• Title, Summary, Keyword: viscoelastic property

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Study on fatigue life and mechanical properties of BRBs with viscoelastic filler

  • Xu, Zhao-Dong;Dai, Jun;Jiang, Qian-Wei
    • Steel and Composite Structures
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    • v.26 no.2
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    • pp.139-150
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    • 2018
  • In this paper, two kinds of buckling restrained braces (BRBs) are designed to improve the mechanical properties and fatigue life, the reserved gap and viscoelastic filler with high energy dissipation capacity are employed as the sliding element, respectively. The fatigue life of BRBs considering the effect of sliding element is predicted based on Manson-Coffin model. The property tests under different displacement amplitudes are carried out to evaluate the mechanical properties and fatigue life of BRBs. At last, the finite element analysis is performed to study the effects of the gap and viscoelastic filler on mechanical properties BRBs. Experimental and simulation results indicate that BRB employed with viscoelastic filler has a higher fatigue life and more stable mechanical property compared to BRB employed with gap, and the smaller reserved gap can more effectively improve the energy dissipation capacity of BRB.

Identification of Fractional-derivative-model Parameters of Viscoelastic Materials Using an Optimization Technique (최적화 기법을 이용한 점탄성물질의 분수차 미분모델 물성계수 추정)

  • Kim, Sun-Yong;Lee, Doo-Ho
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.16 no.12
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    • pp.1192-1200
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    • 2006
  • Viscoelastic damping materials are widely used to reduce noise and vibration because of its low cost and easy implementation, for examples, on the body structure of passenger cars, air planes, electric appliances and ships. To design the damped structures, the material property such as elastic modulus and loss factor is essential information. The four-parameter fractional derivative model well describes the dynamic characteristics of the viscoelastic damping materials with respect to both frequency and temperature. However, the identification procedure of the four-parameter is very time-consuming one. In this study a new identification procedure of the four-parameters is proposed by using an FE model and a gradient-based numerical search algorithm. The identification procedure goes two sequential steps to make measured frequency response functions(FRF) coincident with simulated FRFs: the first one is a peak alignment step and the second one is an amplitude adjustment step. A numerical example shows that the proposed method is useful in identifying the viscoelastic material parameters of fractional derivative model.

Multi-dimensional seismic response control of offshore platform structures with viscoelastic dampers (II-Experimental study)

  • He, Xiao-Yu;Zhao, Tie-Wei;Li, Hong-Nan;Zhang, Jun
    • Structural Monitoring and Maintenance
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    • v.3 no.2
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    • pp.175-194
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    • 2016
  • Based on the change of traditional viscoelastic damper structure, a brand-new damper is designed to control simultaneously the translational vibration and the rotational vibration for platforms. Experimental study has been carried out on the mechanical properties of viscoelastic material and on its multi-dimensional seismic response control effect of viscoelastic damper. Three types of viscoelastic dampers with different shapes of viscoelastic material are designed to test the influence of excited frequency, strain amplitude and ambient temperature on the mechanical property parameters such as circular dissipation per unit, equivalent stiffness, loss factor and storage shear modulus. Then, shaking table tests are done on a group of single-storey platform systems containing one symmetric platform and three asymmetric platforms with different eccentric forms. Experimental results show that the simulation precision of the restoring force model is rather good for the shear deformation of viscoelastic damper and is also satisfied for the torsion deformation and combined deformations of viscoelastic damper. The shaking table tests have verified that the new-type viscoelastic damper is capable of mitigating the multi-dimensional seismic response of offshore platform.

Computer Simulation of Viscoelastic Flow in a Capillary Die for Rubber Compounds (모세관 다이에서 고무 복합체의 점탄성 거동에 대한 컴퓨터 모사)

  • Park, Dong-Myung;Kim, Hok-Joo;Yoon, Jae-Ryong;Lyu, Min-Young
    • Elastomers and Composites
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    • v.41 no.4
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    • pp.223-230
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    • 2006
  • Rubber compounds have a high viscoelastic property. One of the viscoelastic behaviors during profile extrusion is the swelling of extrudate, and the amount of swelling varies with operational conditions in extrusion. It is well recognized that the elastic portion in the viscoelastic property plays an important role in the extrudate swell. In this study computer simulation of the die swell at the capillary die for several rubber compounds has been performed using commercial CFD code, Polyflow. A non-linear differential viscoelastic model, Phan-Thien-Tanner (PTT) model, was used in the computer simulation. Non-isothermal behavior was considered in the calculation. Distribution of pressure, velocity and temperature in the reservoir and capillary die, and extrudate profiles were predicted through the simulation. The amount of the die swell fur the different rubber compounds was investigated for various flow rates and three types of length to diameter of the capillary die. It is concluded that the PTT model successfully represented viscoelastic behavior of rubber compounds.

