• Title/Summary/Keyword: Material damping ratio

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Hybrid vibration control of smart laminated composite beams using piezoelectric and viscoelastic material (압전재료와 점탄성 재료를 이용한 지능 적층보의 하이브리드 진동 제어)

  • 강영규;김재환;최승복
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.05a
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    • pp.133-137
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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 have 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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Nonlinear free vibration analysis of moderately thick viscoelastic plates with various geometrical properties

  • Nasrin Jafari;Mojtaba Azhari
    • Steel and Composite Structures
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    • v.48 no.3
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    • pp.293-303
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    • 2023
  • In this paper, geometrically nonlinear free vibration analysis of Mindlin viscoelastic plates with various geometrical and material properties is studied based on the Von-Karman assumptions. A novel solution is proposed in which the nonlinear frequencies of time-dependent plates are predicted according to the nonlinear frequencies of plates not dependent on time. This method greatly reduces the cost of calculations. The viscoelastic properties obey the Boltzmann integral law with constant bulk modulus. The SHPC meshfree method is employed for spatial discretization. The Laplace transformation is used to convert equations from the time domain to the Laplace domain and vice versa. Solving the nonlinear complex eigenvalue problem in the Laplace-Carson domain numerically, the nonlinear frequencies, the nonlinear viscous damping frequencies, and the nonlinear damping ratios are verified and calculated for rectangular, skew, trapezoidal and circular plates with different boundary conditions and different material properties.

Design of EDM Machine Tool Structures for Microfactory with High Stiffness and Damping Characteristics (마이크로팩토리 용 미세방전 공작기계의 고강성/고감쇠 설계)

  • Kim, Ju-Ho;Chang, Seung-Hwan
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.16 no.6
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    • pp.205-211
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    • 2007
  • In this paper, foam-composite sandwich structures for EDM machine tool components such as column and column block designed by controlling stacking sequences and cross-sectional dimensions of the composite structures. The original column block is a box-shaped structure made of aluminum connecting a column and a Z-stage of the system. This research was focused on the design of efficient column block structure using a foam-composite sandwich structure which have good bending stiffness and damping characteristics to reduce the mass and increase damping ratio of the system. Vibration tests for getting damping ratio with respect to the stacking angle and thickness of the composites were carried out. Finite element analyses for static defection and vibration behaviour were also carried out to find out the appropriate stacking conditions; that is, stacking sequence and rib configuration. From the test and analysis results it was found that composite-foam sandwich structures for the microfactory system can be successful alternatives for high precision machining.

Dynamic Performance of Rubber-Filled Sandwich Composite (Rubber-Filled 샌드위치 복합재료의 진동 특성 평가)

  • Huang, Hao;Joe, Chee-Ryong;Kim, Dong-Uk
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.238-243
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    • 2004
  • A new sandwich composite was investigated in this paper. The honeycomb core of this composite was filled with viscoelastic material in order to obtain an improved damping performance. The viscoelastic fillings in the honeycomb cells was hoped to act as dampers and provide the function of energy dissipation in this combined material system. Dynamic test was set up to the specimens with various stacked carbon/epoxy 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 material design concept.

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Vibration Characteristics of Laminated Composite Beams with Passive Constrained Layer Damping (수동 구속감쇠층을 갖는 복합적층보의 진동특성)

  • Kang, Young-Kyu
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.12 no.12
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    • pp.964-969
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    • 2002
  • The flexural vibration of laminated composite beams with passive constrained layer damping has been investigated to design structure with maximum possible damping capacity. The equations of motion are derived for flexural vibrations of symmetrical, multi-layer laminated beams. The damping ratio and modal damping of the first bending mode are calculated by means of Iterative complex eigensolution method. This paper addresses a design strategy of laminated composite under flexural vibrations.

Damping Measurements of Structural Rectangular Beam (구조용 사각 보의 감쇠측정)

  • Ryu, Bong-Jo;Song, Seon-Ho;Yoon, Choong-Sup;Ahn, Byung-Wook;Lee, Young-Yeob
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.05a
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    • pp.1071-1074
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    • 2006
  • The frequency response functions and loss factors, $\eta$, of structurally hollowed, rectangular, metal cantilever beams have been measured in bending vibrations within low strain amplitudes. The beams were heat treated or fined with aluminum to vary the material conditions. The measured frequency response functions at the end of the cantilevered beam were processed to calculate the structural damping ratios. The results showed that the modal frequencies and damping ratios of heat treated beam are increased due to the increase of beam rigidity with the predictions of the classical beam theory. When the beams are fined with aluminum, however, the frequencies are decreased due to the increase of mass, while the damping ratios are increased. As the agreement between measurement and classical theory is good, the performance of a beam with heat treated or fined with dissimilar material can be duplicated, for industrial and most practical purposes, by the theory developed for an internally damped homogeneous beam.

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Dynamic Deformation Characteristics of Fiber Reinforced Soils Using Resonant Column Tests (공진주 시험을 이용한 섬유보강토의 동적변형특성)

  • Chang, Pyoung-Wuck;Heo, Joon;Park, Young-Kon;Cha, Kyung-Seob;Woo, Chull-Woong
    • Proceedings of the Korean Society of Agricultural Engineers Conference
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    • 2002.10a
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    • pp.349-352
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    • 2002
  • In this paper, dynamic properties of fiber reinforced soils were investigated at shearing strains between $10^{-4}%\;and\;10^{-1}%$ using resonant column test. Resonant column test has been widely used as a primary laboratory testing technique in investigating dynamic soil properties expressed in term of shear modulus and material damping. At strains above elastic threshold, the variations of shear modulus(G) and damping ratio(D) were investigated. Based on test results, the small strain shear modulus($G_{max}$) and damping ratio($D_{min}$) were determined and the effects of confinement on $G_{max}$ and $D_{min}$ were characterized.

