• Title/Summary/Keyword: Variational formulation

검색결과 171건 처리시간 0.029초

장애물 접촉문제에서의 지역 A Posteriori 오차계산 (Local A Posteriori Error Estimates for Obstacle Contact Problems)

  • 이춘열
    • 한국정밀공학회지
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    • 제15권5호
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    • pp.120-127
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    • 1998
  • Differential inequalities occurring in problems of obstacle contact problems are recast into variational inequalities and analyzed by finite element methods. A new a posteriori error estimator, which is essential in adaptive finite element method, is introduced to capture the errors in finite element approximations of these variational inequalities. In order to construct a posteriori error estimates, saddle point problems are introduced using Lagrange parameters and upper bounds are provided. The global upper bound is localized by a special mixed formulation, which leads to upper bounds of the element errors. A numerical experiment is performed on an obstacle contact problem to check the effectivity index both in a local and a global sense.

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LAYERWISE FORMULATION OF PIEZOELECTRIC LAMINATED COMPOSITES

  • Lee, Jaehong-;Ham, Hee-Jung
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 1994년도 가을 학술발표회 논문집
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    • pp.121-128
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    • 1994
  • A layerwise theory for the dynamic response of a laminated composite plate with integrated piezoelectric actuators and sensors subjected to both mechanical and electrical loadings is proposed. The formulation is derived form the variational principle with consideration for both total potential energy of the structures and the electrical potential energy of the piezoceramics. The governing equations of the present theory account for direct and converse effects of piezoelectrics, and layerwise variation of displacement field through the thickness of a laminate.

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Legendre Tau Method for the 2-D Stokes Problem

  • Jun, SeRan;Kang, Sungkwon;Kwon, YongHoon
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • 제4권2호
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    • pp.111-133
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    • 2000
  • A Legendre spectral tau approximation scheme for solving the two-dimensional stationary incompressible Stokes equations is considered. Based on the vorticity-stream function formulation and variational forms, boundary value and normal derivative of vorticity are computed. A factorization technique for matrix stems based on the Schur decomposition is derived. Several numerical experiments are performed.

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A CONVERGENCE RESULTS FOR ANTIPLANE CONTACT PROBLEM WITH TOTAL SLIP RATE DEPENDENT FRICTION

  • AMMAR, DERBAZI
    • Journal of applied mathematics & informatics
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    • 제39권5_6호
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    • pp.813-823
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    • 2021
  • In this work, we present the classical formulation for the antiplane problem of a eletro-viscoelastic materialswith total sliprate dependent friction and write the corresponding variational formulation. In the second step, we prove that the solution converges to the solution of the corresponding electro-elastic problem as the viscosity converges to zero.

비압축성 문제에 대한 비적합 복합유한요소 정식화 (A new incompatible mixed formulation for incompressible and nearly-incompressible media)

  • 주상백;신효철
    • 대한기계학회논문집A
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    • 제22권2호
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    • pp.365-371
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    • 1998
  • In the present study, we attempted to add the incompatible functions as additional variable terms to the conventional u-p formulation. It is derived from the four-field generalized variational principle that encompasses velocity, pressure, velocity strains and stress fields as independent interpolated variables. As a severe test of the present formulation, we have investigated the driven cavity with the corner velocity singularity like leaky lid. Through the test, the present element performs very well without unstable oscillation of pressure distribution.

VARIATIONAL ANALYSIS OF AN ELECTRO-VISCOELASTIC CONTACT PROBLEM WITH FRICTION AND ADHESION

  • CHOUGUI, NADHIR;DRABLA, SALAH;HEMICI, NACERDINNE
    • 대한수학회지
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    • 제53권1호
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    • pp.161-185
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    • 2016
  • We consider a mathematical model which describes the quasistatic frictional contact between a piezoelectric body and an electrically conductive obstacle, the so-called foundation. A nonlinear electro-viscoelastic constitutive law is used to model the piezoelectric material. Contact is described with Signorini's conditions and a version of Coulomb's law of dry friction in which the adhesion of contact surfaces is taken into account. The evolution of the bonding field is described by a first order differential equation. We derive a variational formulation for the model, in the form of a system for the displacements, the electric potential and the adhesion. Under a smallness assumption which involves only the electrical data of the problem, we prove the existence of a unique weak solution of the model. The proof is based on arguments of time-dependent quasi-variational inequalities, differential equations and Banach's fixed point theorem.

