• Title/Summary/Keyword: Effective Strain

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Strain Hardening Behavior in the Tube Hydroforming (튜브 액압성형품의 가공 경화 특성 연구)

  • Park, H.K.;Yim, H.S.;Yi, H.K.;Kim, K.S.;Moon, Y.H.
    • Transactions of Materials Processing
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    • v.17 no.8
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    • pp.564-569
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    • 2008
  • Strain hardening behavior during hydroforming has been experimentally investigated. The variation of flow stress was used as an index of strain hardening during respective processes and the flow stress was estimated from the correlationship between flow stress and effective strain. The local hardness after hydroformig was also predicted by effective strain. By using the inter-relationships between hardness-flow stress-effective strain at variable pre-strains, the strain hardening behavior during hydroforming has been successfully analyzed. The comparison of predicted hardness with measured hardness confirmed that the methodology used in this study was feasible and the strain hardening behavior can be quantitatively estimated.

The Improvement of Formability using the Polar-coordinate FLD with Strain Path Independence (경로의존성 없는 극좌표계 성형한계도를 이용한 판재 성형성 향상 기술)

  • Bae, M.K.;Hong, S.H.;Choi, K.Y.;Yoon, J.W.;Kim, Y.S.
    • Transactions of Materials Processing
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    • v.24 no.5
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    • pp.348-353
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    • 2015
  • The PEPS(Polar-coordinated Effective Plastic Strain) FLD(Forming Limit Diagram), a new type of FLD based on a polar representation of the EPS(Effective Plastic Strain), appears to be an effective solution to the problem of non-linear strain path effects. This method has the advantages of the familiar strain-based diagram for linear loading, but without the strain-hardening limitations of the stress-based diagram, or non-intuitive aspects of alternate Cartesian diagrams based on effective plastic strain. In the current study, the PEPS FLD was applied to the development process of an aluminum automobile-body panel, including the necking or crack prediction, die design, and die modification. As a result, the PEPS FLD provided improved formability of aluminum sheet as compared to deriving the potential formability with non-linearity.

A Study on Hardness and Effective Strain of Cold-Worken Products (냉간 가공 제품의 경도와 유효 변형률에 관한 연구)

  • Choi, Young;Park, Jun-Hong
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.9
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    • pp.142-148
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    • 2004
  • It is already known that hardness number of cold-forged product is in close conjunction with its effective strain. This paper presents the method to predict the relation between effective strains and hardness by using FE-simulation of hardness test from the conception that hardness indicates resistance to plastic deformation. The results of FE-simulation for the materials are compared with those of experiments and also compared with those of experiments in reference to show the feasibility of the proposed method. In addition, the present method was applied to the cold-forged product to verify the relation between hardness and effective strain. As a result, the predicted hardness number by the present method is in good agreement with experimental values. Prediction of hardness fur a cold-forged product comes to be possible by estimating the relation between effective strain and hardness using the proposed method in this study.

Study on Tensile Properties of Carbon Fiber Reinforced Polymers (CFRP) Laminate with Strain Distribution (변형률 분포를 가진 탄소섬유복합체의 인장특성에 대한 연구)

  • Kim, Yun-Gon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.24 no.6
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    • pp.25-33
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    • 2020
  • To investigate the relationship between strain distribution and tensile properties of brittle material, five types of tensile coupon of carbon fiber reinforced polymer (CFRP) modified the tab portion in order to have a strain distribution including S0, SD1, SD2, SV1, SV2 were tested. The ultimate stress and strain of SD2 and SV2 which was intended to have larger strain distribution were smaller than those of SD1 and SV1, that was more clearly shown in the test results of the symmetric coupons (SV series) than the asymmetric coupons (SD series). In addition, the ultimate stress and strain of most coupons with strain distribution in this study were decreased when compared to the control group with uniform strain. These results were analyzed in various ways through 1) the average of the strain values directly measured by the strain gages, 2) the converted strain calculated by dividing the total deformation by the effective length, and 3) the ultimate effective strain derived from both the elastic modulus and the ultimate load. The values measured by strain gage indicates response of the local region precisely, but it does not represent the response from whole section. However, the converted strain and effective strain can supplement disadvantage of gage because they represent the average response of whole section. In particular, the effective strain can provide rupture strain conservatively, which can be utilized in practice, when the value obtained by strain gage was not effective due to gage damage or abnormal gage readings near ultimate load. This value provides a value that can be used even when partial rupture has occurred and is reasonably useful for specimens with strain distribution.

The development of On-line Model for the Prediction of Effective Strain Distribution by Non-dimensionalization on FEM Basis (유한요소법 기반의 무차원화를 이용한 판 유효 변형률 분포 예측 온라인 모델 개발)

  • Kim S. H.;Lee J. H.;Hwang S. M.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2004.08a
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    • pp.359-367
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    • 2004
  • In this research on-line model for the prediction of the effective strain distribution in strip on finishing mill process is presented. To describe the effective strain distribution in strip, three guide points and a distribution fitting variable are used. On-line models to get these points and fitting variable non-dimensionalization method and least square method were used with FEM simulation results. The model is developed using strip only FEM simulation as reference sets and compared with roll coupled FEM simulation results as perturbed sets. The on-line model to describe effective strain distribution shows good agreement with coupled FEM analysis results.

