• 제목/요약/키워드: Plastic Strain Ratio

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알루미늄 합금판재의 집합조직 제어 (Texture Control in Aluminum Alloy Sheets)

  • 김근환;강형구;최창희;이동녕
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 1997년도 추계학술대회논문집
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    • pp.198-201
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    • 1997
  • Aluminum alloy sheets are considered as one of the high potential substitutes for steel sheets considering weight reduction of automobiles. However, aluminum alloy sheets have drawbacks in higher prices and inferior formability compared to steel sheets. In order to achieve good deep drawability, it is imperative to obtain well developed {111} texture which gives rise to higher plastic strain ratio. It is difficult to obtain this texture from conventional rolling and annealing processes. Therefore, an unconventional rolling process which enhances shear deformation has been experimentally studied to obtain the well developed {111} texture, which in turn gives rise to a substantial increase in plastic strain ratio.

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재료 특성에 기반한 철근콘크리트 휨부재의 소성회전능력 산정 (Evaluation of Plastic Rotational Capacity Based on Material Characteristics in Reinforced Concrete Flexural Members)

  • 최승원;김우
    • 콘크리트학회논문집
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    • 제22권6호
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    • pp.825-832
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    • 2010
  • 철근콘크리트 구조물은 위험 단면이 휨강도에 도달하더라도 이 단면에서 소성힌지가 형성되어 휨모멘트가 재분배되어 곧바로 파괴에 도달하지 않는다. 이러한 소성힌지 영역에서 발생하는 비탄성 변형에 의해 소성 회전이 발생한다. 소성힌지길이는 주로 재료 특성에 영향을 받는다. 이 연구에서는 유로코드2에서 제시하고 있는 재료 모델로부터 산정된 휨곡률 분포로부터 소성힌지길이와 소성회전각을 일관되게 산정하였다. 재료 모델의 한계값 즉, 콘크리트 극한변형률, 철근 극한변형률 및 철근의 경화비(k)가 소성회전능력에 미치는 영향을 분석하였다. 해석 결과 콘크리트 극한변형률 및 철근 극한변형률이 증가함에 따라 소성회전능력이 증가하였고 특히, 철근의 경화비(k)가 증가함에 따라 소성 회전각은 크게 증가되는 것으로 나타났다. 따라서 각 재료 모델의 한계값 결정에 세심한 주의가 필요할 것으로 나타났다.

평면변형률상태에서의 von Mises 항복기준의 특성에 관한 이론적 연구 (Analytical Study on Characteristics of von Mises Yield Criterion under Plane Strain Condition)

  • 이승현;김병일
    • 한국산학기술학회논문지
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    • 제16권9호
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    • pp.6391-6396
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    • 2015
  • 2차원 응력조건에 대한 von Mises 항복기준의 특징을 살펴보기 위해 탄성변형률이 0이 되는 평면변형률 조건과 소성변형률증분이 0이 되는 평면변형률 조건을 고려해 보았다. 탄성변형률이 0인 평면변형률조건을 통해 얻은 항복함수와 평면응력조건에서의 항복함수는 기하학적으로 타원을 나타내는데 두 경우에 대한 기하하적 비교를 타원의 장, 단축의 길이비와 이심률의 비로 나타낼 때 단축비는 같았으나 장축비 및 이심률의 비는 포아송비의 함수로 표현되었다. 탄성변형률이 0인 평면변형률조건을 통해 얻은 von Mises 항복기준에 대하여 탄성거동을 보이는 영역은 포아송비가 커짐에 따라 넓어짐을 알 수 있었다. 소성변형률증분이 0인 평면변형률조건을 통해 관련유동법칙을 써서 항복함수를 구하였는데 기하하적으로 볼 때 평면응력조건에서의 항복함수가 타원임과는 달리 직선을 나타내었으며 평면응력조건일 때보다 탄성거동영역이 컸다.

