共查询到20条相似文献,搜索用时 187 毫秒
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被动式颗粒阻尼器原理简单、性能优越,广泛应用于结构减震领域。极端环境容易激起结构的高频振动,颗粒阻尼的非线性特性使得多模态振动的减振特性相互耦合。采用模态综合法分析自由端带集中质量块的悬臂梁、离散单元法模拟颗粒阻尼器中颗粒集的运动,基于多尺度分析的球-墙耦合模型建立了揭示结构多模态振动条件下颗粒阻尼减振机理的半解析分析模型。分析表明,颗粒阻尼器具有良好的减震效果,减振性能受结构振动模态影响很大。与单一模态振动减振性能相比,多阶模态振动同时存在时,低阶模态幅值的衰减出现了滞后,而高阶模态幅值的衰减则明显加快。因此,采用单一模态获得的等效阻尼比不足以表征复杂振动条件下颗粒阻尼器的减振性能。 相似文献
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《振动与冲击》2016,(12)
采用阻尼动力吸振器对中空轴系纵向多阶模态进行振动控制,结合子结构综合法和传递矩阵法,建立了多个阻尼动力吸振器-轴系耦合系统的动力学模型,并进行了动力学特性分析。考虑到各阶阻尼动力吸振器间的相互影响,以极小化目标频段范围内轴系位移响应的均方值为目标函数,对各阶阻尼动力吸振器的参数进行了联合优化;针对轴系中空特点,设计了阻尼动力吸振器的具体结构形式,利用有限元仿真对理论计算进行了验证。研究表明:轴系多模态控制时,在多阶阻尼动力吸振器作用下,目标频段范围内的轴系纵向共振峰得到抑制,频响曲线趋于平缓;对多阶吸振器进行联合优化后,吸振器的吸振效果得到进一步提升;提出的多阶吸振器设计方法能为连续系统多模态振动控制提供参考。 相似文献
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斜拉索振动是危害缆索桥梁安全性和适用性的一个工程难题,实际中常采用附加阻尼器的方法实现减振。在拉索-阻尼器系统分析中,多将阻尼器系数考虑为常数;现有理论和试验表明,阻尼器动力特性包括刚度和阻尼系数存在明显的频率依存性,相关研究尚缺乏。并且,拉索随着长度的增大,基频降低,分析和设计中更需要考虑索的多模态(多频率)阻尼。因此,研究索阻尼器性能的频率依存性对索多模态阻尼效果的影响。研究选取工程中广泛应用的黏性剪切阻尼器(viscous shear damper,VSD)。首先,开展阻尼器单体试验研究,结果表明在固定位移幅值情况下,随着振动频率的增大,阻尼器的阻尼系数变小而刚度系数增大,系数与频率之间近似呈现指数函数的关系;进一步,采用小垂度拉索附加带刚度阻尼器模型,分析索-阻尼器系统的动力特性,讨论阻尼器性能频率依存性对索多模态阻尼效果的影响;最后,通过实索动力测试得到阻尼器对索多阶模态阻尼效果,与理论分析结果吻合。试验结果表明,实际阻尼器的设计需要考虑阻尼器性能的频率依存性,结合阻尼器单体试验和索-阻尼器系统理论分析是一种精确和实用的方法。 相似文献
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基于多模态耦合颤振理论桥梁颤振MTMD控制鲁棒性分析 总被引:2,自引:0,他引:2
基于多模态耦合颤振理论和结构的固有模态坐标,导出带有多重调谐质量阻尼器(MTMD)桥梁系统颤振运动微分方程。通过将系统广义位移和速度作为状态空间向量,进一步将系统颤振运动微分方程转化为状态空间方程,最后将带MTMD桥梁颤振问题归结为数学上一个非对称实矩阵的广义特性值问题,并编制了多模态耦合颤振MTMD控制和参数分析程序。以崖门斜拉桥为算例,分析了MTMD对桥梁颤振控制的有效性和鲁棒性,计算结果表明与传统TMD相比,MTMD具有更高的鲁棒性。 相似文献
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基于双向流固耦合理论,建立了调谐液体阻尼器(tuned liquid damper, TLD)与多层多模态平台结构的数值模型,系统性研究TLD减振频率和安装高度对多层结构前两阶共振模态的影响,通过数值方法将阻尼力做功定量化,结合晃荡波、平台运动的相位延滞关系,分析TLD对多层多模态平台结构的阻尼特性。研究表明,TLD不同安装位置的控制效果与结构对应模态的最大振型相关,晃荡过程中产生的倍频激励可拓宽TLD的减振频带。此外,保持2%的质量比不变,多TLD联合减振系统对多层结构的减振效果更为稳定,无局部负面激励,两个共振点处的平均减振率均高于其他方案。 相似文献
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刘亚宁周嘉明董龙雷刘建赵建平 《振动与冲击》2023,(16):101-109
以四边固支铝合金板(框架薄壁类结构)为研究对象开展了基于压电分流阻尼电路的多模态减振试验研究。首先,开展扫频激励下单压电片单模态减振试验,电路最优参数试验结果与理论计算结果相互吻合,同时发现电路最优参数可在一个区间内取值,而不需要与理论计算值保持绝对一致,表明压电分流阻尼电路具有良好的工程实用性;然后,基于阻塞电路开展了扫频激励下多模态减振试验,通过多个压电片实现了20~2 000 Hz内振动能量下降20.2%的减振效果,同时在一些主要模态频率处峰值控制效果可达63%,试验充分验证了多压电片多模态减振的可行性;最后,在噪声载荷激励下开展了多模态电路减振试验,在20~2 000 Hz内铝合金板三个位置处加速度响应的均方根值分别降低了19.1%,18.2%,15.3%,在648 Hz处峰值分别下降了34.1%,33.3%,31.0%。试验结果表明,多模态电路在实际工程载荷条件下仍然具有一定的减振能力。 相似文献
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目的基于仿生学概念,探索多模态交互设计研究方法。方法以仿生学为视角,研究生物控制、耦合原理,比较耦元、耦合与模态、多模态交互异同,并进行仿生学耦联关系的方法研究。以分析法中的分别测试法、个别去除法以及层次分析法为基础,对多模态交互设计方法进行研究。结论发现耦合仿生的"耦元"与多模态交互的"模态"具有关联,两者均需要经过输入、处理、输出的过程,且都注意效率最大化。针对耦元分析方法进行方法演绎得出面向执行流程的多模态设计研究模型。流程主要包括明确目标、分析模态、归类整理、排序测验、模态设计、细化变量、关联逻辑、模型制作、测试验证。并以儿童性侵教育互动产品为例对该方法进行实践论证,为多模态交互设计提供新思路。 相似文献
