• Title, Summary, Keyword: Constitutive model

Search Result 1,064, Processing Time 0.047 seconds

A constitutive model for confined concrete in composite structures

  • Shi, Qing X.;Rong, Chong;Zhang, Ting
    • Steel and Composite Structures
    • /
    • v.24 no.6
    • /
    • pp.689-695
    • /
    • 2017
  • The constitutive relation is an important factor in analysis of confined concrete in composite structures. In order to propose a constitutive model for nonlinear analysis of confined concrete, lateral restraint mechanism of confined concrete is firstly analyze to study the generalities. As the foundation of the constitutive model, peak stress and peak strain is the first step in research. According to the generalities and the Twin Shear Unified Strength Theory, a novel unified equation for peak stress and peak strain are established. It is well coincident with experimental results. Based on the general constitutive relations and the unified equation for peak stress and peak strain, we propose a unified and convenient constitutive model for confined concrete with fewer material parameters. Two examples involved with steel tube confined concrete and hoop-confined concrete are considered. The proposed constitutive model coincides well with the experimental results. This constitutive model can also be extended for nonlinear analysis to other types of confined concrete.

A viscoelastic constitutive model of rubber under small oscillatory loads superimposed on large static deformation (정적 대변형에 중첩된 미소 동적 하중을 견디는 고무재료의 점탄성 구성방정식에 관한 연구)

  • Kim, Bong-Kyu;Youn, Sung-Kie
    • Proceedings of the KSME Conference
    • /
    • /
    • pp.280-285
    • /
    • 2000
  • A viscoelastic constitutive equation of rubber that is under small oscillatory load superimposed on large static deformation is proposed. The proposed model is derived through linearization of Simo's viscoelastic constitutive model and reference configuration transformation. The proposed constitutive equation is extended to a generalized viscoelastic constitutive equation that includes widely used Mormin's model as a special case using objective stress increment. Static deformation correction factor is introduced to consider the influence of Pre-strain on the relaxation function. The proposed constitutive model is tested fer dynamic behavior of rubber specimens with different carbon black contents. It is concluded from the test that the viscoelastic constitutive equation for filled rubber must include the influence of the static deformation on the time effects. The suggested constitutive equation with static deformation correction factor shows good agreement with test values.

  • PDF

DEVELOPMENT OF THE HANSEL-SPITTEL CONSTITUTIVE MODEL GAZED FROM A PROBABILISTIC PERSPECTIVE

  • LEE, KYUNGHOON;KIM, JI HOON;KANG, BEOM-SOO
    • Journal of the Korean Society for Industrial and Applied Mathematics
    • /
    • v.21 no.3
    • /
    • pp.155-165
    • /
    • 2017
  • The Hansel-Spittel constitutive model requires a total of nine parameters for flow stress prediction. Typically, the parameters are estimated by least squares methods for given tensile test measurements from a deterministic perspective. In this research we took a different approach, a probabilistic viewpoint, to see through the development of the Hansel-Spittel constitutive model. This perspective change showed that deterministic least squares methods are closely related to statistical maximum likelihood methods via Gaussian noise assumption. More intriguingly, this perspective shift revealed that the Hansel-Spittel constitutive model may leave out deterministic trends in residuals despite nearly perfect agreement with measurements. With tensile test measurements of AA1070 aluminum alloy, we demonstrated this deficiency of the Hansel-Spittel constitutive model, suggesting room for improvement.

A Viscoelastic Constitutive Model of Rubber Under Small Oscillatory Loads Superimposed on Large static Deformation (정적 대변형에 중첩된 미소 동적 하중을 받는 고무재료의 점탄성 구성방식에 관한 연구)

  • Kim, Bong-Gyu;Yun, Seong-Gi
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.25 no.4
    • /
    • pp.619-628
    • /
    • 2001
  • A viscoelastic constitutive equation of rubber is proposed under small oscillatory load superimposed on large static deformation. The proposed model is derived through linearization of Simos nonlinear viscoelastic constitutive model and reference configuration transformation. Statically pre-deformed state is used as reference configuration. The model is extended to a generalized viscoelastic constitutive equation including widely-used Mormans model. Static deformation correction factor is introduced to consider the influence of pre-strain on the relaxation function. The model is tested for dynamic behavior of rubbers with different carbon black fractions. It is shown that the constitutive equation with static deformation correction factor agrees well with test results.

A Micromechanics based Elastic Constitutive Model for Particle-Reinforced Composites Containing Weakened Interfaces and Microcracks (계면손상과 미세균열을 고려한 입자강화 복합재료의 미세역학 탄성구성모델)

  • Lee, Haeng-Ki;Pyo, Suk-Hoon;Kim, Hyeong-Ki
    • Journal of the Computational Structural Engineering Institute of Korea
    • /
    • v.21 no.1
    • /
    • pp.51-58
    • /
    • 2008
  • A constitutive model based on a combination of a micromechanics-based weakened interface elastic model (Lee and Pyo, 2007) and a crack nucleation model (Karihaloo and Fu, 1989) is proposed to predict the effective elastic behavior of particle-reinforced composites. The model specifically considers imperfect interfaces in particles and microcracks in the matrix. To exercise the proposed constitutive model and to investigate the influence of model parameters on the behavior of the composites, numerical simulations on uniaxial tension tests were conducted. Furthermore, the present prediction is compared with available experimental data in the literature to verify the accuracy of the proposed constitutive model.

