• 제목/요약/키워드: Effective Strain

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압입시험 모델링을 통한 진응력-진변형율 관계 해석 (Analysis of True Stress - True Strain Relations through the Modeling of Ball Indentation Test)

  • 이호진;김기백;이봉상;이병섭
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2003년도 춘계학술대회
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    • pp.660-665
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    • 2003
  • The true stress - true strain relation of SA508 steel was evaluated with analytical and experimental equation on the base of the indentation load-depth curve obtained from the modeling of ball indentation test. The evaluated relation between true stress and true strain is agreed well with that of SA508 teel defined in the modeling. The distribution of effective stress along the center axis of indentation depth was calculated with Tresca criteria in the modeling. The representative strain, which are defined in this study as the corresponding strains obtained from the maximum effective stress, have a linear relation with the true strain. The true stress - true strain relation of austenitic stainless steel was evaluated by the modeling of ball indentation test to verify the case of A508 steel.

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전자기 성형에서의 변형률 속도 효과 해석 (Analysis of the Strain Rate Effect in Electro-Magnetic Forming)

  • 곽신웅;신효철;이종수
    • 대한기계학회논문집
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    • 제14권5호
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    • pp.1043-1058
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    • 1990
  • 본 연구에서는 전자기 성형법에 의한 원통형상의 가공재의 자유 확관성형 가 공에 대해서 유한요소해석법을 이용한 변형 및 응력해석을 수행하였다. 탄소성 재료 모형을 확장하여 변형 경화율이 변형률 및 변형률 속도의 지배를 받는 변형률 속도 종 속 탄소성 재료 모형을 도입하였고, 1차 제하 이후까지 포함하여 고속 성형시 변형률 속도 효과에 의해 발생하는 현상들에 대해서 연구하였다.결과의 비교 및 논의를 위 하여, 해석대상과 성형조건, 그리고 가공재에 작용하는 자기압력은 Suzuki의 것과 동 일한 것을 사용하였다.

Solution for a circular tunnel in strain-softening rock with seepage forces

  • Wei, Luo;Zo, Jin-feng;An, Wei
    • Geomechanics and Engineering
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    • 제22권6호
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    • pp.553-564
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    • 2020
  • In this study, a simple numerical approach for a circular tunnel opening in strain-softening surrounding rock is proposed considering out-of-plane stress and seepage force based on Biot's effective stress principle. The plastic region of strain-softening surrounding rock was divided into a finite number of concentric rings, of which the thickness was determined by the internal equilibrium equation. The increments of stress and strain for each ring, starting from the elastic-plastic interface, were obtained by successively incorporating the effect of out-of-plane stress and Biot's effective stress principle. The initial value of the outmost ring was determined using equilibrium and compatibility equations. Based on the Mohr-Coulomb (M-C) and generalized Hoek-Brown (H-B) failure criteria, the stress-increment approach for solving stress, displacement, and plastic radius was improved by considering the effects of Biot's effective stress principle and the nonlinear degradation of strength and deformation parameters in plastic zone incorporating out-of-plane stress. The correctness of the proposed approach is validated by numerical simulation.

저탄소 Dual Phase강의 가공시효에 미치는 탄소유효확산 및 전위분포의 영향 (Effects of Dislocation Distribution and Carbon Effective Diffusion on Strain Aging Behavior of a Low Carbon Dual Phase Steel)

