成任意角度连接的两块平板转角处阻振质量对平面弯曲波传递的影响分析

运用波分析法对于成任意角度连接的两块平板转角处的振动能量传递问题进行了理论分析,目的在于探讨附加在转角处的阻振质量对结构波传递的阻挡作用。通过引入两个局部坐标系及6个新的无量纲数,不仅简化了理论公式的推导,而且将透射及反射系数与模型的特征阻抗直接联系起来,揭示了这些参数的物理意义。本文同时还进行了简化模型实验,测试所得的插入损失与按照理论公式进行数值计算的结果进行比较,变化趋势一致。研究表明,转角处的阻振质量对于平面弯曲波透射所起的作用类似于一个“低通滤波器”,“阻带”区插入损失的量值主要取决于阻振质量的质量大小,而“阻带”宽度则取决于其转动惯量。     

弹性基础隔振系统的简化性能指标和有源控制力

系统研究了基础弹性对单层隔振系统、双层隔振系统及浮筏隔振系统隔振性能的影响。分析了不同隔振系统与不同弹性基础间的振动耦合特性,讨论了不同隔振系统的振级落差和力传递率特性,给出了振级落差和力传递率的简化计算方法。针对不同隔振系统的有源隔振问题,比较了不同作动器安装方式所需的控制力。研究表明,对于所有隔振系统,增加基础的刚度和阻尼有利于提高振级落差和力传递率;对于浮筏隔振系统,增加筏架的刚度和阻尼有利于提高隔振性能和减少有源隔振所需的控制力。      

磁流变液构成的类梯度结构振动传递特性

提出了一种磁流变液构成的类梯度结构,并通过理论建模、数值计算和实验研究了该结构的振动传递特性.磁流变液在磁场作用下具有液固转换的特殊理化性质,而液固转换过程就是磁流变液的振动传递阻抗变化过程.因此,基于磁流变液的这一特性,通过控制磁场,构建了类梯度结构.基于弹性波传递的一维波动方程,建立了垂直入射的弹性波在类梯度结构中传递的波动方程.然后,使用连续介质的离散化方法和传递矩阵法进行求解,得到振级落差的表达式,对其进行数值计算,分析类梯度结构的振级落差随弹性波频率和磁场强度的变化趋势.最后,对类梯度结构的振动传递特性进行了实验研究,分析了磁场强度对类梯度结构振动传递特性的影响.研究结果表明,与均匀场作用的磁流变液相比,类梯度结构对弹性波的衰减效果更好,且该结构具备良好的可调控特性.     

菱形HSLDS隔振器负刚度机构质量及摩擦力影响分析

以菱形负刚度机构HSLDS（high static low dynamic stiffness）隔振器（简称菱形HSLDS隔振器）为研究目标,采用虚功法建立负刚度机构等效摩擦力模型,并以拉格朗日方法建立包含负刚度机构质量及摩擦力因素的动力学方程;利用谐波平衡法（HBM）求解动力学方程,分析了负刚度机构质量及摩擦力对隔振的影响及其优化措施,并通过实物样机验证了理论模型的合理性。实验结果表明:负刚度机构质量及摩擦力对隔振均产生不利影响,应尽量减小;将负刚度机构连杆较短侧连接于载荷平台端,可以减小负刚度机构质量对较高频段隔振性能的影响;在限定隔振器刚度参数以及铰接副接触参数且同时满足刚度与摩擦力优化条件下,通过增大连杆机构杆长差的方式可以优化低频段隔振性能,并降低负刚度机构摩擦力对高频段隔振的影响。     

多级复合抑振系统的设计与研究

研究了多级复合抑振系统的动力学特性,以多级抑振系统刚体空间一般运动的坐标变换,系统的动能、势能和阻尼耗散函数,系统的拉格朗日方程为理论基础, 得出适用于质量块之间或质量块与平台之间具有多个相对运动自由度的多级隔振系统的运动微分方程组.分析了主动控制力与抑振器参数之间的关系.结果表明：对于多级复合抑振系统,抑制中高低频振动时,抑振作动器置于抑振对象与刚体之间的抑振性能较好,所需的主动抑振控制力也不大,并且易于实现各种先进的抑振控制.     

