• Title/Summary/Keyword: Strain-Hardening Behavior

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Damage and Fracture Analysis of Concrete using Homogenized Crack Model (혼합균열모델을 적용한 콘크리트의 손상 및 파괴해석)

  • Kim Kwang-Soo;Song Ha-Won;Nam Jin-Won
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.05a
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    • pp.155-158
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    • 2005
  • Damage and fracture of concrete is characterized as the degradation of strength and stiffness. There can be modeled as the so-called homogenized crack model which can overcome the mesh sensitivity. But the plasticity and damage modeling for damage behavior before the fracture of concrete should be combined with the crack model. In this study, a damage function and an unified hardening-softening function are applied to the homogenized crack model to develope a 3-dimensional FEM program for nonlinear damage and fracture analysis of concrete. The comparison of numerical results and experimental data show that the combined modeling in this study can simulate the damage and fracture of concrete without the mesh-sensitivity. It is also shown that the behavior of the so-called Engineering Cementitious Composite(ECC) characterized by strain-hardening and multiple cracks can be well simulated using the modeling.

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Study on Precipitation and Mechanical Properties of High Strength Invar Alloy (고강도 인바합금의 석출거동과 기계적 특성 연구)

  • Jeong, J.Y.;Lee, K.D.;Ha, T.K.;Jeong, H.T.
    • Transactions of Materials Processing
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    • v.17 no.7
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    • pp.507-510
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    • 2008
  • Effect of V addition on the precipitation behavior and strength of Fe-36Ni based high strength Invar alloy for power transmission wire was investigated. Fe-36Ni Invar alloy plates were fabricated using conventional ingot casting followed by hot rolling. High strength can be obtained through precipitation hardening and strain hardening by cold rolling. Simulation using FactSage$^{(R)}$ revealed that equilibrium phases which can be formed are two kinds of MC-type precipitates, $Mo_{2}C$ and $M_{23}C_6$ carbide. The latter stoichiometric carbide was expected to be formed at relatively lower temperature of $800^{\circ}C$.

Prediction of Drawbead Restraining Force by Hybrid Membrane/Bending Method (하이브리드 박막/굽힘 방법을 이용한 드로비드력의 예측)

  • Lee, M.G.;Chung, K.;Wagoner, R.H.;Keum, Y.T.
    • Transactions of Materials Processing
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    • v.15 no.8 s.89
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    • pp.533-538
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    • 2006
  • A simplified numerical procedure to predict drawbead restraining forces(DBRF) has been developed based on the hybrid membrane/bending method which superposes bending effects onto membrane solutions. As a semi-analytical method, the new approach is especially useful to analyze the effects of various constitutive parameters. The present model can accommodate general anisotropic yield functions along with non-linear isotropic-kinematic hardening under the plane strain condition. For the preliminary results, several sensitivity analyses for the process and material effects such as friction, drawbead depth, hardening behavior including the Bauschinger effect and yield surface shapes on the DBRF are carried out.

Evaluation of Single Hardening Constitutive Model for Sand (모래에 대한 단일항복면 구성모델의 평가)

  • Jeong, Jin-Seob;Park Moung-Bae
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.40 no.6
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    • pp.95-103
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    • 1998
  • Solutions of geotechnical engineering problems require calculation of deformation and stresses during various stages of loading. Powerful numerical methods are available to make such calculation even for complicated problems. To get accurate results, realistic stress-strain relationships of soil are dependent on a number of factors such as soil type, density, stress level and stress path. Attempts are continuously being made to develope analytical models for soils incorporating all such factors. The nature of stress-path dependency, the principle that governs deformations in sand, and the use of Lade's single work-hardening model for predicting sand response for a variety of stress-paths have been investigated and are examined. The test results and the analyses presented show that under some conditions sand exhibits stress-path dependent behavior. The strains calculated from Lade's single work-hardening model are in reasonable agreement with those measured, but some discrepancies occur. The largest difference between measured and calculated strains occurs for proportional loading with increasing stresses and for stress-path directions.

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Hardening slip model for reinforcing steel bars

  • Braga, Franco;Caprili, Silvia;Gigliotti, Rosario;Salvatore, Walter
    • Earthquakes and Structures
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    • v.9 no.3
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    • pp.503-539
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    • 2015
  • A new constitutive model for the representation of the seismic behaviour of steel bars including hardening phenomena is presented. The model takes into account relative slip between bars and concrete, necessary for the estimation of the structural behaviour of r.c. elements and of the level of strain induced by earthquakes on bars. The present work provides the analytical formulation of the post-yielding behaviour of reinforcements, resulting in a continuous axial stress-slip relationship to be implemented in engineering software. The efficacy of the model is proved through the application to a cantilever column, for whose bars the constitutive law is derived.

Ratcheting assessment of austenitic steel samples at room and elevated temperatures through use of Ahmadzadeh-Varvani Hardening rule

  • Xiaohui Chen;Lang Lang;Hongru Liu
    • Structural Engineering and Mechanics
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    • v.87 no.6
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    • pp.601-614
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    • 2023
  • In this study, the uniaxial ratcheting effect of Z2CND18.12N austenitic stainless steel at room and elevated temperatures is firstly simulated based on the Ahmadzadeh-Varvani hardening rule (A-V model), which is embedded into the finite element software ABAQUS by writing the user material subroutine UMAT. The results show that the predicted results of A-V model are lower than the experimental data, and the A-V model is difficult to control ratcheting strain rate. In order to improve the predictive ability of the A-V model, the parameter γ2 of the A-V model is modified using the isotropic hardening criterion, and the extended A-V model is proposed. Comparing the predicted results of the above two models with the experimental data, it is shown that the prediction results of the extended A-V model are in good agreement with the experimental data.

