• Title/Summary/Keyword: Material damping ratio

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Dynamic Property Evaluation of Four-Harness Satin Woven Glass/epoxy Composites for a Composite Bogie Frame (복합소재 대차프레임용 4매 주자직 유리섬유/에폭시 복합소재의 진동특성평가)

  • Kim, Il Kyeom;Kim, Jung Seok;Seo, Sung Il;Lee, Woo Geun
    • Journal of the Korean Society for Railway
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    • v.16 no.1
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    • pp.1-6
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    • 2013
  • In this study, the natural frequency and damping ratio of a four-harness satin woven glass/epoxy composite material are evaluated by means of modal tests and a finite element analysis. To achieve this goal, glass/epoxy beam specimens with different lengths and thicknesses were manufactured via autoclave curing. In the test, the maximum damping ratio was found to occur at the lowest test frequency. As the test frequency increased, the damping ratio decreased exponentially to a critical value. After that value, the damping ratio increased gradually to the maximum test frequency.

An Experimental Study on Dynamic Properties of Concrete with Vibration-Mitigation Materials (제진재 혼입 콘크리트의 동적물성에 관한 실험적 연구)

  • Chung, Young-Soo;Park, Yong-Goo
    • Magazine of the Korea Concrete Institute
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    • v.11 no.2
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    • pp.261-270
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    • 1999
  • In these days, construction activities have caused civil petitions associated with vibration-induced damages or nuisances. Therefore, it is strongly needed to develop a remedial technique to mitigate unfavorable effects. The objective of this experimental research is to investigate material and structural dynamic characteristics of vibration-controlled concretes which have been proportionally mixed with various vibration reducing material, such as latex, rubber powder, plastic resin, polystyrofoams and etc. Normal and high strength concrete specimens are also prepared for corresponding comparison. As part of the recycling research for obsolete rubber and plastic materials, 32 concrete cylinders and 10 concrete flexural beams have been made for material and structural dynamic properties, respectively. In accordance with the resonance test on concrete cylinders, it can be concluded that concrete with vibration-reducing material have relatively larger material damping ration than normal or high strength concrete. Styrofoam is determined to be very effective vibration-reducing mixtures. From the vibration test on 10 concrete flexural beams, meamwhile, of importance observations was that material damping ratio is very smaller than structural damping ratio of corresponding specimen. But further vibration test on more flexural beams should be strongly needed by varying support conditions.

The Collapse Characteristics of Vehicle Thin-walled Members Coated Damping Material (댐핑재가 도포된 차체 박육부재의 압궤특성)

  • 송상기;박상규;송찬일
    • Journal of Advanced Marine Engineering and Technology
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    • v.27 no.1
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    • pp.76-81
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    • 2003
  • The purpose of this study is to analyze the collapse characteristics of widely used spot welded section members coated damping material Y1000 and to develop an analysis method for acquiring exact collapse loads and energy absorption ratio. Hat-shaped thin-walled members have the biggest energy absorbing capacity in a front-end collision. The sections were tested on quasi-static and impact loads. Specimens with two type thickness, width ratio and spot weld pitch on the flange have been tested in impact velocities(6.73n0sec and 7.54n1sec) which imitate a real-life car collision. As a result, it was developed the system for acquiring impact energy absorbing characteristics of structure united thin-walled member and damping materials.

Vibration Control of Smart Laminated Composite Plates Using Piezoceramic Sensor/Actuators and Viscoelastic Material (압전 세라믹 감지기/작동기와 점탄성 재료를 이용한 지능형 복합 적층판의 진동 제어)

  • 강영규;서경민;이시복
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.11 no.4
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    • pp.37-42
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    • 2001
  • Active vibration control of laminated composite plates has been carried out to design structure with maximum possible damping capacity, using piezoceramic sensor/actuators and passive constrained-layer damping treatment. The equations of motion are derived for symmetrical, multi-layer laminated plates. The damping ratio(ζ) and modal damping(2ζ$\omega$) of the first bending and torsional modes are calculated by means of iterative complex eigensolution method for both passive and active vibration control. This paper addresses a design strategy of laminated composite plate under structural vibrations.

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Hybrid Vibration Control of Smart Laminated Composite Beams using Piezoelectric and Viscoelastic Material (압전재료와 점탄성 재료를 이용한 지능 복합적층보의 하이 브리드 진동제어)

  • Kang, Young-Kyu
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.10
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    • pp.148-153
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    • 2001
  • Active control of flexural vibrations of smart laminated composite beams has been carried out using piezoceramic sensor/actuator and viscoelastic material. The beams with passive constrained layer damping hale been analyzed by formulating the equations of motion through the use of extended Hamilton's principle. The dynamic characteristics such as damping ratio and modal damping of the beam are calculated for various fiber orientations by means of iterative complex eigensolution method. This paper addresses a design strategy of laminated composite under flexural vibrations to design structure with maximum possible damping capacity.

