• Title/Summary/Keyword: Complex modulus

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Vibration Analysis of Damped Sandwich Beam Using Finite Element Method (유한요소법을 이용한 샌드위치형 감쇠 보구조물의 진동해석)

  • Seo, Young-Soo;Jeong, Weui-Bong;Shin, Joon-Yub
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.05a
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    • pp.978-981
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    • 2005
  • The vibration analysis of damped sandwich beam is conducted using finite element method. The equation of motion presented by Mead and Markus is used to formulate FEM. Also as the thickness of the core in the damped sandwich beam goes to zero, conventional beam theory based on the transformed-section method and the equation of Mead and Markus are compared. According to the change of thickness and loss factor of the core, the forced frequency response of beam is calculated and discussed. And then using the half-power band width method, the damping ratio of each mode is calculated and discussed about each case.

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Optimal Treatment of Unconstrained Visco-elastic Damping Layer on Beam to Minimize Vibration Responses (동적응답을 최소화하는 비구속형 제진보의 제진부위 최적설계)

  • Lee, Doo-Ho
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.05a
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    • pp.656-661
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    • 2005
  • An optimization formulation of unconstrained damping treatment on beams is proposed to minimize vibration responses using a numerical search method. The fractional derivative model is combined with RUK's equivalent stiffness approach in order to represent nonlinearity of complex modulus of damping materials with frequency and temperature. The loss factors of partially covered unconstrained beam are calculated by the modal strain energy method. Vibration responses are calculated by using the modal superposition method, and of which design sensitivity formula with respect to damping layout is derived analytically. Plugging the sensitivity formula into optimization software, we can determine optimally damping treatment region that gives minimum forced response under a given boundary condition. A numerical example shows that the proposed method is very effective in minimizing vibration responses with unconstrained damping layer treatment.

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Time Dependence of the Rheological Properties of the Solutions of Polyacrylontrile and Acrylonitrile-Itaconic Acid Copolymer in Dimethyl sulfoxide (아크릴 중합체 및 아크릴-이타코닉산 공중합체/ 디메틸술폭시드 용액의 유변학적 특성의 시간의존성)

  • 이남순
    • Textile Coloration and Finishing
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    • v.13 no.6
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    • pp.435-440
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    • 2001
  • This study investigates the rheological properties of in-situ polymerized solutions of polyacrylonitrile(PAN) and acrylonitrile(AN) -itaconic acid(IA) in dimethyl sulfoxide(DMSO) in terms of temperature, concentration, and time. The complex viscosity and storage modulus of the solutions were generally increased with elapsing time, which is ascribable to the three-dimensional pseudostructures formed by strong inter- or Intra-molecular attractions through Polar -CN and -COOH groups. The three-dimensional pseudonetworks would lead to relation of the acrylic solutions in long term. This was more noticeable at higher temperature within the temperature range examined. In the case of 20% solutions one can not observe lower Newtonian flow region in the viscosity curve. Disappearance of lower Newtonian flow region is indicative of heterogeneity of the solution system. Casson Plot of the viscosity data revealed that 20% solutions of PAN and AN-IA copolymer in DMSO clearly demonstrated positive yield stress, ascertaining formation of pseudostructures in the solution systems.

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Time Dependence of the Rheological Properties of the Solutions of Polyacrylontrile and Acrylonitrile-Itaconic Acid Copolymer in Dimethyl sulfoxide (아크릴 중합체 및 아크릴-이타코닉산 공중합체/디메틸술폭시드 용액의 유변학적 특성의 시간의존성)

  • Lee, Nam Sun
    • Textile Coloration and Finishing
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    • v.13 no.6
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    • pp.77-77
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    • 2001
  • This study investigates the rheological properties of in-situ polymerized solutions of polyacrylonitrile(PAN) and acrylonitrile(AN)-itaconic acid(IA) in dimethyl sulfoxide(DMSO) in terms of temperature, concentration, and time. The complex viscosity and storage modulus of the solutions were generally increased with elapsing time, which is ascribable to the three-dimensional pseudostructures formed by strong inter- or intra-molecular attractions through Polar -CN and -COOH groups. The three-dimensional pseudonetworks would lead to gelation of the acrylic solutions in long term. This was more noticeable at higher temperature within the temperature range examined. In the case of 20% solutions one can not observe lower Newtonian flow region in the viscosity curve. Disappearance of lower Newtonian flow region is indicative of heterogeneity of the solution system. Casson Plot of the viscosity data revealed that 20% solutions of PAN and AN-IA copolymer in DMSO clearly demonstrated positive yield stress, ascertaining formation of pseudostructures in the solution systems.

