• 제목/요약/키워드: Equivalent Strain

검색결과 520건 처리시간 0.022초

On the Contact Behavior Analysis and New Design of O-ring Seals

  • Kim, Chung-Kyun;Cho, Seung-Hyun;Kim, Young-Gyu
    • 한국윤활학회:학술대회논문집
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    • 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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    • pp.121-122
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    • 2002
  • This paper presents contact behavior of an Polyperfluoroalkoxyethylene(PTFE) ring seals by a non-linear finite element method using the thermomechanical analysis. PTFE elastomer was assumed as odgen model for numerical analysis in FEM commercial code because elastomer has nonlinear behaviour character. The shape effects are investigated for sealing performance of ring seal in boundary conditions which as gas pressure, groove temperature and various O-ring seal models. Also contact stress and equivalent total strain are investicated. An O-ring seals was modeled four shape which are circle, two sunflower and X. The highest contact stress occurs at sunflower-ring seal with groove deapth of 0.35mm. the equivalent total strain of sunflower-ring seal is lower than that of the others under low gas pressure condition but under gas pressure condition over 4Mpa, that of sunflower-ring seal is higher. The calculated FEM results shows that the Sunflower-ring seal with groove depth of 0.35mm has excellent performance compared with other seal models.

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전선작업용 고소작업차의 복합재 절연붐 개발 (A Study on the Composite Insulation Boom Development of the Aerial Work Platform for Electric Work)

  • 강동명;조규춘;황택주;심기중;국호영;김진수;박문호
    • 한국기계가공학회지
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    • 제17권2호
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    • pp.137-144
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    • 2018
  • This study describes the 3D design and analysis of a composite insulation boom of an aerial work platform for electric work. Structural analysis of the composite insulation boom was performed using ANSYS and the total deformation, equivalent stress, and normal elasticity were investigated at 150 mm, 500 mm, 1,000 mm, and 1,500 mm using a mounted strain gauge. The results of the analysis and test were similar in a linearly increasing slope and the difference in the strain value was about 10%. This difference depends on the compressive force in the manufacturing process.

PRACTICAL MODELLING OF STONE-COLUMN REINFORCED GROUND

  • Tan By S.A.;Tjahyono S.
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2006년도 추계 학술발표회
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    • pp.291-311
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    • 2006
  • The acceleration of consolidation by stone columns was mostly analysed within the framework of a basic unit cell model (i.e. a cylindrical soil body around a column). A method of converting the axisymmetric unit cell into the equivalent plane-strain model would be required for two-dimensional numerical modelling of multi-column field applications. This paper proposes two practical simplified conversion methods to obtain the equivalent plane-strain model of the unit cell, and investigates their applicability to multi-column reinforced ground. In the first conversion method, the soil permeability is matched according to an analytical equation, whereas in the second method, the column width is matched based on the equivalence of column area. The validity of these methods is tested by comparison with the numerical results of unit-cell simulations and with the field data from an embankment case history. The results show that for the case of linear-elastic material modelling, both methods produce reasonably accurate long-term consolidation settlements, whereas for the case of elasto-plastic material modelling, the second method is preferable as the first one gives erroneously lower long-term settlements, where plastic yielding of stone column are ignored.

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지반응답해석기법의 차이에 의한 지반응답 분산도 평가 (Influence of Analysis Models on Variation of Ground Response during Earthquake)

  • 김성렬;최재순;김수일;박대영;박성용;김기풍
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2007년 가을학술발표회
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    • pp.317-333
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    • 2007
  • The Round-Robin Test (RRT) for ground response analysis was performed by Division of Geotechnical Earthquake Engineering of Korean Geotechnical Society. This research analyzed the influence of analysis methods on variation of ground response by using the results of this RRT. The analysis methods include equivalent linear analysis, non-linear analysis and effective stress analysis. A total of 5 teams among 12 teams applied two kinds of analysis methods. This research compared the results of these 5 teams and analyzed the variation of the results according to analysis methods. The compared results were shear stress-shear strain relation, transfer function, time history and the response spectrum of ground surface acceleration, peak ground acceleration, peak shear strain and maximum excess pore pressure ratio.