  • 유상협;정기채;홍기하;박경태
    • 소성∙가공
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    • 제30권5호
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    • pp.226-235
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    • 2021
  • The strain aging behavior of a low carbon dual phase steel was examined in two conditions: representing room temperature strain aging (100 ℃ × 1 hr after 7.5 % prestrain) and bake hardening process (170 ℃ × 20 min after 2 % prestrain), basing on carbon effective diffusion and dislocation distribution. The first principle calculations revealed that (Mn or Cr)-vacancy-C complexes exhibit the strongest attractive interaction compared to other complexes, therefore, act as strong trapping sites for carbon. For room temperature strain aging condition, the carbon effective diffusion distance is smaller than the dislocation distance in the high dislocation density region near ferrite/martensite interfaces as well as ferrite interior considering the carbon trapping effect of the (Mn or Cr)-vacancy-C complexes, implying ineffective Cottrell atmosphere formation. Under bake hardening condition, the carbon effective diffusion distance is larger compared to the dislocation distance in both regions. Therefore, formation of the Cottrell atmosphere is relatively easy resulting in to a relatively large increase in yield strength under bake hardening condition.

New nirS-Harboring Denitrifying Bacteria Isolated from Activated Sludge and Their Denitrifying Functions in Various Cultures

  • LEE, SOO-YOUN;LEE, SANG-HYON;PARK, YONG-KEUN
    • Journal of Microbiology and Biotechnology
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    • 제15권1호
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    • pp.14-21
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    • 2005
  • By using PCR with nirS gene primers, three nirSharboring denitrifying bacteria (strain N6, strain N23, and strain R13) were newly isolated from activated sludge of a weak municipal wastewater treatment plant. Small-subunit rRNA gene-based analysis indicated that strain N6, strain N23, and strain R13 were closely related to Arthrobacter sp.,Staphylococcus sp., and Bacillus sp., respectively. In an attempt to identify their roles in biological nitrate and nitrite removal from sewage, we investigated their specific denitrification rates (SDNRs) for $NO_-^3$ - and $NO_-^2$ - in various cultures. All purecultures of each isolated nirS-harboring bacterial strain could remove $NO_-^3$ - and $NO_-^2$ - simultaneously in high efficiency, and the carbon requirements for $NO_-^3$ - removal of strain N6 and strain R13 were effectively low at 3.1 and 4.1 g COD/g $NO_3N$, respectively. In the case of mix-cultures of the strains (N6+N23, N6+R13, N23+R13, and N6+N23+R13), their SDNRs for $NO_-^3$ - were also effective, and their carbon requirements for $NO_-^3$ - removal were also effective at 3.0- 3.8 g COD/g NO3N. However, all tested mix-cultures accumulated $NO_-^2$ - in their culture media. On the other hand, the continuous culture of activated sludge mixed with strain N6 showed no significant increase of $NO_-^3$ - removal in comparison with strain N6's pure culture. These results suggest that nitrate and nitrite removal in biological wastewater treatment might be dependent on complicated bacterial interactions, including several effective denitrifying bacteria isolated in this study, rather than the specific bacterial types present and the number of bacterial types in activated sludge.

코너각이 용기에 성형에 미치는 영향에 관한 연구 (A Study on the Effect of corner Angle on Cup Drawing)

  • 김진무;유호영
    • 소성∙가공
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    • 제8권1호
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    • pp.14-21
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    • 1999
  • Trapezoid cups and square ones have been deep-drawn to 45mm in depth. Displacements and strains have been analysed by FEM and experiment. Strains and effective strains in the corner flanges of trapezoid cups have been compared with those in square cups. The results have shown that because of shear strains on the corner flange, it is necessary to adopt effective strain for comparing strains, mean vale of effective strains in the corner flange with a corner angle of 72 degrees is narly equal to those with a corner angle of a right angle and mean value of effective strains with a corner angle of 102 degrees is smaller than those with a corner angle of a right angle.