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Consolidation Characteristics at the Constant Rate of Strain(CRS) Test (일정변형률(CRS) 시험에서의 압밀특성)

  • Lee, Dal-Won;Kim, Si-Jung
    • Korean Journal of Agricultural Science
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    • v.37 no.3
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    • pp.491-499
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    • 2010
  • This study was carried out to investigate the consolidation characteristics of the remolded clay by the oedometer and the constant rate of strain(CRS) consolidation tests. As the rate of strain increases, the settlement rapidly decreased. As the ratio of the sand in the specimen increases, its effect on the rate of strain to the settlement was reduced. As the effective stress increased, the void ratio decreased, while the rate of strain increased, it did not show a clear variation. The reduction of the void ratio was shown to be less than the oedometer test. The coefficient of vertical consolidation with effective stress showed very large variation around preconsolidation stress, but the rate of strain did not provide significant effects. The rate of strain with effective stress gradually decreased at all tests and mixed ratio of sand. The rate of strain at the constant rate of strain tests showed smaller than in the oedometer test. The coefficient of consolidation at the constant rate of strain tests showed much more increase than in the oedometer test. The ratio of the vertical coefficient of consolidation by the odometer and the constant rate of strain tests showed a large difference according to various tests method and mixing ratio. Therefore, it is recommended that careful attention should be paid to designing the soft ground improvement.

Energy-based evaluation of liquefaction potential of uniform sands

  • Sonmezer, Yetis Bulent
    • Geomechanics and Engineering
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    • v.17 no.2
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    • pp.145-156
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    • 2019
  • Since behaviors of loose, dense, silty sands vary under seismic loading, understanding the liquefaction mechanism of sandy soils continues to be an important challenges of geotechnical earthquake engineering. In this study, 36 deformation controlled cyclic simple shear tests were performed and the liquefaction potential of the sands was investigated using three different relative densities (40, 55, 70%), four different effective stresses (25, 50, 100, 150 kPa) and three different shear strain amplitudes (2, 3.5, 5%) by using energy based approach. Experiments revealed the relationship between per unit volume dissipated energy with effective stress, relative density and shear strain. The dissipate energy per unit volume was much less affected by shear strain than effective stress and relative density. In other words, the dissipated energy is strongly dependent on relative density and effective stress. These results show that the dissipated energy per unit volume is very useful and may contain the non-uniform loading conditions of the earthquake spectrum. When multiple regression analysis is performed on experiment results, a relationship is proposed that gives liquefaction energy of sandy soils depending on relative density and effective stress parameters.

The Development of On-Line Model for the Prediction of Strain Distribution in Finishing Mill by FEM (유한요소법을 이용한 열간 사상 압연에서의 판 변형률 분포 예측 온라인 모델 개발)

  • 김성훈;이중형;황상무
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2003.05a
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    • pp.180-183
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    • 2003
  • In this research, on-line model for prediction of effective strain distribution hi strip on finishing mill process is prescribed. It has been developed using several selected non-dimensional parameters and previously made average effective strain model via series of finite element process simulations, $\Delta$$\varepsilon$ was introduced to describe the effective strain distribution in strip. To confirm adequate non-dimensional variables uniqueness test was done. And to decide the order of polynomial in on-line model equation tendency test for each variables was done. The prediction accuracy of the proposed model is examined through comparison with finite element calculation results.

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Pathogenicity of Entomopathogenic Nematodes to Some Agro-Forest Insect Pests (농림해충에 대한 곤충병원성 선충의 병원성)

  • 이상명;이동운;추호렬;김도완;김준범
    • The Korean Journal of Soil Zoology
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    • v.2 no.2
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    • pp.76-82
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    • 1997
  • Mortality of some agro-forest insect pests, Agrotis segetum, Blitopertha orientalis, Agerastica coerulea, Glyphodes perspectalis and Acantholyda parki caused by entomopathogenic nematodes was investigated in laboratory and in pot. Steinernema carpocapsae All and Pocheon strain were effective against 2nd of 3rd instar larvae of A. segetum showing 100% mortalities at the concentration of 10Ijs/larva but not effective against 4th inster larvae. Mortality of B. orientalis was 100% after 26 days in H. bacteriopora NC 1, H. bacteriophora Hamyang and S. glageri NC strain treatment. S. monticulum also showed 100% mortalities against A. coerulea andd G. perspectalis at the concentration of 80 and 40 Ijs/larva. However, H. bacteriophora Cheju and S. glaseri Cheju strain were not effective against A. parki, i.e., showing 23.3 and 20.0% mortalities, respectively at the concentration of 160Ijs/larva. S. glaseri Hanrim strain was more effective than H. bacteriophora Cheju strain against Pryeria sinica.

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Prediction of Radial Direction Strain in Drawn Wire (인발 선재의 반경 방향 변형률 분포 예측)

  • Lee, Sang-Kon;Hwang, Sun-Kwang;Cho, Yong-Jae
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.18 no.9
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    • pp.100-105
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    • 2019
  • In wire drawing, aterial deformation is concentrated on the surface of the drawn wire because of surface contact with the drawing die. Therefore, strain varies from the center to the surface of the drawn wire. In this study, based on the upper bound method, an effective strain prediction method from the center to the surface of a drawn wire was proposed. Using the proposed method, the effective strain of the drawn wire was calculated verify the proposed prediction method, the predicted effective strain was compared with the result of finite element analysis.