On the characteristics of an ultra-low frequency nonlinear isolator using sliding beam as negative stiffness

A novel structured ultra-low frequency nonlinear passive isolator is presented. The isolator is composed of a knife-edge supported sliding beam which offers negative stiffness and a vertical mechanical spring in parallel to get quasi-zero dynamic stiffness. The static characteristics of the isolator are studied. Assuming light viscous damping, the dynamic behavior is investigated and the response under harmonic excitation is derived using a simple approximation. Frequency response curves (FRCs), which exhibit complex double jump phenomenon, are obtained by harmonic balance method (HBM). The limitation of the excitation force level is obtained. The force transmissibility is derived and compared with an equivalent linear system with the same damping ratio. The isolation performance of the nonlinear isolator is shown to outperform the linear system for providing a wider isolation region. The influence of system parameters on the transmissibility is examined and some useful guidelines are given.     

金属橡胶环形隔振器弹性阻尼性能的计算

利用金属环形元件弹性模量的计算方法，推导出金属椽胶环形隔振器弹性模量的计算公式，并通过了实验验证。通过对大量实验结果的分析，推导出金属橡胶环形隔振器平均刚度、内摩擦力及能量耗散系数与金属丝直径、环形隔振器的几何参数、金属橡胶元件的相对密度之间的关系。基于弹性迟滞同线的形成原理，建立了该种隔振器的弹性迟滞回线的数学模型，并通过了实验验证。借助该数学模型和有限元计算方法，可以直接求得任意金属橡胶环形隔振器的弹性阻尼性能，大大减少了实验工作量。     

橡胶减振器动刚度有限元数值预测方法研究

提出了一种基于有限元的橡胶减振器动刚度预测方法,对方法中的材料本构模型、有限元模型、动刚度预测流程进行了分析和研究。利用此方法对某惯导减振器进行预测,获得减振器动刚度和阻尼值,代入单自由度分析模型后预报出的动响应结果与试验结果基本一致。用该方法能捕捉到由于减振器刚度变化而引入的高频率共振峰,表明该方法具有更高的精度。     

汽车悬架磁流变减振器的优化设计及仿真

基于磁流变减振器在汽车悬架减振系统半主动控制中的广泛应用,根据磁流变液的特点和磁流变减振器阻尼力与结构参数的关系,设计了新型的磁流变减振器,并对影响磁流变减振器性能的参数进行了优化和仿真.仿真计算表明,该磁流变减振器设计是一种能优化阻尼力的有效算法.     

准零刚度扭转隔振器振动传递特性研究

针对一种应用连杆弹簧负刚度结构所设计的正负刚度并联扭转隔振器,通过分析其设计参数,得到了其在静平衡位置达到准零刚度的条件。针对所述系统,建立二自由度非线性动力学微分方程,应用谐波平衡法求解了准零刚度隔振器的振动响应。考虑激励幅值、系统阻尼和转动惯量等因素,从扭转振动力矩传递和扭转振动功率流传递两个角度分析了准零刚度隔振系统的非线性振动传递特性。结果表明,此隔振系统具有良好的低频隔振效果,且表现为振动传递的硬特性;从功率流角度的分析还表明,系统的瞬时传递功率流峰值与输入功率流和耗散功率流的变化趋势保持一致。在低于共振区域的低频区间内,隔振系统前后两端的转动惯量对系统振动具有较大影响。最后,对扭转隔振器的振动隔离特性进行了试验验证,试验结果表明,隔振器具有良好的低频振动隔离特性。     

Experimental investigation on the hysteresis behavior of the wire rope isolators

Vibration isolation has been widely applied to filter the external excitation energy and impact forces in building structures and equipment. Wire rope isolator (WRI), a kind of isolator for vibration and shock isolation, shows a better performance in attenuating these forces. WRIs are able to deviate these external forces through their mechanical configuration and high-energy dissipative capabilities. The application of WRI demands knowledge of its behavior and the relation between various geometrical properties and input force. The present work investigates the influence of geometrical parameters, such as wire rope diameter, number of coils, and displacement amplitude on the hysteresis behavior of WRI under quasi-static loading in both vertical and horizontal directions. The hysteresis behavior of different WRIs was evaluated using the calculated parameters from hysteresis force-displacement curves: energy loss ratio (ELR), and effective stiffness. The study indicates that the geometric properties significantly influence the effective stiffness than the energy loss ratio. It is observed that, increased displacement amplitude results in decreased ELR and hence damping capabilities. The study also confirms that the wire rope isolator possesses a good ability in damping through its stiffness and high-energy dissipation capability.     

