• Title, Summary, Keyword: Viscoelastic Analysis

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Boundary Element Analysis of Strain Energy Release Rate G(t) for Cracked Viscoelastic Solids (균열이 있는 선형 점탄성체의 변형에너지 방출률 G(t)에 대한 경계요소 해석)

  • 박명규;이상순;서창민
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.12
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    • pp.2072-2078
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    • 2003
  • In this paper, the boundary element analysis of viscoelastic strain energy release rate G(t) for the cracked linear viscoelastic solids has been attempted. This study proposes the G(t) equation and the calculating method of G(t) by time-domain boundary element analysis for the viscoelastic solids. The G(t) is defined as the derivative of the viscoelastic potential energy II(t) with respect to crack length a. Two example problems are presented to show the applicability of the proposed method to the analysis of the cracked linear viscoelastic solids. Numerical results of example problems show the accuracy and effectiveness of the proposed method.

Analysis of building frames with viscoelastic dampers under base excitation

  • Shukla, A.K.;Datta, T.K.
    • Structural Engineering and Mechanics
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    • v.11 no.1
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    • pp.71-87
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    • 2001
  • A frequency domain response analysis is presented for building frames passively controlled by viscoelastic dampers, under harmonic ground excitation. Three different models are used to represent the linear dynamic force-deformation characteristics of viscoelastic dampers namely, Kelvin model, Linear hysteretic model and Maxwell model. The frequency domain solution is obtained by (i) an iterative pseudo-force method, which uses undamped mode shapes and frequencies of the system, (ii) an approximate modal strain energy method, which uses an equivalent modal damping of the system in each mode of vibration, and (iii) an exact method which uses complex frequency response function of the system. The responses obtained by three different methods are compared for different combinations of viscoelastic dampers giving rise to both classically and non-classically damped cases. In addition, the effect of the modelling of viscoelastic dampers on the response is investigated for a certain frequency range of interest. The results of the study are useful in appropriate modelling of viscoelastic dampers and in understanding the implication of using modal analysis procedure for building frames which are passively controlled by viscoelastic dampers against base excitation.

Curing Induced Residual Stresses in Laminated Cylindrical Shells

  • Lee, Soo-Yong
    • Journal of Mechanical Science and Technology
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    • v.14 no.1
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    • pp.19-29
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    • 2000
  • A viscoelastic finite element analysis is presented to investigate residual stresses occurred in a laminated cylindrical shell during cure. An incremental viscoelastic constitutive equation that can describe stress relaxation during the cure is derived as a recursive formula which can be used conveniently for a numerical analysis. The finite element analysis program is developed on the basis of a 3-D degenerated shell element and the first order shear deformation theory, and is verified by comparing with an one dimensional exact solution. Viscoelastic effect on the residual stresses in the laminated shell during the cure is investigated by performing both the viscoelastic and linear elastic analyses considering thermal deformation and chemical shrinkage simultaneously. The results show that there is big difference between viscoelastic stresses and linear elastic stresses. The effect of cooling rates and cooling paths on the residual stresses is also examined.

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Dynamic Analysis of Building Structures with Viscoelastic Dampers (탄성감쇠를 가진 건축구조물의 동적해석)

  • 이동근
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.196-203
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    • 1998
  • Viscoelastic dampers have been successfully applied to building structures for reduction of vibration induced by wind or earthquakes. But accurate estimation of responses of building structures with viscoelastic dampers is very difficult, because the properties of viscoelastic damper is dependent on temperature and frequency of vibration. For efficient control of building vibration, required damping of viscoelastic damping device need be estimated and dynamic analysis method which can estimate the response of building structure with viscoelastic damper system is indispensable. In this paper, an efficient dynamic analysis method of a building structure with viscoelastic dampers is proposed. Efficiency and accuracy of the proposed method are verified comparing analytic results with shaking table test results using reduced building models.

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A Viscoelastic Analysis for Spent Pressurized Water Reactor Nuclear Fuel Disposal Canister (가압경수로 고준위폐기물 처분용기에 대한 점탄성 해석)

  • 권영주;하준용
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.327-330
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    • 2003
  • In this paper, a viscoelastic structural analysis for the spent pressurized water reactor(PWR) nuclear fuel disposal canister is carried out to predict the collapse of the canister while the canister is stored in a deep repository for long time. There may exist some subterranean heat in a deep repository while the nuclear fuel disposal canister is stored for long time. Then, a time-dependent viscoelastic structural deformation may occur in the canister due to the subterrnean heat Hence, the viscoelastic stress variation according to time should be computed to predict the structural strength of the canister. A viscoelastic material model is adopted. Analysis results show that even though some subterrnean heat may exist for quite a long time, the canister structure still endures stresses below the yield strength of the canister. Hence, some subterranean heat cannot seriously affect the structural strength of the canister.

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Shaking Table Test of a Structure with Added Viscoelastic Dampers (점탄성 감쇠기가 설치된 구조물의 진동대 실험)

  • Kim., Jin-Koo;Kwon., Young-Jip
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.5 no.4
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    • pp.197-203
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    • 2001
  • This study presents the results of shaking table test of scaled model structures with added viscoelastic dampers, which are considered to be one of the most efficient means of upgrading existing structures against seismic loads. The experimental results were compared with those from analysis based on the linear modeling of viscoelastic dampers. The parameters obtained from free vibration test were utilized in the analysis. According to the results the added viscoelastic dampers turned out to be effective in reducing the responses of the model structures. It was also found that the analysis with linear modeling of viscoelastic dampers could simulate the test results accurately.

