• Title/Summary/Keyword: 임계하중

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Critical Loads of Tapered Cantilever Columns with a Tip Mass (자유단 집중질량을 갖는 변단면 캔틸레버 기둥의 임계하중)

  • Jeong, Jin Seob;Lee, Byoung Koo;Kim, Gwon Sik;Kim, Jong Ung
    • Journal of Korean Society of Steel Construction
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    • v.17 no.6
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    • pp.699-705
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    • 2005
  • This paper investigates critical loads of tapered cantilever columns with a tip mass, subjected to a follower force. The linearly tapered solid rectangular cross-sections are adopted as the column taper. The differential equation governing free vibrations of such columns, also called Beck's columns, is derived using the Bernoulli-Euler beam theory. Both divergence and flutter critical loads are calculated from the load-frequency curves that are obtained by solving the differential equation. The critical loads are presented as functions of various non-dimensional system parameters, namely, the taper type, the subtangential parameter, and the mass ratio.

Critical Loads of Tapered Beck's Columns with Clamped and Spring Supports (일단고정 타단스프링으로 지지된 변단면 Beck 기둥의 임계하중)

  • Kim Suk-Ki;Park Kwang-Kyou;Lee Byoung-Koo
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.19 no.1
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    • pp.85-92
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    • 2006
  • This paper investigates critical loads of the tapered Beck's columns with clamped and spring supports, subjected to a subtangential follower force. The linearly tapered columns with the solid rectangular cross-section is adopted as the column taper. The differential equation governing free vibrations of such Beck's columns is derived using the Bemoulli-Euler beam theory. Both divergence and flutter critical loads are calculated from the load-frequency curves which are obtained by solving the differential equation. The critical loads are presented as functions of various non-dimensional system parameters: the taper type, the subtangential parameter and the spring stiffness.

A study on critical load due to external force influencing on flight characteristics of a small slender body rocket. (가늘고 긴 소형로켓의 비행특성에 영향을 주는 외력에 기인한 임계하중에 관한 연구)

  • Go, Tae-Sig;Na, Seon-Hwa
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.393-397
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    • 2007
  • The aim of this study is to investigate critical load, which can influence on flight path of a small slender body rocket, due to external forces such as thrust, drag and weight. The critical load was firstly obtained from Euler column equation, and compared with analysis results using Finite Element Method to evaluate the theoretical critical load.

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Critical Loads and Post-Buckling Behaviour of Simply Supported Tapered Columns (단순지지(單純支持) 변단면(變斷面) 기둥의 임계하중(臨界荷重) 및 후좌굴(後挫屈) 거동(擧動))

  • Lee, Byoung Koo;Oh, Sang Jin;Mo, Jeong Man
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.11 no.4
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    • pp.17-26
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    • 1991
  • Numerical methods are developed to obtain the critical loads and to analyze the post-buckling behaviour of the linearly varying tapered columns. The non-dimensional differential equations governing the elastica of post buckled column are derived by third order and solved numerically using the Runge-Kutta method and Regula-Falsi method. Three kinds of cross-sectional shape with simply supported end constraint are applied in unmerical examples. As the numerical results, the equlibrium paths. the typical elastica of post buckled columns and the critical load vs. section ratio curves are presented in figures. Also, the effects of cross-sectional shape factor on critical loads and postbuckling behaviour are presented in tables.

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Elastic Critical Loads of Tapered Compression Members with Simply Supported Ends (단순지지 변단면 압축재의 임계하중)

  • Song, Chang-Young
    • Journal of Korean Association for Spatial Structures
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    • v.7 no.5
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    • pp.83-87
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    • 2007
  • Elastic critical loads of sinusoidally tapered bars with simply supported ends are determined by finite element method. The parameters considered in the analysis are taper parameter (=a) and section property parameter (=m). The analysis result for the special case of porismatic bar (a=0) shows good agreement with the existing value. The changes of the critical load coefficients are expressed by an algebraic equation. The coefficients appearing in the equations are determined by regression technique. The critical loads coefficients estimated by the proposed equations reveal little errors when they are compared with those determined by finite element method.

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Microhardness measurement for a few micron thick TiN thin films (수미크론 두께를 갖는 TiN코팅층의 미소경도 측정법)

  • Jo, Yeong-Rae;Fromm, E.
    • Korean Journal of Materials Research
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    • v.5 no.3
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    • pp.310-315
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    • 1995
  • 기계적으로 연마한 고속도강과 구리 두 종류의 서로 다른 기판상에 dc 마그네트론 스파터법으로 TiN 박막을 성막시켜 코팅층의 비커스 미소경도를 측정하였다. 압입체의 침투깊이와 시험하중과의 관계를 log-log 좌표상에 도시함으로써 기판의 영햐응ㄹ 받지 않고 코팅층만의 경도를 측정할수 있는 최대하중인 임계하중(critical load)을 구할수 있었다. 임계하중을 가했을 때 압입체의 침투깊이와 코팅층 두께간의 비율은 코팅층의 두께에 무관하였고 기판의 경도에 크게 의존하였다.

