啄木鸟玩具演示自激振动

啄木鸟玩具可作为演示自激振动的教具,文中对啄木鸟玩具的自激振动过程作理论分析.     

曾逐东风拂舞筵——————再谈自激振动

叙述自激振动的产生机理，以及日常生活和工程技术中存在的各种自激振动.     

摩擦自激振动引起摩擦面波状磨耗的试验研究

在销-盘摩擦磨损试验机上进行金属干摩擦试验,研究摩擦自激振动对盘试件磨痕表面轮廓的影响,采用激光位移传感器测量盘试件摩擦表面轮廓尺寸,用加速度传感器测量销试件的摩擦自激振动.试验结果表明：在干摩擦状态下,销-盘系统容易发生持续的摩擦自激振动,当摩擦时间达到一定数值后,盘试件的磨痕表面轮廓会出现明显的波浪形磨耗,波浪形磨损机理主要是疲劳磨损.分析表明波浪形磨耗的波长近似等于摩擦自激振动的周期与滑动速度的乘积,由此推断摩擦自激振动引起了摩擦表面的波浪形磨耗.     

消除初轧机系统自激振动的理论分析

 在研究初轧机因打滑等因素产生自激振动时,本文考虑了连接轴转动的影响;从而提出一个新的力学模型,建立了具有运动边界问题的微分方程,得到消除自激振动的条件．     

平面滑移铰内发生自激振动的充分条件

自激振动是含摩擦机械系统最严重也最具破坏性的运动形式. 目前, 通常以增加润滑的方式 尽可能减少自激振动. 本文以平面滑移铰为研究对象, 假设铰连接的物体为刚体, 并且认为 铰内的间隙为小量, 推导了平面滑移铰内产生不符合物理事实解的条件. 这可看作是导致系 统产生自激振动的一种诱因. 该条件适用于任何含平面滑移铰的机械系统.     

再谈荡秋千——兼谈自激振动

通过荡秋千运动解释自激振动的特征，叙述其在航天技术中的应用。附录中应用相平面方法作定性分析。 关键词 秋千， 绳系卫星， 自激振动， 相平面法     

柔管自激振动特性与减阻效果的实验研究

为弄清柔管自激振动的湍流减阻效果的初步机理,在通过实验确认柔管确有湍流减阻效果的基础上,采用双重管结构和激光测位仪,对柔管的自激振动特性及湍流减阻效果及其两者的关系进行了实验研究．结果表明:管的壁厚越小,管外壁的自激振动的脉动位移有效值越大,湍流减阻效果越好;管壁外为压力平衡空气且雷诺数约为17500时,壁厚为2mm,3mm及4mm柔管的自激振动减阻率依次约为12％,10％,9％．这将为开发有效的管道流体输送技术提供参考．     

非线性转子的低频振动失稳机理分析

包括两部分内容：１）材料内阻作用下转子自激振动的局部分岔分析；２）考虑湍流因素的滑动轴承油膜力作用下转子轴承系统油膜失稳机理的全面分析。结果表明，非线性转子的自激振动表现出复杂的动力学现象，这些低频振动现象的揭示，为工程上转子故障的识别和预防提供了理论依据。     

近壁面柱体涡激振动的迟滞效应

柱体涡激振动是典型的流固耦合问题,其响应规律标识码在升速流动和远离壁面条件下获得的. 而自然环境流动通常不断经历升速和降速过程,近壁面柱体的涡激振动可呈现与远离标识码体不同的响应特征. 本研究结合大型波流水槽,设计了具有微结构阻尼的柱体涡激振动装置. 基于量纲分析,开展系列水槽标识码验,通过同步测量柱体涡激振动位移时程和绕流流场变化,研究了升降流速作用下柱体涡激振动触发和停振的临界速度(即上临标识码临界速度)变化规律,探究了近壁面柱体涡激振动迟滞效应. 采用自下向上激光扫射的 PIV 流场测量系统,对比分析了固定柱体标识码振动柱体的绕流特征. 实验观测表明,近壁面柱体涡激振动触发的临界速度呈现随壁面间距比减小而逐渐减小的变化趋势;但标识码速条件下的涡激振动停振所对应的下临界速度却明显小于升速时的涡激振动触发所对应的上临界速度. 采用上临界与下临界约标识码差值可定量表征涡激振动迟滞程度,研究发现该值随着柱体间距比减小呈线性增大趋势. 涡激振动迟滞现象通常伴随振幅阶跃标识码阶跃值则随着间距比减小而非线性减小.      

