• Title/Summary/Keyword: overall strain

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Developement of Hyperbolic Model Considering Strain Dependency (변형률 의존성을 고려한 쌍곡선 모델의 개발)

  • Lee, Yong-An;Kim, You-Seong
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.03a
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    • pp.644-655
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    • 2008
  • Conventional hyperbolic model does not satisfactorily predict the overall stress-strain behaviors of various geomaterials. Tatsuoka and Shibuya(1992) suggest the generalized hyperbolic equation(GHE) considering strain dependency and calculated performance is in good agreement with precise triaxial compression test results of stress-strain relations over wide range of strains before peak stress condition in some cases, but GHE model also does not satisfactorily predict stress-strain relations as strain goes on state of peak stress in most cases. For improve a weak point of the GHE, in this study, modified form of generalized hyperbolic equation (MGHE model) is proposed which can predict highly nonlinear stress-strain behavior for various geomaterials from small strain to peak stress condition.

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

  • Oh Se-Boong;Lee Jin-Gu;Kim Tae-Gyeong
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2005.04a
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    • pp.343-350
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    • 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.

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Preparation of Kimchi Containing Bifidobacterim animalis DY-64

  • Chae Myoung-Hee;Jhon Deok-Young
    • Journal of Microbiology and Biotechnology
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    • v.16 no.3
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    • pp.431-437
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    • 2006
  • Aero-tolerant microorganisms were isolated from healthy Koreans over the age of 95 years. The microorganisms were then identified based on their morphological and biochemical characteristics and 16S rDNA sequences. The growth properties of the isolated strains were investigated in kimchi. The characteristics of kimchi containing the microorganisms were studied microscopically, physicochemically, and organoleptically. Among 7 aero-tolerant strains, a strain with a 16S rDNA sequence exhibiting 99% homology with Bifidobacterim animalis strain B83 was selected and named B. animalis DY-64. The new strain showed a better acid resistance and salt resistance (p<0.05) than B. animalis ATCC 25527. After 15 days of fermentation in kimchi, the viability of B. animalis DY-64 was about 10%, and the kimchi had a better overall edible quality than conventional kimchi. Thus, it was found that the application of B. animalis DY-64 to kimchi preparation produced a good overall edible quality.

Nonlinear Modeling and Dynamic Analysis of Flexible Structures Undergoing Overall Motions Employing Mode Approximation Method

  • Kim, Jung-Young;Hyun, Sang-Hak;Yoo, Hong-Hee
    • Journal of Mechanical Science and Technology
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    • v.16 no.7
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    • pp.896-901
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    • 2002
  • This paper presents a nonlinear modeling method for dynamic analysis of flexible structures undergoing overall motions that employs the mode approximation method. This method, different from the naive nonlinear method that approximates only Cartesian deformation variables, approximates not only deformation variables but also strain variables. Geometric constraint relations between the strain variables and the deformation variables are introduced and incorporated into the formulation. Two numerical examples are solved and the reliability and the accuracy of the proposed formulation are examined through the numerical study.

Dynamic Analysis of Simply Supported Flexible Structures Undergoing Large Overall Motion (전체운동을 하는 단순지지 유연 구조물의 동적해석)

  • 유홍희
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.6
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    • pp.1363-1370
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    • 1995
  • A nonlinear dynamic modeling method for simply supported structures undergoing large overall motion is suggested. The modeling method employs Rayleigh-Ritz mode technique and Von Karman nonlinear strain measures. Numerical study shows that the suggested modeling method provides qualitatively different results from those of the Classical Linear Cartesian modeling method. Especially, natural frequency variations and residual deformation due to membrane strain effects are observed in the numerical results obtained by the suggested modeling method.

Nonlinear Modeling and Dynamic Analysis of Flexible Structures Undergoing Overall Motions Employing Mode Approximation Method (모드 근사화 방법을 이용한 대변위 운동을 하는 유연구조물의 비선형 모델링 및 동적해석)

  • Kim, J.Y.;Hyun, S.H.;Yoo, H.H.
    • Proceedings of the KSME Conference
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    • 2001.11a
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    • pp.550-555
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    • 2001
  • This paper presents a nonlinear modeling method for dynamic analysis of flexible structures undergoing overall motions that employs the mode approximation method. This method, different from the naive nonlinear method that approximates only Cartesian deformation variables, approximates not only deformation variables but also strain variables. Geometric constraint relations between the strain variables and the deformation variables are introduced and incorporated into the formulation. Two numerical examples are solved and the reliability and the accuracy of the proposed formulation are examined through the numerical study.