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A Safety Analysis on the Structural Rupture of Cylindrical Shell by Finite Difference Method (차분법에 의한 실린더형 쉘구조의 안정성 연구)

  • Kim, Chi-Kyung;Park, Hwa-Yong
    • Journal of the Korea Safety Management & Science
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    • v.13 no.3
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    • pp.37-43
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    • 2011
  • 본 연구에서는 실린더 형 쉘 구조물의 구조적 안정성에 대하여 해석 하였다. 임계하중은 하중을 점차적으로 증가 하여 구조물이 파괴가 발생 할 때의 상태에서 가장 작은 하중을 의미한다. 셀 구조의 안정성을 임계하중의 크기로 기초를 두고 해석 하였다. 실린더 형 쉘의 차분해석은 일차적 원통형 판구조와 같으므로 최근에 많은 연구의 대상이 되어왔다. 차분법은 복잡한 구조물에서도 물론, 다양한 경계조건을 포함하는 문제에 이르기까지 효과적인 수치방법이다. 본 연구에서는 기본 쉘의 지배방정식을 유도하고 차분화 하여 직접적으로 접근하였다. 등분포 하중의 내압을 받고 있는 갇힌 실린더 형 쉘의 처짐 및 응력을 해석 하였다. 수치해석 결과를 해석해와 비교 검토하였으며 안정성에 대하여 임계 하중강도의 범위를 산출하였다.

Buckling Analysis of Pipelines with Reduced Cross Section (단면감소를 고려한 파이프의 좌굴에 관한 연구)

  • Choi, Dong-Ho;Ko, Young-Chan;Gwon, Sun-Gil;Lee, Joung-Sun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.33 no.3
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    • pp.865-873
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    • 2013
  • This paper proposes a theoretical solution of elastic critical buckling load of infinitely long pipelines with non-uniform thickness under external pressure. The non-uniform cross section of pipelines can be considered as corroded or stiffened pipelines so that this paper can be a fundamental research of pipelines that are essential technology for offshore industries. The theoretical solution of pipelines with non-uniform thickness is derived with an assumption that a cylindrical shell under external pressure can be considered as a simple ring. The eigenfunctions are derived to obtain the critical buckling load. The reduced thickness and the reduced range are considered as variables in parametric analysis. The finite element analysis is performed to verify the theoretical solutions and the results of the analytic method and the finite element method are in good agreement.

Extensional Buckling Analysis of Asymmetric Curved Beams Using DQM (미분구적법(DQM)을 사용한 비대칭 곡선 보의 신장 좌굴해석)

  • Kang, Ki-Jun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.22 no.4
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    • pp.594-600
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    • 2021
  • Curved beam structures are generally used as components in structures such as railroad bridges and vehicles. The stability analysis of curved beams has been studied by a large number of researchers. Due to the complexities of structural components, it is difficult to obtain an analytical solution for any boundary conditions. In order to overcome these difficulties, the differential quadrature method (DQM) has been applied for a large number of cases. In this study, DQM was used to solve the complicated partial differential equations for buckling analysis of curved beams. The governing differential equation was deduced and solved for beams subjected to uniformly distributed radial loads. Critical loads were calculated with various opening angles, boundary conditions, and parameters. The results of the DQM were compared with exact solutions for available cases, and the DQM gave outstanding accuracy even when only a small number of grid points was used. Critical loads were also calculated for the in-plane inextensional buckling of the asymmetric curved beams, and two theories were compared. The study of a beam with extensibility of the arch axis shows that the effects on the critical loads are significant.

Buckling Behavior of Transversely Isotropic Composite Shells Subjected to Axial Compression (축방향 압축 하중을 받는 횡등방성 복합재료 쉘의 좌굴거동)

  • 김성도;정진환
    • Computational Structural Engineering
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    • v.11 no.3
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    • pp.229-239
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    • 1998
  • 복합재료는 강도-무게비가 다른 재료들에 비해 훨씬 크기 때문에 부재의 좌굴문제가 대단히 중요하게 취급되며, 본 논문에서는 축방향 압축력을 받는 복합재료로 된 쉘 부재의 좌굴해석이 수행된다. 이 재료는 일반적으로 이방성 재료 특성을 나타내 보이나, 섬유들이 한 방향으로만 배치되어 있는 경우 섬유방향에 연직한 평면에서의 강도나 탄성계수들은 모두 일정한 횡 등방성 재료성질을 가진 것으로 간주할 수 있다. 9 절점 degenerate 쉘 유한요소를 사용한 선형안정해석, LUSAS 범용 프로그램을 이용한 구조해석, 그리고 고전적 쉘 좌굴방정식에 의한 해석들을 수행하였으며, 그 결과들을 서로 비교, 분석하였다. 고려된 등방성 재료나 횡 등방성 재료의 경우 모두, degenerate 유한요소해석으로 계산한 임계하중들은 고전적 이론해에 의한 결과들 보다 낮았으며, LUSAS 결과들과는 거의 같았다. 이는 degenerate 유한요소에 의한 선형안정해석 결과들이 안전측에 듬을 의미하며, 복합재료로 된 쉘 구조물의 좌굴해석에 degenerate 유한요소를 효율적으로 적용할 수 있음을 의미한다.

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