Design of distributed dynamic absorbers for vibration suppression of panel structures

Distributed dynamic absorbers have many advantages such as wide frequency bandwidth for vibration suppression,strong detuning adaptability,and high system stability,making them very suitable for the vibration and noise control of continuous structures.Therefore,they have broad application prospects in various fields such as transportation,aviation,and aerospace.However,there are still many challenges in the engineering applications of distributed dynamic absorbers for vibration suppression,including the engineering realization of the optimal damping of traditional optimal coherence dynamic absorbers,and the engineering applicability of the finite periodic array dynamic absorbers.Based on the damping material properties obtained by the dynamic mechanical analyzer tests,this paper establishes the finite element model of the cantilever-beam-type dynamic absorber with constrained damping layers,aiming to realize the accurate determination of the optimal damping.Experiments are conducted by attaching the traditional dynamic absorbers with the optimal damping to a thin-walled panel with four clamped edges.Results show that the vibration of the panel is well suppressed,with the reduction of the frequency response peak larger than 14 dB and the reduction ratio of RMS larger than 58%within 500 Hz.Afterwards,the periodically arrayed dynamic absorbers are designed according to the bandgap regulation method.The tuning behavior of the arrayed dynamic absorbers by changing designing parameters is investigated.The vibration reduction effect of arrayed dynamic absorbers is compared with that of the traditional dynamic absorbers under the same mass ratio through experiments.Results indicate that the arrayed dynamic absorbers are easier to design,and have a similar reduction effect on the modal vibration of the thin panel as the traditional dynamic absorbers within a narrow frequency range near the natural frequency,while they perform unsatisfactory in a broad band.Significantly,if the appropriate frequency and damping of the arrayed absorbers are chosen,a relatively wide bandgap can also be generated,which shows high engineering applicability.The research work in this paper provides beneficial reference for the design of distributed dynamic absorbers suitable for vibration suppression of thinwalled panel structures.

Attenuation of ground vibrations due to different technical sources

The attenuation of technically induced surface waves is studied theoretically and experimentally. In this paper, nineteen measurements of ground vibrations induced by eight different technical sources including road and rail traffic, vibratory and impulsive construction work or pile driving, explosions, hammer impulses and mass drops are described, and it is shown that the technically induced ground vibrations exhibit a power-law attenuation v - r ~ where the exponents q are in the range of 0.5 to 2.0 and depend on the source types. Comparisons performed demonstrate that the measured exponents are considerably higher than theoretically expected. Some potential effects on ground vibration attenuation are theoretically analyzed. The most important effect is due to the material or scattering damping. Each frequency component is attenuated exponentially as exp（-kr）, but for a broad-band excitation, the sum of the exponential laws also yields a power law but with a high exponent. Additional effects are discussed, for example the dispersion of the Rayleigh wave due to soil layering, which yields an additional exponent of 0.5 in cases of impulsive loading.

A Review on Methods for Determining the Vibratory Damping Ratio

This article aims to popularize the methods for determining the vibratory damping ratio, to explain the various mathematical and physical theorems related to the establishment of literal expressions. Vibration damping is an essential parameter to reduce the dynamic responses of structures. The study aimed at its determination is necessary and essential for the safeguard of buildings and human lives during the earthquake. Among the main methods studied in this article, the free vibration attenuation method seems to be easy to implement but requires a state-of-the-art device to capture the responses. In addition to this device, the other methods require other equipment for the vibration of the system and the transformation of the responses in the frequency domain.

二级柔性减振系统设计及力学性能分析

为解决二级减振引起个别仪器振动的局部放大、使得力学环境不能满足运行要求的问题,首先,针对金属橡胶双层减振系统,充分考虑安装板的柔性刚度,建立了刚柔复合的二级减振系统模型;其次,基于目标频率对二级减振的频率响应函数进行系统的刚度解耦,实现了减振器刚度的求解,并应用有限元进行随机振动分析,验证了刚柔复合二级减振系统理论模型的可行性;最后,利用振动台进行了试验验证。结果表明,当二级减振系统满足工程刚度需求,其一阶固有频率低于40 Hz时,减振效率可达到70%以上,试验与仿真结果基本一致。

