半主动电流控制阻尼器的调谐减振性能研究

随着建筑高度不断增加,低频振动严重影响其安全运行。被动式阻尼器仅在调谐点处具有良好的减振效果,存在减振带宽较窄的问题,磁性液体为解决这个问题提供了新的途径。以磁性液体为工作液体,提出一种半主动调谐式电流控制阻尼器。首先,建立了阻尼器固有频率的理论模型,表明通过调节电流可改变固有频率。其次,搭建测试平台,进行了不同激励下阻尼器的调谐减振能力测试。结果表明半主动电流控制阻尼器的减振率为22%左右,调谐液体滚球阻尼器的减振率仅为12.3%左右,且调谐液体滚球阻尼器与主结构的频率比>1.11时,减振率将低于10%,半主动电流控制阻尼器则具有良好的鲁棒性,可以有效降低位移响应,弥补了被动式阻尼器减振带宽较窄的不足。     

双调谐液体柱形阻尼器及其基本动力性能

借鉴被动调谐质量阻尼器(tuned mass damper,简称TMD)和调谐液体柱形阻尼器(tuned liquid column damper,简称TLCD)各自的优缺点,结合土木工程结构减震装置的经济性和适用性,提出了一种双调谐液体柱形阻尼器(doubly tuned liquid column damper,简称DTLCD),建立了简谐激励作用下单自由度DTLCD控制体系(DTLCD-SDOF)的运动方程,推导了其动力反应放大系数。提出了针对DTLCD的调优策略及优化评价函数,通过相关算法获得DTLCD-SDOF系统的参数优化程序,并利用该程序得到了DTLCD的最优参数。具体分析了不同参数对DTLCD共振峰值和调频宽度的影响,并对阻尼器阻尼参数或受控结构频率发生变化后DTLCD的鲁棒性进行了评价。对DTLCD,TMD,TLCD及DTMD的有效性和鲁棒性进行了对比分析。理论与数值研究结果表明,DTLCD的控制效果明显优于TMD和TLCD,与DTMD效果相同,并且在主结构频率的摄动方面拥有更佳的鲁棒性。事实证明,DTMD比TMD和TLCD更具工程适用性。     

自适应阻尼器试验研究

自适应阻尼器是在磁场作用下,利用新型智能材料——MR流体（Magnetorheological fluids）为工作介质的智能器件。笔者在自适应阻尼器的结构设计的基础上,对阻尼器进行了性能测试,通过减振试验装置对所设计的自适应阻尼器进行了减振试验研究,取得很好效果。试验结果及分析对自适应阻尼器的结构设计有重要的参考价值。     

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.     

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。     

基于压电自感减振器的振动控制研究

针对压电材料作为减振器来减少振动的实用性问题,对智能材料作为传感元件及驱动元件技术应用到压电自感减振器进行了研究,建立了压电自感减振器的模型,对自感反馈的效果以及对智能结构振动的控制进行了评价,提出了改变压电自感减振器模型的电容值来改变固有频率,以及改变模型的阻尼比来为自感提供反馈,并通过实验分析了压电自感减振器对振动的控制。研究结果表明,该系统能很好地实现自感反馈的效果,以及对智能结构振动的控制。     

金属丝网减振元件的性能研究

对AAW-400型金属丝网减振器中的阻尼元件——金属丝网网块进行实验研究。得出金属丝网块的静刚度特性,同时也考察网块的广义密度（成型密度）、载荷和不同激励等对金属丝网块性能的影响。研究表明。适当调节金属丝网的相关参数,可有效提高对承载体的减振效果。     

风洞模型主动抑振器的设计与实验

研究了风洞模型主动振动的抑制原理,并结合叠堆式压电陶瓷作动器的压电效应设计了一套并联式主动抑振器。首先,针对模型支杆系统及其动力学特征,分析了支杆抑振原理,提出了一种基于叠堆式压电陶瓷作动器的风洞模型抑振器。然后,构建了抑振器实时控制系统,针对其驱动位移滞后的特点,研究了基于PD调节器的控制方法。最后,搭建了地面实验平台,利用锤击法和激振法对抑振器进行了地面实验。实验结果表明:抑振器具有提高支杆系统阻尼的能力,对风洞模型在俯仰和偏航两个方向上的抑振效果明显,特别是俯仰方向上,抑制器工作后系统阻尼比可由0.009提高到0.092,抑振后剩余振幅比例约为25%。试验结果验证了该风洞模型主动抑振器的可行性与有效性。     

