• Title/Summary/Keyword: Constitutive Equation

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A Rate-Dependent Elastic Plastic Constitutive Equation in Finite Deformation Based on a Slip Model (슬립모델을 이용한 변형률의존 유한변형 탄소성재료의 구성방정식 개발)

  • Nam, Yong-Yun;Kim, Sa-Soo;Lee, Sang-Gab
    • Journal of the Society of Naval Architects of Korea
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    • v.34 no.1
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    • pp.77-86
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    • 1997
  • The advanced development in many fields of engineering and science has caused much interests and demands for crashworthiness and non-linear dynamic transient analysis of structure response. Crash and impact problems have a dominant characteristic of large deformation with material plasticity for short time scales. The structural material shows strain rate-dependent behaviors in those cases. Conventional rate-independent constitutive equations used in the general purposed finite analysis programs are inadequate for dynamic finite strain problems. In this paper, a rate-dependent constitutive equation for elastic-plastic material is developed. The plastic stretch rate is modeled based on slip model with dislocation velocity and its density so that there is neither yielding condition, nor loading conditions. Non-linear hardening rule is also introduced for finite strain. Material constants of present constitutive equation are determined by experimental data of mild steel, and the constitutive equation is applied to uniaxile tension loading.

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Design charts for consolidation settlement of marine clays using finite strain consolidation theory

  • Jun, Sang-Hyun;Lee, Jong-Ho;Park, Byung-Soo;Kwon, Hyuk-Jae
    • Geomechanics and Engineering
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    • v.24 no.3
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    • pp.295-305
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    • 2021
  • In this study, design charts for estimating consolidation settlement are proposed according to finite strain consolidation theory using a nonlinear constitutive relationship equation. Results of parametric sensitivity analysis shows that the final settlement, initial height, and initial void ratio exerted the greatest effect, and the coefficients of the void ratio-effective-stress. Proposed design charts were analyzed for three regions using a representative constitutive relationship equation that enables major dredged-reclaimed construction sites in Korea. The regional design charts can be calculated accurately for the final settlement because it is applied directly to the numerical analysis results, except for reading errors. A general design chart applicable to all marine clays is proposed through correlation analysis of the main parameters. A final self-weight consolidation settlement with various initial void ratios and initial height conditions should be estimated easily using the general design chart and constitutive relationship. The estimated final settlement using the general design chart is similar to the results of numerical analysis obtained using finite strain consolidation theory. Under an overburden pressure condition, design charts for estimating consolidation settlement are proposed for three regions in Korea.

Modeling of Stress-strain Curve for Cold Rolled Electrical Steel (냉간 압연된 전기강판의 응력-변형률 곡선 모델)

  • Yoo, U.K.;Byon, S.M.;Lee, Y.
    • Transactions of Materials Processing
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    • v.17 no.4
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    • pp.272-277
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    • 2008
  • A constitutive equation of the electrical steel strip used for a raw material of transformer is proposed. The stress-strain behavior of electrical steel strip is quite different from that of common carbon steel and/or alloy steel. A series of tensile tests were performed with the specimens made from cold rolled strip. Several thicknesses of the strip were produced by a two-high (with upper and lower rolls) cold rolling pilot mill as reduction ratio increases from 10% to 90%. Its initial thickness of the strip was 2.5mm. Tensile specimens are cut out from the cold rolled strips. Mechanical properties of the steel are examined through rolling direction. Ramberg-Osgood model and the proposed equation are combined to describe the total behavior of stress-strain including instability region. The stress-strain curves calculated from the present constitutive equation are compared with those from experimentally obtained at each test condition of reduction ratios of specimen. Results show that the predicted stress-strain curves are in overall in a good agreement with measured ones.

Modelling creep behavior of soft clay by incorporating updated volumetric and deviatoric strain-time equations

  • Chen Ge;Zhu Jungao;Li Jian;Wu Gang;Guo Wanli
    • Geomechanics and Engineering
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    • v.35 no.1
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    • pp.55-65
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    • 2023
  • Soft clay is widely spread in nature and encountered in geotechnical engineering applications. The creep property of soft clay greatly affects the long-term performance of its upper structures. Therefore, it is vital to establish a reasonable and practical creep constitutive model. In the study, two updated hyperbolic equations based on the volumetric creep and deviatoric creep are respectively proposed. Subsequently, three creep constitutive models based on different creep behavior, i.e., V-model (use volumetric creep equation), D-model (use deviatoric creep equation) and VD-model (use both volumetric and deviatoric creep equations) are developed and compared. From the aspect of prediction accuracy, both V-model and D-model show good agreements with experimental results, while the predictions of the VD-model are smaller than the experimental results. In terms of the parametric sensitivity, D-model and VD-model are lower sensitive to parameter M (the slope of the critical state line) than V-model. Therefore, the D-model which is developed by incorporating the updated deviatoric creep equation is suggested in engineering applications.

