• Title/Summary/Keyword: Plastic Strain Ratio

Search Result 244, Processing Time 0.024 seconds

Flexural Behavior of Composite HSB I-Girders in Positive Moment (HSB 강합성거더 정모멘트부 휨거동)

  • Cho, Eun-Young;Shin, Dong-Ku
    • Journal of Korean Society of Steel Construction
    • /
    • v.22 no.4
    • /
    • pp.377-388
    • /
    • 2010
  • The flexural behavior of composite HSB600 and HSB800 I-girders under a positive moment was investigated using the material non-linear moment-curvature analysis method. Three representative composite sections with different ductility properties were selected as the baseline sections in this study. Using these baseline sections, the moment-curvature program was verified by comparing the flexural strength and the moment-curvature curve obtained from the program with those obtained using the non-linear FE analysis of ABAQUS. In the FE analysis, the composite girders were modeled three-dimensionally with flanges, the web, and the concrete slab as thin shell elements, and initial imperfections and residual stresses were imposed on the FE model. In the moment-curvature and FE analyses, the 28-day compressive strength of the concrete slab was assumed to be 30-50 MPa, and the HSB600 and HSB800 steels were modeled as elasto-plastic strain-hardening materials, with the concrete as the CEB-FIP model. The effects of the ductility ratio of the composite girder, the type of steel, the compressive strength of the concrete deck, and the location of the plastic neutral axis on the flexural characteristics were analyzed.

Analysis of the Axisymmetric Hydro-Mechanical Deep Drawing Process by Using the Finite Element Method (유한 요소법을 이용한 축대칭 하이드로 미케니칼 디프 드로잉 공정의 해석)

  • 양동열;김한경;이항수;김경웅
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.16 no.5
    • /
    • pp.873-882
    • /
    • 1992
  • The study is concerned with the rigid-plastic element analysis for axisymmetric hydromechanical deep drawing in which the fluid flow influences the metal deformation. Due to the fluid pressure acting on the sheet material hydromechanical deep drawing is distinguished from the conventional deep drawing processes. In considering the pressure effect, the governing equation for fluid pressure is solved and the result is reflected on the global stiffness matrix. The solution procedure consists of two stages ; i.e., initial bulging of the sheet surface before the initiation of steady fluid flow in the flange and fluid-lubricated stage. The problem is decoupled between fluid analysis and analysis of solid deformation by deformation by iterative feedback of mutual computed results. The corresponding experiments are carried out for axisymmetric hydro-mechanical deep drawing of annealled aluminium sheet as well as for deep drawing. It has been shown from the experiments that the limit drawing ratio for hydro-mechanical deep drawing is improved as compared with deep drawing. The computed results are in good agreement with the experiment for variation of punch head and chamber pressure with respect to the punch travel and for distribution of thicknees strain. It is thus shown that the present method of analysis can be effectively applied to the analysis of axisymmetric hydro-mechanical deep drawing processes.

Semi-Empirical Prediction of Crack Width of the Strengthened Bridge Deck with External Bonding Plastic (외부부착 보강된 교량 바닥판 균열폭의 반경험적인 예측)

  • 심종성;오홍섭
    • Journal of the Korea Concrete Institute
    • /
    • v.14 no.2
    • /
    • pp.231-238
    • /
    • 2002
  • Dry shrinkage md temperature change cause to develope concrete bridge decks on main girders have initial unidirectional cracks in longitudinal or transverse direction. As they receive traffic loads, the crack gradually propagate in different directions depending on the concrete dimension and reinforcement ratio. Since existing equations that predict crack width are mostly based on the one directional bond-slip theory, it is difficult to determine the actual crack width of a bridge deck with varying the spacing of rebar or strengthening material and to estimate the improvement rate in serviceability of the strengthened bridge deck. In this study, crack propagation mechanism is identified based on the test results and a new crack prediction equation is proposed for evaluation of serviceability. Although more accurate results are derived using the proposed equation, the extent of error is increased as the strain of the rebar or the strengthening material increases after the yielding of rebar Therefore, further research is required to better predict the crack width after the rebar yields under fatigue loading condition.