复杂弹性系统的结构噪声控制及最优化设计研究

本文研究了复杂线性振动系统的结构噪声控制问题，着重分析了设备弹性与振源输出特性对系统结构噪声抑制效果的影响，从理论上对高频隔振进行了深入探讨，给出了考虑设备与基础阻抗时复杂线性弹性系统的力传递率；建立了同时带频率及结构装配关系约束的优化设计数学模型，并就所关心的频段进行了优化分析。     

考虑弯曲和轴向振动模态的一维梁压电阻抗模型及试验研究

同时考虑一维梁结构的弯曲和轴向振动,对其压电阻抗模型进行建模分析和试验验证。在0.02～42 kHz频段内区分并标记了一维钢梁弯曲振动模态前18阶及轴向振动模态前3阶。结果表明:在0.02～7.5kHz频段内,数值计算和试验结果中谐振峰对应频率的相对误差较大:11.7%～16.5%,其原因可能是低频时振动能量较低且波的传播受结构阻尼、边界条件及环境噪音等因素影响较为明显;在7.5～42kHz范围内,两者谐振峰位置符合良好,相对误差较小:0.11%～2.31%,表明该模型在高频段具有较好的适用性;轴向振动模态对应频率大于弯曲振动模态。本研究为结构健康监测过程中检测频段的选取及损伤信息的提取提供参考。     

2007年作者索引

Arthur Arthur Newhall:(见汪俊等:一种基于时延估计的双辅助声源阵形校准方法)················……No.2(165 (见张永斌等:基于等效源法的平面近场声全息及其实验研究)······················……No.6(489)陈端石:成任意角度连接的两块平板转角处阻振质量对平面弯曲波传递的影响分析······……No.3(282陈国跃李双潘浩然:分布式位移传感下的有源声学结构误差传感策略··········……No.1(42) (见陈克安等:分布式位移传感下的有源声学结构误差传感策略)·············…     

反射型光变色超表面滤光结构

提出了一种反射型超表面滤光结构,该滤光结构由基底、低折射率纳米光栅、Ag光栅、SiNx高折射率介质层组成.理论模拟结果表明:45°入射角下,在垂直于光栅栅线的入射平面内,反射谱峰值出现在475 nm波长处;在平行于光栅栅线的入射平面内,反射谱峰值出现在550 nm波长处.其电场分布特性表明,在不同的平面内TE偏振入射光激发的导模共振区域不同,TM偏振下激发的导膜共振强度与表面等离子体共振强度不同,导致该结构在垂直于光栅栅线方向与平行于光栅栅线方向的两个平面内表现出两种截然不同的颜色.基于此制备的超表面结构样品不但光变色效果明显,且易于与纳米压印工艺相结合实现大幅面光变色结构制备,在防伪和图案信息编码等领域有广阔的应用前景.     

降低加肋双层圆柱壳辐射噪声线谱的结构声学设计

为降低双层圆柱壳辐射噪声线谱,从控制内壳振动响应和衰减壳间振动传递率进行结构声学设计。采用机械阻抗理论分析了环肋圆柱壳模态响应控制机理;由环肋振动方程推导分析了环肋径向机械阻抗特性;基于阻抗失配、波形转换原理提出一种阻抗加强环肋,分析了振动波阻抑特性;利用阻尼减振技术,综合考虑肋板的刚度、阻尼特性,设计了金属橡胶层叠肋板;结合数值计算实例,分析了设计双层壳模型的声辐射性能。结果表明:设计的双层加肋圆柱壳结构能有效降低辐射噪声线谱,在分析频段内辐射声压线谱平均降低约6.6 dB。研究结果对研制低噪声水下航行器具有良好的工程价值和应用前景。      

The effects of floating slab bending resonances on the vibration isolation of rail viaduct

This paper compared the performance of several isolation designs to control vibration transmissions from concrete rail viaducts. The isolation systems analysed includes medium- and short-length floating slabs, and floating ladders. The vibration was measured in Japan, Korea and Hong Kong. The study aimed to assess the effects of bending resonances of the floating slab systems. Simple formulae of estimating the significant bending resonance frequency and support passage frequency of a floating slab system are proposed. The resonance peaks obtained in site measurement are found to be in agreement with the calculation results. The results show that other than the vertical rigid body resonances for the isolation systems, the bending resonances of slabs have significant effects on vibration isolation performance. In particular, bending resonance frequencies should not coincide with the vertical isolator resonance and support passage frequency. According to the in-situ measurement results, a mini-type concrete floating slab can reduce the vibration level by more than 30 dB in the frequency range of 63-200 Hz. This should be achieved by designing the first bending resonances of the floating slab to be out of the dominant frequency range of concrete rail viaduct vibration.     

