Dramatic Effect of Vibrations on Dynamics of Rotating Hydrodynamic Systems

The results of theoretical and experimental investigation of the average dynamics of inhomogeneous systems in rotating cavity in the presence of oscillating force field are highlighted and analyzed. Average behavior of nonisothermal liquid as well as different multiphase systems (two liquids, liquid and gas, solid in liquid, granular matter in liquid) in quickly rotating horizontal cylinder subjected to vibrations of different direction is described. The specificity of dynamics of all the systems is determined by the Coriolis force which defines not only the average flows but the fluid oscillations also. The resonant excitation of inertial oscillations of liquid results in generation of intensive mean flows. The structure of vibrational streams is essentially determined by the type of inertial waves. So, excitation of an azimuthal wave generates azimuthal streams (outrunning or lagging, depending on frequency of the wave), three-dimensional standing waves (in the systems with deformable interface) generate regular spatial flows of high intensity. Under the resonant conditions the influence of vibrations appears to be very strong, the speed of mean streaming can achieve the values comparable with the speed of rotation of the container.     

Lift Force Acting on Body in Liquid in the Vicinity of Boundary Executing Tangential Oscillations

The average force acting on a cylindrical or spherical body placed near the boundary of cylindrical cavity filled with liquid and executing rotational vibrations is experimentally studied. The repulsive lift force acting on solid is found and measured using the method of body suspension in the gravity field. In horizontal cavity the repulsive force provides steady state of light cylinder near the upper boundary at a distance comparable with the thickness of the Stokes layer. The heavy sphere which hangs on thread repulses from the wall of vertical cylindrical cavity under torsional vibration. The dependence of the average lift force on the amplitude and frequency of vibrations and on distance between the body and the boundary has been investigated. Results are presented on the plane of dimensionless parameters. In the examined frequency range the lift force acting on cylinder decreases exponentially with distance from the boundary. Lift force acting on sphere decreases with distance and strongly depends on dimensionless frequency of vibration. Conclusion that lift force is generated by body oscillations excited by its viscous interaction with the oscillating boundary is done. The found phenomenon is important for control of inclusions under microgravity conditions.     

Performance evaluation of dual-frequency driving plate ultrasonic motor based on an analytical model

An analytical model is presented to explain the effects of dual-frequency drive on the plate ultrasonic motor in this paper. The experimental prototype is a plate ultrasonic motor using single-phase asymmetric excitation, which can work under a single vibration or multiple vibration modes. Based on the linear superposition of vibrations with two different excitation frequencies, an analytical model is established using the classic Coulomb friction model, and the non-load rotation speed and maximum stall torque are deduced. Moreover, some crucial parameters such as preload and dead-zone in dual-frequency superposition model are identified or modified automatically by searching for the maximum correlation coefficient between simulation and experimental data using single-frequency drive. It is found that simulation and experiment results agree well when no excitation frequency component is at resonance.     

Dynamics of Rotating Two-phase System Under Transversal Vibration

Mean dynamics of light granular matter in liquid in the rotating horizontal cylinder subjected to transversal vibrations is experimentally investigated. The excitation of outstripping and lagging azimuth motion of the interface with respect to the cavity is revealed at definite ratios of rotation and vibration frequencies ${\Omega _\upsilon } \mathord{\left/ {\vphantom {{\Omega _\upsilon } {\Omega_r }}} \right. \kern-0em} {\Omega _r }$ . The motion is generated by the inertial oscillations arising in the system in a resonant way. The formation of regular spatial structures on the interface is revealed at intensive outstripping motion. These structures have azimuth and axial periodicity and their shape depends on the type of inertial waves arising in the cavity. Intensity and direction of azimuth flows as well as shape of patterns on the granular matter–liquid interface are determined by the ratio $ {\Omega _\upsilon } \mathord{\left/ {\vphantom {{\Omega _\upsilon } {\Omega _r}}} \right. \kern-0em} {\Omega _r }$ . It is shown, that the lagging motion exists at $ {\Omega _\upsilon } \mathord{\left/ {\vphantom {{\Omega _\upsilon } {\Omega _r }}} \right. \kern-0em} {\Omega _r }<1$ , and the outstripping one exists at $ {\Omega _\upsilon } \mathord{\left/ {\vphantom {{\Omega _\upsilon } {\Omega _r }}} \right. \kern-0em} {\Omega _r }>1 $ . Combined action of vibrations and rotation provides an efficient mechanism of mass transfer control, the intensity of mean flows in the cavity frame can be of the same order of magnitude as the rotation velocity.     