Split Hopkinson Pressure Bar(SHPB)에 의한 고 변형률 재료의 구성방정식 시뮬레이션

  • 이억섭;정주호;김종호
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1995.10a
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    • pp.724-727
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    • 1995
  • Dynamic deformation behavior under the high strain rate loading condition obtained with the aid of Split Hopkinson Pressure Bar(SHPB) technique is simulated by DYNA2D (an hydrodynamic code). A constitutive equation such as Johnson-Cook model is used by adjusting various parameters to fit experimentally determined dynamic stress-strain relationship.

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Finite Element Modeling of Low Density Polyurethane Foam Material (저밀도 폴리우레탄 포옴재료의 유한요소 모델링)

  • 김원택;최형연
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.2
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    • pp.183-188
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    • 1996
  • The compressive stress-strain response of Low Density Polyurethane foam material is modeled using the finite element method. A constitutive equation which include experimental constants based on quasi-static and dynamic uniaxial compression test is proposed. Impact test with different impactor masses and velocities are performed to verify the proposed model. The comparison between impact test and finite element analysis shows good agreements.

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On Stability of the Steady State, Thermodynamic Stabililty and Corresponding States in Rheology of Dense Simple Fluids$^\dag$

  • Ohr, Young-Gie;Eu, Byung-Chan
    • Bulletin of the Korean Chemical Society
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    • v.7 no.3
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    • pp.204-210
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    • 1986
  • It is shown that the linear stability coincides with the thermodynamic stability in the case of stress tensor evolution for simple dense fluids even if the constitutive (evolution) equation for the stress tensor is nolinear. The domain of coincidence can be defined in the space of parameters appearing in the constitutive equation and we find the domain is confined in an elliptical cone in a three-dimensional parameter space. The corresponding state theory in rheology of simple dense fluids is also further examined. The validity of the idea is strengthened by the examination.

Constitutive Models for Final Stage Densification of Powder Compacts with Power-Law Creep Deformation (Power-law 크리프 변형을 따르는 분말 성형체의 말기 치밀화 모델)

  • Yang, Hoon-Chul;Kim, Ki-Tae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.7
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    • pp.930-939
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    • 2004
  • Constitutive models for final stage densification of metal powder compacts with power-law creep deformation were investigated. The constitutive models were implemented into a finite element program (ABAQUS) by using user subroutine CREEP and, from FEM results, useful densification curves were obtained when hydrostatic and uniaxial stress were applied to the powder compacts at various pressures and temperatures. Because the densification behavior varied as the constitutive models, the equivalent stress surface on each constitutive equation was investigated to analyze the difference of densification behavior.

Finite Element Analysis of the Mandibular Canine for Nonlinear Deformation of the Periodontal Ligament (치주인대의 비선형 거동을 고려한 하악 견치의 유한요소해석)

  • Yang, Hoon-Chul;Kim, Ki-Tae;Ha, Man-Hee;Son, Woo-Sung
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.550-557
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    • 2003
  • Hyperelastic constitutive equations for nonlinear deformation of the periodontal ligament were investigated. The parameters in the strain energy potentials were obtained from experimental data for uniaxial and shear responses of the human periodontal ligament. The hyperelastic constitutive equations based on two strain energy potentials was also compared with the linear elastic equation, which is recently reported. The best fitted parameters in the strain energy potentials was applied to finite element program (ABAQUS) to simulate special orthodontic treatment of a mandibular canine.

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Analysis of 3-D non-linear truss smart actuator using SMA (형상기억합금을 이용한 3 차원 비선형 트러스 지능작동기 해석)

  • Yang, Seong-Pil;Kim, Sang-Haun;Li, Ningxue;Ryu, Jung-Hyun;Cho, Maeng-Hyo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.04a
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    • pp.557-561
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    • 2008
  • Shape memory alloys (SMA) have interesting features which are the superelastic effect (SE), shape memory effect (SME), two-way SME (TWSME), and so on. These are utilized in actuation factor. The thermo-mechanical constitutive equations of SMA proposed by Lagoudas et al. were employed in the present study for simulating SMA truss structures. The constitutive equation includes the necessary internal variables to account for the material transformations and is utilized in the non-linear finite element procedure of three dimensional truss structures that composed SMA bar (wholly or partially). In this study, we observed which element should be actuated to get a desired shape (actuation shape) from computational analysis. To reach this goal, we apply SMA constitutive equation to non-linear finite element formulation. And then, we simulate two-way shape memory effect as well as superelastic effect of various three dimensional truss using SMA.

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