Vibrational power flow from machines into built-up structures,part III: Power flow through isolation systems

The power flowing through the isolators and into the supporting foundation of a machine is examined by approximating the driving point frequency response function of the foundation. One and two stage isolation of machines with internal force or velocity sources is considered. Two stage isolation is superior to single stage isolation in reducing power flow in those circumstances where the excitation spectra do not cover the two resonances of the system.     

Direct energy flow measurement in magneto-sensitive vibration isolator systems

The effectiveness of highly nonlinear, frequency, amplitude and magnetic field dependent magneto-sensitive natural rubber components applied in a vibration isolation system is experimentally investigated by measuring the energy flow into the foundation. The energy flow, including both force and velocity of the foundation, is a suitable measure of the effectiveness of a real vibration isolation system where the foundation is not perfectly rigid. The vibration isolation system in this study consists of a solid aluminium mass supported on four magneto-sensitive rubber components and is excited by an electro-dynamic shaker while applying various excitation signals, amplitudes and positions in the frequency range of 20–200 Hz and using magneto-sensitive components at zero-field and at magnetic saturation. The energy flow through the magneto-sensitive rubber isolators is directly measured by inserting a force transducer below each isolator and an accelerometer on the foundation close to each isolator. This investigation provides novel practical insights into the potential of using magneto-sensitive material isolators in noise and vibration control, including their advantages compared to traditional vibration isolators. Finally, nonlinear features of magneto-sensitive components are experimentally verified.     

船舶机械磁悬浮气囊混合隔振技术

有源无源混合隔振是控制船舶低频线谱噪声的重要技术,但工程应用的实例还非常少见。在磁悬浮-气囊混合隔振理论和原理样机研究的基础上,针对船用机械低频线谱的隔振需求,进一步突破了体积小、输出力大、功耗低、频响平直、波形失真度低等磁悬浮作动器工程化设计技术;解决了混合隔振器的稳定性和冲击、摇摆适应性等技术难题;研究了工程实用的控制算法,采用非线性逆模型补偿使控制系统线性化,并提出了窄带Fx-Newton时域算法,可在机械设备运行时的多线谱、多通道耦合、线谱振幅非稳态等情况下实现快速稳定控制;研制了船用200 kW柴发机组混合隔振装置,实验结果表明该技术具有优良的宽频隔振效果和低频线谱控制能力,性能可满足工程实用要求。      

Asymmetric multimode interference isolator based on nonreciprocal phase shift

This paper presents an asymmetric multimode interference-based (MMI) optical isolator, by utilizing the magneto-optical nonreciprocal phase shift (NPS). Equivalent beam propagation method (BPM) simulation of symmetric and asymmetric isolators are performed using configuration of Air/Ce:YIG/SiO₂ on silicon substrate for integration. The asymmetric isolator is found to be much more compact in size and efficient in isolation compared with symmetric isolator. Simulation results show that the isolation of asymmetric structure is 23.8 dB higher than that of symmetric one. It is mainly because both symmetric mode and anti-symmetric mode are excited in asymmetric structure and hence can interfere destructively. The proposed device may play an important role in the optical communication systems and photonic integrated devices.     

Moment induced structure-borne sound emission of resiliently mounted machines

I.IntroductionInmanypractica1cnginccringsituations,suchasinbui1dings,carsandships,machinesaremountedonseatingstructurcsthroughcompliantiso1atorsinordertoreducethetransmissionofunwantedmachinevibrations.Thercsidualtransmissionresu1tsfromacombinationofforcesandmomcntsatthccontactpointsandinordcrtoidcntifytheimportanttransmissionmechanjsms,eachshou1didea1lybcasscsscdbymcasurcmcntorprediction.MuchofpreviousworkontranRmissionatmountingshasconccntratcdonvcrtica1forceinduccdpower["l.Itmaybethatsucha…     