Analysis of a rotating elastic beam with piezoelectric films as an angular rate sensor

The flexural vibration of an elastic beam with surface-bonded piezoelectric films rotating about its axis is studied. One-dimensional equations governing the motion of the beam are developed, including the effects of Coriolis and centrifugal forces. The equations are used in the analysis of the flexural vibration of the beam under the excitation of an alternating electric voltage. The forced vibration solution is obtained. The beam can be used as a gyroscope for detecting the angular rate of the rotation. Voltage sensitivity and its dependence on various geometric and physical parameters are examined     

基于谱元法的车辆-轨道结构频域振动特性研究

基于谱元法建立车辆-轨道结构频域振动模型,其中轨道结构模拟为三层铁木辛柯梁,车辆部分考虑为整车模型,运用Lagrange方程实现车辆与轨道结构的耦合,并采用虚拟激励法将轨道不平顺模拟为虚拟荷载,通过求解车辆-轨道整体结构的谱元法方程,得到车辆-轨道结构在频域内的振动响应。结果表明:钢轨、轨道板和底座板的第一、二、四阶振动峰值分别由车体、转向架、车轮自振引起,其他振动峰值由轨道结构系统自振引起;钢轨、轨道板和底座板的振动能量分布在较宽的频率范围;在离开车辆一侧且距离端轮对2.5 m处,1～800 Hz内钢轨振动迅速衰减,当大于800 Hz时,钢轨振动衰减缓慢;在距离端轮对18 m处,25～1 171 Hz内钢轨振动衰减基本稳定;在距离端轮对20.5 m处,小于25 Hz时,钢轨振动随着离开端轮对距离的增加迅速衰减,当大于1 171 Hz时,钢轨振动则衰减较小。     

Vibration and buckling of rotating flexible rods at transitional parameter values

Summary We consider the connection between vibration and buckling problems for a uniform flexible rod which is clamped at one end and rotates in a plane perpendicular to the axis of rotation. The rod is assumed off-clamped, i.e. the axis of rotation does not pass through the rod's clamped end. The resulting fourth-order boundary value problem with a turning point for the free vibrations is solved using uniform approximations in a transitional parameter range where high rotation rates balance small off-clampings. Second approximations to the vibration eigenvalues are used to determine critical buckling rotation rates for the slightly off-clamped rods. Buckling is unexpected in this situation as the rod is wholly under tension.     

一种准零刚度车载隔振系统的设计与试验研究

针对车辆行驶工况环境以及振动频率,研制了一种空间占比小、安装方便的准零刚度(quasi-zero-stiffness,QZS)车载隔振系统。将垂向弹簧与两个对称的负刚度结构并联,负刚度机构用于刚度校正,通过静力学特性分析,初步确定了系统在平衡位置具有准零刚度的参数条件,在推导中引入了加工误差系数,分析了加工误差系数对系统准零刚度的影响机理。建立了系统非线性动力学方程,采用平均法求解了系统在车体简谐位移激励下的动力学响应,分析了系统参数和激励幅值对位移传递率的影响。在此基础上,设计制作了准零刚度隔振系统,进行了不同激励幅值、激励频率下的测试,得到了实测的位移传递率幅频响应曲线,并与理论计算结果进行了比较。另外,还通过TruckSim/Simulink联合仿真进行了车载随机激励工况仿真分析。研究表明,试验与理论结果吻合较好,验证了准零刚度隔振系统理论建模和分析方法的正确性。准零刚度的起始隔振频率在1.4 Hz左右,优于线性系统的起始隔振频率2.9 Hz。与车体相应相比,隔振后的位移响应均方根值降低80%以上,加速度均方根值降低90%左右,且稳态时准零刚度隔振系统的稳定性较好,具有良好的隔振性能。     

滚筒洗衣机瞬态脱水振动的分析与控制

为控制滚筒洗衣机瞬态脱水振动,建立了带有磁流变阻尼器的滚筒洗衣机平面振动模型;通过数值求解,分析了脱水过程按指数规律启动时,系统最大振幅随加速时间常数的变化;讨论了不同稳态转速下,系统最大振幅平均值随衣物负载质量和阻尼器控制电流的变化,结果表明:磁流变阻尼器控制电流对系统最佳加速时间常数的影响不大,对于1～9 kg的衣物而言,采用0.7的加速时间常数可取得较好的综合控制效果。此外,为综合考虑悬挂系统的瞬态抑振与稳态隔振,提出一种简单的磁流变阻尼器控制策略:采用短时傅里叶变换追踪盛水桶振动频率,当该频率大于预设的基准频率后,将阻尼器控制电流从最大降为最小以取得较好的隔振效果,最后,通过仿真验证了该策略的有效性。     