복합재료적층판의 진동해석을 위한 유한요소모델 I. 변분원리의 유도 (Finite Element Analysis for Vibration of Laminated Plate Using a Consistent Discrete Theory Part I : Variational Principles)

  • 홍순조
    • 전산구조공학
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    • 제7권4호
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    • pp.85-101
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    • 1994
  • 적층판의 동적거동에 대한 유한요소해석모델개발을 목적으로 전단변형을 적합하게 고려한 적층판이론에 대한 변분원리를 유도하였다. 유도방법은 Sandhu 등에 의해 개발된 다변수 경계치문제의 변분원리이론을 따랐으며, 지배방정식의 미분연산자 매트릭스를 self-adjoint로 만들기 위하여 convolution을 이중선형사상으로 사용하였다. 유도된 적층판의 범함수에는 경계조건, 초기조건뿐만 아니라 유한요소해석모델에서 생길 수 있는 요소간 불연속조건도 포함시킬 수 있다. 상태변수의 적합함수공간을 확장하거나 특정조건을 적용하므로서 다양한 형태의 범함수를 유도할 수 있으며, 이를 통해 다양한 유한요소해석모델의 개발이 가능함을 논하였다.

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속도-응력 변분식을 이용한 3차원 SEM 탄성파 수치 모사에 대한 ADE-PML경계조건의 적용 (Application of ADE-PML Boundary Condition to SEM using Variational Formulation of Velocity-Stress 3D Wave Equation)

  • 조창수;손민경
    • 지구물리와물리탐사
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    • 제15권2호
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    • pp.57-65
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    • 2012
  • 탄성파 수치 모형 계산에 있어서 다양한 방법들이 개발되어 적용되었다. 최근에는 특히 탄성파 수치 모형 계산에 있어 혁신적인 방법인 SEM (Spectral Element Method)가 개발되어 사용되어 왔다. 이 방법은 지형을 자유롭게 표현하는데 있어 유연한 유한요소법의 장점에 정확성을 높인 방법이다. 일반적으로 Weak Formulation 형태의 파동방정식에 육면체 요소와 Gauss-Lobatto-Legendre 적분법을 적용한 방법이 널리 사용된다. 일반적인 SEM에서는 PML (Perfectly Matched Layer)경계조건을 적용하기 어려워 속도-응력 변분식으로 파동방정식을 변경하였다. CFS-PML (Complex frequency Shifted PML)경계조건을 ADE (Auxiliary Differential Equation)방정식으로 변경하여 속도-응력 파동방정식에 적용함으로써 분리할 필요가 없는 PML을 적용한 SEM 수치 모형 계산 알고리듬을 구현하였다. 1차원 수치모형과 3차원 수치모형 실험을 통하여 SEM에 적용한 비분리 CFS-PML이 유한경계에서 인공적으로 반사되는 반사파를 효과적으로 제거하는 것을 확인하였다.

A method to evaluate the frequencies of free transversal vibrations in self-anchored cable-stayed bridges

  • Monaco, Pietro;Fiore, Alessandra
    • Computers and Concrete
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    • 제2권2호
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    • pp.125-146
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    • 2005
  • The objective of this paper is setting out, for a cable-stayed bridge with a curtain suspension, a method to determine the modes of vibration of the structure. The system of differential equations governing the vibrations of the bridge, derived by means of a variational formulation in a nonlinear field, is reported in Appendix C. The whole analysis results from the application of Hamilton's principle, using the expressions of potential and kinetic energies and of the virtual work made by viscous damping forces of the various parts of the bridge (Monaco and Fiore 2003). This paper focuses on the equation concerning the transversal motion of the girder of the cable-stayed bridge and in particular on its final form obtained, restrictedly to the linear case, neglecting some quantities affecting the solution in a non-remarkable way. In the hypotheses of normal mode of vibration and of steady-state, we propose the resolution of this equation by a particular method based on a numerical approach. Respecting the boundary conditions, we derive, for each mode of vibration, the corresponding frequency, both natural and damped, the shape-function of the girder axis and the exponential function governing the variability of motion amplitude in time. Finally the results so obtained are compared with those deriving from the dynamic analysis performed by a finite elements calculation program.