Parameter identification of analytical and experimental rubber isolators represented by Maxwell models

A parameter identification method based on constraint optimization is developed for a single mass elastomeric isolation system where the isolator is represented by a Maxwell model with two or more Maxwell elements. The method utilizes measured static stiffness and frequency response of the isolator in a single mass configuration with constraints on the natural frequency and damping ratio. It is revealed through analytical examples that Maxwell models consisting of only one or two Maxwell elements can accurately replicate the dynamic behavior of Maxwell systems having two or more Maxwell elements. To experimentally evaluate the method, three different rubber isolators are considered. For all three rubber isolators, it is shown that Voigt models are incapable of accurately representing the measured static stiffness and frequency response. Although identified Maxwell models having only one Maxwell element can match the measured natural frequency, damping ratio and static stiffness, they cannot match the measured frequency response curves well. However, identified Maxwell models with two Maxwell elements can accurately represent the measured static and dynamic characteristics of the real elastomeric isolation systems.     

电子设备橡胶隔振器静动态特性分析方法研究

橡胶隔振器采用粘弹性阻尼材料进行振动、冲击防护与控制,传统做法是依靠大量的经验公式和试验数据进行试错设计,效率低,成本高.文中针对电子设备中橡胶隔振器的静动态特性分析方法问题,系统建立了一套基于非线性有限元方法的求解策略.以某型橡胶隔振器为例,获得了其静刚度、蠕变和松弛特性等静态特性以及迟滞回环、谐响应和冲击响应等动态特性,并对橡胶隔振器设计和选型中的2个关键参数(橡胶超弹性和匹配质量)进行了讨论,可供橡胶隔振器设计方法研究参考.     

磁流变减振器磁场特性分析及试验研究

设计了磁流变减振器磁芯磁路,建立了磁路的仿真模型,仿真研究了磁路的磁场特性,用实验的方法对仿真模型进行了验证和修正;在此基础上,建立了整个磁流变减振器的仿真模型,仿真研究了其磁场分布规律及不同参数下阻尼孔附近的磁通密度.研究结果表明,磁芯直径、工作缸壁厚、阻尼通道长度和线圈电流是影响磁场特性的主要因素,合理选择磁路结构参数可使其性能得到最大发挥.设计并制造出一种车辆单筒充气式磁流变减振器,对其进行了台架试验,得到不同电流下的减振器示功特性图,研究发现,通过调节减振器励磁线圈中的电流获得不同强度的磁场,在磁场作用下,磁流变液粘度发生变化,从而改变减振器的阻尼特性,减振器的饱和工作电流约为2A.试验验证了磁路设计的正确性,并为实现车辆磁流变半主动空气悬架控制研究奠定了基础.     

单层隔振系统中弹性基座的振动与声辐射特性

通过电－力类比的方法建立了单层隔振系统的导纳分析模型,研究了输入到弹性 基座的振动功率流与基座辐射声功率,并通过计算机仿真分析了隔振参数对弹性基 座声振特性的影响,以及隔振装置安装位置对弹性基座振动及其声辐射的影响,提 出了单层隔振系统中弹性基座噪声控制的基本原则。     

圆筒形囊式隔振器静态和动态特性研究

介绍了利用材料试验机测试囊式空气弹簧隔振器静态、动态特性的原理及方法,并对某试样进行了测试和分析。结果表明,囊式空气弹簧隔振器的额定荷载及额载静刚度与充气气压基本成线性关系,额载动刚度随气压的增加而变大,振动频率对动刚度影响不大。     