一种光电载荷非线性隔振装置的研究

针对光电载荷对隔振性能的需求,提出一种采用菱形连杆机构作为负刚度组件,具有高静、低动刚度特点的非线性隔振器（简称菱形HSLDS隔振器）。采用静力学分析方法,建立了隔振器数学模型,研究了刚度参数设定以及非线性调节方法;利用谐波平衡法（HBM）求解动力学方程,分析了各参数对隔振性能的影响关系;采用动力学仿真软件ADAMS及实物样机对理论模型与结论进行了验证。测试结果表明:菱形HSLDS隔振器具有较方便的参数调整能力,零位刚度及刚度非线性可通过拉簧参数与连杆参数进行设定、优化,隔振的刚度非线性优化程度受主隔振器阻尼以及零位刚度参数影响。相比于传统线性隔振器,菱形HSLDS具有显著的非线性隔振优势,可较好地满足光电载荷隔振需求。     

3D analysis of in-filled trench as passive barriers for ground vibration isolation

The three-dimensional (3D) problem of the ground vibration isolation by an in-filled trench as a passive barrier is studied theoretically. Integral equations governing Rayleigh wave scattering are derived based on the Green’s solution of Lamb problem. The integral equations are solved accurately and efficiently with an iteration technique. They are used to evaluate the complicated Rayleigh wave field generated by irregular scatterers embedded in an elastic half-space solid. The passive isolation effectiveness of ground vibration by the in-filled trench for screening Rayleigh wave is further studied in detail. Effects of relevant parameters on the effectiveness of vibration isolation are investigated and presented. The results show that a trench filled with stiff backfill material gets a better isolation effect than a soft one, and increasing the depth or width of the in-filled trench also improves its screening effectiveness. The effectiveness and the area of the screened zone are surging with the increase in the length of the in-filled trench. Supported by the National Natural Science Foundation of China (Grant Nos. 50678128 and 50538010) and the Research Fund for PhD Student of Chinese College (Grant No. 20050247030)     

Effect of viscous damping on power transmissibility for the vibration isolation of building services equipment

Vibration isolation plays an important role in both the vibration and noise control of building services equipment. To evaluate vibration isolation performance, the force transmissibility method is commonly adopted. However, increasing the damping effect in the force transmissibility method reduces both the resonance peak value and the isolation performance in the “isolation region”. The limitation of the method is that the transmitted displacement of a floor structure and the interaction of mounting points are neglected. To include the floor displacement and the interaction of mounting points, Mak and Su recently proposed the power transmissibility method to assess the performance of vibration isolation. In this paper, the effect of viscous damping on power transmissibility is investigated. A practical procedure for experimentally determining the damping ratio is also given.     

双稳态结构中的1/2次谐波共振及其对隔振特性的影响

以典型的双稳态系统——屈曲梁结构为例,基于等效模型,结合解析、数值和实验手段,研究了双稳态结构中的1/2次谐波共振特性、演化过程、参数调节规律及其对隔振特性的影响.研究发现,当非线性刚度系数或激励幅值增加到一定程度时,系统会在一定带宽下产生显著的1/2次谐波共振;随着激励幅值增加,阻尼系统的1/2次谐波遵循“产生-增强-衰退-消失”的过程,该过程对峰值频率和峰值传递率有重要影响;适当提高非线性强度能有效改善双稳态结构隔振特性.针对双稳态屈曲梁结构开展的实验验证了1/2次谐波特性和隔振特性变化规律.     

用于汽车低频振动控制的局域共振声子晶体*

低频振动的控制是评估汽车舒适性的重要指标。针对汽车板件结构的低频振动控制问题,提出了一种基于局域共振机理的新型准二维声子晶体板。其结构由单侧复合圆柱共振单元周期排布在基板上构成。通过有限元方法得到了该结构的带隙特性,并结合其振型和传输谱分析了低频完全带隙的形成机理。研究表明,不同形式的板振动模式与圆柱共振单元的局域共振模式相互耦合形成面内带隙与面外带隙,两者叠加形成完全带隙。进一步研究发现,通过改变结构的材料和尺寸参数可以将共振带隙调节到满足实际应用要求的极低频范围,可在低于100 Hz的频段形成完全带隙,并可在更宽的频带内抑制z方向振动的弯曲波,为声子晶体在车身板件减振中的实际应用提供了依据。     