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Effect of strain rate and stress triaxiality on fracture strain of 304 stainless steels for canister impact simulation

  • Seo, Jun-Min;Kim, Hune-Tae;Kim, Yun-Jae;Yamada, Hiroyuki;Kumagai, Tomohisa;Tokunaga, Hayato;Miura, Naoki
    • Nuclear Engineering and Technology
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    • v.54 no.7
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    • pp.2386-2394
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    • 2022
  • In this paper, smooth and notched bar tensile tests of austenitic stainless steel 304 are performed, covering four different multi-axial stress states and six different strain rate conditions, to investigate the effect of the stress triaxiality and strain rate on fracture strain. Test data show that the measured true fracture strain tends to decrease with increasing stress triaxiality and strain rate. The test data are then quantified using the Johnson-Cook (J-C) fracture strain model incorporating combined effects of the stress triaxiality and strain rate. The determined J-C model can predict true fracture strain overall conservatively with the difference less than 20%. The conservatism in the strain-based acceptance criteria in ASME B&PV Code, Section III, Appendix FF is also discussed.

Numerical Ductile Tearing Simulation of Circumferential Cracked Pipe Tests under Dynamic Loading Conditions

  • Nam, Hyun-Suk;Kim, Ji-Soo;Ryu, Ho-Wan;Kim, Yun-Jae;Kim, Jin-Weon
    • Nuclear Engineering and Technology
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    • v.48 no.5
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    • pp.1252-1263
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    • 2016
  • This paper presents a numerical method to simulate ductile tearing in cracked components under high strain rates using finite element damage analysis. The strain rate dependence on tensile properties and multiaxial fracture strain is characterized by the model developed by Johnson and Cook. The damage model is then defined based on the ductility exhaustion concept using the strain rate dependent multiaxial fracture strain concept. The proposed model is applied to simulate previously published three cracked pipe bending test results under two different test speed conditions. Simulated results show overall good agreement with experimental results.

Multi-Dimensional Effects on a tow Strain Rate Flame Extinction Under Microgravity Environment (미소 중력장에 있는 저신장율 화염소화에 미치는 다차원 효과)

  • Oh Chang Bo;Kim Jeong Soo;Hamins Anthony;Park Jeong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.9 s.240
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    • pp.988-996
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    • 2005
  • Flame structure and extinction mechanism of counterflow methane/air non-premixed flame diluted with nitrogen are studied by NASA 2.2 s drop tower experiments and two-dimensional numerical simulations with finite rate chemistry and transport properties. Extinction mechanism at low strain rate is examined through the comparison among results of microgravity experiment, 1D and 2D simulations with a finite burner diameter. A two-dimensional simulation in counterflow flame especially with a finite burner diameter is shown to be very important in explaining the importance of multidimensional effects and lateral heat loss in flame extinction, effects that cannot be understood using a one-dimensional flamelet model. Extinction mechanism at low strain rate is quite different from that at high strain rate. Low strain rate flame is extinguished initially at the outer flame edge, the flame shrinks inward, and finally is extinguished at the center. It is clarified from the overall fractional contribution by each term in energy equation to heat release rate that the contribution of radiation fraction with 1D and 2D simulations does not change so much and the overall fractional contribution is decisively attributed to radial conduction ('lateral heat loss'). The experiments by Maruta et at. can be only completely understood if multi-dimensional heat loss effects are considered. It is, as a result, verified that the turning point, which is caused only by pure radiation heat loss, has to be shifted towards much lower global strain rate in microgravity flame.

The improvement of productivity of a photosynthetic purple bacterium, Rhodobacter sphaeroides by manipulating the photosynthetic apparatus (광합성 기구 조작을 통한 비유황 자색 광합성 세균, Rhodobacter sphaeroides의 생산성 증대)

  • Kim, Nak-Jong;Lee, Cheol-Gyun
    • 한국생물공학회:학술대회논문집
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    • 2000.04a
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    • pp.189-192
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    • 2000
  • The objective of this study was to investigate the effect of high content of light-absorbing pigments on overall photosynthetic efficiency in high density microalgal cultures. The light harvesting complex II (LHC II) regulating gene of Rhodobacter sphaeroides, photosynthetic purple bacterium, was removed to construct a mutant strain that had less pigment content. The mutant and wild type strains were cultured under various light intensity by adjusting the distance from the light source. The productivity of the mutant strain was higher at high light intensity (over 118 ${\mu}E/m^2/s$) compared with one of the wild type , and was lower at low light intensity (34 ${\mu}E/m^2/s$). Especially, the concentration of LHC II mutant strain was 56% higher at 118 ${\mu}E/m^2/s$. The reduction of per cell pigment contents in the mutant strain lessened the degree of the mutual shading and thus enhanced the overall photosynthetic efficiency.

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