• Title/Summary/Keyword: 임계하중

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Parametric Study on Dynamic Stability Behaviors of Beck's Column considering Shear Deformation and Damping Effects (전단변형 및 감쇠효과를 고려한 비보존력을 받는 외팔기둥의 동적 안정성거동에 대한 매개변수연구)

  • Lee, Jun-Seok;Kim, Nam-Il;Kim, Moon-Young
    • Journal of the Earthquake Engineering Society of Korea
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    • v.9 no.6 s.46
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    • pp.1-12
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    • 2005
  • For a shear-deformable beam-column element subjected io non-conservative forces, equations of motion and a finite element formulation are presented applying extended Hamilton's principle. The influence of non-conservative force's direction parameter, internal and external damping forces, and shear deformation and rotary inertia effects on divergence and flutter loads of Beck's columns are intensively investigated based on element stiffness, damping and mass matrixes derived for the non-conservative system.

Evaluation on Tensile Properties and Fracture Toughness of Glass Fiber/Aluminum Hybrid Laminates (유리섬유/알루미늄 혼성 적층판의 인장특성과 파괴인성 평가)

  • Woo Sung-Choong;Choi Nak-Sam
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.6 s.237
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    • pp.876-888
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    • 2005
  • Tensile properties and fracture toughness of monolithic aluminum, fiber reinforced plastics and glass fiber/aluminum hybrid laminates under tensile loads have been investigated using plain coupon and single-edge-notched specimens. Elastic modulus and ultimate tensile strength of GFMLs showed different characteristic behaviors according to the Al kind, fiber orientation and composition ratio. Fracture, toughness of A-GFML-UD which was determined by the evaluation of $K_{IC}$ and $G_{IC}$ based on critical load was similar to that of GFRP-UD and was much higher than monolithic Al. Therefore, A-GFML-UD presented superior fracture toughness as well as prominent damage tolerance in comparison to its constituent Al. By separating Al sheet from GFMLs after the test, optical microscope observation of fracture zone of GFRP layer in the vicinity of crack tip revealed that crack advance of GFMLs depended on the orientation of fiber layer as well as Al/fiber composition ratio.

In-Plane Buckling Analysis of Curved Beams Using DQM (미분구적법(DQM)을 이용한 곡선보의 내평면 좌굴해석)

  • Kang, Ki-Jun;Kim, Young-Woo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.7
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    • pp.2858-2864
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    • 2012
  • The differential quadrature method (DQM) is applied to computation of the eigenvalues of in-plane buckling of the curved beams. Critical moments and loads are calculated for the beam subjected to equal and opposite bending moments and uniformly distributed radial loads with various end conditions and opening angles. Results are compared with existing exact solutions where available. The DQM gives good accuracy even when only a limited number of grid points is used. More results are given for two sets of boundary conditions not considered by previous investigators for in-plane buckling: clamped-clamped and simply supported-clamped ends.

A Study on the Nonlinear Instability Behavior of Hybrid Structures(II) -Characteristic of Dynamic In-Plane Torsional Buckling under the STEP Load- (Hybrid 구조물의 비선형 불안정 거동에 관한 연구(II) -STEP 하중에서의 동적 면내비틀림 좌굴 특성-)

  • Kim, Seung Deog;Kim, Hyung Seok;Kang, Moon Myung
    • Journal of Korean Society of Steel Construction
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    • v.13 no.5
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    • pp.599-608
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    • 2001
  • Many papers which deal with the dynamic instability of shell-like structures under the STEP load has been published but there have been few papers related to the dynamic instability of hybrid cable domes. And also there are a few researches which treat the essential phenomenon of the dynamic buckling using the phase for investigating occurrence of chaos. In this study the indirect buckling of hybrid cable domes considering geometric nonlinearity are investigated numerically and compared it with the static critical load The dynamic critical loads are determined by the numerical integration of the geometric nonlinear equation of motion and the mechanism of the indirect buckling is examined by using the phase curves.

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Thermo-Mechanical stress analysis for partial or entire crack closure (크랙의 부분 또는 완정닫힘에 관한 열 및 기계적 응력해석)

  • Lee, Kang Yong
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.5 no.3
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    • pp.193-198
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    • 1981
  • Muskhelishvili 의 복소수방법에 의해 일반적 하중 즉 열 및 기계적 하중을 받는 무한 탄성체내에 공동을 가정하고 그 주위의 응력 및 변위를 유도하였다. 선형트랙(line rack)이 부분적으로 또는 완정히 닫힐 임계하중조건과 그때의 응력세기 계수 (stress intensity factor)를 McClintork와 Walsh 의 크랙닫힘에 관한 결정에 기초를 두고 해석학적으로 유도하였다.