海洋柔性结构涡激振动的流固耦合机理和响应

对近几十年来国内外在涡激振动的基础研究包括机理认识和动响应分析等方面的进展进行了论述,尤其针对海洋油气平台中的立管、隔水管等细长柔性结构的涡激振动.描述了涡激振动这种典型的非线性流固耦合现象所具有的特征,包括自激、自限制、展向相关、尾迹水动力与结构动力的流固耦合等及其主要影响参数.介绍了目前常用的结构响应预测方法和相关实验.通过讨论当前理论研究和实际工程中的热点问题,诸如多模态宽带振动、浮体运动与水下立管的耦合、响应抑制措施、双向振动、高雷诺数下的大尺度物理实验等,对今后该领域的研究方向进行了力所能及的展望.     

Self-excited vibration of the shell-liquid coupled system induced by dry friction

The nonlinear vibration theory and the experimental modal analysis are used in this paper to study the self-excited vibration of the shell-liquid coupled system induced by dry friction. The effect of dry friction stick-slip coefficients and rubbing velocity on self-excited vibration, and the limit cycle and Hopf bifurcation solution of the system are obtained. In particular, it is shown that the phenomenon of 4 point (or 6 point) water droplet spurting of the Chinese cultural relic Dragon Washbasin is the result of the perfect combination of the self-excited vibration induced by dry friction and its special modes, which indicates the significant scientific value of the Chinese cultural relic Dragon Washbasin.     

Self-excited vibration caused by dry friction between two elastic structures

Based on our previous work^[1], self-excited vibration of a multi-degree-of-freedom system caused by dry friction between two elastic structures is investigated using the Chinese cultural relic dragon washbasin as an example. Some new characteristics of the self-excited vibration in this kind of system are found. The conditions under which self-excited vibration occurs at low-order or high-order modes are discussed. Effects of changes in parameters of the system on the self-excited vibration are analyzed. The vibration mechanism of the water droplets spurting phenomenon of the Chinese cultural relic dragon washbasin is further explained. This investigation presents a new idea for modeling the self-excited vibration caused by dry friction interaction between two elastic structures. The project supported by the National Natural Science Foundation of China     

Approximate analytical solution of the self-excited vibration of piecewise-smooth systems induced by dry friction —The vibration mechanism of the Chinese cultural relic Dragon Washbasin

Based on our previous work, a mathematical model of piecewise-smooth systems is established by means of phase-plane orbit analysis, and it is then used to study the intersting phenomena of Chinese cultural relic Dragon Washbasin. The mechanism of nonlinear damping is analyzed; the approximate analytical solution of self-excited vibration of piecewise-smooth nonlinear systems induced by dry friction is derived by means of KB Method, the results of which agree well with that of the numerical solution. Therefore, the method presented in this paper is proved to be very efficient in analyzing the self-excited vibration of piecewise-smooth systems induced by dry friction.     

Nonlinear vibration analysis by an extended averaged equation approach

The paper presents an extended averaged equation approach to the investigation of nonlinear vibration problems. The proposed method is applied to some free and self-excited oscillators, the Duffing's forced oscillators including main resonance, subharmonic resonance and super harmonic resonance. The results in analyzing the vibration systems with arbitrary non-linearity show advantages of the method.     

机械系统摩擦动力学研究进展

摩擦环节对机械系统动力学行为有重要、甚至可能是关键的影响. 深入研究摩擦及摩擦动力学特点,对于解决机械系统中摩擦带来的不利影响, 发挥其有利作用, 是非常重要的. 本文介绍和评述了机械系统摩擦动力学的研究进展, 包括常用的摩擦模型及其特性, 摩擦系统自激振动、强迫振动和摩擦振动控制等. 除理论研究方法之外, 重点讨论了制动噪声振动、摩擦耗能和多领域摩擦振动控制等摩擦动力学的应用研究.     

An elastic rotative nonlinear vibration absorber (ERNVA) as a passive suppressor for vortex-induced vibrations

Nonlinear Dynamics - Vortex-induced vibration (VIV) is a self-excited and self-limited flow-induced vibration phenomenon of importance for both the academic and the technological communities....