• 제목/요약/키워드: Elastic-Plastic Theory

검색결과 142건 처리시간 0.029초

멱함수 가공경화 모델을 이용한 복합실린더의 자긴가공해석 (Autofrettage Analysis of Compound Cylinder with Power Function Strain Hardening Model)

  • 박재현;이영신;심우성;김재훈;차기업;홍석균
    • 대한기계학회논문집A
    • /
    • 제32권6호
    • /
    • pp.488-495
    • /
    • 2008
  • In order to achieve long fatigue lifetimes for cyclically pressurized thick cylinders, multi-layered compound cylinder has been proposed. Such compound cylinder involves a shrink-fit procedure incorporating a monobloc tube which has previously undergone autofrettage. The basic autofrettage theory assumes elastic-perfectly plastic behaviour. Because of the Bauschinger effect and strain-hardening, most materials do not display elastic-perfectly plastic properties and consequently various autofrettage mo dels are based on different simplified material strain-hardening models, which is assumed that combination of linear strain-hardenig and power strain-hardening model. This approach gives a more accurate prediction than the elastic-perfectly plastic model and is suitable for different strain-hardening materials. In this paper, a general autofrettage model that incorporates the material strain-hardening relationship and the Bauschinger effect, based upon the actual tensile-compressive stress-strain curve of a material was proposed. The model was obtained using the von Mises yield criterion and plane strain condition. The tensile-compressive stress-strain curve was obtained by experiment. The parameters needed in the model were determined by fitting the actual tensile-compressive curve of the material. Finally, strain- hardening model was compared with elastic-perfectly plastic model.

압축하중을 받는 박판 4각튜브의 소성좌굴 연구 (Study on the Plastic Buckling of Thin Rectangular Tubes under Compression)

  • 김천욱;한병기;김종민
    • 대한기계학회:학술대회논문집
    • /
    • 대한기계학회 2000년도 춘계학술대회논문집A
    • /
    • pp.357-362
    • /
    • 2000
  • In the present paper the plastic buckling of thin-walled rectangular tube is analyzed. The stress-strain relations of the plates of the tube are idealized into nonlinear material of Ramberg and Osgood. Computing elastic moduli of the nonlinear material a precise plastic buckling stress has determined. The plastic buckling stress of the wider plate of the tube is considered as the crippling strength of the tube. The present theory is in good agreement with the experiments in various thickness-width ratios and materials.

  • PDF

탄소성이론을 이용한 복합지반의 대표 강도정수 예측 (Determination of Composite Strength Parameter Using Elasto-Plastic Theory)

  • 이주형;김영욱;박용원
    • 한국지반공학회:학술대회논문집
    • /
    • 한국지반공학회 2002년도 봄 학술발표회 논문집
    • /
    • pp.93-100
    • /
    • 2002
  • Vertical reinforcement of soft soils using the deep mixing method has received increasing applications. In this study, the theory of elasticity and plasticity including the upper bound theorem of limit analysis were used to derive the equations for obtaining composite elastic properties and shear strength parameters. The developed equations were validated using the finite element computer program SAGE CRISP. The analysis involved 4 different cases-two different type of soil and replacement ratios. Tile results of the analysis show that the proposed equations could determine the properties of composite material for practical applications.

  • PDF

톱니형상면의 압축에 의한 성장거동 시뮬레이션 (Simulation of Growth Behavior of Sawtoothed Interface by the compression)

  • 정태훈
    • 한국공작기계학회:학술대회논문집
    • /
    • 한국공작기계학회 2002년도 추계학술대회 논문집
    • /
    • pp.90-94
    • /
    • 2002
  • In this paper, Compression in the case where dissimilar blocks are twinned variously are carried out in the condition of lubricated interface. The degree of growth is experimentally investigated. Moreover, numerical simulations are carried out by the elastic-plastic FEM for the case of the dissimilar blocks with the initial sawtooth angle of 60。. The dissimilar blocks are twinned, larger difference between material properties leads smaller growth, and the degreased interface leads smaller growth than that in the lubricated one. Furthermore, by the simulation of compression where dissimilar blocks are twinned, it is confirmed that the tendency of the general deformation pattern is very similar to the experiment.

  • PDF

강교의 초기응력을 고려한 내하력 해석 (Analysis on the Load Carrying Capacity of Steel Bridges Considering Initial Stress)

  • 장경호;강재훈;장갑철
    • 한국공간구조학회논문집
    • /
    • 제4권4호
    • /
    • pp.129-136
    • /
    • 2004
  • Almost the steel bridges are manufactured and constructed by using weld process. The welding is necessary for connecting the flange, web and stiffener of steel bridges. However, residual stress and welding deformation producted by welding is a causes of decreasing the load carrying capacity of steel bridges. therefore, it is need to consider the initial stresses by welding when design the steel bridge. However, the influence of initial stress producted by welding on load carrying capacity of steel bridges is not elucidated. In this paper, the initial stress state on the flange, web and stiffener of steel bridges are clarified by carrying out 3-dimensional non-steady heat conduction analysis and 3-dimensional thermal elastic-plastic analysis. The influence of initial stress by welding on load carrying capacity of steel bridges is clarified by carrying out 3-dimensional elastic-plastic finite element analysis using finite deformation theory.