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유한요소법과 초음파 메카트로닉스 시스템에 의한 강도적 불균질 이음부의 노치위치에 따른 균열발생 한계 조건 (Evaluation of Notch Location Effect on Ductile Crack Initiation at Strength Mismatched Joints by Finite Element Method and Ultrasonic-Mechatronics System)

  • 안규백;방한서;풍전정남
    • Journal of Welding and Joining
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    • 제23권6호
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    • pp.87-92
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    • 2005
  • It has been well hewn that ductile fracture of steels is accelerated by triaxial stresses. The characteristics of ductile crack initiation in steels are evaluated quantitatively using a two-parameters criterion based on equivalent plastic strain and stress triaxiality. The present study focuses on the effects of strength mismatch, which can elevate plastic constraint due to heterogeneous plastic straining, on the critical condition for ductile fracture initiation usinga two-parameter criterion. Fracture initiation testing has been conducted under static loading using notched round bar specimens which had different notch locations. This study provides the fundamental clarification of the effect of strength mismatching and effect of notch location on the critical condition to ductile crack initiation from notch root using fuite element method and ultrasonic-mechatronics system. The critical condition of ductile crack initiation from notch root of strength mismatched tensile specimens under static loading appeared to be almost the same as those of homogeneous tensile specimens with circumferential sharp notch specimen. Also, the effect of notch location in mismatched specimens was estimated using finite element(FE) analyses.

원전 안전 1등급 기기의 유한요소 탄소성 시간이력 지진해석 결과에 미치는 가속도 가진 방법 내 기준선 조정의 영향에 대한 예비연구 (Preliminary Study on Effect of Baseline Correction in Acceleration Excitation Method on Finite Element Elastic-Plastic Time-History Seismic Analysis Results of Nuclear Safety Class I Components)

  • 김종성;박상혁
    • 한국압력기기공학회 논문집
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    • 제14권2호
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    • pp.69-76
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    • 2018
  • The paper presents preliminary investigation results for the effect of the baseline correction in the acceleration excitation method on finite element seismic analysis results (such as accumulated equivalent plastic strain, equivalent plastic strain considering cyclic plasticity, von Mises effective stress, etc) of nuclear safety Class I components. For investigation, finite element elastic-plastic time-history seismic analysis is performed for a surge line including a pressurizer lower head, a pressurizer surge nozzle, a surge piping, and a hot leg surge nozzle using the Chaboche hardening model. Analysis is performed for various seismic loading methods such as acceleration excitation methods with and without the baseline correction, and a displacement excitation method. Comparing finite element analysis results, the effect of the baseline correction is investigated. As a result of the investigation, it is identified that finite element analysis results using the three methods do not show significant difference.

Round robin analysis to investigate sensitivity of analysis results to finite element elastic-plastic analysis variables for nuclear safety class 1 components under severe seismic load

  • Kim, Jun-Young;Lee, Jong Min;Park, Jun Geun;Kim, Jong-Sung;Cho, Min Ki;Ahn, Sang Won;Koo, Gyeong-Hoi;Lee, Bong Hee;Huh, Nam-Su;Kim, Yun-Jae;Kim, Jong-In;Nam, Il-Kwun
    • Nuclear Engineering and Technology
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    • 제54권1호
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    • pp.343-356
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    • 2022
  • As a part of round robin analysis to develop a finite element elastic-plastic seismic analysis procedure for nuclear safety class 1 components, a series of parametric analyses was carried out on the simulated pressurizer surge line system model to investigate sensitivity of the analysis results to finite element analysis variables. The analysis on the surge line system model considered dynamic effect due to the seismic load corresponding to PGA 0.6 g and elastic-plastic material behavior based on the Chaboche combined hardening model. From the parametric analysis results, it was found that strains such as accumulated equivalent plastic strain and equivalent plastic strain are more sensitive to the analysis variables than von Mises effect stress. The parametric analysis results also identified that finite element density and ovalization option in the elbow elements have more significant effect on the analysis results than the other variables.

