• Title/Summary/Keyword: 임계하중

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Experimental Study on the Stability of the Cantilever Beam with Tip Mass Subjected to a Follower Force (종동력을 받는 첨단질량을 갖는 외말보의 안전성에 관한 실험적 연구)

  • 노광춘;박영필
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.10 no.2
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    • pp.183-187
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    • 1986
  • An experimental method to give a tangential follower force to a cantilever beam having a concentrated tip mass by the magnetic force of the electromagnet has been described. The dynamic behaviour of the beam under this nonconservative load has been analysed by experimentally as well as by theoretically. The theoretical and experimental results on the natural frequencies and the critical force of the systems are in good agreement with each other.

A Study on the Stability of Circular Thin Plates by Nonlinear Analysis (비선형 해석에 의한 원형박판의 안정성 연구)

  • Kim, Chi-Kyung
    • Journal of the Korea Safety Management & Science
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    • v.13 no.2
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    • pp.97-102
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    • 2011
  • 본 연구에서는 원형 박판 구조물의 안정성에 대하여 해석 하였다. 임계하중은 하중을 점차적으로 증가하여 구조물이 파괴가 발생하여 안정성을 상실 하는 상태에서 가장 작은 하중을 의미한다. 판구조의 안정성을 임계하중의 크기로 기초를 두고 해석 하였다. 원형 박판구조의 차분해석은 일반 판구조와 같으므로 최근에 많은 연구의 대상이 되어왔다. 차분법은 복잡한 구조물에서도 물론, 다양한 경계조건을 포함하는 문제에 이르기까지 효과적인 수치방법이다. 본 연구에서는 기본 박판구조의 지배방정식을 유도하고 차분화 하여 직접적으로 접근하였다. 원 둘레 의 지점이 힌지 받침으로, 등분포 하중을 받고 있는 박판을 기하학적 비선형 해석으로 수행하여 원형 박판의 처짐 및 응력을 해석 하였다.

Stability Analysis of Beck's Column with a Tip Mass Restrained by a Spring (스프링으로 지지된 자유단에 집중질량을 갖는 Beck 기둥의 안정성 해석)

  • Li, Guangfan;Oh, Sang-Jin;Kim, Gwon-Sik;Lee, Byoung-Koo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.11 s.104
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    • pp.1287-1294
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    • 2005
  • The purpose of this paper is to investigate free vibrations and critical loads of the Beck's columns with a tip spring, which carry a tip mass. The ordinary differential equation governing free vibrations of Beck's column subjected to a follower force is derived based on the Bernoulli-Euler beam theory Both the divergence and flutter critical loads are calculated from the load-frequency corves that are obtained by solving the differential equation numerically. The critical loads are presented in the figures as functions of various non-dimensional system parameters such as the subtangential parameter, mass ratio and spring parameter.

Critical Loads of Eccentrically Loaded Struts with Thin-Walled Open Sections (편심하중을 받는 박벽개단면 압축재의 임계하중)

  • 나영진;이수곤
    • Computational Structural Engineering
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    • v.9 no.4
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    • pp.135-140
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    • 1996
  • Single angle or channel with thin-walled open section can be used as compression member for example as web member in truss. In this case the inevitable eccentricity due to fabrication is commonly neglected in structural design. However eccentricity effect should be considered in the member design, especially in case of compression member. The critical loads of compression members that buckle by twisting or by a combination of bending and twisting are to be determined by solving governing differential equations. In this paper, the investigations are limited to the rolled channels([), equal-leg angles(L), lipped channels(C) and the applied loads are assumed to have some eccentricities.

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Dynamic Stability Analysis of Nonconservative Systems for Variable Parameters using FE Method (유한요소기법을 이용한 비보존력이 작용하는 보-기둥 구조의 다양한 제변수 변화에 따른 동적 안정성 해석)

  • Lee Jun-Seok;Min Byoung-Cheol;Kim Moon-Young
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.17 no.4
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    • pp.351-363
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    • 2004
  • Equation of motion of non conservative system considering mass matrix, elastic stiffness matrix, load correction stiffness matrix by circulatory force's direction change and Winkler and Pasternak foundation stiffness matrix is derived. Also stability analysis due to the divergence and flutter loads is performed. And the influence of internal and external damping coefficient on flutter load is investigated applying the quadratic eigen problem solution. Additionally the influence of non-conservative force's direction parameter, internal and external damping and Winkler and Pasternak foundation on the critical load of Beck's and Leipholz's and Hauger's columns are investigated.