Oscillatory and Steady Dynamics of a Cylindrical Body Near the Border of Vibrating Cavity Filled with Liquid

The results of experimental study of vibrational dynamics of cylindrical solid in a rectangular cavity filled with viscous incompressible fluid are generalized. The cavity performs high-frequency translational oscillations in a horizontal plane. Experiments are carried out with bodies of different relative density: more or less than liquid’s density. The cylinder oscillates in the cavity under the influence of oscillating inertia force. An averaged force repels the body from the boundary and holds a heavy body over the bottom of the cavity and the light one at some distance from the ceiling. The vibrational lift force depends on the amplitude and frequency of vibrations as well as on the properties of liquid. It is shown that the value of the averaged lift force decreases with increasing dimensionless amplitude. Special attention is paid to the oscillatory behavior of a solid. The rotational oscillations of the body, observed in experiments simultaneously with the translational ones, and fluid motion, excited by an oscillating body, are investigated. The different modes of interaction of the body with the container’s boundary were found. The oscillatory dynamics of bodies with different relative density is studied by high-speed video-registration.     

随机路面激励下车辆垂向振动微分几何解耦控制

分析车辆悬挂与非悬挂质量动力学耦合机理,建立装备被动悬架的整车7自由度非线性模型,利用微分几何方法对该非线性模型受到随机路面激励时的垂向振动进行解耦分析。经过解耦的非线性系统成为独立的互不干扰的线性子系统,悬架簧上质量的振动不受路面激励的影响。进行解耦前后仿真对比分析,结果表明:解耦后的车身垂向加速度、车身俯仰角和侧倾角的振动幅值和频率大幅衰减,验证了解耦算法的有效性。     

Vibrations of a rotating membrane with unsteady rotations of the axis of rotation

A method and algorithm are developed for numerical calculation of the vibrations of a rotating circular membrane with a rigid central insert. The vibrations are caused by plane rotation of the rotation axis with a variable angular velocity. A system of differential equations is obtained to describe the motion of the membrane in relation to the stress-strain state caused by the rotation. Calculated results are presented for the case when the angular velocity of the membrane is constant, while the angular velocity of the rotation axis changes over time in accordance with a piecewise-linear law.Translated from Problemy Prochnosti, No. 2, pp. 55–60, February, 1990.     

井下移动式破碎机垂直方向随机振动响应的研究简

 为了研究井下移动式破碎机在破碎头受随机载荷作用下垂直方向的振动特性、探究其工作可靠性低的原因,通过假设与简化,根据多体动力学理论,建立了其动力学模型和垂直方向的运动方程,运用虚拟激励法推导了破碎机垂直向振动响应的数学模型．以国产某型井下移动式破碎机为研究对象,分析确定了破碎头冲击岩石时的随机载荷,运用MATLAB语言程序,得到该破碎机在高位时受随机载荷作用下破碎头、支臂与机身在垂直方向的随机振动响应．结果表明：在载荷峰值为375 kN、均值为186 kN、频率为10 Hz的随机激励作用下,该机各部振幅峰值与均值分别为：破碎头：0.0125 m,0.007 25 m;支臂：0.010 m,0.006 57 m;机身：0.006 1 m,0.003 62 m,可见各部振动比较剧烈．破碎头振动和波动最大,支臂次之,机身最小,与实际情况相符．当各部件振幅达最大时,破碎头、支臂与机身的低频与固有频率接近,容易发生共振,这是导致机器振动剧烈,引起零部件、元器件失效,使用寿命下降的主要原因．所得结论为改进移动式破碎机设计、采取合理的减振措施、延长破碎机使用寿命提供参考．     

基于变胞并联机构的多维隔振研究

在某些变激励和变环境的多维隔振中,目前应用的隔振理论和隔振技术存在诸多的缺陷,从而不能满足实际工程的隔振要求。给出了一种新颖的变胞并联机构,并以此为主体在选定的主动副处安装相应的弹簧阻尼系统建立了多维隔振平台。该变胞隔振平台存在两种形位,可以通过调整rT铰链的配置,使变胞机构变为3-CRR或者CRU-2CRR两种不同的并联机构。推导了隔振系统的运动学和动力学方程,对其模态、动力学特性和隔振效果进行了研究。仿真计算表明,在主动副处辅以适当的弹性和阻尼,可以实现隔振系统多维隔振,并可以通过设定系统的初始位置等获得不同的固有频率,从而适应不同的隔振工况要求。     