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使用反向滤波、反向积分、能级平均等技术构建了衰减法阻尼测试的数据处理系统,研究了衰减法阻尼测试结果与统计能量分析意义下的频段阻尼之间的关系,探讨了频段外模态的阻尼对频段阻尼测试结果的影响,最后使用平板的瞬态冲击有限元仿真数据对相关结论进行了验证。研究表明:在所研究的频段内,当各模态的阻尼相差不大时,衰减法测试结果同统计能量分析意义下的频段阻尼一致,反之衰减法测试结果小于统计能量分析意义下的频段阻尼;当频段外含有阻尼较小的模态时,该模态对该频段的频段阻尼测试结果将产生较大的影响;如果各模态的模态阻尼随频率变化平缓,则各频段的频段阻尼测试结果较为准确,反之相关频段的频段阻尼测试结果误差较大。 相似文献
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Experimental study on vibration and damping of curved panel treated with constrained viscoelastic layer 总被引:2,自引:0,他引:2
This paper presents experimental investigation on the damping effects of constrained layer damping treatment on a curved panel. Vibration attenuation of the curved panel is achieved by attaching constraining layer damping patches at the optimal locations. The placement strategies of constrained layer patches are devised using the modal strain energy (MSE) method. Locations for application of damping patches are those, where modal strain energy is maximum for the particular mode. The treatment is then applied to the elements that have highest MSE in order to target specific modes of vibrations. Extensive experiments are conducted by making number of separate samples of viscoelastic and constrained layer damping patches for each configuration to damp different modes simultaneously or independently. The experimental results demonstrate utility of the modal strain energy technique as an effective tool for selecting the locations of the constrained layer damping treatment to achieve desired damping characteristics over a broad frequency band. 相似文献
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混合结构由不同阻尼特性的材料组成,确定其阻尼矩阵存在困难。分块Rayleigh阻尼模型由于数学上的简易性,被广泛用于构建混合结构的阻尼矩阵,但分块Rayleigh阻尼模型的计算精度与参考频率的选择方法直接相关。针对参考频率的选择问题,依据结构动力响应的组成和特点,提出了一种确定Rayleigh阻尼系数的计算方法,进而实现基于分块Rayleigh阻尼模型的复模态叠加法。求解结构的瞬态反应时,根据结构前两阶振型的自振频率确定阻尼系数;求解结构的稳态反应时,选择结构的基频、与外激励频率接近的结构自振频率确定阻尼系数。依据地震波的频谱特性,提出了基于地震波卓越频率的分块Rayleigh阻尼模型,并结合地震加速度的分段线性假定,建立了混合结构的复模态叠加法。在此基础上,利用三角级数展开得到组成地震波的谐波频率,进一步提出了基于谐波频率的分块Rayleigh阻尼模型和对应的复模态叠加法。算例分析结果表明:所提方法误差更小,且克服了传统方法因振型选择不唯一导致的计算结果具有不确定性的问题;与基于地震波卓越频率的复模态叠加法相比,基于谐波频率的复模态叠加法计算量更大,但计算精度更高、适用范围更广。 相似文献
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将回传射线矩阵法推广至桩土系统的振动分析中,采用基于Timoshenko梁理论的Winkler地基模型,运用回传射线矩阵法及求根法求解桩顶固定且部分桩体埋入弹性地基中时桩的自振特性,并与基于有限元分析软件SAP2000的计算结果比较,验证利用回传射线矩阵法求解埋置结构自振特性的有效性和计算精度。同时,分析桩顶固定且部分桩体埋入黏弹性地基中时土体弹簧系数及土体阻尼系数对桩基自振频率和振型的影响。结果表明:随着土体弹簧系数的增大,埋置结构的各阶自振频率增大,土体弹簧系数对衰减系数没有影响,对埋置结构振型的影响较小;随着土体阻尼系数的减小,埋置结构的各阶自振频率增大,衰减系数相应减小,土体阻尼系数对埋置结构的低阶振型影响尤为明显,对高阶振型的影响较小。 相似文献
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采用激光全息(TV—holography)振动测试技术测量和分析了CD光盘的固有频率、模态振型以及模态分布情况。采用非接触声激励和非接触式激光全息摄像精确地测量出了CD光盘从零节圆到三节圆五节径的振动模态,最高模态频率达6300Hz。分析了节径振型和节圆振型间的关系和出现规律。结果表明:光盘的振型节线是由中心对称和轴对称的节径和节圆组成的,它们对应的振型也是中心对称和轴对称的;光盘的各阶固有频率是按一定的顺序排列的,节径和节圆的出现是有规律的,文中给出了表示这些规律的表达式。 相似文献