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Drag Torque Prediction for Automotive Wheel Bearing Seals Considering Viscoelastic as Well as Hyperelastic Material Properties (초탄성 및 점탄성 물성을 고려한 자동차용 휠 베어링 실의 드래그 토크 예측)

  • Lee, Seungpyo
    • Tribology and Lubricants
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    • v.35 no.5
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    • pp.267-273
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    • 2019
  • Wheel bearings are important automotive parts that bear the vehicle weight and translate rotation motion; in addition, their seals are components that prevent grease leakage and foreign material from entering from the outside of the bearings. Recently, as the need for electric vehicles and eco-friendly vehicles has been emerging, the reduction in fuel consumption and $CO_2$ emissions are becoming the most important issues for automobile manufacturers. In the case of wheel bearings, seals are a key part of drag torque. In this study, we investigate the prediction of the drag torque taking into consideration the hyperelastic and viscoelastic material properties of automotive wheel bearing seals. Numerical analysis based on the finite element method is conducted for the deformation analyses of the seals. To improve the reliability of the rubber seal analysis, three types of rubber material properties are considered, and analysis is conducted using the hyperelastic material properties. Viscoelastic material property tests are also conducted. Deformation analysis considering the hyperelastic and viscoelastic material properties is performed, and the effects of the viscoelastic material properties are compared with the results obtained by the consideration of the hyperelastic material properties. As a result of these analyses, the drag torque is 0.29 Nm when the hyperelastic characteristics are taken into account, and the drag torque is 0.27 Nm when both the hyperelastic and viscoelastic characteristics are taken into account. Therefore, it is determined that the analysis considering both hyperelastic and viscoelastic characteristics must be performed because of its reliability in predicting the drag torque of the rubber seals.

Analysis of Crack Induced in Polymeric Layer (고분자 층에서 발생하는 균열 해석)

  • Lee Sang Sun
    • Proceedings of the International Microelectronics And Packaging Society Conference
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    • pp.247-250
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    • 2003
  • In this paper, the boundary element analysis of viscoelastic strain energy release ,ate G(t) for the cracked linear viscoelastic materials is attempted. This study proposes the G(t) equation and the calculating method of G(t) by time-domain boundary element analysis for the viscoelastic solids. The G(t) is defined as the derivative of the viscoelastic potential energy $\Pi(t)$ with respect to crack length a. Two example problems are presented to show the applicability of the proposed method to the analysis of the cracked linear viscoelastic solids. Numerical results of example problems show the accuracy and effectiveness of the proposed method.

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Thermo-electro-elastic nonlinear stability analysis of viscoelastic double-piezo nanoplates under magnetic field

  • Ebrahimi, Farzad;Hosseini, S. Hamed S.;Selvamani, Rajendran
    • Structural Engineering and Mechanics
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    • v.73 no.5
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    • pp.565-584
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    • 2020
  • The nonlinear thermo-electro-elastic buckling behavior of viscoelastic nanoplates under magnetic field is investigated based on nonlocal elasticity theory. Employing nonlinear strain-displacement relations, the geometrical nonlinearity is modeled while governing equations are derived through Hamilton's principle and they are solved applying semi-analytical generalized differential quadrature (GDQ) method. Eringen's nonlocal elasticity theory considers the effect of small size, which enables the present model to become effective in the analysis and design of nano-sensors and nano actuators. Based on Kelvin-Voigt model, the influence of the viscoelastic coefficient is also discussed. It is demonstrated that the GDQ method has high precision and computational efficiency in the buckling analysis of viscoelastic nanoplates. The good agreement between the results of this article and those available in literature validated the presented approach. The detailed mathematical derivations are presented and numerical investigations are performed while the emphasis is placed on investigating the effect of the several parameters such as electric voltage, small scale effects, elastomeric medium, magnetic field, temperature effects, the viscidity and aspect ratio of the nanoplate on its nonlinear buckling characteristics. It is explicitly shown that the thermo-electro-elastic nonlinear buckling behavior of viscoelastic nanoplates is significantly influenced by these effects. Numerical results are presented to serve as benchmarks for future analyses of viscoelastic nanoplates as fundamental elements in nanoelectromechanical systems.

Analysis of an electrically actuated fractional model of viscoelastic microbeams

  • Bahraini, Seyed Masoud Sotoodeh;Eghtesad, Mohammad;Farid, Mehrdad;Ghavanloo, Esmaeal
    • Structural Engineering and Mechanics
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    • v.52 no.5
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    • pp.937-956
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    • 2014
  • The MEMS structures usually are made from silicon; consideration of the viscoelastic effect in microbeams duo to the phenomena of silicon creep is necessary. Application of the fractional model of microbeams made from viscoelastic materials is studied in this paper. Quasi-static and dynamical responses of an electrically actuated viscoelastic microbeam are investigated. For this purpose, a nonlinear finite element formulation of viscoelastic beams in combination with the fractional derivative constitutive equations is elucidated. The four-parameter fractional derivative model is used to describe the constitutive equations. The electric force acting on the microbeam is introduced and numerical methods for solving the nonlinear algebraic equation of quasi-static response and nonlinear equation of motion of dynamical response are described. The deflected configurations of a microbeam for different purely DC voltages and the tip displacement of the microbeam under a combined DC and AC voltages are presented. The validity of the present analysis is confirmed by comparing the results with those of the corresponding cases available in the literature.