Modeling the fine particle impact damper

The fine particle impact dampers (FPIDs) using plastic deformation of fine particles as irreversible energy sink can exhaust much more vibration energy than single mass impact dampers (SMIDs) and thus can work well in low frequency domain. A numerical model is set up in this paper to capture the complex physics involved in the FPID. Experimental results on a cantilever beam with FPID showed good agreement with the model predictions. We show that in all cases the damping performances of the FPID are much better than that of the SMID, and fine particles enrolled in the FPID play a key role in vibration energy dissipation. The damper clearance and the mass ratio are two important parameters for the damping ability of the FPID, for which an optimal combination of them exists targeting the largest damping ability.     

Free vibration analysis of sandwich beam carrying sprung masses

In this paper, free vibration of three-layered symmetric sandwich beam carrying sprung masses is investigated using the dynamic stiffness method and the finite element formulation. First the governing partial differential equations of motion for one element are derived using Hamilton’s principle. Closed form analytical solution of these equations is determined. Applying the effect of sprung masses by replacing each sprung mass with an effective spring on the boundary condition of the element, the element dynamic stiffness matrix is developed. These matrices are assembled and the boundary conditions of the beam are applied, so that the dynamic stiffness matrix of the beam is derived. Natural frequencies and mode shapes are computed by the use of numerical techniques and the well known Wittrick–Williams algorithm. Free vibration analysis using the finite element method is carried out by increasing one degree of freedom for each sprung mass. Finally, some numerical examples are discussed using the dynamic stiffness method and the finite element formulation. After verification of the present model, the effect of various parameters such as mass and stiffness of the sprung mass is studied on the natural frequencies.     

Effect of viscous heating in fluid damper on the vibration isolation performance

Fluid viscous damper is an important component of a whole spacecraft vibration isolator and many other isolators applied in different areas. In this paper, the interaction between viscous heating and damping force in a fluid viscous damper is considered. And a thermodynamic model of the fluid viscous damper, which includes a dynamic equation and the thermal balance equation, is developed. As the system is time varying in the application of whole spacecraft vibration isolation, the effect of viscous heating on the vibration isolation performance is numerically studied both in the frequency domain and the time domain. From the numerical analysis, it is found that the temperature rise mainly causes shifts of resonant frequencies and larger amplification factors at resonances.     

无阻尼动力吸振器吸振的理论分析与试验研究

本文分析了无限尼动力吸振器吸振的频率特性以及无阻尼动力吸振器多数的选择。模型试验结果与理论分析结果吻合。     

粘滞阻尼器在蒸汽发生器振动响应中的应用与研究

我国是一个多震国家,核电站关键设备如蒸汽发生器、蒸汽管道等都需要采用主动或者被动控制方式进行减振,以防止在地震灾害中受到破坏。为了提高蒸汽发生器在地震载荷作用下的振动性能,必须对比安装与未安装阻尼器的蒸汽发生器在相同地震载荷下的响应参数,根据对响应的安全校核,验证阻尼器的减振效果是否达到要求。然后根据最优设计理论,计算出最佳阻尼器安装方式,使得蒸汽发生器在给定条件下变形位移最小。分析结果表明,通过优化阻尼器参数和安装位置,能够明显提高蒸汽发生器减振的效果。     

新型挤压油膜阻尼器OSFD的理论研究

将O型环阻尼器与挤压油膜阻尼器组合使用，可以克服SFD设计中固有的缺陷，通过对刚性转子的不平衡响应分析表明，OSFD的设计既可以满足正常设计工况下的小不平衡量，又可以对较大的不平衡量起到良好的减振作用，从而扩大了阻尼器的适用范围，且结构简单，有利于广泛应用。     

被动式电磁阻尼器对转子振动进行控制的机理探讨和实验研究

设计了一种新型的被动式电磁阻尼器,其采用直流稳压电源供电,无需控制。本文对该阻尼器用于转子振动控制的机理进行了探讨,实验研究了该阻尼器的减振、增稳效果。结果表明,该阻尼器减振效果明显,结构简单,性能可靠,成本低,有推广应用价值。     

Free vibration analysis of Euler-Bernoulli beam with double cracks

In this paper, the influence of two open cracks on the dynamic behavior of a double cracked simply supported beam is investigated both analytically and experimentally. The equation of motion is derived by using the Hamilton’s principle and analyzed by numerical method. The simply supported beam is modeled by the Euler-Bemoulli beam theory. The crack sections are represented by a local flexibility matrix connecting three undamaged beam segments. The influences of the crack depth and the position of each crack on the vibration mode and the natural frequencies of a simply supported beam are analytically clarified for the single and double cracked simply supported beam. The theoretical results are also validated by a comparison with experimental measurements.     