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P.K. Ambattu G. Burt V.F. Khan R.M. Jones A. Dexter V. Dolgashev 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2011,657(1):27-37
The Compact Linear Collider requires a crab cavity on each beamline prior to the interaction point to rotate the bunches before collision. The cavities are X-band travelling wave type and are located close to the final doublet of the beam delivery system. This makes the beam very sensitive to transverse momentum imparted by wakefields; hence the wakefields must be tightly controlled. Of special concerns are the orthogonal polarisation of the operating mode and the fundamental monopole mode of the crab cavity. The former mode is at the same frequency as the operating mode of a cylindrically symmetric cavity and the latter one is at a lower frequency and hence is difficult to damp using a single means. In this paper major problematic modes of the crab cavity are investigated and damping requirements for them are calculated. Possibility of meeting the required wakefield control using waveguide damping and choke damping is thoroughly investigated. As a comparison, damped-detuning is also investigated. 相似文献
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通过对橡胶阻尼材料动态热机械性能进行测试,研究了测试频率、升温速率、测试模式等参数对测试结果的影响。结果表明:测试频率和升温速率都对测试结果有较大影响,橡胶阻尼材料的动态力学性能参数随着测试频率和升温速率的增大均向高温方向移动,为了更好地表征材料的阻尼性能,最好采用较低的升温速率;另外,测试模式的选择、静态力动态力以及振幅的设定都会影响测试结果的准确性。 相似文献
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Vibration damping characteristics of carbon fiber-reinforced composites containing multi-walled carbon nanotubes 总被引:1,自引:0,他引:1
Shafi Ullah Khan Chi Yin Li Naveed A. SiddiquiJang-Kyo Kim 《Composites Science and Technology》2011,71(12):1486-1494
Vibration damping characteristic of nanocomposites and carbon fiber reinforced polymer composites (CFRPs) containing multiwall carbon nanotubes (CNTs) have been studied using the free and forced vibration tests. Several vibration parameters are varied to characterize the damping behavior in different amplitudes, natural frequencies and vibration modes. The damping ratio of the hybrid composites is enhanced with the addition of CNTs, which is attributed to sliding at the CNT-matrix interfaces. The damping ratio is dependent on the amplitude as a result of the random orientation of CNTs in the epoxy matrix. The natural frequency shows negligible influence on the damping properties. The forced vibration test indicates that the damping ratios of the CFRP composites increase with increasing CNT content in both the 1st and 2nd vibration modes. The CNT-epoxy nanocomposites also show similar increasing trends of damping ratio with CNT content, indicating the enhanced damping property of CFRPs arising mainly from the improved damping property of the modified matrix. The dynamic mechanical analysis further confirms that the CNTs have a strong influence on the composites damping properties. Both the dynamic loss modulus and loss factor of the nanocomposites and the corresponding CFRPs show consistent increases with the addition of CNTs, an indication of enhanced damping performance. 相似文献
