• 제목/요약/키워드: Constitutive Equation

검색결과 470건 처리시간 0.025초

Non-linear rheology of tension structural element under single and variable loading history Part I: Theoretical derivations

  • Kmet, S.
    • Structural Engineering and Mechanics
    • /
    • 제18권5호
    • /
    • pp.565-589
    • /
    • 2004
  • The present paper concerns the macroscopic overall description of rheologic properties for steel wire and synthetic fibre cables under variable loading actions according to non-linear creep and/or relaxation theory. The general constitutive equations of non-linear creep and/or relaxation of tension elements - cables under one-step and the variable stress or strain inputs using the product and two types of additive approximations of the kernel functions are presented in the paper. The derived non-linear constitutive equations describe a non-linear rheologic behaviour of the cables for a variable stress or strain history using the kernel functions determined only by one-step - constant creep or relaxation tests. The developed constitutive equations enable to simulate and to predict in a general way non-linear rheologic behaviour of the cables under an arbitrary loading or straining history. The derived constitutive equations can be used for the various tension structural elements with the non-linear rheologic properties under uniaxial variable stressing or straining.

포화점성토의 비배수 CREEP 성질에 의한 공극수압의 거동 (Pore Water Pressure Behavior due to Undrained Creep of Saturated Clay)

  • 강우묵;조성섭;지인택
    • 한국농공학회지
    • /
    • 제30권3호
    • /
    • pp.38-50
    • /
    • 1988
  • carried out to present a rheology model which is able to treat time-dependent properties of clay. The results were summarized as follow ; 1. The slope (a(e1)) of deviator stress in strain rate test was independent on axial strain, and pore water pressure was decreased with increment of strain rate. 2. The pore water pressure in a stress relaxation condition was not changed when the strain rate before stress relaxation was 0.05%/min., but it was increased with increment of time when the strain rate before stress relaxation was 0.2%/min 3. The greater the stress condition (q/qmax) and the strain rate before creep test became, the greater the increment rate of axial strain in creep test became. 4. SEKIGUCHI's constitutive equation was slightly overpredicted while empirical equation proposed in the study was well coincided with measured values. 5. The constitutive equation induced by a strain function could be dealed with a behavior of the pore water pressure increased with increment of elapsed time after primary consolidation.

  • PDF

Computation of viscoelastic flow using neural networks and stochastic simulation

  • Tran-Canh, D.;Tran-Cong, T.
    • Korea-Australia Rheology Journal
    • /
    • 제14권4호
    • /
    • pp.161-174
    • /
    • 2002
  • A new technique for numerical calculation of viscoelastic flow based on the combination of Neural Net-works (NN) and Brownian Dynamics simulation or Stochastic Simulation Technique (SST) is presented in this paper. This method uses a "universal approximator" based on neural network methodology in combination with the kinetic theory of polymeric liquid in which the stress is computed from the molecular configuration rather than from closed form constitutive equations. Thus the new method obviates not only the need for a rheological constitutive equation to describe the fluid (as in the original Calculation Of Non-Newtonian Flows: Finite Elements St Stochastic Simulation Techniques (CONNFFESSIT) idea) but also any kind of finite element-type discretisation of the domain and its boundary for numerical solution of the governing PDE's. As an illustration of the method, the time development of the planar Couette flow is studied for two molecular kinetic models with finite extensibility, namely the Finitely Extensible Nonlinear Elastic (FENE) and FENE-Peterlin (FENE-P) models.P) models.

몰리브데늄 분말의 치밀화 거동 및 기계적 물성의 이론적 연구 (Theoretical Study on the Consolidation Behavior and Mechanical Property for Molybdenum Powders)

  • 김영무
    • 한국분말재료학회지
    • /
    • 제15권3호
    • /
    • pp.214-220
    • /
    • 2008
  • In this study, consolidation behavior and hardness of commercially available molybdenum powder were investigated. In order to analyze compaction response of the powders, the elastoplastic constitutive equation based on the yield function by Shima and Oyane was applied to predict the compact density under uniaxial pressure from 100MPa to 700MPa. The compacts were sintered at $1400-1600^{\circ}C$ for 20-60 min. The sintered density and grain size of molybdenum were increased with increasing the compacting pressure and processing temperature and time. The constitutive equation, proposed by Kwon and Kim, was applied to simulate the creep densification rate and grain growth of molybdenum powder compacts. The calculated results were compared with experimental data for the powders. The effects of the porosity and grain size on the hardness of the specimens were explained based on the modified plasticity theory of porous material and Hall-Petch type equation.

Partition method of wall friction and interfacial drag force model for horizontal two-phase flows

  • Hibiki, Takashi;Jeong, Jae Jun
    • Nuclear Engineering and Technology
    • /
    • 제54권4호
    • /
    • pp.1495-1507
    • /
    • 2022
  • The improvement of thermal-hydraulic analysis techniques is essential to ensure the safety and reliability of nuclear power plants. The one-dimensional two-fluid model has been adopted in state-of-the-art thermal-hydraulic system codes. Current constitutive equations used in the system codes reach a mature level. Some exceptions are the partition method of wall friction in the momentum equation of the two-fluid model and the interfacial drag force model for a horizontal two-phase flow. This study is focused on deriving the partition method of wall friction in the momentum equation of the two-fluid model and modeling the interfacial drag force model for a horizontal bubbly flow. The one-dimensional momentum equation in the two-fluid model is derived from the local momentum equation. The derived one-dimensional momentum equation demonstrates that total wall friction should be apportioned to gas and liquid phases based on the phasic volume fraction, which is the same as that used in the SPACE code. The constitutive equations for the interfacial drag force are also identified. Based on the assessments, the Rassame-Hibiki correlation, Hibiki-Ishii correlation, Ishii-Zuber correlation, and Rassame-Hibiki correlation are recommended for computing the distribution parameter, interfacial area concentration, drag coefficient, and relative velocity covariance of a horizontal bubbly flow, respectively.

