、结构动力响应放大倍数、结构与TMD运动相位差等,证实微型永磁式电涡流阻尼TMD用于结构模型减振实验的可行性与有效性。     

竖向TMD用板式电涡流阻尼器磁路对比分析

为提升竖向TMD用板式电涡流阻尼器(PECD)的耗能效率,分别开展了典型竖向电涡流TMD样机的阻尼性能测试与有限元仿真分析,基于相邻永磁体有效耦合率性能指标,采用三维电磁场有限元分析方法分别优化了外置式与内置式PECD的磁路设计,并对比分析了各磁路的耗能效率、耐久性与占用空间等。研究结果表明:提出的相邻永磁体有效耦合率可以很好地表征永磁体相互作用对PECD等效阻尼系数的影响程度,有助于指导磁路优化设计;外置式与内置式PECD磁路优化设计方案在相邻永磁体磁极布置、水平与竖向适宜间距等方面均存在较大差别;各最优磁路永磁体用量一定时,内置式PECD的等效阻尼系数略低于外置式PECD(附加导磁钢板),但远高于外置式PECD(无导磁钢板);装配内置式PECD的竖向TMD结构相对紧凑,且耐久性也相对较高。     

板式电涡流阻尼器有限元仿真与参数优化

为了实现板式电涡流阻尼器的精确、高效和优化设计,首先以某一电涡流调谐质量阻尼器为计算模型,验证了采用三维电磁场有限元稳态分析方法计算板式电涡流阻尼器阻尼系数的准确性。利用三维磁场有限元稳态分析法,分析了板式电涡流阻尼器的各设计参数对阻尼比的影响。结果表明,三维磁场有限元稳态分析方法能够准确计算板式电涡流阻尼器的阻尼系数;导体板厚度、导磁钢板厚度、永磁体间距、空气间隙和永磁体的排列方式对板式电涡流阻尼器的阻尼性能影响显著,在设计中应综合考虑。     

冲击载荷下圆筒型电涡流阻尼器动力特性研究

为研究圆筒型电涡流阻尼器在冲击载荷下的动力特性,建立冲击载荷下电涡流阻尼器动力学模型,利用Maxwell分析软件建立圆筒型电涡流阻尼器在冲击载荷作用下的有限元模型,分析电涡流阻尼器工作时的气隙磁场与涡流分布。研究了制动减速阶段电涡流阻尼力和阻尼系数随速度变化的关系,分析工作气隙、导体筒厚度及磁轭厚度等参数对电涡流阻尼器制动性能的影响。研制了电涡流阻尼器冲击加载试验装置,试验结果与仿真结果吻合较好。研究结果表明:在保证动子运动精度的前提下,工作气隙尽可能小,磁轭厚度取永磁体厚度的3/4,导体筒厚度取1～2 mm有利于提高电涡流阻尼器的阻尼系数;电涡流阻尼器在冲击载荷作用下具有良好的缓冲制动性能,在武器发射、列车制动等冲击制动领域具有重要的应用价值。     

多层板式电涡流阻尼器构型与磁路优化分析

为提升板式电涡流阻尼器(PECD)的耗能效率,对比分析了单层与多层PECD典型构型的紧凑性与材料利用率,发展与完善了多层PECD构型与磁路优化设计。基于某单排式多层PECD样机阻尼性能测试结果,校验了三维电磁场有限元稳态分析法预测PECD等效阻尼系数的精度;仿真分析获得了永磁体与导体铜板之间的磁场间隙、永磁体的固定材料、间距与布置方式等参数对多层PECD等效阻尼系数的影响规律,据此提出了多层PECD的优化构型与磁路。结果表明:与单层PECD相比,多层PECD耗能效率得到有效提升,结构也更为紧凑;磁场间隙及永磁体的固定材料、布置方式与间距等对PECD等效阻尼系数均有显著影响,其中磁场间隙、相邻永磁体磁极布置与间距等存在最优参数。多层PECD的优化构型与磁路为:磁场间隙宜尽可能减小;采用非导磁材料固定永磁体;同侧永磁体宜阵列布置;永磁体沿阻尼器运动方向磁极宜相反布置,间距取0.2倍永磁体同向尺寸;永磁体沿垂直于阻尼器运动方向磁极宜相同,且间距越小越好。     

电涡流单摆式TMD阻尼特性的有限元分析

在高层及超高层建筑的抗风和抗震中,单摆式调谐质量阻尼器(PTMD)有着较为广泛的应用。传统的PTMD采用油阻尼器作为阻尼装置。然而,油阻尼器具有施工不便、耐久性差、阻尼难以调节等缺点,而且这还会给PTMD带来附加刚度,不利于PTMD的频率设计。在前人的研究成果基础上,利用电涡流阻尼代替油阻尼器,提出一种新型的电涡流单摆式TMD(EC-PTMD),并利用大型电磁场有限元分析软件Opera3D对其进行建模分析。对导体板厚度、导磁钢板厚度及其磁导间距进行了参数分析,结果表明:电涡流阻尼的大小随着导体板、导磁钢板厚度的增加基本呈非线性增长;随着磁导间距的增大,电涡流阻尼呈非线性减小。在用二次函数拟合磁导间距与有效电涡流阻尼系数间关系的基础上,提出一种有较强适用性的EC-PTMD的设计方法。     