Improved identification of squeeze-film damper models for aeroengine vibration analysis

Numerical solution of the Reynolds equation imposes a prohibitive computational cost on the dynamic analysis of practical squeeze film damped turbomachinery. To surmount this problem, the present paper develops the use of Chebyshev polynomial fits to identify finite difference (FD) solution of the incompressible Reynolds equation. The proposed method manipulates the Reynolds equation to allow efficient and accurate identification in the presence of cavitation, the feed-groove, feed-ports, end-plate seals and supply pressure. The ability of Chebyshev polynomials to rapidly reproduce FD routines is demonstrated. The bearing models developed are experimentally proven to give more accurate results than alternative analytical bearing models.     

Design and test of a solid material damper for a rotor bearing system

For a rotor bearing system operating at high speed, a solid material flexible damped support called here a solid material damper has been designed and tested. The properties of the damper can be selected and adjusted to provide the necessary damping levels to get the vibration of the rotor under control. This is especially useful for a flexible rotor running in the vicinity of a critical speed or over the threshold speed obtained from calculations on the basis of linearized hydrodynamic forces. The damper was fabricated and installed and its ability to restrain effectively the rotor from vibration was demonstrated by means of an operating test.     

Modelling of viscoelastic damper support for reduction in low frequency residual vibration in machine tools

Residual vibrations deteriorate the accuracy and productivity of precision machine tools. Rocking vibration is excited by feed motion. Rocking vibration is the mode in which the entire machine vibrates and is the main source of residual vibrations at low frequencies. The characteristics of rocking vibration are influenced by the characteristics of the machine support structure. Thus, it is necessary to increase the damping of the machine support structure to reduce the residual vibrations caused by rocking vibration. In addition, it is important for machine tools to be stiff to reduce vibrations caused by the acceleration of feed drives. Conventional passive damper supports decrease the stiffness of a machine support structure while increasing the damping. Consequently, a passive viscoelastic damper system is developed to increase support damping without decreasing stiffness by focusing on the horizontal component of rocking vibration. However, the proposed damper damping capacity has a magnitude dependency. This makes it difficult to quantitatively determine the damper area in machine tools to reduce rocking vibrations to the required level. In this study, the developed damper is modeled using a viscoelastic four element model. Because of the nonlinearity of the model, an iterative time domain calculation method is introduced for the simulation. This method enables us to quantitatively estimate the effect of the damper on the machine tool. Based on the model proposed in this study, the proposed damper system can be applied to various machine tools to reduce the residual vibration without adjusting the damper area on the machine tool by a trial and error method.     

汽车动力传动系双质量飞轮式扭振减振器特性分析

分析几种典型双质量飞轮式扭振减振器的结构,对其工作原理进行详细阐述,着重研究四种典型双质量飞轮式扭振减振器的弹性特性和扭转刚度,对汽车动力传动系双质量飞轮式扭振减振器的选型和设计具有一定的参考价值.     

高耸闪蒸塔调谐质量阻尼减振技术的数值分析

针对高耸闪蒸塔在强风作用下振动响应过大的问题,将调谐质量阻尼器（TMD）减振技术应用到高耸闪蒸塔风振控制中,以保证设备运行安全并延长其使用寿命.通过Matlab数值模拟,研究了TMD安装后闪蒸塔顶端的风振能量减少率以及寻找最优参数.在此基础上,总结了能量减少率等值线图,可以通过协调二者的关系来解决TMD运行空间有限的难题.研究结果表明：TMD可以有效控制高耸闪蒸塔进行风振响应,在最优匹配参数下,TMD能够降低闪蒸塔的顶端振动能量约47.07％,为工程实际应用提供了一定参考.     