Determination of the mechanical properties of coated layer in the sheet metal (표면처리강판 코팅층의 기계적 특성결정에 관한 연구)

  • 고영호;이정민;김병민
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2004.10a
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    • pp.343-346
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    • 2004
  • In recent years, various forms of indentation testing have been increasingly used to determine the material properties of specimens. This technique, particularly the nano-indentation method , has been extended to the testing of coating systems in order to calculate the individual properties of the thin coatings and the substrates. However, the interpretation of the test data to achieve this is complex and continues to be a widely studied subject. Based on the finite element method of coated surfaces indented by a Berkovich diamond tip, this paper describes methods for combining FEM and experimental indentation testing to determine coating modulus and hardness independent of substrate effects. Using this proposed methodology, testing and FEM to measure coefficients of friction of sheet steel for outer panel were studied.

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Investigation of Dynamic Models for Longitudinal Vibration of a Rod-Type Specimen and Their Useful Range (막대형 시편의 종진동에 대한 동적모형 및 그 적용범위의 고찰)

  • 안태길;강기호;김광준
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.1
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    • pp.161-169
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    • 1995
  • One of the most influential factors on estimating the complex modulus by using longitudinal vibration of a rod-type specimen is the accuracy of the approximate models for describing the dynamic behavior of the specimen. Performance of several approximate models is investigated analytically on the basis of the Pochhammer-Chree theory in case of infinite specimen and numerically on the basis of the finite element analysis in case of finite specimen. The frequency range where each model gives good approximation and its accuracy in that range are determined.

A consistent FEM-Vlasov model for laminated orthotropic beams subjected to moving load

  • Ozgan, Korhan
    • Structural Engineering and Mechanics
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    • v.64 no.1
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    • pp.23-31
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    • 2017
  • In the study, dynamic behavior of laminated orthotropic beams on elastic foundation is investigated. Consistent model presented here combines the finite element solution of the system with SAP2000 software and the calculation of soil parameters with MATLAB software using Modified Vlasov Model type elastic foundation. For this purpose, a computing tool is coded in MATLAB which employs Open Application Programming Interface (OAPI) feature of SAP2000 to provide two-way data flow during execution. Firstly, an example is taken from the literature to demonstrate the accuracy of the consistent FEM-Vlasov Model. Subsequently, the effects of boundary conditions, subsoil depth, elasticity modulus of subsoil, slenderness ratio, velocity of moving load and lamination scheme on the behavior of laminated orthotropic beams on elastic foundation are investigated on a new numerical example. It can be concluded that it is really convenient to use OAPI feature of SAP2000 to model this complex behavior of laminated orthotropic beams on elastic foundation under moving load.

Material Charcterization of MR Fluids at High Frequencies (고주파 영역에서의 MR유체 특성연구)

  • Park, Kyoung-mi;Kim, Jae-hwan;Park, Seung-Bok;Kim, Kyung-Su
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11a
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    • pp.327.1-327
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    • 2002
  • MR(Magnetorheogical) fluid composed of fine iron powders dispersed in silicon oil is utilized to many smart structures and devices because of its significant rheological property change by the application of an external magnetic field. When we deal with the shock wave attenuation of warship structures, we should be able to characterize the high frequency behavior of MR fluids. So far, however, much efforts have been focused on the material characterization of MR fluids at low frequencies below 100㎐. (omitted)

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A CMOS Frequency Synthesizer for 5~6 GHz UNII-Band Sub-Harmonic Direct-Conversion Receiver

  • Jeong, Chan-Young;Yoo, Chang-Sik
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.9 no.3
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    • pp.153-159
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    • 2009
  • A CMOS frequency synthesizer for $5{\sim}6$ GHz UNII-band sub-harmonic direct-conversion receiver has been developed. For quadrature down-conversion with sub-harmonic mixing, octa-phase local oscillator (LO) signals are generated by an integer-N type phase-locked loop (PLL) frequency synthesizer. The complex timing issue of feedback divider of the PLL with large division ratio is solved by using multimodulus prescaler. Phase noise of the local oscillator signal is improved by employing the ring-type LC-tank oscillator and switching its tail current source. Implemented in a $0.18{\mu}m$ CMOS technology, the phase noise of the LO signal is lower than -80 dBc/Hz and -113 dBc/Hz at 100 kHz and 1MHz offset, respect-tively. The measured reference spur is lower than -70 dBc and the power consumption is 40 m W from a 1.8 V supply voltage.

Optimal Treatment of Unconstrained Visco-elastic Damping Layer on Beam to Minimize Vibration Responses (진동응답을 최소화하는 비구속형 제진보의 제진 부위 최적설계)

  • Lee, Doo-Ho
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.7 s.100
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    • pp.829-835
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    • 2005
  • An optimization formulation of unconstrained damping treatment on beam is proposed to minimize vibration responses using a numerical search method. The fractional derivative model is combined with RUK's equivalent stiffness approach in order to represent nonlinearity of complex modulus of damping materials with frequency and temperature. Vibration responses are calculated by using the modal superposition principle, and of which design sensitivity formula with respect to damping layout is derived analytically. Plugging the sensitivity formula into optimization software, we can determine optimally damping treatment region that gives minimum forced response under a given boundary condition. A numerical example shows that the proposed method is very effective in suppressing nitration responses by means of unconstrained damping layer treatment.