• Title/Summary/Keyword: Biaxial strain

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Anisotropic damage modelling of biaxial behaviour and rupture of concrete structures

  • Ragueneau, F.;Desmorat, R.;Gatuingt, F.
    • Computers and Concrete
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    • v.5 no.4
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    • pp.417-434
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    • 2008
  • This paper deals with damage induced anisotropy modeling for concrete-like materials. A thermodynamics based constitutive relationship is presented coupling anisotropic damage and elasticity, the main idea of the model being that damage anisotropy is responsible for the dissymmetry tension/compression. A strain written damage criterion is considered (Mazars criterion extended to anisotropy in the initial model). The biaxial behavior of a family of anisotropic damage model is analyzed through the effects of yield surface modifications by the introduction of new equivalent strains.

The Evaluation of Mechanical Properties and Fatigue Life for Domestic 304 Stainless Steel Used as Membrane Material in LNG Storage Tank (LNG저장탱크의 멤브레인용 국산 304 스테인리스강의 기계적성질 및 피로수명 평가)

  • Kim, Hyeong-Sik
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.10
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    • pp.1644-1650
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    • 2001
  • Mechanical properties of domestic 374 stainless steel have been evaluated fur membrane material used in LNG storage tank. LNG tank is operated around -162$^{\circ}C$. The temperature of membrane depends on LNG level. Accordingly, the membrane material is deteriorated by variation of liquid pressure and temperature. Tensile test and fatigue life test were performed at room temperature and -l62$^{\circ}C$ per code requirements. Especially the biaxial fatigue life test was conducted with shaped membrane sheet at a thermal strain of $\Delta$T=190$^{\circ}C$ The test results obtained with the domestic 304 stainless steel showed better properties compared to the values required by code.

Nonlinear analysis of reinforced concrete beam elements subject to cyclical combined actions of torsion, biaxial flexure and axial forces

  • Cocchi, Gian Michele;Tiriaca, Paolo
    • Structural Engineering and Mechanics
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    • v.17 no.6
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    • pp.829-862
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    • 2004
  • This paper presents a method for the nonlinear analysis of beam elements subjected to the cyclical combined actions of torsion, biaxial flexure and axial forces based on an extension of the disturbed compression field (DSFM). The theoretical model is based on a hybrid formulation between the full rotation of the cracks model and the fixed direction of the cracking model. The described formulation, which treats cracked concrete as an orthotropic material, includes a new approach for the evaluation of the re-orientation of both the compression field and the deformation field by removing the restriction of their coincidence. A new equation of congruence permits evaluating the deformation of the middle line. The problem consists in the solution of coupled nonlinear simultaneous equations expressing equilibrium, congruence and the constitutive laws. The proposed method makes it possible to determine the deformations of the beam element according to the external stresses applied.

Dimensionless analysis of composite rectangular and circular RC columns

  • Massumi, Ali;Badkoubeh, Alireza
    • Steel and Composite Structures
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    • v.19 no.2
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    • pp.327-348
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    • 2015
  • A numerical procedure is presented that provides ultimate curvature and moment domains for composite rectangular and circular cross-sections of reinforced concrete columns with or without an embedded steel section subjected to combined axial loading and biaxial bending. The stress resultants for the concrete and reinforcement bars are calculated using fiber analysis and the stress resultants for the encased structural steel are evaluated using an exact integration of the stress-strain curve over the area of the steel section. A dimensionless formula is proposed that can be used for any section with similar normalized geometric and mechanical parameters. The contribution of each material to the bearing capacity of a section (resistance load and moments) is calculated separately so that the influence of each geometric or mechanical parameter on the bearing capacity can be investigated separately.

Strain-Modulated Photoluminescence in Single-Layer $MoS_2$

  • Go, Taek-Yeong;Park, Gwang-Hui;Ryu, Sun-Min
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.02a
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    • pp.620-620
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    • 2013
  • When $MoS_2$ is thinned to single layer (1L), photoluminescence (PL) quantum yield drastically increases due to emergence of direct band gap. A recent theory predicts that the electronic structure of 1L $MoS_2$ is very sensitive to its lattice constants. We investigated the response of 1L $MoS_2$ to biaxial tensile strain using spatially resolved PL and Raman spectroscopy. Changes in the lattice constants were monitored by the Raman frequency of the in-plane ($E^1{_2g}$) mode. Systematic correlations between PL and Ramanspectral features, revealed in the preliminary results, will be further tested with samples on other substrates and against thermal stress. The results will also be discussed in regard to the theory which predicts that 1L $MoS_2$ becomes an indirect semiconductor at small tensile strain and turns metallic when further extended.

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Characterization of Superplasticity Using Cone-Type Bulge Test (원뿔형 금형을 이용한 초소성 변형 특성 평가)

  • Kwon Y.-N.;Lee S. J.;Lee Y. S.;Lee H. S.;Lee J. H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2004.10a
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    • pp.180-183
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    • 2004
  • Superplastic formability depends on flow parameters such as temperature, strain rate, strain and stress, microstructures. Usually, superplastic properties of materials are characterized with using a uni-axial tension testing. However, superplastic sheet is formed under mutiaxial loading condition in most forming practices. In the present study, superplastic characteristics of A15083 alloys were determined with using both a uni-axial and biaxial bulging tests. Specially, cone-type die was used to achieve constant strain rate under constant pressure condition. Even though constant strain rate under a certain pressure was achieved only approximately, a cone-type bulging test was found to be quite beneficial to get a multiaxial formability of superplastic materials.