Effect of Aspect Ratio on Direct Tensile Response of Strain Hardening Cement Composites with PET and PVA Fiber (PET 및 PVA섬유를 사용한 변형경화형 시멘트 복합체의 직접인장거동에서 섬유 형상비의 영향)

  • Jeon, Esther;Yun, Hyun-Do;Park, Wan-Shin;Kim, Yong-Chul;Kim, Yun-Su
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.913-916
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    • 2008
  • Direct tensile response of strain hardening cement composites(SHCC) depends primarily on the material's tensile response, which is a water cement ratio, direct function of fiber and matrix characteristics, the bond between them, and the fiber volume fraction. This paper discusses effect of aspect ratio of the direct tensile response of SHCC with PET and PVA fibers. The main variables considered include the aspect ratio of PET fibers(Aspect ratio, ${\ell}/d_f$ : 150, 300, 600). For the same mixture proportion, PET1.5+PVA0.5-300 and PET1.5+PVA 0.5-600(Aspect ratio 300, 600) showed better overall behavior(Pseudo strain-hardening, Multiple cracking) than specimens with PET1.5+PVA0.5-150(Aspect ratio 150). Tensile strain of PET1.5+PVA0.5-300 and PET1.5+PVA 0.5-600 at ultimate tensile stress were 0.5, 2.0% respectively.

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Evaluation of constitutive relations for concrete modeling based on an incremental theory of elastic strain-hardening plasticity

  • Kral, Petr;Hradil, Petr;Kala, Jiri
    • Computers and Concrete
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    • v.22 no.2
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    • pp.227-237
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    • 2018
  • Today, the modeling of concrete as a material within finite element simulations is predominantly done through nonlinear material models of concrete. In current sophisticated computational systems, there are a number of complex concrete material models which are based on theory of plasticity, damage mechanics, linear or nonlinear fracture mechanics or combinations of those theories. These models often include very complex constitutive relations which are suitable for the modeling of practically any continuum mechanics tasks. However, the usability of these models is very often limited by their parameters, whose values must be defined for the proper realization of appropriate constitutive relations. Determination of the material parameter values is very complicated in most material models. This is mainly due to the non-physical nature of most parameters, and also the large number of them that are frequently involved. In such cases, the designer cannot make practical use of the models without having to employ the complex inverse parameter identification process. In continuum mechanics, however, there are also constitutive relations that require the definition of a relatively small number of parameters which are predominantly of a physical nature and which describe the behavior of concrete very well within a particular task. This paper presents an example of such constitutive relations which have the potential for implementation and application in finite element systems. Specifically, constitutive relations for modeling the plane stress state of concrete are presented and subsequently tested and evaluated in this paper. The relations are based on the incremental theory of elastic strain-hardening plasticity in which a non-associated flow rule is used. The calculation result for the case of concrete under uniaxial compression is compared with the experimental data for the purpose of the validation of the constitutive relations used.

Mathematical Expressions for Stress-Strain Curve of Metallic Material (금속재료 응력-변형률 곡선의 수학적 표현들)

  • Hyun, Hong-Chul;Lee, Jin-Haeng;Lee, Hyung-Yil
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.32 no.1
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    • pp.21-28
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    • 2008
  • Stress-strain curves based on Ramberg-Osgood and Hollomon relations are strongly dependent upon the regressed range of strain. This work investigates mathematical expressions of true stress-strain curves of metallic materials. We first observe the variation of yield strength, strain hardening exponent and stress-strain curve with regressed range of stain. Based on sectional regression and expression using one or two parameters, we propose an optimal strain range for which yield strength and nonlinear material behavior are quite appropriate.

Cracking Behavior and Flexural Performance of RC Beam with Strain Hardening Cement Composite and High-Strength Reinforcing Bar (고강도 철근과 변형경화형 시멘트복합체를 사용한 보의 균열거동 및 휨 성능)

  • Jang, Seok-Joon;Kang, Su-Won;Yun, Hyun-Do
    • Journal of the Korea Concrete Institute
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    • v.27 no.1
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    • pp.37-44
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    • 2015
  • This paper describes the effect of strain hardening cement composite (SHCC) material on structure performance of reinforced concrete (RC) beams with high-strength reinforcing bar. Also, this paper explores the structure application of SHCC in order to mitigation cracking damage and improve the ductility of flexural RC members. The prediction model for flexural strength of doubly reinforced SHCC beams are investigated in this study. To achieve the these objectives, a total of 6 rectangular beam specimens were tested under four point monotonic loading condition. The main parameters included the types of cement composite and reinforcing bar. Test results indicated that reinforced beam specimens with SHCC material were improved the structure performances and damage characteristics. Specifically, replacement of conventional high-strength concrete with SHCC materials has the potential of high-strength steel bar as flexural reinforcement on RC members. It is remarkable that suggested method of reinforced SHCC beams with high-strength reinforcing bar could be used usefully to the structure design.