Free vibration analysis of a resilient impact damper

The free vibration of a vibratory system equipped with a resilient impact damper is studied. A simple model of impact damper is constructed using spring, mass and viscous damper. The important feature to be carried out in the analysis of this model is that the deformation of an impact damper during the collision with and the main mass can be formulated; therefore, the contact time is taken into consideration. This feature is important for a resilient rather than a rigid impact damper when the noise issue is concerned. The investigation showed that the effective reduction of the vibration response depends not on the number of impacts but primarily on the type of collision that the impact mass collides with the main mass face-to-face. Results also show that the clearance of an effective impact damper should be smaller than twice of the initial displacement of the main mass of the vibration system if the system is stimulated by an initial displacement only. Finally, an example of application of an impact damper on a cantilever beam is demonstrated.     

Tuned dynamic performance of circular step bearings

In view of the increasing need for stable support the response of a dynamically loaded circular step bearing is investigated in which the resulting axial oscillations of the shaft runner can be damped out using a viscous damped vibration absorber. The stability analysis is intended to provide definite design parameters, to establish stability criteria and to indicate the influencing parameters. This paper presents the conditions necessary for the design of the proposed supporting system.     

Modified liquid column damper for vibration control of structures

A modified version of the traditional tuned liquid column damper (TLCD) absorber is proposed as a passive vibration control device for structures vibrating at low frequencies. This new version, denoted as tuned liquid column ball damper (TLCBD), is equipped with a coated steel ball, in place of the orifice in TLCD, immersed inside the horizontal column of the damper. The current study examines the performance of TLCBD for a harmonic excitation which is a simplified model for the vortex shedding forces on structures in the cross wind direction. A parametric study to investigate the effect of the ball size and absorber mass on the suppression capacity is carried out. The absorber damping characteristics is identified experimentally using a single point laser vibrometer system and the measured damping factor is used in the mathematical model. Intensive numerical simulations were conduced and the results are compared with the traditional TLCD with optimum parameters. The results revealed an improvement of the vibration suppression capability of the proposed version that exceeds around 66% reduction.     

活塞式磁性液体减振器的阻尼分析和实验研究

根据磁性液体的磁粘特性,当磁性液体周围施加垂直于其涡旋矢量方向的磁场时,磁性液体的粘度增加,利用磁性液体作为减振器的阻尼液,通过改变磁场可以调节振动系统的阻尼比,从而达到减振的目的。根据这一特性,提出一种活塞式磁性液体减振器。根据磁性液体的流动方程和连续性方程,建立了减振器中磁性液体的动力学模型,并得到减振器阻尼力与振动速度之间的表达式以及减振系统的阻尼比。设计实验,将磁性液体减振器安装在悬臂梁自由端,利用线圈对减振器施加均匀磁场,研究不同线圈电流时磁性液体减振器对梁振动阻尼比的影响。实验表明,在所假设的条件下,实验结果与理论结果的一致性较好。同时得出,在一定范围内,活塞式磁性液体减振器的阻尼效果随着线圈电流的增大而增大。     

The experiment of flow induced vibration in PWR RCCAs

Recently, severe wear on the shutdown rod cladding of Ulchin Nuclear Power Plant #1, #2 were observed by the Eddy Current Test (E.C.T.). In particular, the wear at the sixth card location was up to 75%. The test results indicated that the Flow Induced Vibration (F.I.V.) might be the cause of the fretting wear resulting from the contact between Rod Cluster Control Assemblies (RCCAs) and their spacing cards (guide plates) arranged in the guide tube. From reviewing RCCAs fretting wear reports and analyzing the general characteristics of F. I. V. mechanism in the reactor, geometric layout and flow conditions arround the control rod, it is concluded that the turbulence excitation is the most probable vibration mechanism of RCCA. To identify the governing mechanism of RCCA vibration, an experiment was performed for a representative rod position in which the most serious fretting wear was experienced among the six rod positions. The experimental rig was designed and set up to satisfy the governing nondimensional numbers which are Reynolds number and mass damping parameter. The vibration amplitude measurement by the non-contact laser displacement sensor showed good agreements in the frequency and the maximum wearing (vibration) location with Ulchin E. C. T. results and Framatome report, respectively. The sudden increase in the vibration amplitude was sensed around the 6th guide plate with mass flow rate variation. Comparing the similitude rod behaviour with the idealized response of a cylinder in flow induced vibration, it was found that the dominant mechanism of vibration was transferred from turbulence excitation to periodic shedding at the mass flow rate 90l/min. Also the critical velocity of the vibration in RCCAs was determined and the vibration can be prevented by reducing the bypass flow rate below the critical velocity.     