高功率脉冲光隔离器非线性及热效应分析

从理论上分析了脉冲情况下,磁光晶体横向温度梯度引起的光弹效应、消光比以及克尔效应对光隔离器隔离度的影响,并与连续入射情况进行了对比。结果表明:在平均功率相同的情况下,脉冲光束入射比连续光束入射情况隔离度更低;当平均功率较小时,消光比对隔离度的影响较大;当平均功率较大时,消光比对隔离度的影响有限,主要表现出光弹效应对隔离度的影响;当峰值功率密度较大时,克尔效应将显著降低隔离度,并且峰值功率密度越大,对隔离度的降低程度越大。     

A power transmissibility method for assessing the performance of vibration isolation of building services equipment

Force transmissibility is commonly adopted in building services engineering to assess the performance of vibration isolation. However, it neglects the effect of floor mobility on structure-borne sound power transmitted from a vibratory machine to the floor/roof and the interactions among several contact points between the vibratory machine and the floor/roof. The problem that motivated this study is the occasional occurrence of unsatisfactory performance of vibration isolators observed in building services engineering. This problem may be due to the over-simplification of the vibratory problem in the usual definition of the un-damped force transmissibility or isolation efficiency commonly used in engineering practice. In this paper, use of a “power transmissibility”, which includes the effect of floor mobility and the interaction of all dynamic forces transmitted to the floor through the vibration isolators, is proposed.     

模块化固体开关脉冲功率源触发技术

为满足高功率脉冲源小型化和高重复频率运行的研制需要,提出了一种基于固体开关(可控硅)的电感隔离型高压脉冲发生器触发控制设计方案。这种方案采用光纤收发器件及其驱动电路和高耐压脉冲变压器,研究了固体开关脉冲功率源控制技术中的触发信号高压隔离、光分多路及脉冲变压器分立或并联使用等关键技术。给出了单模块触发控制电路的设计及测试结果:5级LC回路在每级充电电压4 kV输入时,实现最终32 kV的输出,功率源模块输出/输入电压转换效率达到80%。同时对其应用特点进行了分析和讨论。     

InGaAsP/InP evanescent mode waveguide optical isolators and their application to InGaAsP/InP/Si hybrid evanescent optical isolators

We theoretically investigated InGaAsP/InP evanescent mode waveguide optical isolators and proposed their application to InGaAsP/InP/Si hybrid evanescent optical isolators. InGaAsP/InP evanescent optical isolators are composed of semiconductor optical amplifier (SOA) waveguides having InGaAsP multiple quantum well (MQW) active layer and upper InGaAsP waveguide layer with ferromagnetic layer. Optical isolation is obtained for evanescent optical mode in the InGaAsP waveguide layer. InGaAsP/InP/Si hybrid evanescent optical isolators are theoretically proposed based on the idea of InGaAsP/InP evanescent optical isolators. InGaAsP/InP/Si hybrid evanescent optical isolators are composed of ferromagnetic metal loaded silicon evanescent waveguides with wafer-bonded InGaAsP/InP optical gain material. The optical isolation and propagation loss are discussed with the structure of silicon evanescent waveguides, and optical isolation of 8.0 dB/mm was estimated. The concept of semiconductor evanescent mode optical isolators is feasible with InP based photonic integrated circuits and advanced silicon photonics.     

A study of the effect of inertia blocks on the stability of the vibratory system and the performance of vibration isolation

Resilient vibration isolators and inertia blocks are commonly used by building services engineers to isolate vibratory machines in buildings. They are selected in practice according to the force transmissibility method and some crude methods or the experience of building services engineers. These methods, however, can produce inaccurate predictions, and a power transmissibility method has recently been proposed to assess the performance of vibration isolation. In this paper, normalized average vibration velocities and overall rotational velocities are proposed to study the stability of the vibratory system. The result shows that the use of an inertia block primarily does not improve the performance of vibration isolation, but does increase the stability of the vibratory system regardless of whether the machine is of even or uneven mass distribution and whether it is driven by the vibratory force or the rocking moment.     

Research on performance indices of vibration isolation system

Power flow transmissibility is proposed as a performance index to evaluate the performance of isolation system. It is defined as the ratio of the power flow input into the equipment and the power flow transmitted into the receiver. Based on a simple vibration isolation system, its relationship with other performance indices is given by theoretical and numerical analysis. The results show that power flow transmissibility can reflect the response characteristics of the whole isolation system effectively. In addition, power flow transmissibility can be estimated easily according to vibration acceleration level difference and does not involve the measurement of power flow. Furthermore, the influences of several parameters such as the damping, loss factor and stiffness of isolator on power flow transmissibility are analyzed.     