钻柱纵向和扭转振动分析

介绍钻柱的振动状态和产生振动的原因.针对钻柱的纵向振动,分别建立了力激励法和位移激励法的数学模型;计算结果表明,力激励法与位移激励法求得的消振转速相反,即力激励法的消振转速恰恰是位移激励法的共振转速,反之亦然;传统多以力激励为边界条件来研究钻柱纵向振动的频率响应,并指导现场消振作业的,这样给出的最佳消振转速,恰恰是共振转速;在钻井作业中,钻头的纵向跳动比纵向受力的变化要稳定得多,钻柱的动负荷比动位移重要得多,应该用位移激励法研究钻柱的纵向振动问题.针对钻柱的扭转振动问题,分别建立了扭矩激励法和转角激励法的钻柱扭转振动数学模型;证明用转角激励法来研究钻柱的扭转振动更符合实际.     

运行列车引起地面振动的理论模型及振动特性分析

根据车辆动力学、轨道动力学及地基土振动Green函数,建立了列车-轨道-地基土相互作用理论分析模型.该模型不仅考虑了车辆自身的振动,而且考虑了由轴重荷载组成的准静态激励力和单一波长轨道不平顺引起的轮轨问动态激励力.列车模型、轨道模型和地基土模型之间分别通过轮对-钢轨之间的Hertz接触和轨枕-地基土的动力平衡关系进行耦合.根据该模型通过-算例对地面的振动特性进行了分析,并通过移动的单位常力荷载和单位简谐荷载作用下的地面振动分析了车速和地基土特性的影响.计算结果表明,运行列车引起的地面振动特性与荷载移动速度和地基土特性紧密相关,列车移动速度线和地基土频散曲线的相交频率是引起地面振动放大的一种共振频率;运行列车存在临界速度,且临界速度接近地基土模型中的最小表面波波速;轮轨接触表面不平顺引起的动激励力振源对地面振动的高频成分产生较大的影响.     

水中弹性体的特征频率与声特性

对弹性壳体的特征频率与声散射、声辐射的谐振特性进行了对比研究。应用最小势能原理建立弹性体的有限元方程,并结合边界积分方程得到水中弹性体特征方程,采用Lanczos方法直接求解特征频率并进行固有振动模态分析。通过几种弹性壳体的特征频率与声特性的对比,验证了激励源频率在特征频率处会产生较强的谐振散射和谐振辐射,谐振对声特性影响的大小则与激励方式有关。具有附加结构的复杂线形长壳体的固有振动模态表明,低阶振动模态主要是主体部分径向和轴向振动,而附加结构对振动影响较小,但会使前几阶的特征频率偏移;高阶固有振动模态的主体和附加部分都产生形变,但主体的轴向振动是主要特征。     

双线性双滞后环系统非线性振动

研究含双线性双环滞后单自由度系统非线性振动的响应特点。先用平均法得到主共振情况下系统的幅频响应方程。然后讨论了外激励振幅变化对幅频响应的影响。给出了模式变化的临界参数条件,找到了四种不同类型的幅频响应并分析了其特点。在四种响应中,只有一种能充分发挥滞后环的耗能作用,适于减振设计。     

Vibration analysis of logs with electronic speckle pattern interferometry

Electronic speckle pattern interferometry combined with phase-shifting techniques for vibration analysis of logs is presented. Changes in the vibration pattern were followed on a television monitor at the video rate. We determined resonant vibrations by scanning through the frequency range of interest and by changing the point of excitation. We observed bending and torsional modes of vibration by changing the support and point of excitation. The vibrational modes reflect the structural properties of the material. The longitudinal modulus of elasticity and the shear modulus were calculated, giving valuable information for the strength grading of logs.     

悬索承重梁索耦合结构的垂向运动动力学模型及主共振分析

该文建立了描述结构大变形和主缆初始曲率产生的几何非线性对系统动力学影响的悬索承重梁索耦合结构垂向运动动力学偏微分方程组。通过Galerkin方法一次截断把偏微分方程组化为时域上的两自由度常微分方程组。使用多尺度法得到简谐激励下常微分方程组主共振时的一次近似解。结果显示,当外激励仅激发低频或高频主共振时,系统的振幅随激励的幅值或激励频率的变化出现突然的跳跃。当激励同时激发低频和高频主共振时则有两种情况：1) 若固定高频激励幅值和频率,则系统的低频和高频振动成分的振幅随低频激励参数变化同时增加或减小;2) 若固定低频激励的幅值和频率,则系统的低频和高频振动成分的振幅随高频激励参数变化以相反的趋势变化。即高频振动幅值增大时,低频振幅减小,反之亦然。