A study of power transmissibility for the vibration isolation of coherent vibratory machines on the floor of a building

Vibration isolation is commonly adopted by engineers to reduce the vibratory effect caused by building services equipment. However, the relationship between the amount of sound power transmitted to the floor and the interaction between the mounting points of several machines is uncertain, as it is common to install several coherent machines on the same floor, for example, two water pumps of the same type in a plant room. We conduct an analytical study of the effects of the interaction between two coherent vibratory sources on the power transmitted to the floor. The study is based on two simple vibratory sources with a single contact point, two rectangular machine models of even-mass distribution with four symmetrical supports and the calculated mobilities of a simply supported concrete floor. We find that the total power obtained from coherent sources (point sources or machine models) differs considerably from that obtained from independent sources at some frequencies in a vibration isolation region. To predict the performance of isolators more accurately, the power transmissibility method proposed previously by Mak and Su should consider not only the effect of effective floor mobility and the interactions of the mounting points of the same sources, but also the interactions of the mounting points of different sources on the floor.     

Stability and performance limits for active vibration isolation using blended velocity feedback

This paper presents a theoretical study of active vibration isolation on a two degree of freedom system. The system consists of two lumped masses connected by a coupling spring. Both masses are also attached to a firm reference base by a mounting spring. The lower mass is excited by a point force. A reactive control force actuator is used between the two masses in parallel with the coupling spring. Both masses are equipped with an absolute velocity sensor. The two sensors and the actuator are used to implement velocity feedback control loops to actively isolate the upper mass from the vibrations of the lower mass over a broad range of frequencies. The primary concern of the study is to determine what type of velocity feedback configuration is suitable with respect to the five parameters that characterise the system (the three spring stiffnesses and the two masses). It is shown analytically that if the ratio of the lower mounting spring stiffness to the lower mass is larger than the ratio of the upper mounting spring stiffness to the upper mass (supercritical system), feeding back the absolute upper mass velocity to the reactive force actuator results in an unconditionally stable feedback loop and the vibration isolation objective can be fully achieved without an overshot at higher frequencies. In contrast, if the ratio of the lower mounting spring stiffness to the lower mass is smaller than the ratio of the upper mounting spring stiffness to the upper mass (subcritical system), the upper mass velocity feedback is conditionally stable and the vibration isolation objective cannot be accomplished in a broad frequency band. For subcritical systems a blended velocity feedback is proposed to stabilise the loop and to improve the broad-band vibration isolation effect. A simple inequality is introduced to derive the combinations between the two error velocities that guarantee unconditionally stable feedback loops.     

A cylindrical standing wave ultrasonic motor using bending vibration transducer

A cylindrical standing wave ultrasonic motor using bending vibration transducer was proposed in this paper. The proposed stator contains a cylinder and a bending vibration transducer. The two combining sites between the cylinder and the transducer locate at the adjacent wave loops of bending vibration of the transducer and have a distance that equal to the half wave length of bending standing wave excited in the cylinder. Thus, the bending mode of the cylinder can be excited by the bending vibration of the transducer. Two circular cone type rotors are pressed in contact to the end rims of the teeth, and the preload between the rotors and stator is accomplished by a spring and nut system. The working principle of the proposed motor was analyzed. The motion trajectories of teeth were deduced. The stator was designed and analyzed with FEM. A prototype motor was fabricated and measured. Typical output of the prototype is no-load speed of 165 rpm and maximum torque of 0.45 N m at an exciting voltage of 200 V_rms.     

Ultrawide low frequency band gap of phononic crystal in nacreous composite material

The band structure of a nacreous composite material is studied by two proposed models, where an ultrawide low frequency band gap is observed. The first model (tension-shear chain model) with two phases including brick and mortar is investigated to describe the wave propagation in the nacreous composite material, and the dispersion relation is calculated by transfer matrix method and Bloch theorem. The results show that the frequency ranges of the pass bands are quite narrow, because a special tension-shear chain motion in the nacreous composite material is formed by some very slow modes. Furthermore, the second model (two-dimensional finite element model) is presented to investigate its band gap by a multi-level substructure scheme. Our findings will be of great value to the design and synthesis of vibration isolation materials in a wide and low frequency range. Finally, the transmission characteristics are calculated to verify the results.