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Characteristics of Epoxy-Granite Composite Material For Ultra-Precision Machine Bed Structures (초정밀 가공기계 베드 구조물용 에폭시-그래나이트재의 특성에 관한 연구)

  • Kim, Jong-Ho;Won, Si-Tae;Maeng, Huee-Young;Park, Yeong-Il
    • Journal of the Korean Society for Precision Engineering
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    • v.7 no.2
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    • pp.74-84
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    • 1990
  • The machine tool structures for ultra-precision machining muxt be manufactured with materials which have high static and dynamic stiffness, high damping, a long term dimensional and thermal stability. This study aims at the development of new composite material Epoxy-Granite which exhibits the satisfactory characteristics as a material of ultra-precision mchine tool bed. The Epoxy-Granite testpieces that use epoxy resins as a binder and granite particles as a aggregate have been manufactured so as to examine the material properties about mechanical, thermal and damping characteristics. Experiments were carried out to obtain the proper manufacturing conditions of Expoxy-Granite specimens by varying the several testing conditions such as types of epoxy resins, particle sizes of granite and mixture ratio of epoxy resin and aggregate. Also, when Epoxy-Granite was compared with cast iron, GRANITAN which was imported from CMS of U.K. and granite materials, it has exhibited the superior or almost the same mechanical and damping properties and thermal conductivity, except for the thermal expansion.

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Effects of Distributed Load on the Dynamic Response of the Reinforced Concrete Slabs (분포하중이 철근 콘크리트 슬래브의 동적 거동에 미치는 영향)

  • Oh, Kyung-Yoon;Cho, Jin-Goo;Choi, Soo-Myung;Hong, Chong-Hyun
    • Journal of The Korean Society of Agricultural Engineers
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    • v.50 no.2
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    • pp.19-26
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    • 2008
  • This study has been carried out to investigate the dynamic characteristics of RC slabs. For this purpose, the 20-node solid element has been used to discretize the RC slabs into two parts of concrete and rebar. The material non-linearity considering elasto-visco plastic model and the smeared crack model have been adopted in the finite element formulation. The applied load can handle step load, load intensity of harmonic load, area of distributed load and frequency. The frequency of harmonic load has an significant effect on dynamic behaviour in terms of displacement. As the frequency is increased, the effect of load amplitude is more serious. Especially, if the frequency of harmonic load exceeds 30 Hz, it is noted that the displacement by harmonic load is greater than that by step load. In case of harmonic load, the damping effect shows no certain tendency with respect to frequency of load. In details, the damping is effective when the frequency of harmonic load is 2 Hz, but there is no consistent tendency according to damping ratio. The dynamic response when the frequency of harmonic load is 3 Hz shows same result for undamped case as well as for damped case with 5% damping ratio. It is also noted that we can get the largest deflection for damped case with 1% damping ratio. However, there is not any damping effect when the frequency of harmonic load is greater than 4 Hz.

Investigation of Viscoelastic Properties of EPDM/PP Thermoplastic Vulcanizates for Reducing Innerbelt Weatherstrip Squeak Noise of Electric Vehicles (전기차 인너벨트 웨더스트립용 EPDM/PP Thermoplastic Vulcanizates 재료설계인자에 따른 점탄성과 글라스 마찰 소음 상관관계 연구)

  • Cho, Seunghyun;Yoon, Bumyong;Lee, Sanghyun;Hong, Kyoung Min;Lee, Sang Hyun;Suhr, Jonghwan
    • Composites Research
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    • v.34 no.3
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    • pp.192-198
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    • 2021
  • Due to enormous market growing of electric vehicles without combustion engine, reducing unwanted BSR (buzz, squeak, and rattle) noise is highly demanded for vehicle quality and performance. Particularly, innerbelt weatherstrips which not only block wind noise, rain, and dust from outside, but also reduce noise and vibration of door glass and vehicle are required to exhibit high damping properties for improved BSR performance of the vehicle. Thermoplastic elastomers (TPEs), which can be recycled and have lighter weight than thermoset elastomers, are receiving much attention for weatherstrip material, but TPEs exhibit low material damping and compression set causing frictional noise and vibration between the door glass and the weatherstrip. In this study, high damping EPDM (ethylene-propylene-diene monomer)/PP (polypropylene) thermoplastic vulcanizates (TPV) were investigated by varying EPDM/PP ratio and ENB (ethylidene norbornene) fraction in EPDM. Viscoelastic properties of TPV materials were characterized by assuming that the material damping is directly related to the viscoelasticity. The optimum material damping factor (tanδ peak 0.611) was achieved with low PP ratio (14 wt%) and high ENB fraction (8.9 wt%), which was increased by 140% compared to the reference (tanδ 0.254). The improved damping is believed due to high fraction of flexible EPDM chains and higher interfacial slippage area of EPDM particles generated by increasing ENB fraction in EPDM. The stick-slip test was conducted to characterize frictional noise and vibration of the TPV weatherstrip. With improved TPV material damping, the acceleration peak of frictional vibration decreased by about 57.9%. This finding can not only improve BSR performance of electric vehicles by designing material damping of weatherstrips but also contribute to various structural applications such as urban air mobility or aircrafts, which require lightweight and high damping properties.