Wire Rope Isolators for Seismic Base Isolation

Tall and slender substation equipment is prone to failure under seismic excitations. The consequences of such failure can be devastating and lead to weeks or months of lost power.
The IEEE Std 693-2005 ensures that all substation equipment installed in high seismic areas are designed to withstand earthquakes of a severity related to that area.
There are numerous ways to increase the seismic strength of substation equipment and this paper will discuss doing so by base isolation, specifically using wire rope isolators (WRIs).
It is the purpose of this paper to present a case study in which the Socitec Group provided a WRI base isolation design for a high voltage surge arrester. The simulation results show that the moment at the base of the surge arrester was reduced by 55% when using the Socitec designed WRI base isolation system.     

VIBRATIONAL POWER TRANSMISSION FROM A MACHINE TO ITS SUPPORTING CYLINDRICAL SHELL

Power flows from a vibratory machine to its supporting structure are of primary concern in a passive or active isolation system design. Although in the literature there is a fair number of investigations on the power inputs to beams, plates or the like, few attempts have been made for other commonly used structures such as cylindrical shells. In this paper, the vibratory power flows from a rigid-body machine to an elastic cylindrical shell are studied considering the contributions of the non-radial (tangential and axial) displacements and forces. In particular, it is argued that the notion that the motion of a thin shell is primarily radial does not necessarily dictate that the power transmissions are predominantly carried out by the radial displacement. This point is subsequently illuminated through numerical examples. Another issue discussed here is concerned with the effects on the power flows of the cross couplings of the (different) displacement components. It is shown that even though the contributions of the cross couplings are usually insignificant, they may become important if the vibration isolators are substantially hard as compared with the local shell stiffness or impedance. This assertion is particularly useful when an experimental technique is used to measure the vibratory power flows into a supporting structure.     

Reduction of vibration and noise radiation of an underwater vehicle due to propeller forces using periodically layered isolators

Using periodic structure theory, the suppression of vibration and noise radiation from an underwater vehicle due to excitation from propeller forces is investigated. The underwater vehicle is modelled in two parts (the hull and the propeller/shafting system). A model of the propeller/shafting system is constructed using a modular approach and considers the propeller, shaft, thrust bearing, isolation structure and foundation. Different forms of isolator are considered – a simple spring-damper system, a continuous rod and a periodically layered structure. The dynamic properties of the underwater vehicle and the isolation performances of various isolators are compared and analysed. The stop band properties of the periodic isolator are used to enhance the passive control performance. Furthermore, an integrated isolation device is proposed that consists of the periodic isolator and a dynamic absorber, and its isolation performance is investigated. The effects of the absorber parameters on the performance of the integrated device are also analysed. Finally, the radiated sound pressure is calculated to verify the attenuation. The numerical results show that the vibration and noise radiation are greatly attenuated in the stop bands. By optimising the design of the periodic isolators and its integrated structures, the suppression of the vibration and noise radiation can be improved effectively.     

Compact asymmetric sound absorber at the exceptional point

We present an asymmetric absorber at an exceptional point(EP) with a compact configuration and deep-subwavelength thickness.Unlike conventional side-branched sound absorbers in dual-port systems, the proposed asymmetric absorber exhibits a compact shape that is coaxial with the waveguide. By tuning the loss and geometric parameters of the non-Hermitian system to reach an EP, we observe extreme asymmetric absorption. This phenomenon is theoretically and experimentally validated by observing a quasi-perfect absorption and a near-total reflection for opposite incidences at the ultra-thin(1/28 th of the operating wavelength)neck-embedded tube employed in this study. Furthermore, we demonstrate an EP-induced tunable asymmetric absorption. Our study proposes novel approaches to manipulate the EP-induced wave phenomena, paving the way for the development of novel acoustic absorbers, sensors, isolators, and directional devices.     