Behavior of Underground Flexible Pipes Subject to Vehicle Load (차량하중을 받는 지중연성관의 거동특성)

  • 이대수;상현규;김경열
    • Journal of the Korean Geotechnical Society
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    • v.18 no.4
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    • pp.65-73
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    • 2002
  • Underground flexible pipes for electric cables are subject to external loads and surrounding soil pressure. Particularly, strain of flexible pipes is of great concern in terms of safety and maintenance for electric cables. In this paper, stress and strain of flexible pipes with various depth are compared using traditional formula, FEM analysis and model soil box test. The results show that theoretical values are more conservative in strain in comparison with model soil box test and FEM analysis. Considering the strain criteria - maximum 3.5%, flexible pipes can be buried at the depth of 40cm without additional soil improvement. From the result of this study, deformation formula compatible with the field condition was proposed.

Evaluation of Adhesive Properties in Polymeric Thin Film by Ultrasonic Atomic Force Microscopy (UAFM을 이용한 폴리머 박막의 접합 특성 평가)

  • Kwak, Dong-Ryul;Park, Tae-Sung;Park, Ik-Keun;Miyasaka, Chiaki
    • Journal of the Korean Society for Nondestructive Testing
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    • v.32 no.2
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    • pp.142-148
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    • 2012
  • This study presents the assessment results of adhesive properties on the interface between a silicon wafer and nano-scale polymer thin film pattern through UAFM images by using the contact resonance frequency of the cantilever. For the experiment, we varied surface treatment processes for the silicon wafer and fabricated a 300nm polymer thin film pattern through lithography. Images from the optical microscope were used to compare the produced test specimens for adhesive condition and the critical load value from the nano scratch test was used to verify the adhesive condition of the nano pattern. Each test specimen resulted in a $1{\mu}m{\times}1{\mu}m$ surface image and subsurface adhesive image. Adhesive condition was evaluated by image contrast differences on the interface according to the changing amplitudes and phases of contact resonance frequency.

Analysis for Torsion of Hollow Beam by Least Squares and Boundary Elements Method (최소자승법 및 경계요소에 의한 중공단면 보의 비틀림 해석)

  • Kim, Chi-Kyung;Bae, Joon-Tai
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.25 no.2
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    • pp.175-182
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    • 2012
  • In this paper we are concerned with the performance of structural stability of torsion in square cross section of a beam with holes. The critical load is defined as the smallest load at which the equilibrium of the structure fails to be stable as the load is slowly increased from zero. The beams subjected to torsion are frequently encountered in general structures and these forces influence to the stability of structure. The boundary element method is found to be very efficient and accurate for the analysis of torsion problems including complex boundary conditions with respect to its simplicity and generality. In this paper, it is required to derive the boundary element formulation for torsion problem and integrate directly on the discrete boundary. To investigate the validity of the developed computer program, three distinctly solid cross-sections which are elliptical, rectangular and triangular one are analyzed, and comparisons are made with analytical approaches where these can also be used.

Determination of Eigenvalues of Sinusoidally Tapered Members by Finite Element Method (유한요소법을 이용한 정현상으로 taper진 부재의 고유치 산정)

  • Lee, Soo-Gon;Kim, Soon-Chul
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.13 no.1
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    • pp.87-95
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    • 2000
  • The two eigenvalues (elastic critical load and natural frequency of lateral vibration) of sinusoidally tapered bats with simply supported ends were determined by the finite element method. For the convenience of structural engineers who are engaged in the structural design or vibration analysis of tapered beam-columns, eigenvalue coefficients were expressed by simple algebraic equations. The validity of each algebraic equation was confirmed by the value of unity for each correlation coefficient. The influence of axial thrust on the lateral vibration frequency was also investigated. For this purpose, the axial thrust was increased successively and the corresponding frequency was calculated. The approximate linear relationship between the axial thrust and the square of the frequency was confirmed lot each of the tapered members.

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A Finite Element Analysis of Circular Plate Resting on Elasto-Plastic Soil Medium (탄소성(彈塑性) 지반(地盤)위에 놓인 원형평판(圓形平板)의 유한요소(有限要素) 해석(解析))

  • Kim, Sung Deuk;Chang, Sung Pil
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.7 no.4
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    • pp.91-102
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    • 1987
  • In this study, the finite element method using 8-node isoparametric element is developed theoretically and simulated to see the deformation of soil and plate, when the circular plate resting on Boussinesq's soil type is loaded axisymmetrically. The results of numerical analysis using the Mohr-Coulomb yield criterion, and experimental analysis are approximative, assuming that soil is elasto-plastic medium. The paper shows that the plastic zone of soil medium is displayed at the near the edge of plate at the first place; when the plastic zone of soil medium is linked around central axis, the external load is termed by critical load, and then the contact pressure changes abruptly, in this case it is approved to be the risk of shear failure.

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