  • PDF

Inelastic general instability of ring-stiffened circular cylinders and cones under uniform external pressure

  • Ross, C.T.F.
    • Structural Engineering and Mechanics
    • /
    • 제5권2호
    • /
    • pp.193-207
    • /
    • 1997
  • Experimental tests are described on three ring stiffened machined circular cylinders and three ring stiffened machined circular cones, which were tested to destruction under uniform external pressure. All six vessels failed by inelastic general instability. The experiments showed that the vessels initially deformed plastically at mid-bay in the circumferential direction, and this caused the circumferential tangent modulus to become much less than the elastic Young's modulus, causing the vessels to fail through plastic general instability at pressures much less than that predicted by elastic theory. Based on a thinness ratio, two semi-empirical design charts are provided, which are intended to be used for design purposes in conjunction with the finite element method and a plastic reduction factor.

고속철도에서의 소성침하를 고려한 강화노반 설계기법 개발 (Development of Design Method for Reinforced Roadbed Considering Plastic Settlement for High-speed Railway)

  • 최찬용;최원일;한상재;정재현
    • 한국지반공학회논문집
    • /
    • 제29권9호
    • /
    • pp.55-69
    • /
    • 2013
  • 본 설계법은 기존 탄성이론에 근거한 강화노반 설계방법의 대안으로 노반의 소성침하와 열차 반복하중에 따른 응력-변형 특성을 고려한 노반 설계 방법이다. 특징은 설계자가 요구하는 허용설계기준에 따라 교통하중과 열차 년간 통과톤수에 따라 노반의 탄성변위 뿐만 아니라 소성침하량을 평가할 수 있다. 본 설계법을 이용하여 허용 탄성 및 소성 침하량, 열차 속도 및 총통과톤수등의 설계조건을 고려하여 호남고속철도 표준노반단면에 적용하였다. 그 결과 노반의 회복탄성계수 모델인자($A_E$), 일축압축강도, 흙 재료 종류 등의 요구수준 등을 평가할 수 있다.

변형률 독립 강소성 구성 방정식에서의 이중 후방 응력 경화 모델 (Two Back Stress Hardening Models in Rate Independent Rigid Plasticity)

  • 윤수진
    • 소성∙가공
    • /
    • 제14권4호
    • /
    • pp.327-337
    • /
    • 2005
  • In the present work, the two back stress kinematic hardening models are proposed by combining Armstrong-Frederick, Phillips and Ziegler's hardening rules. Simple combination of hardening rules using simple rule of mixtures results in various evolutions of the kinematic hardening parameter. Using the combined hardening models the ultimate back stress fur the present models is also derived. The stress rate is co-rotated with respect to the spin of substructure due to the assumption of kinematic hardening rule in finite deformation regime. The work piece under consideration is assumed to consist of the elastic and the rigid plastic deformation zone. Then, the J2 deformation theory is facilitated to characterize the plastic deformation behavior under various loading conditions. The plastic deformation localization behaviors strongly depend on the constitutive description namely back stress evolution and its hardening parameters. Then, the analysis for Swift's effects under the fixed boundaries in axial directions is carried out using simple shear deformation.

평면판의 탄소성 좌굴 특성 해석 (Analysis of Elasto-Plastic Buckling Characteristics of Plates)

  • 김문겸;김소운;황학주
    • 한국전산구조공학회:학술대회논문집
    • /
    • 한국전산구조공학회 1990년도 가을 학술발표회 논문집
    • /
    • pp.16-21
    • /
    • 1990
  • Recently, the finite element method has been sucessfully extended to treat the rather couplet phenomena such as nonlinear buckling problems which are of considerable practical interest. In this study, a finite element program to evaluate the elasto-plastic buckling stress is developed. The Stowell's deformation theory for the plastic buckling of flat plates, which is in good agreement with experimental results, is used to evaluate bending stiffness matrix. A bifurcation analysis is performed to compute the elasto-plastic buckling stress. The subspace iteration method is employed to find the eigenvalues. The results are compared with corresponding enact solutions to the governing equations presented by Stowell and also with experimental data due to Pride. The developed program Is applied to obtain elastic and elasto-plastic buckling stresses for various loafing cases. The effect of different plate aspect ratio is also investigated.

  • PDF

탄성 변형 영역을 고려한 비정상 평면 변형 이상 공정 이론 (Nonsteady Plane-strain ideal forming with elastic dead zone)

  • 이원오;정관수
    • 한국소성가공학회:학술대회논문집
    • /
    • 한국소성가공학회 2004년도 춘계학술대회 논문집
    • /
    • pp.190-193
    • /
    • 2004
  • Ever since the ideal forming theory has been developed fur process design purposes, application has been limited to sheet forming and, for bulk forming, to two-dimensional steady flow. Here, application for the non-steady case was performed under the plane-strain condition based on the theory previously developed. In the ideal flow, material elements deform following the minimum plastic work path (or mostly proportional true strain path) so that the ideal plane-strain flow can be effectively described using the two-dimensional orthogonal convective coordinate system. Besides kinematics, for a prescribed final part shape, schemes to optimize a preform shape out of a class of initial configurations and also to define the evolution of shapes and boundary tractions were developed. Discussions include the two problematic issues on internal tractions and the non-monotonous straining. For demonstration purposes, numerical calculations were made for a bulk part under forging.

  • PDF