基于动力吸振器的微耕机扶手架减振设计

微耕机的扶手架结构较为简单,在田间作业时会造成扶手架的强烈振动,长时间的强烈振动会给操作者身心带来不适甚至严重伤害,针对此问题,对微耕机扶手架进行了减振设计。对于结构相对简单的构件,振动问题大多是由于主振动系统自身结构阻尼的不足导致的。为此,结合微耕机实际情况,将动力吸振器的设计方法应用于微耕机扶手架上,对动力吸振器进行结构设计并试制样件。最后,对动力吸振器样件的减振效果进行试验测试,结果表明:在安装动力吸振器样件后,其手把处的振动强度在空挡和耕作状态下分别降低了13.9%和11.2%。

聚氨酯复合泡沫的制备以及应用前景展望

综述了聚氨酯复合泡沫的最新发展和突破。添加高性能纳米材料是目前研究聚氨酯泡沫方向的新趋势。聚氨酯复合泡沫的纳米添加剂包括碳纳米管、碳纤维、石墨烯、纳米金属单质、纳米金属氧化物和纳米金属合金材料等。主要综述了聚氨酯复合泡沫的类型、合成方法。此外,重点介绍了聚氨酯复合泡沫在吸波屏蔽、压阻传感、阻燃和减震阻尼等领域的前沿进展。

粒子阻尼悬臂管道减振特性试验研究与仿真分析

粒子阻尼技术是一种被动减振降噪技术,已成功应用于多个领域。以附加在悬臂管道上的粒子阻尼为研究对象,试验验证粒子阻尼器对悬臂管道振动的减振能力,同时仿真模拟研究不同粒子阻尼器参数对悬臂管道的减振特性影响。结果说明粒子阻尼器对悬臂管道有显著减振效果。试验结果与仿真结果相吻合,使算法的有效性得到验证;该研究可为管道减振措施提供重要参考。

阻尼调控下两类动力吸振器的H_(∞)设计与试验

动力吸振器凭借其出色的吸振能力得到了学术界和工程界的广泛关注.然而其对共振频率、阻尼系数等系统参数的高敏感性给系统设计及其应用带来了极大的挑战.传统的油液式黏滞阻尼器难以实现阻尼的有效调节,新兴磁流变阻尼器高昂的造价也限制了该技术的实际应用.近年来可调电磁分支电路阻尼的发展为动力吸振器现场最优调谐提供了新的可行性.文章基于直线式电磁分支电路阻尼器的结构特点,采用永磁体同极对置的方法提升了阻尼器的机电耦合效率,通过数值仿真得出了六段对置式电磁分支电路阻尼器的机电耦合系数及等效阻尼系数.电磁分支电路阻尼器可通过调整外接分支电路的阻抗实现阻尼力的实时调整,并将其应用于悬置式和接地式动力吸振器系统中,实现了两类动力吸振系统基于H_(∞)优化方法的最优化吸振效果,有效抑制了主系统的振动响应.两类动力吸振系统的试验测试结果与理论预测一致,充分证明了可调电磁分支电路阻尼器的有效性,为动力吸振器的进一步发展应用提供了设计准则和依据.

转子叶盘结构减振方法研究

转子叶盘结构在高速和超高速的运行状况下,可能因为失稳而剧烈振动,进而引发严重的安全事故。增大叶盘结构阻尼是减轻其振动的有效方法之一。国内外学者针对叶盘结构,开展了大量的研究,为了充分了解叶盘结构减振方法的研究进展,推动相关问题的深入研究,提出了将叶盘结构减振分为干摩擦、内摩擦和其他能量转换方式。对叶盘结构减振方法的相关研究进展进行了总结,并展望了叶盘结构减振的未来研究方向。

SEMI ACTIVE VIBRATION CONTROL BASED ON A VIBRATION ABSORBER WITH ADJUSTABLE CLEARANCE

Presented in this paper is a semi active vibration control strategy based on the vibration absorber with adjustable clearance in elastic component. The control law of the clearance for alleviating the vibration of primary system is derived by means of harmonic balancing technique so that the working frequency of the vibration absorber can trace the frequency variation of the harmonic excitation. The efficacy of the strategy is demonstrated by numerical simulations for attenuating the steady state vibration of a SDOF system and a 2 DOF system, which are under the harmonic excitation with slowly varied frequency in a wide range.