Comparative study of constitutive relations implemented in RELAP5 and TRACE - Part I: Methodology & wall friction

  • Shin, Sung Gil;Lee, Jeong Ik
    • Nuclear Engineering and Technology
    • /
    • 제54권9호
    • /
    • pp.3526-3539
    • /
    • 2022
  • Nuclear thermal-hydraulic system analysis codes have been developed to simulate nuclear reactor systems, which solve simplified governing equations by replacing source terms with constitutive relations for simulating entire reactor systems with low computational resources. For half a century, many efforts have been made for wider versatility and higher accuracy of system codes, but various factors can affect the code analysis results, and it was difficult to isolate these factors and interpret them individually. In this study, two system codes, RELAP5 and TRACE, which have many users and are highly reliable, are selected to analyze only the effects of constitutive relations. The influence of constitutive relations is analyzed using in-house platforms that replicate constitute relations of RELAP5 and TRACE equally to exclude factors that may affect analysis results, such as governing equation solvers and user effects. Among the various constitutive relations, the analysis is performed on the wall variables expected to have the most influence on the analysis results. Part 1 paper presents the methodology and wall friction model comparison, while Part 2 paper shows wall heat transfer comparison of the two selected codes.

지반재료의 비등방경화 구성모델에 대한 응력적분 알고리즘 (Stress Integration Algorithm for an Anisotropic Hardening Constitutive Model of Geomaterials)

  • 오세붕;이진구;김태경
    • 한국전산구조공학회:학술대회논문집
    • /
    • 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
    • /
    • pp.343-350
    • /
    • 2005
  • A constitutive model was implemented in ABAQUS code. The constitutive equation can model the behavior for overall range of strain level from small to large deformation, which is based on anisotropic hardening rule and total stress concept. The formulation includes (1) finite strain formulation on the basis of Jaumann rate, (2) implicit stress integration and (3) consistent tangent moduli. Therefore the mathematical background was established in order that large deformation analysis can be performed accurately and efficiently with the anisotropic constitutive model. In the large deformation analyses, geometric nonlinearity was considered and the result of analyses with the proposed model was compared with that of Mises model for the overall strain range behavior.

  • PDF

변형률 속도가 고려된 발포 폴리프로필렌의 구성방정식 (A Constitutive Equation Including Strain Rate Effect for the Expanded Polypropylene)

  • 김한국;전성식
    • Composites Research
    • /
    • 제27권4호
    • /
    • pp.130-134
    • /
    • 2014
  • 본 논문에서는 Kim 등[7]이 제시한 4가지의 다른 밀도를 갖는 원통형 시험편으로한 EPP(Expanded polypropylene)의 준정적(Quasi-static test) 및 충격 시험(Impact test) DB를 바탕으로 Jeong 등[12]이 제시한 폴리우레탄(Polyurethane)에 대한 구성방정식을 EPP 폼에 대하여 다시 정의 하여 충격량-운동량 이론을 접목시켜 새로운 구성방정식을 제안하기위한 DB 구축을 목표로 하였다.

SPH를 이용한 봉충돌 해석에서 구성방정식의 특성 (Characteristics of Constitutive Equations under Rod Impact Analysis by Smoothed Particle Hydrodynamics)

  • 김용환;김용석;이정민
    • 한국군사과학기술학회지
    • /
    • 제6권3호
    • /
    • pp.62-73
    • /
    • 2003
  • The characteristics of constitutive equations, for hydrocodes, were Investigated by the comparison between the smoothed particle hydrodynamcis simulation and the experiment of rod impact test which resulted in a deformation history of impacting front where high strain and high strain rate dominate. The constitutive equations used in the simulation Is J-C(Johnson-Cook) model, Z-A(Zerilli-Armstrong) model, and S-C-G(Steinberg-Cochran-Guinan) model. The modification of Z-A model, based on the increased effect of strain-rate hardening, showed better correlation with expriment.

Integration of Stress-Strain Rate Equations of CASM

  • Koh, Tae-Hoon
    • International Journal of Railway
    • /
    • 제3권4호
    • /
    • pp.117-122
    • /
    • 2010
  • In transportation geotechnical engineering, stress-strain behavior of earth structures has been analyzed by numerical simulations with the implemented plasticity constitutive model. It is a fact that many advanced plasticity constitutive models on predicting the mechanical behavior of soils have been developed as well as experimental research works for geotechnical applications in the past decades. In this study, recently developed, a unified constitutive model for both clay and sand, which is referred to as CASM (clay and sand model), was compared with a classical constitutive model, Cam-Clay model. Moreover, integration methods of stress-strain rate equations using CASM were presented for simulation of undrained and drained triaxial compression tests. As a conclusion, it was observed that semi-implicit integration method has more improved accuracy of capturing strain rate response to applied stress than explicit integration by the multiple correction and iteration.

  • PDF