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Microstructure Evolution and Tensile Properties of Al-Mg Alloy Containing a High Content of Mg by Biaxial Alternative Forging (고함량의 Mg을 함유한 Al-Mg 합금의 이축교번단조 변형에 따른 미세조직 및 인장특성 변화)

  • Shin, Y.C.;Ha, S.H.;Yoon, Y.O.;Kim, S.K.;Choi, H.J.;Hyun, K.H.;Hyun, S.K.
    • Transactions of Materials Processing
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    • v.28 no.6
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    • pp.361-367
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    • 2019
  • Microstructure evolution and tensile properties of Al-8mass%Mg alloy casting billet by biaxial alternative forging were investigated in this study. An alternative forging system tailored in this study was used to allow continuous strain accumulations on the alloy workpiece. A finite element (FE) simulation results revealed that the strain was mainly concentrated in the core and that the shear bands developed into a form with an X shape in the cross-section of workpiece after the alternative forging using octangular rod shaped dies. With increasing the forging passes, it was observed that the Al-8mass%Mg alloy workpieces were significantly deformed, and cracks began to form and propagate on the both ends of the forged workpieces after five passes at room temperature. In as-forged microstructures taken by microscopes, twins, clustering of dislocations, and fine subgrains were found. Tensile strengths of the forged specimens showed significant increases depending on the number of forging passes, and a trade-off relationship was observed between the elongation and strength. At room temperature and 100℃ the workpieces showed similar behaviors in microstructural evolution and tensile properties depending on forging passes, while the increase range in strength was reduced at 200℃.

Modified Rectangular Stress Block for High Strength RC Columns to Axial Loads with Bidirectional Eccentricities (2축 편심 축력을 받는 고강도 콘크리트 기둥의 수정 등가응력블럭)

  • Yoo, Suk-Hyeong;Bahn, Byong-Youl;Shin, Sung-Woo
    • Journal of the Korea Concrete Institute
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    • v.15 no.2
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    • pp.335-343
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    • 2003
  • In the previous experimental study, it is verified that the ultimate strain of concrete (${\varepsilon}$$_{cu}$=0.003) and coefficient of equivalent stress block (${\beta}$$_1$) can be used for the analysis of RC beams under biaxial and uniaxial bending moment. However, the characteristics of stress distribution of non rectangular compressed area in the RC columns are different to those of rectangular compressed area. The properties of compressive stress distribution of concrete have minor effect on the pure bending moment such as beams, but for the columns subjected to combined axial load and biaxial bending moment, the properties of compressive stress distribution are influencing factors. Nevertheless, in ACI 318-99 code, the design tables for columns subjected to axial loads with bidirectional eccentricities are based on the parameters recommended for rectangular stress block(RSB) of rectangular compressed areas. In this study the characteristics of stress distribution through both angle and depth of neutral axis are observed and formulated rationally. And the modified parameters of rectangular stress block(MRSB) for non rectangular compressed area is proposed. And the computer program using MRSB for the biaxial bending analysis of RC columns is developed and the results of MRSB are compared to RSB and experimental results respectively.

Improved phenomenological modelling of transient thermal strains for concrete at high temperatures

  • Nielsen, Claus V.;Pearce, Chris J.;Bicanic, Nenad
    • Computers and Concrete
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    • v.1 no.2
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    • pp.189-209
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    • 2004
  • Several extensions to the Thelandersson phenomenological model for concrete under transient high temperatures are explored. These include novel expressions for the temperature degradation of the elastic modulus and the temperature dependency of the coefficient of the free thermal strain. Furthermore, a coefficient of thermo mechanical strain is proposed as a bi-linear function of temperature. Good qualitative agreement with various test results taken from the literature is demonstrated. Further extensions include the effects of plastic straining and temperature dependent Poisson's ratio. The models performance is illustrated on several simple benchmark problems under uniaxial and biaxial stress states.

계산과학을 통한 MoSe2 물분해 광촉매 성질 연구

  • Gang, Seong-U
    • Proceeding of EDISON Challenge
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    • 2016.03a
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    • pp.273-276
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    • 2016
  • 최근 single-layer $MoSe_2$와 같은 2차원의 TMD 화합물들이 물분해 광촉매로서 각광받고 있다. TMD 화합물 중 single-layer $MoSe_2$는 수소 발생 반응을 일으킬 수 있으나 산소 발생 반응은 일으킬 수 없어 산화 반응을 진행시킬 추가적인 전극이 필요하다. 이 연구에서는 strain과 doping을 통해 valence band를 아래로 이동시켜 $MoSe_2$를 더 좋은 물분해 광촉매로 변화시키는 방법을 모색하였다. 먼저 Armchair, zigzag, biaxial isotropic, z-axis direction으로 strain을 걸어줄 때 전자구조의 변화를 관찰하였다. z-axis 방향으로 -2.5% strain을 걸어주었을 때 VBM이 0.07eV만큼 감소하였다. 또한 Mo를 Nb로 치환하고 Se를 P, As로 치환한 다음 전자구조를 관찰하였다. Nb와 doping의 경우 VBM이 감소함을 확인하였으며 As doping의 경우 산화반응이 일어날 수 있고 산화력과 환원력이 비슷해짐을 알아내었다. 또한 산화반응과 환원반응이 일어나는 위치가 분리됨을 확인하였다.

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