冲击载荷下永磁式电涡流减振器设计及动态特性分析

为研究轮式车辆的电涡流减振器在行进间冲击载荷下的动态特性,结合电涡流理论设计了一种永磁式电涡流减振器,并基于等效磁路模型和麦克斯韦方程分析了其导体筒表面空气间隙处磁感应强度与阻尼力之间的关系;同时,利用有限元法对永磁式电涡流减振器的静、动态磁场分布进行了研究,并分析了不同结构参数对其阻尼特性的影响及不同运动速度下的示功特性曲线。通过建立1/4车辆悬架动力学模型和基于高斯滤波白噪声的随机路面激励模型,对车辆行进间冲击载荷下永磁式电涡流减振器的动态特性进行了分析。结果表明：永磁式电涡流减振器的磁场在动态条件下会发生退磁以及磁感线趋速聚集现象,各结构参数对其阻尼特性的影响较大;永磁式电涡流减振器的响应速度快,压缩、复原阻尼力恒定且平稳,可以高效、快速地消除轮式车辆越野时受到的路面激励和车载武器射击时的冲击载荷,能够有效抑制车体振动。研究结果对提高轮式车辆的越野机动性以及车载武器的射击精度具有重要意义。     

新型竖向电涡流-磁力混合阻尼装置试验研究

针对大跨轻质结构的减振需要,研制了一种新型竖向电涡流-磁力混合阻尼器样机.介绍混合阻尼器的减振原理及振动方程;接着介绍了3种不同的磁路设计和制作过程;随后对样机进行试验,测量其动力参数和减振性能.结果 表明:在铜板后方和底板上方安装磁铁均能改变阻尼器的附加刚度;特定磁路设计减少电涡流阻尼系数,增大等效磁力阻尼系数和负刚...     

双质量磁吸振器理论与试验研究

在单质量磁吸振器的基础上提出了双质量磁吸振器的设计方案，并对其减振性能进行了理论和试验研究。正弦扫描和窄带随机振动试验结果表明，平板小阻尼系统在添加双质量磁吸振器后，比单质量磁吸振器振动水平明显减小。     

Use of paired, bonded NdFeB magnets in redox magnetohydrodynamics

Bonded neodymium-iron-boron (NdFeB) permanent magnets in a paired configuration were successfully used to control mass transport in redox-based, magnetohydrodynamics (MHD). Control of fluid flow based on magnetic fields has potential for use in portable lab-on-a-chip (LOAC) and analytical devices. Bonded magnets, composed of magnetic powder and organic binder materials, are less expensive and easier to fabricate and pattern than electromagnets and sintered permanent magnets, which have been previously used in MHD studies on electrochemical systems. The ability to pattern bonded magnets near and around the electrodes is expected to allow for better control over the magnetic field distribution and solution flow. Current was generated at an 800-microm-radius platinum disk electrode in a solution of 0.06 M nitrobenzene and 0.5 M tetra-n-butylammonium hexafluorophosphate in acetonitrile. Increases in limiting current in the presence of the magnetic field, which indicate enhancement in mass transport, for sintered (210+/-14%, N = 4, where B(r) = 1.23 T and magnetic field strength is 0.55 T) and bonded (94+/-8%, N = 4, where B(r) = 0.41 T and magnetic field strength is 0.20 T) magnets, were similar to those obtained using an electromagnet with the same magnetic flux densities. The magnetic field strength and not the magnet type is important in controlling fluid flow, which is encouraging for integration of bonded permanent magnets into LOAC devices.     

阻尼柔性连接TMD的最优动力特性

本文研究了阻尼柔性连接TMD在控制结构地震反应时的最优动力特性。基于导出的设置阻尼柔性连接TMD结构位移传递函数，建立了结构的动力放大系数（DMF）设计公式。于是TMD的优化准则可选为：最大动力放大系数中最小值的最小化（Min.Min.Max.DMF)。通过最优搜寻得不同刚度比R时TMD最优调谐频率比、最优阻尼比和相应的Min.Min.Max.DMF。为比较，阻尼刚性连接（R＝0）的TMD也被考虑。数值结果表明，阻尼柔性连接TMD的刚性比R最好取为0.5。因此，目前的研究拓宽了TMD的应用范围。     

General Expressions for the Magnetic Flux Density Produced by Axially Magnetized Toroidal Permanent Magnets

This paper presents analytical-integral expressions which evaluate the magnetic flux density radial and axial components' on- and off-axis of axially magnetized toroidal permanent magnets. The pieces, when used in magnetic electron beam focusing structures called periodic-permanent magnets (PPMs), can be employed in microwave vacuum electronics devices. These expressions can be adapted to computational algorithms, especially those developed based on mathematical commercial codes, aiding the investigation of the effect of magnetic fields on electron beam dynamics. Comparisons between analytical-integral expressions and theoretical and experimental data are also presented and discussed.     