橡胶减振元件加速寿命试验的仿真研究

针对橡胶减振元件疲劳寿命试验时间较长的问题,采用计算机仿真开展了加速寿命试验研究。利用CATIA和ABAQUS软件分别建立了橡胶减振元件的三维实体及有限元模型,采用二参数的Mooney-Rivilin模型模拟橡胶材料。通过模态分析,结合橡胶减振元件的工作状态,确定了试验系统的极限加载频率。施加3种不同的随时间变化的位移载荷,对橡胶减振元件进行了瞬态动力学分析,获得了其应力分布,从而确定了易于发生疲劳破坏的危险部位。提取橡胶减振元件危险部位的应变值,利用Manson-Coffin关系,根据橡胶材料的应变幅-疲劳寿命关系曲线,确定了3种加载条件下橡胶减振元件的破坏周期。研究结果表明,在同样的累积损伤、疲劳破坏模型条件下,通过合理提高加载频率和加载等级,可以大大缩短橡胶减振元件的疲劳寿命试验周期。     

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.     

Process analysis and test of manufacturing of sleeve spring-type torsional vibration damper

In diesel engines, engine torque fluctuation inevitably produces torsional vibration. A sleeve spring-type damper commonly is used to reduce this vibration. In this paper, closed form equations to predict the spring constant of a sleeve spring and the torsional characteristics of a torsional vibration damper are proposed for calculation of the stiffness of the damper. The equations were verified through finite element analysis (FEA) and experiments. In addition, the stability of the sleeve spring-type torsional vibration damper was verified in an analysis of the inner star and outer star (the core components of the damper). A two-roll bending process, proposed in this paper, was determined to be the most suitable for manufacture of the sleeve springs. A closed form equation to calculate the forming radius, taking account of the springback effect, was derived, and a FEA method used to analyze the elasto-plastic problem was verified through an analysis of a 90° bending process. The results of the analysis were in good agreement with the experiment. It is recommended that our proposed method, an advanced technique that can significantly reduce production costs, replace the conventional forming process.     

装配式钢桁架桥振动模态分析与试验研究

桥梁结构的动力学特性是其结构分析与优化设计的基础,以某型装配式钢桁架桥为研究对象,利用有限元软件ANSYS建立了该桥的三维空间有限元分析模型,并采用分块兰索斯法对其进行了模态分析,得到了桥梁的10阶固有频率和振型,而后基于环境激励的工作模态试验方法开展试验研究,通过试验数据的对比,验证了该分析方法的可靠性,为该型钢桁架桥的动力特性分析提供了直接的数据支持。     

机械阻尼器圆柱铣刀模型的建立及减振理论的分析

高速铣削加工过程中,由于刀具颤振会对机床、刀具、工件表面产生不良影响,因此通过增加机械阻尼器来抑制刀具的颤振;通过建立铣刀模型,并对模型进行理论分析,找出随着刀指内径、刀指数目、刀指初始安装角的变化与阻尼耗徽功率之间的变化关系.     

Fundamental dynamic performance of fluid-pivot and squeeze-film damper bearings

Due to the increase in rotational speeds and performance of modern turbomachinery the rotordynamic stability of such machinery has reduced. In order to improve rotordynamic stability, fluid-pivot and squeeze-film damper bearings have been developed. By using a simple analytical model to predict the unbalance response of a single mass rotor and by modelling the above bearings as a two-mass-spring and damper system the fundamental performance of these types of bearings has been determined. The results are that these bearings can significantly improve rotordynamic performance over a certain frequency range. This is mainly due to the ability of these bearings to reduce the effective bearing stiffness and hence improve the damping efficiency of the bearings. These auxiliary damped bearings increase the bearing damping efficiency rather than increase the bearing damping.