Shear and Normal Damping Effects of Square Sandwich Plates with Four Edges Clamped (네변이 고정된 사각 샌드위치 평판에서의 수직 및 전단 감쇠 효과)

  • 이병찬;김광준
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.217-223
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    • 1996
  • A structure's vibration characteristic is determined by modal property of the system. Through proper vibration analysis or experiments, the structure can be modified to reduce of vibration and noise. This paper is concerned with the natural frequency and modal loss factor of sandwich plates with viscoelastic core. The effects of shear and normal strain in the viscoelastic layer are investigated on modal properties, natural frequency and modal loss factor, by changing geometry parameter and viscoelastic material property of sandwich plates. The errors of modal parameters resulting from neglecting the extension or compression in the core material for simply supported(S-S-S-S) case are compared with those for clamped(C-C-C-C) boundary condition. Finite difference method(FDM) is utilized as numerical analysis technique of square sandwich plates for fixed boundary conditions. In order to reduce computation time and increase accuracy, improved finite difference expression with fourth order truncation error was used.

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Sealing Performance Prediction of Thermoplastic Rubber Component using Non-linear Large Deformation F.E.M. (비선형 대변형 유한요소법을 이용한 열가소성 고무부품의 밀봉성능 예측)

  • Park, Sun;Lee, Shin-Young;Kang, Eun
    • Proceedings of the KSME Conference
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    • pp.669-673
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    • 2001
  • The objective of this paper is to predict and evaluate the sealing performance of the thermoplastic rubber component in the proto-design stage. The large strain and large deformation properties of rubber are modeled by strain energy function and the related material constants are calculated from the test data. The viscoelastic property of the rubber is also considered using the coefficients in a Prony series representation of a viscoelastic modulus ken the compression stress relaxation test. The results show that the current design of cap mount system has 2-different stiffness caused by the cap-mount contact and the viscoelastic property of rubber plays an important role in time dependent deformation.

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Seismic response Analysis of Building Structures considering the Nonlinear Property of Viscoelastic Dampers (점탄성 댐퍼의 비선형 특성을 고려한 건물의 지진응답해석)

  • Choi, Hyun;Kim, Doo-Hun;Min, Kyung-Won;Lee, Sang-Jo
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.228-235
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    • 1999
  • As a seismic damper the viscoelastic damper is known the effective method to control the drift of the flexible building. As the viscoelastic damper has the characteristics of both damping and stiffness specially when the rubber material used hysteretic damping. The behavior of the hysteretic damping is quite different from that of the viscous damping. For the evaluation of the viscoelastic damper for the seismic purpose the nonlinear response spectrum was generated based on the dynamic test of the viscoelastic damper and the results is compared to that of the typical linear response spectrum,

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Numerical analysis on heat transfer due to buoyancy force of viscoelastic fluid (점탄성 유체의 부력에 의한 열전달 수치해석)

  • Ahn S. T.;Sohn C. H.;Shin S. H.
    • Journal of computational fluids engineering
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    • v.4 no.2
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    • pp.9-16
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    • 1999
  • The present study investigates flow character and heat transfer behaviors of viscoelastic non-Newtonian fluid in a 2:1 rectangular duct. An axially-constant heat flux on bottom wall and peripherally constant temperature boundary condition(H1) was adopted. The Reiner-Rivlin fluid model is used as the normal stress model for the viscoelastic fluid and temperature-dependent viscosity model is adopted. The present results show a signifiant change of the main flow field which causes a large heat transfer enhancement. This phenomena can be explained by the combined effect of buoyancy, temperature-dependent viscosity and viscoelastic property on the flow.

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An Application of Non-linear Viscoelastic Model to Capillary Extrusion of Rubber Compounds (고무복합체의 모세관 압출에서 비선형 점탄성 모델의 적용)

  • Choi, S.H.;Lyu, M.Y.
    • Transactions of Materials Processing
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    • v.16 no.4
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    • pp.260-265
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    • 2007
  • Rubber compounds have high viscoelastic property. One of the viscoelastic behaviors during profile extrusion is the swelling of extrudate. In this study, die swells of rubber compounds at the capillary die have been investigated through experiment and computer simulation. Experiments and simulations have been performed using fluidity tester and commercial CFD code, Polyflow respectively. Die swells of rubber compounds in a capillary die were predicted using non-linear differential viscoelastic model, Phan-Thien-Tanner(PTT) model for various relaxation times and relaxation modes. The results of simulation were compared with the experiments. Pressure and velocity distribution, and circulation flows at the comer of capillary die have been investigated through computer simulation. It is concluded that the PTT model successfully represented the amount of the die swell of rubber compounds for various relaxation times at different modes.