Development of Uneven Excavation Method for Reinforcement of Ground Slope (사면보강을 위한 요철형 암반굴착 공법개발)

  • Kim, Hyun-Gi
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.21 no.10
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    • pp.259-266
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    • 2020
  • In this study, required drill bits and excavation methods were developed for an uneven drilling method that can solve the problem of performance degradation of rock bolts. The developed drill bit's excavation performance was verified using rock with a strength of 100 MPa or more. In addition, for the relative evaluation of the uneven excavation method, experimental specimens were prepared for models with and without irregularities, and tests were performed. As a result of the experiment, the model with unevenness exhibited an average critical draw resistance of 801.6 kN, which is about 1.7 times the value of 468.7 kN for the model without unevenness, thus confirming the effect sufficiently. Therefore, it is expected that the resistance performance will significantly increase despite an increase in the uneven hole diameter of 20 mm. In the future, the results of this study could be used as basic data when performing other studies using numerical analysis models and performance verification through experiments to obtain an optimized rock forming method.

이온교환에 의한 유리의 내마모성 향상

  • 조성재;방건웅;문한규
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1989.11a
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    • pp.69-72
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    • 1989
  • 구형의 압자를 유리평판 위에 올려 놓고 미끄럼 시험을 할 때 하중이 임계치보다 크면 유리평판 표면에 소위 "semi-circular cone-crack(SCCC)"들이 형성된다. 그리고 이 SCCC형성에 필요한 임계하중은 유리의 강도에 의하여 결정된다. 한편 소석회 유리에서 크기가 작은 이온인 $Na^+$를 큰 이온인 $K^+$로 대치시켜주는 경우 시편표면에 잔류압축응력이 생성되어 강도가 크게 증가한다. 따라서 유리의 내마모성도 이온교환을 하면 크게 향상될 것임을 예측할 수 있다. 본 연구의 목적은 이 예측을 실험적으로 확인하는 것이다. 확인하는 것이다.

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Experimental and Finite Element Study of Tribological Characteristics of SU-8 Thin Film (실험 및 유한요소해석에 의한 SU-8 박막의 Tribological 특성 연구)

  • Yang, Woo Yul;Shin, Myounggeun;Kim, Hyung Man;Han, Sangchul;Sung, In-Ha
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.4
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    • pp.467-473
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    • 2013
  • In this study, two-dimensional finite element models were developed and experiments were conducted using an atomic force microscope to investigate the tribological characteristics of an SU-8 layer coated on a patterned wafer for microsystem applications. The results revealed that both the adhesion and the friction forces measured by the atomic force microscope were lower for the SU-8 coated surface than for the bare silicon surface. This is attributed to the hydrophobicity of SU-8. Another important result derived from the finite element analysis was the critical load required to fracture the SU-8 film with respect to the thickness. The critical loads for thicknesses of 200, 400, and 800 nm were approximately 13, 22, and 28 mN, respectively, which corresponded to a Hertzian contact pressure of 1.2-1.8 GPa. These results will aid in the design of a suitable SU-8 thickness for microsystem components that are in contact with one another.

Classification system for figid and semi-rigid connection (강·반강 철골 접합부의 분류체계에 관한 연구)

  • Jang, Mee;Lee, Sang Sup;Mun, Tae Sup
    • Journal of Korean Society of Steel Construction
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    • v.13 no.4
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    • pp.351-361
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    • 2001
  • The connections are classified as rigid, semi+rigid, or pinned. There are two classification systems, EC3 adn Bjorhovede et al., representatively. The EC3 boundary between rigid and semi-rigid connections is in on the whole restrictive in term of the stiffness as well as the moment capacity of connections. The boundary specified by Bjorhovede et al. may not be sufficient to assure the behavior of rigid frames in some cases. In this study, it is proposed the new classification system for steel connection that depends on the reduction factor(R) of critical buckling load for unbraced semi-rigid frame expressed by the stiffness ratio($\rho$) of beam to column and the stiffness ratio(k) of connection to beam. Finally, it is examined by experimental data that new classification criteria provides a practical boundary compared wit hteh existing classifications.

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복합재료 선미익 항공기 날개 하중해석

  • Han, Chang-Hwan;Kim, Eung-Tai;Ahn, Seok-Min;Kim, Jin-Won
    • Aerospace Engineering and Technology
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    • v.1 no.1
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    • pp.8-27
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    • 2002
  • In this study, the load analysis of a composite canard aircraft is performed numerically. Excel visual basic program for PC is used to calculate aerodynamic coefficients, loads and moments etc.. The basic data required for the load analysis such as aircraft configuration and dimension, parts and its weight and coordinate etc. are obtained from Catia modeling, measurement or material density. Aircraft weight, center of gravity, inertia moment, structural design speeds, wing load distribution, forces and moments are evaluated by using these data. V-n diagram is also represented for selecting critical loads applied to the wing and fuselage. The V-n diagram is investigated to decide the flight envelope of canard aircraft for design speed VA, VC, VD and load factor +3.8G, -1.52G at maximum weight of 2,573 lbs and sea level. In the future, the results of the wing and fuselage load analysis is to represented by using selected critical loads.

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