Calculation of equipotentials and flux lines in axially symmetrical permanent magnet assemblies by computer

Two equivalent theoretical models of permanent magnets are used to develop algorithms for numerically computing the magnetic scalar potential and the magnetic vector potential in the vicinity of an axially symmetric array of pole pieces and permanent magnets. A computer program based on these algorithms calculates equipotential surfaces and flux lines in and around the magnets and pole pieces. In deriving the algorithm for numerically calculating the vector potential a relationship between the magnetic scalar potential and the vector potential was found which enables the program to calculate the vector potential from the scalar potential distribution and thus generate equipotentials and flux lines with only one iterative calculation. An algorithm which calculates the scalar potential of a "floating" pole piece, that is, one on which the scalar potential has not been specified, is developed. The vector potential around the pole piece is determined from the scalar potential calculation, and this information is used to calculate the vector potential and the flux lines within the pole piece. The computer program calculates the coordinates of all points at which the equipotential lines and flux lines cross the Liebmann net. This information is fed to a cathode ray tube plotter which generates a field plot. To deal with systems in which macroscopic currents are present as well as permanent magnets, the iterative Liebmann net calculation of the vector potential is developed, and a method of applying Neumann boundary conditions to the vector potential at high-permeability surfaces is described.     

随机地震作用下TMD等效附加阻尼比研究

针对随机地震作用下TMD给结构提供的附加阻尼比展开研究。随机地震动采用过滤白噪声Kanai-Tajimi功率谱模型,并将Kanai-Tajimi功率谱模型描述的场地过滤效应表示成传递函数形式,进而推导出结构相对于基岩的位移动力放大系数。然后,结合SRSS方法,以结构位移响应均方值作为评价准则,提出了随机地震作用下TMD提供给结构任意阶模态的等效附加阻尼比理论公式。最后,以某景观塔作为工程算例展示了TMD等效附加阻尼比的求解流程,并验证了该等效附加阻尼比公式的有效性。算例分析结果表明,使用等效附加阻尼比指标来评估TMD减震性能是合理有效的,且使用推导的TMD等效附加阻尼比理论公式能更准确地评估TMD对结构位移响应的控制效果。     

磁约束阻尼的减振机理

采用在约束层端部上设置永磁体的新方法可使阻尼层获得比传统约束阻尼处理方法更高的剪应变，从而增强粘弹层的阻尼耗能。本文应用Hamilton原理，考虑永磁体的影响，推导了对称双层夹心悬臂梁的运动方程，对模型进行了实验验证；分析了一阶共振时，永磁体对共振振幅、阻尼层剪应变、约束层作用力的影响，阐明了新型的磁机敏约束阻尼方法的减振机理。     

Magnetic Field-Based Eddy-Current Modeling for Multilayered Specimens

Eddy-current inspection for nondestructive evaluation has traditionally been investigated in terms of coil impedance signals via theoretical and experimental methods. However, advanced eddy-current techniques use solid-state sensors such as Hall devices, giant magnetoresistive sensors, anisotropic magnetoresistive sensors, and superconducting quantum interference devices for magnetic field measurement to achieve better sensitivity and high temporal and spatial resolution in material evaluation and characterization. Here, we review the Dodd and Deeds integral model and use the truncated region eigenfunction expansion (TREE) method for computation of the magnetic field. This results in series expressions instead of integral ones. Thus, the computation is both simplified and speeded up so that it becomes convenient for solving one-dimensional eddy-current inverse problems. We compare the theoretical results from the analytical model with the results from a numerical simulation based on the finite-element method in terms of accuracy and computation time.     

Analysis of a Lorentz force based vibration exciter using permanent magnets mounted on a piezoelectric stack

This work presents performance analysis of a Lorentz force based non-contact vibration exciter by mounting a couple of permanent magnets on a piezoelectric stack. A conductor is attached to the structure to be excited and is placed midway between unlike poles of a couple of permanent magnets. The permanent magnets are placed on a piezoelectric stack. This stack, because of its nano-positioning capabilities, can impart an accurate and adjustable harmonic vibratory motion to the couple of permanent magnets. The piezoelectric stack, because of its high stiffness remains uncoupled with the dynamics of the structure. Due to the relative motion between the magnets and the conductor, Lorentz force is generated within the conductor. This Lorentz force is responsible for vibration of the structure in a plane parallel to the pole faces of the magnets. This keeps the magnetic field almost independent of the vibration of the structure and the chance of the structure hitting the magnet during large vibration is totally eliminated. If the amplitude of displacement of the stack is kept constant, the non-contact excitation force in this exciter remains proportional to the excitation frequency. Though use of this exciter eliminates mass (apart from that of the conductor attached to the structure) and stiffness coupling, a known damping term gets added to that of the excited structure.     

具有调谐质量阻尼器(TMD)的干摩擦隔振系统的研究

本文基于增量谐波平衡（IHB）法研究了顶部装有TMD的干摩擦隔振系统及TMD对隔振性能的影响，进而在干摩擦隔振系统中引入了主动控制的概念，分析了主动控制对隔振系统性能的影响，为干摩擦隔振系统在工程上的应用提供了理论依据。