A low-frequency pure metal metamaterial absorber with continuously tunable stiffness

To address the incompatibility between high environmental adaptability and deep subwavelength characteristics in conventional local resonance metamaterials,and overcome the deficiencies in the stability of existing active control techniques for band gaps,this paper proposes a design method of pure metal vibration damping metamaterial with continuously tunable stiffness for wideband elastic wave absorption.We design a dual-helix narrow-slit pure metal metamaterial unit,which possesses the triple advantage of high spatial compactness,low stiffness characteristics,and high structural stability,enabling the opening of elastic flexural band gaps in the low-frequency range.Similar to the principle of a sliding rheostat,the introduction of continuously sliding plug-ins into the helical slits enables the continuous variation of the stiffness of the metamaterial unit,achieving a continuously tunable band gap effect.This successfully extends the effective band gap by more than ten times.The experimental results indicate that this metamaterial unit can be used as an additional vibration absorber to absorb the low-frequency vibration energy effectively.Furthermore,it advances the metamaterial absorbers from a purely passive narrowband design to a wideband tunable one.The pure metal double-helix metamaterials retain the subwavelength properties of metamaterials and are suitable for deployment in harsh environments.Simultaneously,by adjusting its stiffness,it substantially broadens the effective band gap range,presenting promising potential applications in various mechanical equipment operating under adverse conditions.

含分段阻尼特性动力吸振器的吸振性能

利用凸轮机构设计了一种分段阻尼装置。以传统Voigt型动力吸振器为基础,将该装置安装于动力吸振器的主系统与子系统之间,建立了吸振器的动力学方程。利用在一个振动周期内阻尼耗能等效这一原理,在相同振动频率下得到了分段阻尼装置的等效阻尼系数。推导得出了具有分段阻尼特性的动力吸振器的理论解,并用数值解进行了验证。比较分析了无阻尼、传统线性阻尼及具有分段阻尼特性的动力吸振器的吸振特性。结果表明,具有分段阻尼特性的动力吸振器的幅频特性综合了无阻尼和传统线性阻尼动力吸振器的特点,能保证反共振点处主系统的振幅很低,同时对主系统的共振振幅的抑制效果接近于传统线性阻尼动力吸振器。

含机械整流装置的电磁减振器阻尼特性分析

为了明确电磁减振器在不同工况下的阻尼特性,对具有机械整流装置的电磁减振器进行了理论建模与试验测试。首先,从理论角度建立了电磁减振器的动力学传动模型与机电耦合模型,分析其动力学和电力学特性;其次,从工程角度搭建了电磁减振器的测试台架,对其在不同工况下的阻尼特性进行了试验研究;最后,将理论仿真结果与试验测试结果进行对比。结果表明:在不同工况下,理论仿真结果与试验测试结果具有相同的变化趋势。当负载电阻从5Ω增加到100Ω时,电磁减振器的等效阻尼系数从1208 N·s/m下降到496 N·s/m。此外,激励频率从05 Hz增加至2 Hz或激励幅值从20 mm增加至40 mm,均导致电磁减振器等效阻尼系数从874 N·s/m下降至660 N·s/m。

无级调频吸振装置的减振研究

为解决工业厂房楼板高频设备振动问题,提出一种无级调频吸振装置,对吸振装置无级调频工作原理进行了理论推导,并对该装置的吸振效果进行了试验验证,试验结果表明,在按需设定频率下,采用吸振器控制时结构楼板所对应频率的加速度大幅减小,装置减振率可达到56%以上,且水平距离越接近激励源中心处的测点,楼面的减振效果越好。无级调频吸振装置具有良好的减振控制效果,为解决高频设备导致厂房楼板竖向振动难题提供了高效减振方案。

固有频率连续可调的动力吸振器设计研究

振动通常会对周围的人和物造成危害,为避免此危害,在振动体上安装无阻尼动力吸振器是有效控制振动的措施之一。而无阻尼动力吸振器的使用条件是其固有频率需要与振动体的激振频率相等或极为接近。文章提出一种动力吸振器固有频率连续可调的新结构和新理论。在前、后无盖的钢制长方体框架内部,对称安装两根斜置弹簧,两弹簧的上端沿框架上表面可以对称移动,两弹簧下端悬挂同一球形质量块。从理论上确立了弹簧上端的水平位移与弹簧竖向夹角、弹簧的竖向总刚度与弹簧竖向夹角、弹簧的竖向总刚度与弹簧上端的水平位移之间的定量变化关系,并对该动力吸振器的振动控制效果进行实验验证,以期为动力吸振器的设计提供新参考。

The Effect of Mass Ratio and Air Damper Characteristics on the Resonant Response of an Air Damped Dynamic Vibration Absorber

