高速铁路连续梁桥的共振响应与振动控制研究

以液体粘滞阻尼器为振动控制外部装置，主桥采用欧拉伯努利梁，通过中国和谐号动车组CRH380AL、日本新干线Shinkansen700和欧洲高速列车HSLMA8三种不同类型的高速列车对比，模拟分析了高速列车作用下桥梁结构共振响应的影响因素，以及粘滞阻尼器的阻尼系数与安装位置对桥梁结构振动响应的减振效果。研究结果表明，（1）合理有效地布置列车荷载轴距，可使桥梁结构发生基频共振的列车时速在运营时速之外，避免了桥梁结构发生较大振动峰值响应，即桥梁结构的基频共振；（2）随着粘滞阻尼器阻尼系数的增大，桥梁的加速度峰值在列车不同时速下均在减少，对桥梁振动有着不同程度的减振效果；（3）通过合理安置液体粘滞阻尼器，可有效降低高速列车作用下桥梁结构的共振响应；（4）随着粘滞阻尼器与主梁的连接点位置逐渐远离支座，粘滞阻尼器的减振效果逐渐明显；（5）随着粘滞阻尼器与桥台的连接点位置逐渐靠近支座，粘滞阻尼器的减振效果略有提升，但不明显。     

Granular dampers for the reduction of vibrations of an oscillatory saw

Instruments for surgical and dental application based on oscillatory mechanics submit unwanted vibrations to the operator’s hand. Frequently the weight of the instrument’s body is increased to dampen its vibration. Based on recent research regarding the optimization of granular damping we developed a prototype granular damper that attenuates the vibrations of an oscillatory saw twice as efficiently as a comparable solid mass.     

分布振子复合板的模态阻尼及多点激励下阻尼减振相关性

分布阻尼振子可拓宽结构减振频带,因此可将振子分布于板中以形成复合板（简称“分布振子复合板”）,进而实现较宽的减振频带．对于多点支撑处受到宽频非一致激励（例如在不同激励点处的激励频率、幅值与相位有差异）的分布振子复合板,目前还缺乏有效简便的优化控制指标．在作者之前的研究中,针对含分布振子的梁推导了基于模态应变能的模态阻尼计算理论,讨论了模态阻尼与单点激励下梁的减振效果的相关性,并应用于宽频减振设计优化．本文进一步将模态阻尼计算理论推广到分布振子复合板,并将研究从梁的单点激励扩展到板的多点非一致激励下的阻尼减振相关性．首先,在利用模态应变能法推导得到分布振子复合板的模态阻尼计算公式后,从理论上讨论了不同边界条件与模态阶次对计算结果的影响,以及计算理论的适用性．而后,进一步通过有限元参数分析了边界条件、频率比、模态阶次与质量比的影响．最后,通过算例分析了无振子板或分布振子复合板在四个激励点具有多种幅值与相位组合情况下的稳态响应．结果表明,推导的模态阻尼计算公式可正确预测不同边界条件下的模态阻尼,且理论预测的模态阻尼与基板的稳态平均加速度减小率、稳态峰值应变能减小率均有较高的相关性．     

机载多框架光电吊舱两级隔振设计

在分析了目前常用的机载光电设备隔振系统的基础上,针对两轴四框架的结构特点,提出了一种基于多框架的两级隔振方案,克服了目前隔振系统体积、重量大,加工装配要求高的缺点。基于隔振模型的理论计算表明,根据系统给定的质量比和频率比,优化选择内外框架的刚度比,即选择合适的内外框隔振器可达到理想的隔振效果。通过某型光电吊舱的扫频实验...     

Modeling of a magnetorheological damper by recursive lazy learning

Nowadays dampers based on magnetorheological (MR) fluids are receiving significant attention specially for control of structural vibration and automotive suspensions systems. In most cases, it is necessary to develop an appropriate control strategy which is practically implementable when a suitable model for MR dampers is available. It is not a trivial task to model the dynamic of MR dampers because of their inherent non-linear and hysteretic dynamics. In this paper, a recursive lazy learning method based on neural networks is considered to model the MR damper behavior. The proposed method is validated by comparison with experimental obtained responses. Results show the estimated model correlates very well with the data obtained experimentally. The method proposed learns quickly that it is only necessarily a learning cycle, it can learn on-line and it is easy to select the network structure and calculate the model parameters.     