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중탄소강의 동적 재결정에 관한 연구 (Dynamic Recrystallization of Medium Carbon Steels)

  • 김성일;한창훈;유연철;이덕락;주웅용
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2000년도 추계학술대회 논문집
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    • pp.33-36
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    • 2000
  • The dynamic recrystallization (DRX) of medium carbon steels (SCM 440 and POSMA45) was studied with torsion test in the temperature range of $900-1100^{\circ}C$ and the strain rate range of $5.0x10^{-2}\;-\;5.0x10^0/sec$. To establish the quantitative equations for DRX, the evolution of flow stress curve with strain was analyzed. The critical strain (${\varepsilon}_c$) and strain for maximum softening rate ( ${\varepsilon}^{*}$) could be confirmed by the analysis of work hardening rate ($d{\sigma}/d{\varepsilon}\;=\; \theta$). The volume fraction of dynamic recrystallization ($X_{DRX}$) as a function of processing variables, such as strain rate ( $\dot{\varepsilon}$ ), temperature (T), and strain ( $\varepsilon$ ) were established using the ${\varepsilon}_c$ and ${\varepsilon}^{*}$. For the exact prediction, the ${\varepsilon}_c$, ${\varepsilon}^{*}$ and Avrami' exponent (m') were quantitatively expressed by dimensionless parameter, Z/A respectively. The transformation-effective strain-temperature curve for DRX could be composed. It was found that the calculated results were agreed with the experimental data for the steels at any deformation conditions.

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Lead Screw 전조 정밀도 향상을 위한 성형인자의 특성평가 (Characteristics Evaluation of Process Parameters for Improvement the Precision of Thread ]tolling in Lead Screw)

  • 김광호;김동환;고대철;김병민
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2002년도 추계학술대회 논문집
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    • pp.312-315
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    • 2002
  • This paper summarizes the results of a numerical study conducted to analyze the effect of selected process parameters on material flow and thread profile in thread rolling of large diameter blanks. Based on the previous work where a plane strain mode was found to provide a reasonable approximation of the thread rolling process, the effect of varying thread form, friction factor, flow stress, and blank diameter on effective strain and thread height was analyzed using the finite element code DEFORM. This study show that effective strain for flank angle, that blank diameter had important effect on the as-rolled thread while flow stress, friction factor, and crest round of dies had significant impact on effective strain at the thread root and crest and load of thread rolling. While the rate of strain harding was found to have an effect on the crest profile, the results indicate that it is the primary factor responsible for seam formation in rolled threads.

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Steinernematid와 Heterorhabditid 선충의 쥐며느리에 대한 비효용적결과 (Noneffective Results of Steinernematid and Hoterorhabditid Nematodes Agains Pill bug, Armadillidium vulgare (Isopoda : Armadillidae))

  • 추호렬;이동운;허은영;김준범
    • 한국응용곤충학회지
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    • 제35권1호
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    • pp.91-93
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    • 1996
  • Steinernematid와 heterorhabditid 선충은 쥐며느리에 침입하여 치사시킬수는 있었지만 효과는 없었다. Steinernema carpocapsae 포천 strain과 S. glaseri 동래 strain이 S. carpocapse All strain과 Heterorohabditis bacteriophora보다 효과가 있었으며, 병원성 발현에서 선충의 접종농도가 기주의 밀도보다 중요한 요인이었다.

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Draft Genome Sequence of a Chitinase-producing Biocontrol Bacterium Serratia sp. C-1

  • Park, Seur Kee;Kim, Young Cheol
    • 식물병연구
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    • 제21권3호
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    • pp.222-226
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    • 2015
  • The chitinase-producing bacterial strain C-1 is one of the key chitinase-producing biocontrol agents used for effective bioformulations for biological control. These bioformulations are mixed cultures of various chitinolytic bacteria. However, the precise identification, biocontrol activity, and the underlying mechanisms of the strain C-1 have not been investigated so far. Therefore, we evaluated in planta biocontrol efficacies of C-1 and determined the draft genome sequence of the strain in this study. The bacterial C-1 strain was identified as a novel Serratia sp. by a phylogenic analysis of its 16S rRNA sequence. The Serratia sp. C-1 bacterial cultures showed strong in planta biocontrol efficacies against some major phytopathogenic fungal diseases. The draft genome sequence of Serratia sp. C-1 indicated that the C-1 strain is a novel strain harboring a subset of genes that may be involved in its biocontrol activities.