山地地铁浮置板轨道支撑结构钢轨波磨机制研究

基于轮轨系统摩擦自激振动的观点,研究山地地铁线路长大坡道圆曲线段处出现的典型钢轨波磨现象。利用SIMPACK建立山地地铁车辆-轨道动力学模型,验证了列车通过长大坡道圆曲线段外侧轮轨间的蠕滑力处于饱和状态;建立相应区段上由导向轮对-钢轨-道床所组成的轮轨系统有限元模型,采用复特征值分析法从频域角度研究轮轨系统的稳定性;采用控制变量法研究浮置板结构中隔振器的垂向刚度和垂向阻尼、扣件的垂向刚度和垂向阻尼对轮轨系统摩擦自激振动的影响规律。结果表明：在长大坡道圆曲线段上,外侧轮轨间饱和蠕滑力引起的轮轨摩擦自激振动是导致该区段外轨处钢轨波磨产生的主要原因,诱导频率为459.63 Hz。参数化分析表明,轮轨系统摩擦自激振动随隔振器的垂向阻尼和垂向刚度的增大呈增大趋势,随扣件的垂向阻尼的增大呈降低趋势,而随扣件垂向刚度的增加呈先减小后增大的趋势;当扣件的垂向支撑刚度为40 MN/m时,钢轨波磨最不容易发生。     

Friction behavior of magnetorheological fluids with different material types and magnetic field strength

Magnetorheological (MR) fluid is a type of a smart material that can control its mechanical properties under a magnetic field. Iron particles in MR fluid form chain structures in the direction of an applied magnetic field, which is known as MR effect, resulting in variation of stiffness, shear modulus, damping and tribological characteristics of MR fluid. As MR effect depends on the density of particles in the fluid or the strength of a magnetic field, the experiments are conducted to evaluate the friction property under reciprocating motion by changing the types of MR fluid and the strength of a magnetic field. The material of aluminum, brass, and steel are chosen for specimen as they are the most common material in mechanical applications. The surfaces of specimen are also observed by optical microscope before and after experiments to compare the surfaces with test conditions. The comparing results show that the friction coefficient increases as the strength of a magnetic field increases in regardless of types of MR fluid or the material. Also the density of particle in MR fluid affects the friction characteristic. The results from this research can be used to improve the performance of mechanical applications using MR fluid.     

基于磁流变技术的发动机隔振控制

悬置阻尼和刚度可调对发动机在宽频范围内实现积极隔振具有重要意义.在建立发动机3自由度隔振模型基础上,提出用可调阻尼的磁流变阻尼器和可调刚度的磁流变弹性体构成磁流变并联悬置系统,以降低发动机对基座的垂向传递力和抑制横向动反力矩为目标,设计出用仿人智能思想在线修改参数的垂直隔振模糊自适应控制器,并对各磁流变并联悬置的刚度和阻尼进行协调控制.用Matlab对发动机整机隔振进行仿真,搭建出发动机隔振台架试验系统,在宽频激励条件下对不同悬置的隔振效果进行对比研究.仿真表明基于磁流变并联悬置的发动机隔振控制具有明显的优势,台架试验结果表明相对于橡胶和液压悬置,磁流变液悬置能在较宽频范围把力和力矩的绝对传递率降低到约30%以内,可提高乘坐舒适性.     

卫星遥感器微振动隔离用液体阻尼隔振器

针对卫星平台的微振动,提出了具有良好高频衰减及共振峰控制性能的松驰型液体阻尼隔振器。建立了松弛型液体阻尼隔振模型,从传递率的角度分析了提出的松驰型液体阻尼隔振器与传统隔振模型的区别。使用波纹管提供刚度及密封,基于小孔阻尼结构形式,设计了松弛型液体阻尼隔振器并求解了系统的阻尼因子。对所设计的隔振器进行了传递率测试,结果表明,松弛型液体阻尼隔振器在共振频率处能够提供大阻尼,将共振放大倍数控制在2倍以内;在高频隔振区能提供小阻尼,100Hz衰减率超过95%,隔振性能优于传统隔振器。得到的结果和理论预测吻合较好。该项研究对松弛型液体阻尼隔振器的设计以及其在遥感器微振动隔离的应用上具有很强的指导作用。     

