• Title/Summary/Keyword: Material damping ratio

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Airbag Accelerometers Using Silicon Epitaxial Layers (실리콘 에피층을 이용한 자동차 에어백용 가속도계)

  • 고종수;김규현;이창렬;조영호;이귀로;곽병만
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.5
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    • pp.9-15
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    • 1996
  • A silicon microaccelerometer is designed and fabricated using silicon epitaxial layers for automotive electronic airbag applications. A cantilever structure is chosen for high sensitivity and piezoresistive detection method is adopted for circuit simplicity and low cost. An optimum design is used to find optimum microstructure sizes for maximum sensitivity subject to performance requirements and design constraints on natural frequency, damping ratio, maximum allowable stress and microfabrication limitations. The microaccelerometer is fabricated by micromachining processing steps, composed of material-selective and orientation-dependent chemical etching techniques. Fabricated prototype shows a sensitivity of 88.6$\mu\textrm{V}$/g within a resonant frequency of 1.75KHz. Estimated performance of the microaccelerometer is compared with measured one. Discrepancy between the theoretical values and the experimental values is discussed together with possible sources of the errors.

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Multiple-Mode Structural Vibration Control Using Negative Capacitive Shunt Damping

  • Park, Chul-Hue;Park, Hyun-Chul
    • Journal of Mechanical Science and Technology
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    • v.17 no.11
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    • pp.1650-1658
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    • 2003
  • This paper deals with a novel shunt circuit, which is capable of suppressing multimode vibration amplitudes by using a pair of piezoceramic patches. In order to describe the characteristic behaviors of a piezoelectric damper connected with a series and a parallel resistor-negative capacitor branch circuit, the stiffness ratio and loss factor with respect to the non-dimensional frequency are considered. The mechanism of the shunt damper is also described by considering a shunt voltage constrained by shunt impedance. To obtain a guideline model of the piezo/beam system with a negative capacitive shunting, the governing equations of motion are derived through the Hamilton's principle and a piezo sensor equation as well as a shunt-damping matrix is developed. The theoretical analysis shows that the piezo/beam system combined with a series and a parallel resistor-negative capacitor branch circuit developed in this study can significantly reduce the multiple-mode vibration amplitudes over the whole structural frequency range.

Vibration analysis of honeycomb sandwich composites filled with polyurethane foam by Taguchi Method

  • Aydin, Muhammet R.;Gundogdu, Omer
    • Steel and Composite Structures
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    • v.28 no.4
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    • pp.461-470
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    • 2018
  • In this study, the effect of polyurethane foam filler, in addition to surface layer thickness and core material thickness, on vibration characteristics of sandwich structures was investigated. The manufacturing process was carried out according to the Taguchi method. The natural frequencies and damping ratios of the produced samples were determined experimentally for fixed-free boundary conditions. In addition, solid models were developed for test samples and their finite element analyses were performed with $ANSYS^{(R)}$ to obtain their natural frequencies and mode shapes. An acceptably good agreement was found with the comparison of experimental results with the numerically obtained ones. The most effective parameters on the vibration characteristics of the sandwich structure were determined by the Taguchi method.

A Study on the Damping Characteristics of a Hybrid Smart Structure Using Electrorheological Fluids and PZT (전기유동유체와 압전세라믹을 이용한 복합지능구조물의 감쇠특성 연구)

  • 윤신일;박근효;한상보;최윤대
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2003.04a
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    • pp.382-387
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    • 2003
  • Many type of smart materials and control laws are available to actively adjust the structure from various external disturbances. Usually, a certain type of control law to activate a specific smart material is tell established, but the effectiveness of the control scheme is limited by the choice of the smart materials and the responses of the structure. ER fluid is adequate to provide small but arbitrary control forces at any point along the structure. It was found that active vibration control of the structure embedded with ER fluids fluidly to suppress the vibration excited with broad band frequency due to the limited change of the structure characteristics. To compensate this limited effect of the control scheme with ER fluid alone, PPF control using PZT as an actuator is added to construct a hybrid controller.

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Sound Radiation From Infinite Beams Under the Action of Harmonic Point Forces (조화집중하중을 받는 무한보에서의 음향방사)

  • 김병삼;홍동표
    • Journal of KSNVE
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    • v.2 no.1
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    • pp.33-39
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    • 1992
  • The problem of sound radiation from infinite elastic beams under the action of harmonic point forces is studied. The reaction due to fluid loading on the vibratory response of the beam is taken into account. The beam is assumed to occupy the plane z = 0 and to be axially infinite. The beam material and the elastic foundation re assumed to be lossless and Bernoulli-Euler beam theory including a tension force (T), damping coefficient (C) and stiffness of foundation $(\kappa_s)$ will be employed. The non-dimensional sound power is derived through integration of the surface intensity distribution over the entire beam. The expression for sound power is integrated numerically and the results are examined as a function of wavenumber ratio$(\gamma)$ and stiffness factor$(\Psi)$. Here, our purpose is to explain the response of sound power over a number of non-dimensional parameters describing tension, stiffness, damping and foundation stiffness.

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Sound Radiation From Infinite Beams Under the Action of Harmonic Moving Line Forces (조화분포이동하중을 받는 무한보에서의 음향방사)

  • 김병삼;이태근;홍동표
    • Journal of KSNVE
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    • v.3 no.3
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    • pp.245-251
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    • 1993
  • The problem of sound radiation from infinite elastic beams under the action on harmonic moving line forces is studies. The reaction due to fluid loading on the vibratory response of the beam is taken into account. The beam is assumed to occupy the plane z=0 and to be axially infinite. The beam material and elastic foundation are assumed to be lossless and Bernoulli-Euler beam theory including a tension force (T), damping coefficient (C) and stiffness of foundation $(\kappa_s)$ will be employed. The non-dimensional sound power is derived through integration of the surface intensity distribution over the entire beam. The expression for sound power is integrated numerically and the results examined as a function of Mach number (M), wavenumber ratio$(\gamma{)}$ and stiffness factor $(\Psi{)}$. Here, our purpose is to explain the response of sound power over a number of non-dimensional parameters describing tension, stiffness, damping and foundation stiffness.