In this paper, it is shown that, a road vehicle 2DOF air damped quartercar suspension system can conveniently be transformed into a 2DOF air damped vibrating system representing an air damped dynamic vibration absorber (DVA) with an appropriate change in the ratio μ of the main mass and the absorber mass i.e. when mass ratio μ >> 1. Also the effect of variation of the mass ratio, air damping ratio and air spring rate ratio, on the motion transmissibility at the resonant frequency of the main mass of the DVA has been dis- cussed. It is shown that, as the air damping ratio in the absorber system increases, there is a substantial decrease in the motion transmissibility of the main mass system where the air damper has been modeled as a Maxwell type. Optimal value of the air damping ratio for the minimum motion transmissibility of the main mass of the system has been determined. An experimental setup has been designed and developed with a control system to vary air pressure in the damper in the absorber system. The motion transmissibility characteristics of the main mass system have been obtained, and the optimal value of the air damping ratio has been determined for minimum motion transmissibility of the main mass of the

An Effective Approach for Optimal PZT Vibration Absorber Placement on Composite Structures

In this paper, an attempt is made to determine the electric potential that would be generated in the piezoelectric vibration absorber using finite element piezoelectric analysis to determine optimal locations for damping of the first mode. Optimal placement of piezoelectric vibration absorber for passive vibration control application of a cantilever composite plate is investigated. Finite element piezoelectric modal analysis is performed. Models based on placing piezoelectric vibration absorbers at five different locations on the surface of the plate and incorporating piezoelectric properties are built. Modal analysis is used to find the electric potential developed in the piezoelectric vibration absorber. The location that yields the highest amount of electric potential would naturally be the best location for the vibration absorber. First bending mode of the cantilever composite plate is aimed for damping. Results of the analysis are verified with an experimental testing of the composite plate with piezoelectric vibration absorber firmly attached to the plate on the most effective location. A good agreement is found between the analytical and experimental results. Further, a resistive shunt circuit is designed for the passive damping of the first mode and attached to the vibration absorber in which the electric potential developed would be dissipated as heat to obtain passive vibration compensation. The experiment also demonstrates that a damping of 6 percent is obtained in the first mode of vibration and a great amount of damping is achieved in the second and third modes as well.

分数阶黏弹性振子系统响应的代理模型分析

黏弹性缓冲系统由于其具有较高的振动耗散能力,已被广泛应用于车辆阻尼减振。针对分数阶模型描述黏弹性缓冲系统力学特性时存在的复杂度高、难以直接进行参数优化等问题,引入代理模型减少优化时的计算复杂度。首先,通过分数阶建模给出一种用于阻尼减振的分数阶黏弹性缓冲系统;其次,依据分数阶导数算子定义间的关系推导出分数阶微分算子的一种差分格式,用于求解该系统的数值响应,并对系统参数灵敏度进行分析;最后,选用灵敏度较高的系统参数作为优化变量,选用Kriging模型和二次响应面模型对系统的响应函数进行代理。结果表明:相对于Kriging模型,二次响应面代理模型能够在较少样本点时达到较高的精度。研究成果可为分数阶黏弹性振子系统响应分析及工程设计提供理论参考。

利用阻尼振动法检测套筒灌浆饱满度的可行性分析

目的 研究阻尼振动法对灌浆料初凝前后及灌浆口各类灌浆缺陷的检测能力。方法 设计并制作两组装配式混凝土桥墩套筒节点模型,并在套筒中设置了不同种类的缺陷,根据阻尼振动衰减原理对灌浆饱满度进行判断。结果 传感器暴露在空气中时,仪器检测到的振动幅值为255,当灌浆料饱满时,仪器检测到的振动幅值普遍低于100,大概保持在20~60;随着灌浆料的固化,振动幅值继续变小,大概保持在10~40。因此可知,当传感器被灌浆料包裹时,振动能量值小于100便可判定该套筒灌浆饱满。结论 通过对比传感器振幅能量值与预设的灌浆情况,证实了阻尼振动法的可行性,对于脱空类型的缺陷有着较好的检测效果。

粘弹性约束阻尼层结构的动力学性能研究

研究粘弹性约束阻尼层结构(简称约束阻尼层结构)的动力学性能。结果表明:丁基橡胶可以较好地应用于约束阻尼层结构的阻尼层材料;约束阻尼层结构可以有效降低50~2050 Hz范围内共振频率处的振动,同时共振频率向低频移动;随着阻尼层材料的损耗因子、储能模量和厚度的增大,约束阻尼层结构的结构损耗因子增大,振动衰减效果明显;约束阻尼层结构的振动衰减的仿真结果与试验结果一致。本研究可为约束阻尼层结构的设计和优化提供参考。