Modeling and testing of a field-controllable magnetorheological fluid damper

In this study, an experimental and a theoretical study were carried out to predict the dynamic performance of a linear magnetorheological (MR) fluid damper. After having designed and fabricated the MR damper, its dynamic testing was performed on a mechanical type shock machine under sinusoidal excitation. A theoretical flow analysis was done based on the Bingham plastic constitutive model to predict the behavior of the prototyped MR damper. The theoretical results were then validated by comparing them against experimental data, and it was shown that the flow model can accurately capture the dynamic force range of the MR damper. In addition to the flow model, a modified parametric algebraic model was proposed to capture the hysteretic behavior of the MR damper. The superiority of the proposed modified model was shown by comparing it with the Alg model as well as with a widely adopted modified Bouc-Wen model through an error analysis. It is observed that although all the three models are comparable at the excitation velocities of 0.05, 0.10, and 0.15 m/s, the mAlg model is remarkably successful at the highest excitation velocity of 0.2 m/s over the other two. The improvements in the predictions were found to be over 50%, relative to unmodified model especially at lower current inputs. Therefore, it was concluded that the present flow model can be successfully adopted to design and predict the dynamic behavior of MR dampers, while the mAlg model can be used to develop more effective control algorithms for such devices.     

一种碟簧减振器的动态特性分析

采用理论分析与试验相结合的方法,对碟簧减振器的静刚度特性进行了深入研究,确定了描述碟簧减振器负荷一位移关系的三次函数表达式。通过碟簧减振器动态特性试验,获取了系统的阻尼系数,并建立单向约束条件下碟簧减振系统的动力学方程,为研究碟簧减振器减振性能奠定了理论基础。     

汽车座椅头枕的冲击性能研究

根据我国头枕安全性能测试的相关法规标准,运用显式有限元理论和LS-Dyna软件构建了某轿车座椅骨架及其头枕的有限元模型,并对头枕进行了后部和前部碰撞的仿真分析.仿真结果表明,前方碰撞对头枕的冲击破坏更大一些,人的颈部损伤也将会更加严重.因此,根据仿真结果,提出了进一步的改进意见,为此类轿车座椅的设计分析提供依据.     

液压阻尼器试验台控制系统的特性分析

分析了以液压阻尼器为负载的电液力控制系统的性能.通过建立线性化模型,分析系统的性能并在频域调整PID控制器的参数,对系统进行校正.通过仿真可以看出,经校正后的系统的特性明显得到改善.     

一种磁流变阻尼器控制系统的试验方法

在分析磁流变阻尼器阻尼力计算模型的基础上,对电控特性方程进行了分析讨论,通过研究控制系统的激励源、数据采集系统、电流控制器等主要模块,设计了一种基于MTS810材料试验机的磁流变阻尼器控制系统的试验方法,试验结果符合理论计算模型。该方法对于磁流变阻尼器的半主动控制、力学性能测试及结构改进研究十分有效。     

The damping capacity of the squeeze film damper in suppressing vibration of a rotating assembly

A flexible shaft with an overhung disc supported by the squeeze-film damper is investigated theoretically and experimentally. The system is simplified as a three-mass system based on a transfer matrix calculation. Governing equations for both models with and without retainer spring are derived. A fast integration method is used to obtain vibration responses. Both concentric and eccentric responses at the damper are examined. Different imbalances and different supply pressures are supplied to see their influence on the vibration of the system. It is found that for the system with retainer spring, positions of the resonance move between two extremes, one of which is the case with no damping in the system and the other with “full damping” where the SFD is locked-out and the system behaves exactly like one without a retainer spring. Therefore, improvements can be obtained by using a centralizing retainer spring and an accompanying SFD as resonance peaks can be moved to lower frequencies and/or such peaks can be kept down to reasonable limits. Nonlinear subharmonic and superharmonic responses are also found.     

液压冲击耦合振动的特性分析

利用流固互动（FSI）模型对典型液压系统的冲击振动特性进行了仿真研究,该模型考虑了摩擦耦合和泊松耦合。采用特征线法对该模型进行变换,得到了简洁的数学模型表达式,进行了仿真计算。仿真结果与试验结果基本一致,相对误差小于0．7％,证明了数学模型和仿真算法是正确和有效的,可以指导液压系统的设计与改造。