• 제목/요약/키워드: deformation characteristic

검색결과 493건 처리시간 0.03초

콘크리트의 극한변형률 수정모델 (Modified model of ultimate concrete compression strain)

  • 고성현;이재훈
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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    • pp.81-84
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    • 2008
  • The purposes of this study are to verify a reasonable model of material characteristic and to propose a rational model of reinforcement characteristic considering monotonic and cyclic loading about manufactured reinforcing steel in Korea. Longitudinal reinforcements of the plastic hinge region were behaved tensile deformation and compressional deformation by direction of lateral loading. However Confinement steels were behaved only tensile deformation by lateral loading. Transverse steels were laid the state of tension in the lateral loading of time, and they were laid state that stress is zero when it was removed lateral load. The tests for cyclic tension loading were performed for test variable as yield strength and reinforcement bar sizes. It was estimated that the total strain energy per unit volume was 74 $MJ/m^3$. The modified ultimate concrete compression strain model was proposed based on experimental study of cyclic tension test for manufactured reinforcing steel in Korea.

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유한요소법에 의한 타원 판넬의 성형성에 관한 연구 (A Study on the Formability of Ellipse Panel by Finite Element Method)

  • 강대민
    • 동력기계공학회지
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    • 제3권2호
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    • pp.89-97
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    • 1999
  • In this paper the forming simulations of ellipse bulge have been researched by using $PAM-STAMP_{TM}$ to estimate the sheet metal forming and the plastic deformation characteristic of ellipse bulge. Thin elliptical diaphragms of brass, copper, aluminum, and mild steel are bulged in elliptical dies having aspect ratios of 1.33 and 2. In order to compare the simulation results with the experiment and ellipse bulge's theory derived by using Johnson and Duncan's theory, the relations of hydraulic pressure and polar height, polar thickness strain and polar height, were compared. According to this study, the results of simulation and ellipse bulge's theory derived by using Johnson and Duncan's theory, and the bursting pressure and the bursting polar height are good agreement to the experiment. So, the results of simulation by using $PAM-STAMP_{TM}$ and the ellipse bulge's theory will give engineers good information to make assessment the formability and plastic deformation characteristic of hydraulic ellipse bulge test.

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DEM 모델을 이용한 평판재하시험의 토양 수직응력 해석 (Soil Stress Analysis Using Discrete Element Method for Plate-Sinkage Tests)

  • 장기찬;이수진;이규진
    • 한국CDE학회논문집
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    • 제20권3호
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    • pp.230-237
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    • 2015
  • Soil deformation on the off-load ground is significantly affected by soil conditions, such as soil type, water content, and etc. Thus, the soil characteristics should be estimated for predicting vehicle movements on the off-load conditions. The plate-sinkage test, a widely-used experimental test for predicting the wheel-soil interaction, provides the soil characteristic parameters from the relationship between soil stress and plate sinkage. In this study, soil stress under the plate-sinkage situation is calculated by the DEM (Discrete Element Method) model. We developed a virtual soil bin with DEM to obtain the vertical reaction forces under the plate pressing the soil surface. Also parametric studies to investigate effects of DEM model parameters, such as, particle density, Young's modulus, dynamic friction, rolling friction, and adhesion, on the characteristic soil parameters were performed.

불포화토에서 공극비의 추정 (The Prediction of Void Ratio in Unsaturated Soils)

  • 이달원
    • 한국농공학회논문집
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    • 제48권4호
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    • pp.51-57
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    • 2006
  • This study was carried out to investigate the soil water characteristic curve and prediction of void ratio with net stress and matric suction using the linear elastic and volumetric deformation analysis method on unsaturated silty. The unsaturated soil tests were conducted using a modified oedometer cell and specimens were prepared at water content 2 times of liquid limit and required void ratio. The axis translation technique was used to create the desired matric suctions in the samples. It is shown that soil water characteristic curve and volumetric water content were affected significantly by preconsolidation pressure. As a matric suction increases, the reduction ratio of void ratio was shown to considerably small. Also, the predicted and measured void ratio for unsaturated soils using the linear elastic and volumetric deformation analysis showed good agreement as net stress and matric suction increases.

Ti-Ni합금의 반복변형특성에 미치는 pre-strain의 효과 (The Effect of Pre-strain on Cyclic Deformation Characteristic of Ti-Ni Alloy)

  • 박영철;조용배;허선철
    • 한국해양공학회지
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    • 제9권1호
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    • pp.101-110
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    • 1995
  • In SMA(Shape Memory Alloy), the degradation by fatigue is one of the most important problems to be overcome, when SMA is used for robot-actuator materials. The actuator is operated repetitively for long time and its repeating operation develops the fatigue degradation of SMA. The fatigue degradation changes the transformation temperature and deformation behavior and results in inaccurate operation and deformation which results form repeating operation is to be investigated in advance and the scheme to resolve those problems have to be made for the design of actuator. In this paper, for the improvement of the fatigue degradation by repetive movement and better control of the correct movement by the stability of martensite transformation in the development of Robots actuator, Pre-strain(0, 1.5, 5, 8%) are loaded in the specimens and fatigue testing were carried out by the method of heating and cooling in direct condition. From the results of these experiments, the effect on pre-strain which affect the transformation characteristic and fatigue degradation phenomena were correctly investigated.