Strength and Stiffness of Silty Sands with Different Overconsolidation Ratios and Water Contents (과압밀비와 함수비를 고려한 실트질 사질토 지반의 강도 및 변형 특성)

  • Kim Hyun-Ju;Lee Kyoung-Suk;Lee Jun-Hwan
    • Journal of the Korean Geotechnical Society
    • /
    • v.21 no.9
    • /
    • pp.53-64
    • /
    • 2005
  • For geotechnical design in practice, soils are, in general, assumed to behave as a linear elastic or perfect plastic material. More realistic geotechnical design, however, should take into account various factors that affect soil behavior in the field, such as non-linearity of stress-strain response, stress history, and water content. In this study, a series of laboratory tests including triaxial and resonant column tests were peformed with sands of various silt contents, relative densities, stress states, OCR and water contents. This aims at investigating effects of various factors that affect strength and stiffness of sands. From the results in this study, it is found that the effect of OCR is significant for the intermediate stress-strain range from the initial to failure, while it may be ignored for the initial stiffness and peak strength. For the effect of water content, it is observed that the initial elastic modulus decreases with increasing water content at lower confining stress and relative density At higher confining stresses, the effect of water content Is found to become small.

Structural Design of Coupled RC Structural Wall Considering Plastic Behavior (소성거동을 고려한 병렬 RC 구조벽체시스템의 설계)

  • Yu, Seung-Yoon;Eom, Tae-Sung;Kang, Su-Min
    • Journal of the Computational Structural Engineering Institute of Korea
    • /
    • v.30 no.4
    • /
    • pp.351-361
    • /
    • 2017
  • Reinforced concrete(RC) structural walls are major lateral load-resisting structural member in building structures. Generally these RC structural walls are coupled with each other by the coupling beams and slabs, and therefore they behave as RC coupled structural wall system. In the design of these coupled structural wall systems, member forces are calculated using elastic structural analysis. These elastic analysis methodologies for the design of coupled structural wall system was not reasonable because it can not consider their ultimate behavior and assure economic feasibility. Performance based design and moment redistribution method to solve these problems is regarded as a reasonable alternative design method for RC coupled structural wall system. However, it is not verified under various design parameters. In this study, nonlinear analysis of RC coupled structural wall system was performed according to various design parameters such as reinforcement ratio, ultimate concrete strain and wall height. Based on analysis results, design considerations for coupled RC structural wall system was proposed.

Development of Finite Element Program for Analyzing Springback Phenomena of Non-isothermal Forming Processes for Aluminum Alloy Sheets(Part 1 : Experiment) (알루미늄 합금박판 비등온 성형공정 스프링백 해석용 유한요소 프로그램 개발 ( 1부 : 실험 ))

  • 금영탁;유동열;한병엽
    • Transactions of Materials Processing
    • /
    • v.12 no.3
    • /
    • pp.202-207
    • /
    • 2003
  • In order to examine the springback amount and material properties of aluminum alloy sheets (AL1050 and AL5052) in the warm forming which forms the sheet above the room temperature, the stretch bending and draw bending tests and tensile test in various high temperatures are carried out. The warm forming temperature 15$0^{\circ}C$ is a transition in terms of the material properties: over the forming temperature 15$0^{\circ}C$, them $\sigma$$_{YS}$ , $\sigma$$_{TS}$ , E, K, n, etc. are bigger but $\varepsilon$ and plastic strain ratio are smaller. Below the forming temperature 15$0^{\circ}C$, there are no big differences in material properties as the forming temperature changes. AL5052 sheet has more springback effect than AL1050 sheet. While the springbacks of AL5052 and AL1050 sheets show a big reduction over the warm forming temperature 15$0^{\circ}C$ in the stretch bending test, the springback rapidly reduces in the warm forming temperature 15$0^{\circ}C$-20$0^{\circ}C$ for AL5052 sheet and 20$0^{\circ}C$-25$0^{\circ}C$ for AL1050 sheet in the draw bending test.