A constitutive model for fiber-reinforced extrudable fresh cementitious paste

  • Zhou, Xiangming;Li, Zongjin
    • Computers and Concrete
    • /
    • v.8 no.4
    • /
    • pp.371-388
    • /
    • 2011
  • In this paper, time-continuous constitutive equations for strain rate-dependent materials are presented first, among which those for the overstress and the consistency viscoplastic models are considered. By allowing the stress states to be outside the yield surface, the overstress viscoplastic model directly defines the flow rule for viscoplastic strain rate. In comparison, a rate-dependent yield surface is defined in the consistency viscoplastic model, so that the standard Kuhn-Tucker loading/unloading condition still remains true for rate-dependent plasticity. Based on the formulation of the consistency viscoplasticity, a computational elasto-viscoplastic constitutive model is proposed for the short fiber-reinforced fresh cementitious paste for extrusion purpose. The proposed constitutive model adopts the von-Mises yield criterion, the associated flow rule and nonlinear strain rate-hardening law. It is found that the predicted flow stresses of the extrudable fresh cementitious paste agree well with experimental results. The rate-form constitutive equations are then integrated into an incremental formulation, which is implemented into a numerical framework based on ANSYS/LS-DYNA finite element code. Then, a series of upsetting and ram extrusion processes are simulated. It is found that the predicted forming load-time data are in good agreement with experimental results, suggesting that the proposed constitutive model could describe the elasto-viscoplastic behavior of the short fiber-reinforced extrudable fresh cementitious paste.

Microforming of Bulk Metallic Glasses : Constitutive Modelling and Applications (벌크비정질합금의 미세성형 : 구성모델과 적용)

  • 윤승채;백경호;김형섭
    • Transactions of Materials Processing
    • /
    • v.13 no.2
    • /
    • pp.168-173
    • /
    • 2004
  • Microforming can be a good application for bulk metallic glasses. It is important to simulate the deformation behaviour of the bulk metallic glasses in a supercooled liquid region for manufacturing micromachine parts. For these purposes, a correct constitutive model which can reproduce viscosity results is essential for good predicting capability. In this paper, we studied deformation behaviour of the bulk metallic glasses using the finite element method in conjunction with the fictive stress constitutive model which can describe non-Newtonian as well as Newtonian behaviour. A combination of kinetic equation which describes the mechanical response of the bulk metallic glasses at a given temperature and evolution equations fur internal variables provide the constitutive equation of the fictive stress model. The internal variables are associated with fictive stress and relation time. The model has a modular structure and can be adjusted to describe a particular type of microforming process. Implementation of the model into the MARC software has shown its versatility and good predictive capability.

A Progressive Failure Analysis Procedure for Composite Laminates I - Anisotropic Plastic Constitutive Model (복합재료 거동특성의 파괴해석 I - 이방성 소성 적합모델)

  • Yi, Gyu-Sei
    • Journal of the Korean Society for Advanced Composite Structures
    • /
    • v.5 no.4
    • /
    • pp.1-10
    • /
    • 2014
  • A progressive failure analysis procedure for composite laminates is developed in here and in the companion paper. An anisotropic plastic constitutive model for fiber-reinforced composite material, is developed, which is simple and efficient to be implemented into computer program for a predictive analysis procedure of composites. In current development of the constitutive model, an incremental elastic-plastic constitutive model is adopted to represent progressively the nonlinear material behavior of composite materials until a material failure is predicted. An anisotropic initial yield criterion is established that includes the effects of different yield strengths in each material direction, and between tension and compression. Anisotropic work-hardening model and subsequent yield surface are developed to describe material behavior beyond the initial yield under the general loading condition. The current model is implemented into a computer code, which is Predictive Analysis for Composite Structures (PACS), and is presented in the companion paper. The accuracy and efficiency of the anisotropic plastic constitutive model are verified by solving a number of various fiber-reinforced composite laminates with and without geometric discontinuity. The comparisons of the numerical results to the experimental and other numerical results available in the literature indicate the validity and efficiency of the developed model.

Creep Behavior Analysis of High Cr Steel Using the Constitutive Model Based on Microstructure (미세조직기반 구성모델을 이용한 고크롬강의 크리프 거동 해석)

  • 윤승채;서민홍;백경호;김성호;류우석;김형섭
    • Transactions of Materials Processing
    • /
    • v.13 no.2
    • /
    • pp.160-167
    • /
    • 2004
  • In order to theoretically analyze the creep behavior of high Cr steel at $600^{\circ}C$, a unified elasto-viscoplastic constitutive model based on the consideration of dislocation density is proposed. A combination of a kinetic equation describing the mechanical response of a material at a given microstructure in terms of dislocation glide and evolution equations for internal variables characterizing the microstructure provides the constitutive equations of the model. Microstructural features of the material such as the grain size and spacing between second phase particles are directly implemented in the constitutive equations. The internal variables are associated with the total dislocation density in a simple model. The model has a modular structure and can be adjusted to describe a creep behavior using the material parameters obtained from uniaxial tensile tests.

Seismic Response Characteristics of Layered Ground Considering Viscoelastic Effects of Clay (점성토의 점탄성 특성을 고려한 층상지반의 지진응답특성)

  • Kim, Yong-Seong
    • Journal of The Korean Society of Agricultural Engineers
    • /
    • v.53 no.3
    • /
    • pp.19-26
    • /
    • 2011
  • In order to estimate the viscous effects of clay over a wide range of strain levels, we confirmed the performance of a viscoelastic-viscoplastic constitutive model by simulating cyclic undrained triaxial tests to determine the cyclic strength and deformation characteristics of natural marine clay. The viscoelastic-viscoplastic constitutive model was then incorporated into an effective stress-based seismic response analysis to estimate the effects of an intermediate clay layer on the behavior of sand layers. Seismic response was simulated by the cyclic viscoelastic-viscoplastic constitutive model created with data recorded at Rokko Island, Kobe, Japan. The results show that a cyclic viscoelastic-viscoplastic constitutive model can provide a good description of dynamic behavior including viscoelastic effects, within a small strain range.