• 제목/요약/키워드: Viscoelastic Condition

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EXPONENTIAL DECAY FOR THE SOLUTION OF THE VISCOELASTIC KIRCHHOFF TYPE EQUATION WITH MEMORY CONDITION AT THE BOUNDARY

  • Kim, Daewook
    • East Asian mathematical journal
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    • 제34권1호
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    • pp.69-84
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    • 2018
  • In this paper, we study the viscoelastic Kirchhoff type equation with a nonlinear source for each independent kernels h and g with respect to Volterra terms. Under the smallness condition with respect to Kirchhoff coefficient and the relaxation function and other assumptions, we prove the uniform decay rate of the Kirchhoff type energy.

이상적인 점탄성체 항복 조건을 이용한 폭발 시뮬레이션 (Simulation of Explosion Using the Ideal Viscoelastic Object Yield Condition)

  • 성수경;김경수;신병석
    • 한국게임학회 논문지
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    • 제14권6호
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    • pp.49-58
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    • 2014
  • 입자 기반 유체 시뮬레이션에서 유체와 완전탄성체의 중간 형태인 점탄성체는 유체와는 달리 물질의 변형에 대한 항복응력(yield stress)이 필요하다. 기존 입자 기반의 점탄성체 연구에서는 폰 미제스(von Mises) 항복조건을 사용해 점탄성체의 변형을 표현하였으나 폭발을 표현하지는 못하였다. 본 논문은 물체가 받는 수많은 방향의 힘을 계산해야 하는 폰 미제스의 항복조건과는 달리 최대 주응력과 최소 주응력의 차를 이용해 쉽게 근사 할 수 있는 트레스카(Tresca)의 항복조건을 변형한 이상적 점탄성체 항복조건을 제안한다. 폰 미제스의 항복조건을 쉽게 근사화하기 위해 물체가 받는 힘을 변형된 길이로 표현한 기존 입자 기반의 시뮬레이션과 달리, 본 논문은 트레스카의 항복조건을 바탕으로 2차원 물체가 힘을 받아 변형된 넓이를 주응력으로 가정한다. 가장 큰 힘을 받는 순간을 최대주응력, 가장 적은 힘을 받는 순간을 최소 주응력으로 근사 화하여 차이를 계산한다. 점탄성체의 경계면이 이상적 항복 조건 이상으로 줄어들 때 물체가 한계응력을 이기지 못하고 현실감 있게 폭발하는 과정을 표현할 수 있음을 확인하였다.

STABILIZATION FOR THE VISCOELASTIC KIRCHHOFF TYPE EQUATION WITH A NONLINEAR SOURCE

  • Kim, Daewook
    • East Asian mathematical journal
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    • 제32권1호
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    • pp.117-128
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    • 2016
  • In this paper, we study the viscoelastic Kirchhoff type equation with a nonlinear source $$u^{{\prime}{\prime}}-M(x,t,{\parallel}{\bigtriangledown}u(t){\parallel}^2){\bigtriangleup}u+{\int}_0^th(t-{\tau})div[a(x){\bigtriangledown}u({\tau})]d{\tau}+{\mid}u{\mid}^{\gamma}u=0$$. Under the smallness condition with respect to Kirchhoff coefficient and the relaxation function and other assumptions, we prove the uniform decay rate of the Kirchhoff type energy.

역추기법을 이용한 해면골의 점탄성 특성 해석 (Estimation of Viscoelastic Properties of Trabecular Bone Using An Inverse Method)

  • 강신일;이원희;홍정화
    • 대한의용생체공학회:의공학회지
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    • 제18권3호
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    • pp.211-216
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    • 1997
  • An inverse method with regularization has been developed to determine the viscoelastic properties of trabecular bone. A series of stress relaxation experiments were performed under the condition of uniaxial compression stress state. Optimization has been formulated within the framework of nonlinear least-squares and a modified Gauss-Newton method with a zeroth-order regularization technique. The stress relaxation behavior of trabecular bone was analyzed using a standard viscoelastic model. The present study clearly shows that trabecular bone exhibits typical viscoelastic stress relaxation behavior, and the obtained material parameters well represent the viscoelastic behavior of trabecular bone.