무윤활 압연한 알루미늄 판재의 기계적 특성과 성형성 (Mechanical properties and formability of asymmetrically rolled aluminum alloy sheet)

  • 사이드무로드 아크라모프;김인수
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2009년도 춘계학술대회 논문집
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    • pp.429-431
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    • 2009
  • Drawability and other mechanical properties of sheet metals are strongly dependent on their crystallographic orientations. In this paper the formability of the AA 5052 Al alloy sheets was investigated after asymmetric rolling and subsequent heat treatment. In most cases, after asymmetric rolling specimens showed a fine grain size and subsequent heat treated specimens showed that the ND // <111> texture component were observed. The anisotropy of formability is often described by the plastic strain ratios (r-value) as a function of the angle to the rolling direction in sheet metal. For a good formability, a high r-value is required in sheet metals. In the asymmetry rolled and subsequent heat treated Al alloy sheet, the variation of the plastic strain ratios have been investigated in this study, The plastic strain ratios of the asymmetry rolled and subsequent heat treated AA 5052 Al alloy sheets were higher than those of the original Al sheets. These could be related to the formation of ND // <111> texture components through asymmetric rolling in Al sheet.

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알루미늄 비대칭압연 집합조직 (Texture of Asymmetric Rolled Aluminum sheets)

  • 사이드무로드 아크라모프;김인수
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2008년도 춘계학술대회 논문집
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    • pp.477-479
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    • 2008
  • Drawability and other mechanical properties of sheet metals are strongly dependent on their crystallographic orientations. In this paper the formability of the AA 5052 Al alloy sheets was investigated after asymmetric rolling and subsequent heat treatment. In most cases, after asymmetric rolling specimens showed a fine grain size and subsequent heat treated specimens showed that the ND//<111> texture component were observed. The anisotropy of formability is often described by the plastic strain ratios (r-value) as a function of the angle to the rolling direction in sheet metal. For a good formability, a high r-value is required in sheet metals. In the asymmetry rolled and subsequent heat treated Al alloy sheet, the variation of the plastic strain ratios have been investigated in this study. The plastic strain ratios of the asymmetry rolled and subsequent heat treated AA 5052 Al alloy sheets were higher than those of the original Al sheets. These could be related to the formation of ND//<111> texture components through asymmetric rolling in Al sheet.

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소결분말금속의 항복함수 (A Yield Function for Sintered Porous Metals)

  • 박종진
    • 대한기계학회논문집
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    • 제17권5호
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    • pp.1115-1122
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    • 1993
  • Several yield criteria for porous materials are compared with each other, defining the apparent yield stress as the yield stress of the porous material in simple compression. It was found that the plastic Poisson's ratio is the parameter needed to define the yield criterion, rather than the relative density. The plastic Poisson's ratio is regarded as a material characteristic that is obtained from a simple compression test. A new form of yield criterion was suggested, and it was applied to hydrostatic compression as well as uniaxial strain compression of sintered Al-2024 powder. The crossover point in the mean stress vs volume change curves of the processes was predicted. It is presented that the flow stress of the fully densed material can be obtained from that of the porous material using relations obtained from the yield criterion.

다짐된 사약재료의 응력-변형 이론 (A STREE-STRAIN THEORY FOR COMPACTED ROCKFILL)

  • 이영희
    • 한국지반공학회지:지반
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    • 제3권1호
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    • pp.77-96
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    • 1987
  • Based on observation emerged from the undrained tests and the anisotropic consolidation tests, an incremental stress-strain theory for rockfill is proposed in a manner similar to that developed ky Cambridge Group for normally consolidated soils; the volumetric strain due to stress increment is the same as the increment due to an undrained component followed by an increment along the constant stress ratio path. The strains in drained tests are predicted from those in the undrained tests and in the anisotropic consolidation tests. An expression for the undrained stress path is derived based on the bilinear relationship between the pore pressure developed and the stress ratio observed during untrained tests. Good agreement is found between the calculated and measured strains. This trend in behaviour would be helpful in establishing a stress.strain model for rockfill using the elasto-plastic behaviour with the concept of plastic potentials and flow rules.

