• Title, Summary, Keyword: 임계하중

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Solution to Elasticity Problems of Structural Elements of Composite Materials (복합재료 구조 요소의 탄성문제에 대한 해)

  • Afsar, A.M.;Huq, N.M.L.;Mirza, F.A.;Song, J.I.
    • Composites Research
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    • v.23 no.3
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    • pp.19-30
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    • 2010
  • The present study describes a method for analytical solution to elastic field in structural elements of general symmetric laminated composite materials. The two dimensional plane stress elasticity problems under mixed boundary conditions are reduced to the solution of a single fourth order partial differential equation, expressed in terms of a single unknown function, called displacement potential function. In addition, all the components of stress and displacement are expressed in terms of the same displacement potential function, which makes the method suitable for any boundary conditions. The method is applied to obtain analytical solutions to two particular problems of structural elements consisting of an angle-ply laminate and a cross-ply laminate, respectively. Some numerical results are presented for both the problems with reference to the glass/epoxy composite. The results are highly accurate and reliable as all the boundary conditions including those in the critical regions of supports and loads are satisfied exactly. This verifies the method as a simple and reliable one as well as capable to obtain exact analytical solution to elastic field in structural elements of composite materials under mixed and any other boundary conditions.

Ebaluation of Ultimate Stress of Unbonded Tendon in Prestressed Concrete Members(I)-Considereateon of ACI code and the State-of -the Art- (프리스트레스트 콘크리트 부재에서 비부착 긴장재의 극한응력 평가에 관한 연구(I)-기존연구 및 ACI 규준식의 고찰-)

  • 임재형;문정호;음성우;이리형
    • Magazine of the Korea Concrete Institute
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    • v.9 no.4
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    • pp.167-176
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    • 1997
  • The current study is a part of series of research about the evaluation method of the unbonded tendon stress in prestressed concrete member at flexural failure. As the first part. previous design equations were examined in oder to find whether any modifications may be needed. A total of 167 experimental results tested for more than 40 years were gathered to build D/B and then previous proposed and codified equations were evaluated with the experimental relsults. The ACI Code equation and Naaman, Harajli, and Chakrabarti's equations were chosen for the purpose of examination. Then, the followings were obtained from the analytical examination. It is desirable to compute the tendon stress with the member analysis method instead of the sectional analysis method which has been used in the current ACI Code. The tendon stress may also be influenced significantly by the amount of ordinary bonded reinforcements and the loading types. And the current ACI Code overestimated the effect of span/depth ratio. As results, it was concluded that the revision of the ACi Code equation should be considered positively. Then, a new design has to be proposed with the reasonable and comprehensive investigation about influential factors on the tendon stress variation.

Development of Computational Evaluation Method for Fatigue Crack Growth Rate based on Viscoplastic-Damage Model (점소성-손상모델 기반 피로균열 진전속도 전산 평가법 개발)

  • Kim, Seul-Kee;Kim, Jeong-Hyeon;Lee, Chi-Seung;Kim, Myung-Hyun;Lee, Jae-Myung
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.28 no.1
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    • pp.1-8
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    • 2015
  • In this paper, computational evaluation method for fatigue crack growth rate(FCGR) based on material viscoplastic-damage model is proposed. Viscoplastic-damage model expressing material constitutive behavior of 7% nickel steel is introduced and is implemented into commercial finite element analysis(FEA) code, ABAQUS, as a user defined material subroutine(UMAT) for application in the FEA environments. Verification of developed UMAT and material parameters of material model are carried out by uniaxial tensile test simulations of 7% nickel steel. Moreover, jump-in-cycles procedure and rearrangement of critical damage are employed and also implemented to the ABAQUS UMAT for fatigue damage analysis. Typical FCGR test results such as relationship between crack length and number of cycles and relationship between da/dN and ${\Delta}K$ could be obtained from FCGR test simulation using developed UMAT and these results are compared with experimental results in order to verify of proposed computational method.

An Analysis of Running Stability of 1/5 Small Scaled Bogie on Small-Scaled Derailment Simulator (소형탈선시뮬레이터상에서의 1/5 축소대차 주행안정성 해석)

  • Eom, Beom-Gyu;Kang, Bu-Byoung;Lee, Hi-Sung;Song, Moon-Shuk
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.11
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    • pp.1413-1420
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    • 2012
  • To predict the dynamics behavior, running stability, etc. of a railway vehicle and to understand its physical characteristics, analytical methods are used for the testing and manufacturing of a scale model along with numerical simulations in developed countries (England, France, Japan, etc.). The test of the dynamics characteristics of full-scale models is problematic in that it is expensive and time-consuming because an entire large-scale test plant needs to be constructed, difficulties are involved in the test configuration, etc. To overcome these problems, an analytical study involving dynamics tests and computer simulations using a scaled bogie model that applies the laws of similarity was carried out. In this study, we performed stability analysis on a 1/5 small scaled bogie for parameters such as the running speed and carbody weight by using an analysis model. Furthermore, we verified the reliability by using a small-scaled derailment simulator and examined the dynamic characteristic of the 1/5 small scaled bogie.