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점탄성감쇠기를 설치한 구조물의 비용효율성 평가 (Cost-Effectiveness Evaluation of the Structure with Viscoelastic Dampers)

  • 고현무;함대기;조상열
    • 한국지진공학회:학술대회논문집
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    • 한국지진공학회 2001년도 춘계학술대회 논문집
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    • pp.387-393
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    • 2001
  • Installing vibration control devices in the structure rises as a solution instead of increasing structural strength considering construction cost. Especially, viscoelastic dampers show excellent vibration control performance at low cost and are easy to install in existing structures compared with other control devices. Therefore, cost-effectiveness of structure with viscoelastic dampers needs to be evaluated. Previous cost-effectiveness evaluation method for the seismically isolated structure(Koh et al., 1999;2000)is applied on the building structure with viscoelastic dampers, which combines optimal design and cost-effectiveness evaluation for seismically isolated structures based on minimum life-cycle cost concept. Input ground motion is modeled in the form of spectral density function to take into account acceleration and site coefficients. Damping of the viscoelastic damper is considered by modal strain energy method. Stiffness of shear building and shear area of viscoelastic damper are adopted as design variables for optimization. For the estimation of failure probability, transfer function of the structure with viscoelastic damper for spectral analysis is derived from the equation of motion. Results reveal that cost-effectiveness of the structure with viscoelastic dampers is relatively high in how seismic region and stiff soil condition.

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

  • 안성태;손창현;신세현
    • 한국전산유체공학회지
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    • 제4권2호
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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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점탄성 효과를 가진 사출 유동에 관한 연구 (A Study on the Injection Flow with Viscoelastic Effect)

  • 전언찬;박정우;김수용;이철장;안광우
    • 한국기계가공학회지
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    • 제7권3호
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    • pp.25-29
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    • 2008
  • In this paper, we design internal space in plunger-type low pressure vacuum injection molding machine from numerical study. And we study characteristic of viscoelastic flow for searching injection molding condition. Then the flow analysis was performed using the CAE S/W. The result shows optimal value of nozzle and hole in injection chamber. And we investigated qualitatively relationship between injection pressure and injection mass flow with variable shear rate

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ASYMPTIOTIC BEHAVIOR FOR THE VISCOELASTIC KIRCHHOFF TYPE EQUATION WITH AN INTERNAL TIME-VARYING DELAY TERM

  • Kim, Daewook
    • East Asian mathematical journal
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    • 제32권3호
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    • pp.399-412
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    • 2016
  • In this paper, we study the viscoelastic Kirchhoff type equation with the following nonlinear source and time-varying delay $$u_{tt}-M(x,t,{\parallel}{\nabla}u(t){\parallel}^2){\Delta}u+{\int_{0}^{t}}h(t-{\tau})div[a(x){\nabla}u({\tau})]d{\tau}\\+{\parallel}u{\parallel}^{\gamma}u+{\mu}_1u_t(x,t)+{\mu}_2u_t(x,t-s(t))=0.$$ Under the smallness condition with respect to Kirchhoff coefficient and the relaxation function and other assumptions, we prove the uniform decay rate of the Kirchhoff type energy.

정적 대변형을 받고 있는 점탄성 재료의 동적 물성치 규명 시험 (Testing for Identification of Dynamic Properties of Viscoelastic Material Subject to Large Static Deformation)

  • 이완술;이호정;조지현;김진성;윤성기;김광준
    • 한국소음진동공학회논문집
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    • 제13권2호
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    • pp.132-143
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    • 2003
  • Viscoelastic components for vibration isolation or shock absorption in automobiles, machines and buildings are often subject to a high level of static deformation. From the dynamic design point of view, it is requisite to predict dynamic complex stiffness of viscoelastic components accurately and efficiently. To this end, a systematic procedure for complex modulus measurement of the viscoelastic material under large static deformation is often required in the industrial fields. In this paper, dynamic test conditions and procedures for the viscoelastic material under small oscillatory load superimposed on large static deformation are discussed. Various standard test methods are investigated in order to select an adequate test methodology. The influence of fixed boundary condition in the compression tests upon complex stiffness are investigated and an effective correction technique is proposed. Then the uniaxial tension and compression tests are performed and its results are compared with analysis results from conventional constitutive models.

점탄성층이 샌드위치된 복합적층판의 진동감쇠 특성 (Vibration and Damping Characteristics of Viscoelastically Damped Sandwich Plates)

  • 김재호;박태학;신현정
    • 대한기계학회논문집
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    • 제17권9호
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    • pp.2252-2263
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    • 1993
  • The purpose of this study is to verify the vibration and damping characteristics of elastic-viscoelastic-elastic structures, theoretically and experimentally. The forth-order differential equations of motion are derived for the transverse vibration of three-layered plates with viscoelastic core layer. The equations consider both transverse displacements of the constraining layer and the bare base plate as variable and account for the effect of the transverse normal strain and the shear strain of viscoelastic core layer on the vibration of the plates. Finite difference analysis of the equations and experimental measurements are performed on the three-layered plates of completely free boundary condition. Comparative investigations on the theory and the results of direct frequency analysis of NASTRAN are carried out on the same structures.