Effects of isolators internal resonances on force transmissibility and radiated noise

Vibration isolators have been extensively used to reduce the vibration and noise transmitted between the components of mechanical systems. Although some previous studies on vibration isolation considered the inertia of isolators, they only examined its effects on the vibration of single degree-of-freedom (d.o.f.) systems. These studies did not emphasize the importance of the isolators’ inertia, especially from the perspective of noise reduction. This paper shows that the internal dynamics of the isolator, which are also known as internal resonances (IRs) or wave effects, can significantly affect the isolator performance at high frequencies. To study the IR problem, a model of a primary mass connected to a flexible foundation through three isolators is used. In this model, the isolator is represented as a one-dimensional continuous rod that accounts for its internal dynamics. The primary mass is modelled as a rigid body with three d.o.f.'s. The effects of the IRs on the force transmissibility and the radiated sound power from the foundation are examined. It is shown that the IRs significantly increase the force transmissibility and the noise radiation level at some frequencies. These effects cannot be predicted using a traditional model that neglects the inertia of the isolator. The influence of the foundation flexibility on the IRs is also investigated. It is shown that the foundation flexibility greatly affects the noise radiation level but it affects only slightly the force transmissibility, especially at high frequencies where the IRs occur.     

Design and experiment of a compact quasi-zero-stiffness isolator capable of a wide range of loads

This paper proposes the design and experiment of a vibration isolator capable of isolating a wide range of loads. The isolator consists of two oblique springs and one vertical spring to achieve quasi-zero stiffness at the equilibrium position. The quasi-zero-stiffness characteristic makes the isolator attenuate external disturbance more at low frequencies, when compared with linear isolators. Unlike previous studies, this paper focuses on the analysis of the effect of different loads and the implementation of an adjustment mechanism to handle a wide range of loads. To ensure zero stiffness under imperfect stiffness matching, a lateral adjustment mechanism is also proposed. Instead of using coil springs, special planar springs are designed to realize the isolator in a compact space. Static and dynamic models are developed to evaluate the effect of key design parameters so that the isolator can have a wide isolation range without sacrificing its size. A prototype and its associated experiments are presented to validate the transmissibility curves under three different loads. The results clearly show the advantage of quasi-zero-stiffness isolators against linear isolators.     

Static and dynamic stability of pneumatic vibration isolators and systems of isolators

Pneumatic vibration isolation is the most widespread effective method for creating vibration-free environments that are vital for precise experiments and manufacturing operations in optoelectronics, life sciences, microelectronics, nanotechnology and other areas. The modeling and design principles of a dual-chamber pneumatic vibration isolator, basically established a few decades ago, continue to attract attention of researchers. On the other hand, behavior of systems of such isolators was never explained in the literature in sufficient detail. This paper covers a range of questions essential for understanding the mechanics of pneumatic isolation systems from both design and application perspectives. The theory and a model of a single standalone isolator are presented in concise form necessary for subsequent analysis. Then the dynamics of a system of isolators supporting a payload is considered with main attention directed to two aspects of their behavior: first, the static stability of payloads with high positions of the center of gravity; second, dynamic stability of the feedback system formed by mechanical leveling valves. The direct method of calculating the maximum stable position of the center of gravity is presented and illustrated by three-dimensional stability domains; analytic formulas are given that delineate these domains. A numerical method for feedback stability analysis of self-leveling valve systems is given, and the results are compared with the analytical estimates for a single isolator. The relation between the static and dynamic phenomena is discussed.     

Ferrite resonance isolators in coaxial,strip, and rectangular waveguides with a dielectric

An analysis is given of ferrite resonance isolators in coaxial and strip lines and in a rectangular waveguide containing a dielectric. The analysis is based on numerical calculations (using a computer) using the results obtained in [1]. The results enable us to estimate the influence of the thickness of the dielectric, its permittivity, the ferromagnetic resonance line width and other parameters, upon the bandwidth of the system and upon the optimum magnetization ensuring the maximum isolation for the chosen system parameters and center frequency of the band. In this paper the terminology used is the same as in [1].     

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.