Failure analysis of tubes under multiaxial proportional and non-proportional loading paths

  • Mohammad Hossein Iji;Ali Nayebi
    • Steel and Composite Structures
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    • 제47권2호
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    • pp.289-296
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    • 2023
  • The failure of a thin-walled tube was studied in this paper based on three failure models. Both proportional and non-proportional loading paths were applied. Proportional loading consisted of combined tension-torsion. Cyclic non-proportional loading was also applied. It was a circular out-of-phase axial-shear stress loading path. The third loading path was a combination of a constant internal pressure and a bending moment. The failure models under study were equivalent plastic strain, modified Mohr-Coulomb (Bai-Wierzbicki) and Tearing parameter models. The elasto-plastic analysis was conducted using J2 criterion and nonlinear kinematic hardening. The return mapping algorithm was employed to numerically solve the plastic flow relations. The effects of the hydrostatic stress on the plastic flow and the stress triaxiality parameter on the failure were discussed. Each failure model under study was utilized to predict failure. The failure loads obtained from each model were compared with each other. The equivalent plastic strain model was independent from the stress triaxiality parameter, and it predicted the highest failure load in the bending problem. The modified Mohr-Coulomb failure model predicted the lowest failure load for the range of the stress triaxiality parameter and Lode's angle.

Dynamic loading tests and analytical modeling for high-damping rubber bearings

  • Kyeonghoon Park;Taiji Mazda;Yukihide Kajita
    • Earthquakes and Structures
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    • 제25권3호
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    • pp.161-175
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    • 2023
  • High-damping rubber bearings (HDRB) are commonly used as seismic isolation devices to protect civil engineering structures from earthquakes. However, the nonlinear hysteresis characteristics of the HDRB, such as their dependence on material properties and hardening phenomena, make predicting their behavior during earthquakes difficult. This study proposes a hysteretic model that can accurately predicts the behavior of shear deformation considering the nonlinearity when designing the seismic isolation structures using HDR bearings. To model the hysteretic characteristics of the HDR, dynamic loading tests were performed by applying sinusoidal and random waves on scaled-down specimens. The test results show that the nonlinear characteristics of the HDR strongly correlate with the shear strain experienced in the past. Furthermore, when shear deformation occurred above a certain level, the hardening phenomenon, wherein the stiffness increased rapidly, was confirmed. Based on the experimental results, the dynamic characteristics of the HDR, equivalent stiffness, equivalent damping ratio, and strain energy were quantitatively evaluated and analyzed. In this study, an improved bilinear HDR model that can reproduce the dependence on shear deformation and hardening phenomena was developed. Additionally, by proposing an objective parameter-setting procedure based on the experimental results, the model was devised such that similar parameters could be set by anyone. Further, an actual dynamic analysis could be performed by modeling with minimal parameters. The proposed model corresponded with the experimental results and successfully reproduced the mechanical characteristics evaluated from experimental results within an error margin of 10%.

응력 삼축성을 고려한 원자로 내부구조물 배플포머 집합체의 연성저하 평가 (Ductility Degradation Assessment of Baffle Former Assembly Considering the Stress Triaxiality Effect)

  • 김종성;박정순;강성식
    • 한국압력기기공학회 논문집
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    • 제12권2호
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    • pp.50-57
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    • 2016
  • The study presents structural integrity assessment of ductility degradation of a baffle former assembly by performing finite element analysis considering real loading conditions and stress triaxiality. Variations of fracture strain curves of type 304 austenitic stainless steel with stress triaxiality are derived based on the previous study results. Temperature distributions during normal operation such as heat-up, steady state, and cool-down are calculated via finite element temperature analysis considering gamma heating and heat convection with reactor coolant. Variations of stress and strain state during long operation period are also calculated by performing sequentially coupled temperature-stress analysis. Fracture strain is derived by using the fracture curve and the stress triaxility. Finally, variations of ductility degradation damage indicator with the fracture strain and the equivalent inelastic strain are investigated. It is found that maximum value of the ductility degradation damage index continuously increases and becomes 0.4877 at 40 EFPYs. Also, the maximum value occurs at top and middle inner parts of the baffle former assembly before and after 20 EFPYs, respectively.