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On Helmholtz and higher-order resonance of twin floating bodies 总被引:2,自引:0,他引:2
The Helmholtz mode and other symmetric modes of resonance of a moonpool between two heaving rectangular floating cylinders are investigated. The hydrodynamic behavior around these resonant modes is examined together with the associated mode shapes in the moonpool region. It is observed that near each of the resonance frequencies, the damping coefficient can vanish. The Helmholtz mode is characterized by a region of modest variation of added-mass value from negative to positive near the Helmholtz frequency. The peaks are, however, bounded with the cross-over point in sign corresponding to a bounded spike in damping. The higher-order resonant modes are characterized by the presence of standing waves in the moonpool, which leads to large spikes in the hydrodynamic behavior near the resonance frequencies. The Helmholtz frequency has a distinct value, while the higher-order resonances occur at fairly regular intervals of the frequency parameter, σ2(w ? b)/g, where w ? b is the moonpool gap. The parametric dependence of the hydrodynamic behavior on frequency and geometry is discussed. With best wishes to my colleague and good friend, Nick Newman, on the occasion of his 70th birthday. A leader and staunch supporter of marine hydrodynamics, Nick has expanded the reach and influence of this field through his insights and publications. His contributions have been wide-ranged and his graciousness to young researchers is exemplary. May he enjoy the best of health in the years to come. R.W. Yeung 相似文献
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Duan X Son H Gao B Zhang J Wu T Samsonidze GG Dresselhaus MS Liu Z Kong J 《Nano letters》2007,7(7):2116-2121
Resonance Raman spectra of individual strained ultralong single-wall carbon nanotubes (SWNTs) are studied. Torsional and uniaxial strains are introduced by atomic force microscopy manipulation. Torsional strain strongly affects the Raman spectra, inducing a large downshift in the E2 symmetry mode in the G+ band, but a slight upshift for the rest of the G modes and also an upshift in the radial breathing mode (RBM). Whereas uniaxial strain has no effect on the frequency of either the E2 symmetry mode in the G+ band or the RBM, it downshifts the rest of the G modes. The Raman intensity change reflects the effect of these strains on the SWNT electronic band structure. 相似文献