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직접전단시험모델에 의한 뿌리말뚝의 탄소성조인트 유한요소해석 (Elasto-plastic Joint Finite Element Analysis of Root-pile Using the Direct Shear Test Model)

  • 한중근
    • 한국환경복원기술학회지
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    • 제5권4호
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    • pp.19-30
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    • 2002
  • The stability of slope using root-pile like to the reinforcements is affected by the interaction behavior mechanism of soil-reinforcements. Through the studying on the interaction in joint of its, therefore, the control roles can be find out in installed slope. In study, the stress level ratio based on the insert angle of installed reinforcements in soil used to numerical analysis, which was results from the duty direct shear test in Lab. The maximum shear strain variation on the reinforcements was observed at insert angle, which was approximately similar to the calculated angle based on the equation proposed by the Jewell. The elasto-plastic joint model on the contact area of soil-reinforcements was presumed, the reinforced soil assumed non-linear elastic model and the reinforcements supposed elastic model, respectively. The finite element analysis of assumed models was performed. The shear strain variation of non-reinforced state obtained by the FEM analysis including elasto-plastic joint elements were shown the rationality of general limit equilibrium analysis for the slope failure mode on driving zone and resistance zone, which based on the stress level step according to failure ratio. Through the variation of shear strain for the variation of inserting angle of reinforcements, the different mechanism on the bending and the shear resistance of reinforcements was shown fair possibility.

심한 전단변형(ECAP)과 열처리한 알루미늄 AA 1050 합금 판재의 소성변형비와 집합조직 (Texture and Plastic deformation of the Severe Ecaped and Heatreated AA 1050 Aluminum Alloy Sheet)

  • ;이민구;김인수;박병현
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2005년도 춘계학술대회 논문집
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    • pp.148-151
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    • 2005
  • A study on the microstructure and the texture of the samples after ECAP and subsequent heat treatment has been carried out. The specimens after ECAP showed a very fine grain size, a decrease of <100> // ND, and an increase of <111> // ND textures. The $\{111\}<112>,\;\{123\}<634>,\;\{110\}<001>,\;\{112\}<111>,\;\{110\}<111>,\;and\;\{013\}<231>$ texture components were increased in the specimens after the ECAP and subsequent heat-treatment at $400^{\circ}C$ for 1 hour. One of the most important properties in sheet metals is formability. The r-value or plastic strain ratio has been used as a parameter that expresses the formability of sheet metals. The change of the plastic strain ratios after the ECAP and subsequent heat-treatment conditions has been investigated and it was found that they were two times higher than those of the initial Al sheets. This could be attributed to the formation above texture components through the ECAP and subsequent heat-treatment.

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변형률 제어 반복직접단순전단시험에서 세립분이 모래-실트 혼합토의 간극수압에 미치는 영향 (Effect of Non-Plastic Fines Content on the Pore Pressure Generation of Sand-Silt Mixture Under Strain-Controlled CDSS Test)

  • ;박성식;;박재현;성희영;손준혁;황금비
    • 한국지진공학회논문집
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    • 제28권1호
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    • pp.33-39
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    • 2024
  • Understanding the behavior of soil under cyclic loading conditions is essential for assessing its response to seismic events and potential liquefaction. This study investigates the effect of non-plastic fines content (FC) on excess pore pressure generation in medium-density sand-silt mixtures subjected to strain-controlled cyclic direct simple shear (CDSS) tests. The investigation is conducted by analyzing excess pore pressure (EPP) ratios and the number of cycles to liquefaction (Ncyc-liq) under varying shear strain levels and FC values. The study uses Jumunjin sand and silica silt with FC values ranging from 0% to 40% and shear strain levels of 0.1%, 0.2%, 0.5%, and 1.0%. The findings indicate that the EPP ratio increases rapidly during loading cycles, with higher shear strain levels generating more EPP and requiring fewer cycles to reach liquefaction. At 1.0% and 0.5% shear strain levels, FC has a limited effect on Ncyc-liq. However, at a lower shear strain level of 0.2%, increasing FC from 0 to 10% reduces Ncyc-liq from 42 to 27, and as FC increases further, Ncyc-liq also increases. In summary, this study provides valuable insights into the behavior of soil under cyclic loading conditions. It highlights the significance of shear strain levels and FC values in excess pore pressure generation and liquefaction susceptibility.