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Longitudinal vibration of a nanorod embedded in viscoelastic medium considering nonlocal strain gradient theory

  • Balci, Mehmet N.
    • Advances in nano research
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    • v.13 no.2
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    • pp.147-164
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    • 2022
  • This article investigates the longitudinal vibration of a nanorod embedded in viscoelastic medium according to the nonlocal strain gradient theory. Viscoelastic medium is considered based on Kelvin-Voigt model. Governing partial differential equation is derived based on longitudinal equilibrium and analytical solution is obtained by adopting harmonic motion solution for the nanorod. Modal frequencies and corresponding damping ratios are presented to demonstrate the influences of nonlocal parameter, material length scale, elastic and damping parameters of the viscoelastic medium. It is observed that material length scale parameter is very influential on modal frequencies especially at lower values of nonlocal parameter whereas increase in length scale parameter has less effect at higher values of nonlocal parameter when the medium is purely elastic. Elastic stiffness and damping coefficient of the medium have considerable impacts on modal frequencies and damping ratios, and the highest impact of these parameters on frequency and damping ratio is seen in the first mode. Results calculated based on strain gradient theory are quite different from those calculated based on classical elasticity theory. Hence, nonlocal strain gradient theory including length scale parameter can be used to get more accurate estimations of frequency response of nanorods embedded in viscoelastic medium.

Probabilistic free vibration analysis of Goland wing

  • Kumar, Sandeep;Onkar, Amit Kumar;Manjuprasad, M.
    • International Journal of Aerospace System Engineering
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    • v.6 no.2
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    • pp.1-10
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    • 2019
  • In this paper, the probabilistic free vibration analysis of a geometrically coupled cantilever wing with uncertain material properties is carried out using stochastic finite element (SFEM) based on first order perturbation technique. Here, both stiffness and damping of the system are considered as random parameters. The bending and torsional rigidities are assumed as spatially varying second order Gaussian random fields and represented by Karhunen Loeve (K-L) expansion. Here, the expected value, standard deviation, and probability distribution of random natural frequencies and damping ratios are computed. The results obtained from the present approach are also compared with Monte Carlo simulations (MCS). The results show that the uncertain bending rigidity has more influence on the damping ratio and frequency of modes 1 and 3 while uncertain torsional rigidity has more influence on the damping ratio and frequency of modes 2 and 3.

Dynamic Shear Modulus and Damping Ratio of Soft Clay (연약점토의 동력학적 전단탄성계수 및 감쇠비)

  • 하광현
    • Geotechnical Engineering
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    • v.2 no.1
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    • pp.55-66
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    • 1986
  • Considering the effects of confining pressure, initial shear stress, cyclic stress ratio and number of loading cycles, cyclic triaxial tests are carried out to clarify the soil dynamic properties such as shear modulus and value of material damping of clay under undrained cyclic loading conditions. The results show that no obvious dependency on initial shear stress and effective confining stress are recognized in the shear modulus and damping ratio plotted versus strain. However, the shear modulus decreases and the damping ratio increases with increasing axial strain. When compared with others, it is also revealed that the shear moduli are distributed within the range curves obtained using empirical equations derived by Marcuson et al. (3) and Kokusho et al. (4), and damping ratios are distributed between the curves obtained by Kokusho et al. (4) and Ishihara et al. (9).

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Vibration Control of Laminated Composite Beams Using Active Constrained Layer Damping Treatment (능동구속감쇠 기법을 이용한 복합적층보의 진동 제어)

  • 강영규;최승복
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.11 no.7
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    • pp.261-266
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    • 2001
  • The flexural vibration of laminated composite beams with active and passive constrained layer damping has been investigated to design a structure with maximum possible damping capacity. The equations of motion are derived fro flexural vibrations of symmetrical,. multi-layer laminated beams. The damping ratio and model damping of the first bending mode are calculated by means of iterative complex eigensolution method. The direct negative velocity feedback control is used for the active constrained layer damping. It is shown that the flexible laminated beam is more effective in the vibration control for both active and passive constrained layer damping. and this paper addresses a design strategy of laminated composite under flexural vibrations with constrained layer damping.

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Damping Characteristic of Silicone Rubber-Filled Honeycomb Sandwich Composite (Silicone Rubber-Filled 허니콤 샌드위치 복합재료의 댐핑 특성)

  • Joe Chee-Ryong;Hao Huang;Kim Dong-Uk
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2004.10a
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    • pp.290-293
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    • 2004
  • In this paper a new sandwich composite is developed by injection silicone rubber into the honeycomb core. This composite material is designed to have a improved damping performance. For verification damping tests were conducted to the specimens with different stacked USNl25 carbon/epoxy prepreg laminate facesheets, $[0/90]_{4s},\;[0/45-45/90]_{2s},\;[45/-45]_{4s}$. Frequency response, displacement response and damping ratio were checked and compared for the both groups of specimens, with and without rubber fillings. The experimental results provided a good agreement with our original material design concept.

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