基于性能最优的磁流变阻尼器励磁线圈缠绕方法研究

双线圈活塞式磁流变阻尼器是一种通过励磁线圈产生磁场,以控制输出阻尼力的器件,其励磁线圈的缠绕方法直接影响磁流变阻尼器磁场分布和动态响应时间。在磁流变阻尼器性能模型的研究基础上,以阻尼动力和动态性能为最优目标,分析了两励磁线圈多种缠绕方法对阻尼间隙的磁场分布和控制电路的响应时间的影响,综合考虑了外界控制电路的电流负担和电能损耗,获得了励磁线圈采用反向串联的最优缠绕方法。研究结果为磁流变阻尼器的结构设计和参数优化提供了参考依据。     

基于小波变换的金属橡胶干摩擦系统阻尼识别

针对金属橡胶隔振器阻尼系数难于识别的特点，探讨了一种基于小波变换的干摩擦阻尼识别方法，针对金属橡胶隔振器在自由振动下的动态响应信号进行包络的提取，同时采用了Hilbert变换和Morlet小波变换这两种包络提取方法，并将分析结果与利用常规阻尼识别方法得出的结果进行了对比。结果表明，该方法具有足够的精度，并且易于实现。     

金属橡胶与弹簧组合型隔振器动静态性能的分析

研究了金属橡胶与弹簧组合型隔振器的刚度和阻尼性能与弹簧的刚度，金属橡胶元件的相对密度，以及金属橡胶元件的成形工艺之间的关系，建立了单向载荷作用下金属橡胶与弹簧组合型隔振器的能量耗散系数与阻尼系数之间的关系。分析了载荷作用次数及振动频率对隔振器性能的影响，提出了提高其寿命的方法。     

机械密封浮动环处O形密封圈动态刚度和阻尼的测量

利用INSTRON高频疲劳试验机对O形辅助密封圈进行松弛试验,获得气体和水润滑2种状态下O形辅助密封圈载荷随时间的变化曲线,通过数据处理获得其轴向动态刚度和阻尼,根据经验公式进一步确定其角向刚度和阻尼。分析O形辅助密封圈在气体和水润滑下动态刚度和阻尼随着加载频率、位移、转速的变化规律。结果表明:在气体和水润滑下,在一定范围内辅助密封圈的动态刚度和阻尼值随加载频率的升高而增大;在水润滑状态下,随着加载位移量的增大,辅助密封圈的动态刚度和阻尼值逐渐变小;在气体和水润滑下,都存在一转速临界值,在临界值之前,随转速的增加,轴向动态刚度增大,轴向动态阻尼减小;在临界值之后,轴向动态刚度和阻尼值不再变化,稳定在某一值。     

A negative stiffness vibration isolator using magnetic spring combined with rubber membrane

The most important characteristic of a passive vibration isolator is its natural frequency and load capacity. The vibration isolation performance of a passive vibration isolator in low input frequencies is considerably improved by reducing its natural frequency. This paper presents a negative stiffness magnetic suspension vibration isolator (NSMSVI) using a magnetic spring combined with rubber membranes to obtain lower natural frequency. To study the vibration isolation performance of the NSMSVI, the stretching force of the rubber membrane is measured through experiments. The stiffness of the rubber membrane comes from the derivative of the stretching force. A parametric study of load capacity, axial magnetic stiffness, and natural frequency of the magnetic spring is also performed. Consequently, as a case study, the size dimensions of the magnetic spring are determined. An NSMSVI table is set up for experimental validation, after which the transmissibility curves of the NSMSVI are calculated and tested. Experimental results show that the lowest natural frequency of the NSMSVI reaches 1.5 Hz with a maximum attenuation of -40 dB between 0 Hz and 100 Hz, whereas the NSMSVI has the maximum load capacity at the lowest stiffness. This paper essentially provides an efficient method to construct a negative stiffness vibration isolator for practical applications.