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Sound Radiation Analysis for Structure Vibration Noise Control of Vehicle Tire under The Action of Random Moving Line Forces (불규칙 이동분포하중을 받는 차량 타이어의 구조 진동소음 제어를 위한 음향방사 해석)

  • Kim Byoung-sam
    • Proceedings of the Acoustical Society of Korea Conference
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    • autumn
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    • pp.221-224
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    • 2004
  • A theoretical model has been studied to describe the sound radiation analysis for structure vibration noise of vehicle tires under the action of random moving line forces. When a tire is analyzed, it had been modeled as curved beams with distributed springs and dash pots that represent the radial , tangential stiffness and damping of tire, respectively. The reaction due to fluid loading on the vibratory response of the curved beam is taken into account. The curved beam is assumed to occupy the plane y=0 and to be axially infinite. The curved beam material and elastic foundation are assumed to be lossless Bernoulli-Euler beam theory including a tension force, damping coefficient and stiffness of foundation will be employed. The expression for sound power is integrated numerically and the results examined as a function of Mach number, wave-number ratio and stiffness factor. The experimental investigation for structure vibration noise of vehicle tire under the action of random moving line forces has been made. Based on the Spatial Transformation of Sound Field techniques, the sound power and sound radiation are measured. Results strongly suggest that operation condition in the tire material properties and design factors of the tire govern the sound power and sound radiation characteristics.

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Cyclic testing of a new visco-plastic damper subjected to harmonic and quasi-static loading

  • Modhej, Ahmad;Zahrai, Seyed Mehdi
    • Structural Engineering and Mechanics
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    • v.81 no.3
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    • pp.317-333
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    • 2022
  • Visco-Plastic Damper (VPD) as a passive energy dissipation device with dual behavior has been recently numerically studied. It consists of two bent steel plates and segments with a viscoelastic solid material in between, combining and improving characteristics of both displacement-dependent and velocity-dependent devices. In order to trust the performance of VPD, for the 1st time this paper experimentally investigates prototype damper behavior under a wide range of frequency and amplitude of dynamic loading. A high-axial damping rubber is innovatively proposed as the viscoelastic layer designed to withstand large axial strains and dissipate energy accordingly. Test results confirmed all assumptions about VPD. The behavior of VPD subjected to low levels of excitation is elastic while with increasing levels of excitation, a significant source of energy dissipation is provided through the yielding of the steel elements in addition to the viscoelastic energy dissipation. The results showed energy dissipation of 99.35 kN.m under a dynamic displacement with 14.095 mm amplitude and 0.333 Hz frequency. Lateral displacement at the middle of the device was created with an amplification factor obtained ranging from 2.108 to 3.242 in the rubber block. Therefore, the energy dissipation of viscoelastic material of VPD was calculated 18.6 times that of the ordinary viscoelastic damper.

Experimental study of controllable MR-TLCD applied to the mitigation of structure vibration

  • Cheng, Chih-Wen;Lee, Hsien Hua;Luo, Yuan-Tzuo
    • Smart Structures and Systems
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    • v.15 no.6
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    • pp.1481-1501
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    • 2015
  • MR-TLCD (Magneto-Rheological Tuned Liquid Column Damper) is a new developed vibration control device, which combines the traditional passive control property with active controllability advantage. Based on traditional TLCD governing equation, this study further considers MR-fluid viscosity in the equation and by transforming the non-linear damping term into an equivalent linear damping, a solution can be obtained. In order to find a countable set of parameters for the design of the MR-TLCD system and also to realize its applicability to structures, a series of experimental test were designed and carried out. The testing programs include the basic material properties of the MR-fluid, the damping ratio of a MR-TLCD and the dynamic responses for a frame structure equipped with the MR-TLCD system subjected to strong ground excitations. In both the analytical and experimental results of this study, it is found that the accurately tuned MR-TLCD system could effectively reduce the dynamic response of a structural system.

Vibration behavior of large span composite steel bar truss-reinforced concrete floor due to human activity

  • Cao, Liang;Li, Jiang;Zheng, Xing;Chen, Y. Frank
    • Steel and Composite Structures
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    • v.37 no.4
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    • pp.391-404
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    • 2020
  • Human-induced vibration could present a serious serviceability problem for large-span and/or lightweight floors using the high-strength material. This paper presents the results of heel-drop, jumping, and walking tests on a large-span composite steel rebar truss-reinforced concrete (CSBTRC) floor. The effects of human activities on the floor vibration behavior were investigated considering the parameters of peak acceleration, root-mean-square acceleration, maximum transient vibration value (MTVV), fundamental frequency, and damping ratio. The measured field test data were validated with the finite element and theoretical analysis results. A comprehensive comparison between the test results and current design codes was carried out. Based on the classical plate theory, a rational and simplified formula for determining the fundamental frequency for the CSBTRC floor is derived. Secondly, appropriate coefficients (βrp) correlating the MTVV with peak acceleration are suggested for heel-drop, jumping, and walking excitations. Lastly, the linear oscillator model (LOM) is adopted to establish the governing equations for the human-structure interaction (HSI). The dynamic characteristics of the LOM (sprung mass, equivalent stiffness, and equivalent damping ratio) are determined by comparing the theoretical and experimental acceleration responses. The HSI effect will increase the acceleration response.