挤压油膜阻尼器-滑动轴承-柔性转子系统的动力响应分析

建立了挤压油膜阻尼器-滑动轴承-柔性转子非线性系统的动力学模型,采用Runge-Kutta法进行求解,进而对系统的稳定性和分叉行为进行了研究。仿真计算结果表明,系统能够在一定范围内保持稳定,随着转速的变化系统将会出现倍周期、准周期及混沌响应,从而为有效地控制转子的稳定运行状态提供了理论依据。     

磁流变阻尼器半主动控制方法的实验研究

由于磁流变阻尼器是一种高度非线性的装置,因此建立与之相适应的控制系统是半主动控制问题的关键。本文采用改进的Bingham模型建立了磁流变阻尼器的动力学特性模型,根据天棚阻尼开关控制、天棚阻尼连续控制和模糊控制三种控制方法,确立了从系统速度响应到磁流变阻尼器励磁电流之间的关系,并开发了一套半主动控制系统。在一个两自由度的简化车辆试验平台上进行半主动控制试验,对比研究了三种控制方法的控制效果。实验结果表明,在1.3Hz~2.0Hz的低频段内,开关控制的最佳减振效果为15.1%,连续控制的最佳减振效果为14.9%,模糊控制的最佳减振效果为20.1%。可见,三种控制方法都能有效的减小车体的振动,模糊控制的减振效果最佳。     

环形调液阻尼器振动控制中拍的研究

对环形调液阻尼器减振控制中的拍现象进行研究,分析了环形调液阻尼器对结构纯扭转振动控制中的拍现象,分别考虑无阻尼结构体系、主体结构有阻尼而CTLCD无阻尼的体系及主体结构和CTLCD中均有阻尼的体系,从数学角度对拍现象发生的机理进行解释.研究结构表明,当拍现象发生时,主体结构的振动不仅不会受到抑制,有时反而会加强;当环形调液阻尼器的阻尼增大到一定程度时,拍现象会消失;对于受廹振动,发生拍现象时,由于结构反应的瞬态部分不能得到迅速衰减,结构的瞬态响应将会占结构响应的很大一部分,如果仅考虑结构的稳态响应会带来较大的误差.     

Hysteresis-induced bifurcation and chaos in a magneto-rheological suspension system under external excitation

The magneto-rheological damper(MRD) is a promising device used in vehicle semi-active suspension systems, for its continuous adjustable damping output. However, the innate nonlinear hysteresis characteristic of MRD may cause the nonlinear behaviors. In this work, a two-degree-of-freedom(2-DOF) MR suspension system was established first, by employing the modified Bouc–Wen force–velocity(F –v) hysteretic model. The nonlinear dynamic response of the system was investigated under the external excitation of single-frequency harmonic and bandwidth-limited stochastic road surface.The largest Lyapunov exponent(LLE) was used to detect the chaotic area of the frequency and amplitude of harmonic excitation, and the bifurcation diagrams, time histories, phase portraits, and power spectrum density(PSD) diagrams were used to reveal the dynamic evolution process in detail. Moreover, the LLE and Kolmogorov entropy(K entropy) were used to identify whether the system response was random or chaotic under stochastic road surface. The results demonstrated that the complex dynamical behaviors occur under different external excitation conditions. The oscillating mechanism of alternating periodic oscillations, quasi-periodic oscillations, and chaotic oscillations was observed in detail. The chaotic regions revealed that chaotic motions may appear in conditions of mid-low frequency and large amplitude, as well as small amplitude and all frequency. The obtained parameter regions where the chaotic motions may appear are useful for design of structural parameters of the vibration isolation, and the optimization of control strategy for MR suspension system.     

铝蜂窝-铅复合阻尼器的试验研究

提出一种铝蜂窝-铅复合阻尼器,设计了2种类型的6个不同参数阻尼器试件,通过低周循环试验研究了其力学性能,揭示它的工作原理和耗能机制,分析了不同参数阻尼器的等效阻尼比、最大剪应力、存储剪切模量、骨架线等性能参数。结果表明,铝蜂窝-铅复合阻尼器具有屈服位移小、变形能力大、工作性能稳定与耗能性能好等特点,同时具有造价低廉、构造简单、安装方便的优点。相对A型阻尼器,B型阻尼器变形能力大,工作稳定,耗能性能优越。对于阻尼器的等效阻尼比、最大剪应力和存储剪切模量等参数,铝蜂窝/铅复合体的方向、高度和孔棱大小影响较大,复合体的片数影响很小。