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슬릿형 강재이력 감쇠장치의 성능평가를 위한 실험연구 (An Experimental Study on Performance Evaluation of Hysteretic Steel Slit Damper)

  • 최기선;이현지;김민선;유영찬
    • 대한건축학회논문집:구조계
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    • 제34권1호
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    • pp.33-39
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    • 2018
  • This study performed experimental validation of the hysteretic steel slit damper's basic and dependent characteristics, which should be considered for the design. The basic characteristic of the steel slit damper is used for determining design properties of non-linear analysis, such as yielding strength, yielding displacement, elastic stiffness and post-yielding stiffness. In order to evaluate dependent characteristics of the hysteretic steel slit damper, repeated deformation capacity with respect to the displacement, velocity and aspect ratio of the damper was evaluated. In this study, steel slit damper, which is widely used in Korea, was considered. The slit dampers with 55kN and 240kN of yielding strength were produced and tested. It was concluded that the slit damper's hysteresis behavior was affected by the dependent characteristics: displacement, velocity and aspect ratio. In other words, the steel slit damper's behavior was stable within limit displacement, and aspect ratio of the strut affected repeated deformation capacity of the damper subjected to large deformation. In addition, it was observed that the repeated deformation capacity abruptly decreased at the high speed range (${\geq}60mm/sec$). Furthermore, the experimental results were evaluated with the criterion of the damping device specified in ASCE7-10.

냉간 압출시 Chevron Crack 방지에 대한 고찰 (A Study of Preventing Chevron Crack in Cold Extrusion)

  • 최영순;이정환
    • 소성∙가공
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    • 제6권3호
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    • pp.221-226
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    • 1997
  • Chevron crack in cold extrusion has been studied in view of deformation conditions and material characteristics. There is V formed chevron crack is occasionally occurred in core part of shaft by multistage free extrusion. Although many research results were reported and theoretical analyses were accompanied, in this study we discussed practical method to prevent chevron crack in the field of working conditions and material characteristics. We have found that chevron crack is eliminated under condition of high hydrostatic state in deformation and decreased segregation, refinement of micro structure of materials.

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연속 회전 등통로각압축 공정의 유한요소해석 (Finite Element Analysis of Continuous Rotary-Die Equal Channel Angular Pressing)

  • 윤승채;서민홍;김형섭
    • 소성∙가공
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    • 제15권7호
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    • pp.524-528
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    • 2006
  • Although equal channel angular pressing (ECAP), imposing large plastic shear strain deformation by moving a workpiece through two intersecting channels, is a promising severe plastic deformation method for grain refinement of metallic materials, its batch type characteristic makes ECAP inefficient for multiple-passing. Rotary-die ECAP (RDECAP) proposed by Nishida et al. can achieve high productivity by using continuous processing without taking out the samples from the channel. However, plastic deformation behavior during RD-ECAP has not been investigated. In this study, material plastic flow and strain hardening behavior of the workpiece during RD-ECAP was investigated using the finite element method. It was found that plastic deformation becomes inhomogeneous with the number of passes due to an end effect, which was not found seriously in ECAP. Especially, decreasing corner gap with increasing the number of passes was observed and explained by the strain hardening effect.

고질소강 오스테나이트계 스테인레스강의 압축변형특성 (Deformation Characteristic by Compression in High-Nitrogen Austenitic Stainless Steel)

  • 이종욱;김동수;김병구;이명열
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2007년도 추계학술대회 논문집
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    • pp.139-141
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    • 2007
  • Compression tests were carried out to investigate morphologies of compressed specimen, deformation microstructure and stress-strain relation in high-nitrogen austenite stainless steel. Tests were performed under a wide range of temperature and, with true strain rates up to $\dot{\varepsilon}$ =0.05, 0.1, 0.5 and $1.0s^{-1}$. The activation energy of loading force was equal to plastic deformation energy within the temperature range of $900^{\circ}C$ to $1250^{\circ}C$. Dynamically recrystallized grain size decreased with an increasing strain rate and temperature. Flow stresses and deformation microstructures, were used to quantify the critical strain rate and recrystallized grain size. The grain size versus strain rate-temperature map obtained in the study was in good agreement with the deformation microstructures of compressed specimens.

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이상 스테인리스강의 변형거동에 미치는 질소의 영향 (Effects of Nitrogen on Deformation Behavior of Duplex Stainless Steel)

  • 이형직;장영원
    • 소성∙가공
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    • 제12권4호
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    • pp.284-289
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    • 2003
  • The effects of nitrogen on the deformation behavior of duplex stainless steel have been studied. The variation of strength was correlated with the characteristic microstructures pertaining to nitrogen. Analysis based on Hall-fetch relation confirmed that nitrogen enhances phase-boundary strengthening effect. The evolution of dislocation structure, slip traces and misorientation distribution during deformation were also characterized to elucidate the effect of nitrogen on inelastic deformation mechanism. It has been verified in this study that the higher nitrogen content provides a dual-phase microstructure with smaller strength difference between austenite and ferrite resulting into the earlier transfer of inelastic deformation from austenite to ferrite.