A Study on the Volume Change in Unsaturated Clayey Soil (불포화 정성토의 체적변화에 대한 연구)

  • Chang, Pyoung-Wuck;Gil, Sang-Choon
    • Magazine of the Korean Society of Agricultural Engineers
    • /
    • v.40 no.5
    • /
    • pp.37-42
    • /
    • 1998
  • This study was performed to evaluate the characteristics of volume change is unsaturated clayed soil. The medium-plastic clay was selected and compacted by 50% of Proctor standard compaction energy at 6% higher moisture content than its OMC. A series of isotropic compression tests and triaxial shear tests were performed. The results of the study are summarized as follows. At each matric suction, when the matric suction was increased, the yield stress was increased and slope of volume change was decreased. The more net mean stress was, the less the quantity of volume change was. In shear test, the volumetric strain was much rapidly changed in large matric than in low matric suctions. But the effect of matric suction to volume change disappeared under high net mean stress. At lower deviator stress the more matric suction was, the higher volume change was. But As the matric suction was increasing, the behavior of the unsaturated clayey soil was similar to that of saturated clayey soil. Volume change in the unsaturated clayey soil can be represented as a unique plane in three-dimensional space, which is the axes of net mean stress, matric suction and void ratio.

  • PDF

Fabrication and Electrical Characteristics of Transparent and Bendable a-IGZO Thin-film Transistors (투명 유연 a-IGZO 박막트랜지스터의 제작 및 전기적 특성)

  • Park, Sukhyung;Cho, Kyoungah;Oh, Hyungon;Kim, Sangsig
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.29 no.2
    • /
    • pp.120-124
    • /
    • 2016
  • In this study, we fabricate transparent and bendable a-IGZO (amorphous indium gallium zinc oxide) TFTs (thin-film transistors) with a-IZO (amorphous indium zinc oxide) transparent electrodes on plastic substrates and investigate their electrical characteristics under bending states. Our a-IGZO TFTs show a high transmittance of 82% at a wavelength of 550 nm. And these TFTs have an $I_{on}/I_{off}$ ratio of $1.8{\times}10^8$, a field effect mobility of $15.4cm^2/V{\cdot}s$, and a subthreshold swing of 186 mV/dec. The good electrical characteristics are retained even after bending with a curvature radius of 18 mm corresponding to a strain of 0.5% owing to mechanical durability of the transparent electrodes used in this study.

Effect of Alloying Composition and Plastic Deformation on the Microstructure of 22Cr Micro-Duplex Stainless Steel (합금원소와 소성변형이 22Cr 마이크로 듀플렉스 스테인리스강의 미세조직에 미치는 영향)

  • Park, Jun-Young;Ahn, Yong-Sik
    • Korean Journal of Metals and Materials
    • /
    • v.50 no.11
    • /
    • pp.793-800
    • /
    • 2012
  • The effect of cold rolling on the microstructural evolution in 22Cr-0.2N micro-duplex stainless steel was investigated. The 22Cr-xNi-yMn-0.2N duplex stainless steel plates with various Ni and Mn contents were fabricated. The steels were vacuum induction melted and hot rolled, followed by annealing treatment at the temperature range of $1000-1100^{\circ}C$, in which both the austenite and ferrite phases were stable. The volume fraction of the ferrite phase depending on the alloy compositions of Ni and Mn increased with an increase in the annealing temperature. Grain growth in the ferrite phase occurred markedly after cold rolling followed by annealing, while fine recrystallised grains were still found in the austenite phase. A large number of martensite laths was found in the microstructure of cold rolled steels, which should be formed by strain-induced martensite from the austenite phase. The intersections of stacking faults were revealed by TEM observation. The volume fraction of the martensite phase increased with an increase of the reduction ratio by cold rolling.

The performance effect of shroud split for turbopump turbine rotor (터보펌프 터빈 로터의 슈라우드 스플릿이 성능에 미치는 영향)

  • Lee, Hang-Gi;Jung, Eun-Hwan;Yoon, Suk-Hwan;Park, Pyun-Gu;Kim, Jin-Han
    • Proceedings of the Korean Society of Propulsion Engineers Conference
    • /
    • 2012.05a
    • /
    • pp.117-122
    • /
    • 2012
  • A blisk with rotor shroud is usually adopted in LRE turbine to maximize its performance. However it experiences severe thermal load and resulting damage during engine stating and stop. Shroud splitting is devised to relieve thermal stress on the turbine rotor. Structural analysis confirmed the reduction of plastic strain at the blade hub and tip. However, split gap at the rotor shroud entails additional tip leakage and results performance degradation. In order to assess the effect of shroud split on the turbine performance, tests have been performed for various settings of shroud split. For the maximum number of shroud splitting, measured efficiency reduction ratio was 2.65% to the value of original shape rotor.

  • PDF