• Title, Summary, Keyword: 임계하중

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Numerical Analyses of Critical Buckling Loads and Modes of Anisotropic Laminated Composite Plates (비등방성 복합 적층판의 임계좌굴하중 및 모드의 수치 해석)

  • Lee, Sang Youl;Yhim, Sung Soon;Chang, Suk Yoon
    • Journal of Korean Society of Steel Construction
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    • v.10 no.3
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    • pp.451-461
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    • 1998
  • The solution of anisotropic plate via the classical methods is limited to relatively load and boundary conditions. If these conditions are more complex, the analysis becomes increasingly tedious and even impossible. For many plate problems of considerable practical interest, analytic solutions to the governing differential equations cannot be found. Among the numerical techniques presently available, the finite difference method and the finite element method are powerful numerical methods. The objective of this paper is to compare with each numerical methods for the buckling load and modes of anisotropic composite laminated plates considering shear deformation. In applying numerical methods to solve differential equations of anisotropic plates, this study uses the finite difference method and the finite element method. In determining the eigenvalue by Finite Difference Method, this paper represent good convergence compared with Finite Element Method. Several numerical examples and buckling modes show the effectiveness of various numerical methods and they will give a guides in deciding minimum buckling load and various mode shapes.

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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.

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.

The Evaluation of Mechanical Properties for Alumina Ceramics (알루미나 세라믹스의 기계적 특성 평가)

  • 임헌진;조덕호;김무경;한상미;이와사미키오
    • Journal of the Korean Ceramic Society
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    • v.33 no.3
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    • pp.339-347
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    • 1996
  • Mechanical properties(flexural strength hardness fracture toughness) of alumina ceramics were evaluated. Alumina products of four companies were selected and three of those were made in Korea and one of those was made in Japan. The large differences according to manufacturing companies had resulted from flexural strength and weibull modulus which had a wide ranges of 300 to 400 MPa and 5 to 15 respectively. Critical indenstation load which could be neglected the effect of elastic recovery was about 9.8N and Vickers' hardness were about 15 GPa. Fracture toughnesses were evaluated by IF and ISB method. It was more preferable to the average at one indentation load that fracture toughness were obtained from the slope of the relationship between indentation load and crack length in IF method and between indentation load and fracture load in ISB method and fracture toughness was about 4 MPa·m1/2.

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Presumption on Wear life of TiN Film (TiN 경질박막의 마모 수명 예측에 관한 연구)

  • 정기훈;이영제
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.41-46
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    • 1997
  • TiN 코팅은 마모에 대한 저항성 및 고체 윤활 효과가 매우 우수하여 내마모성 및 저마찰이 요구되는 절삭공구나 피스톤 베어링 및 각종 축계의 코팅막으로 사용이 증가되고 있다. 일반적으로 재료의 경도와 인성은 서로 상반 관계를 갖고 있어 공학적으로 경도와 인성을 모두 요구하는 표면을 얻기 위해 연질 모재 위의 세라믹 코팅은 그 요구를 만족시킬 수 있는 가장 각광받는 표면처리 방법중의 하나이다. 그러나, TiN과 같은 경질 박막의 공학적 적용시 가장 요구되는 마모수명은 모재의 조도나 경도, 증착 방법, 접촉 상태, 코팅막의 두께 및 마모의 발생 기구 등에 따라 마찰 및 마모 메커니즘의 현저한 차이를 나타내기 때문에 예측이 거의 불가능한 실정이고, 아직까지 이러한 마모수명 비교 평가방법에 대한 기준 설정 및 정량적 정립이 이루어지지 않고 있다. 본 연구에서는 모재의 경도, 조도, 코팅 두께가 다른 TiN 경질 박막에 압입시험과 스크래치시험시 발생되는 균열 발생 메커니즘과 미끄럼 시험시 발생되는 마모 메커니즘의 연계성을 밝히고 압입 및 스크래치 시험시 코팅막이 손상되는 임계하중과 미끄럼 시험시 접촉하중 변화에 따른 마모수명의 정량적 연관성을 찾아보고자 한다.

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Estimation of fully plastic crack tip stresses of unequally notched specimen under bending and tension (굽힘 모멘트와 인장 하중이 작용하는 비대칭 노치 시편의 완전 소성 균열 선단 응력의 예측)

  • Oh, Chang-Kyun;Kim, Yun-Jae;Park, Jin-Moo
    • Proceedings of the KSME Conference
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    • pp.37-42
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    • 2004
  • This paper presents a simple method to estimate fully plastic crack tip stresses of unequally notched specimen based on the equilibrium condition of the least upper bounds for plane strain deformation fields. The method is applied to unequally notched specimens under bending and tension. For various notch angle the limit loads and crack tip stresses are estimated from the present method and compared with results from finite element limit analyses.

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Stability Analysis of Beck's Column (Beck 기둥의 안정성 해석)

  • Lee, Byoung-Koo;Lee, Tae-Eun;Kang, Hee-Jong;Kim, Gwon-Sik
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.903-906
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    • 2005
  • The purpose of this paper is to investigate free vibrations and critical loads of the uniform Beck's columns with a tip spring, carrying a tip mass. The ordinary differential equation governing free vibrations of such 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 curves 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 mass moment of inertia and spring parameter.

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The Improved Load/Displacement Incremental Method (개선된 하중 및 변위 증분법)

  • Kim, Moon-Young;Chu, Seok-Beom;Chang, Sung-Pil
    • Journal of Korean Society of Steel Construction
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    • v.8 no.4
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    • pp.31-42
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    • 1996
  • 본 연구에서는 박벽 구조물의 기하학적 비선형 해석을 수행하기 위하여 개선된 하중 및 변위 증분의 조합법이 제시되었다. 제안된 알고리즘은 기존의 하중 및 변 변위 증분의 조합법 이 고정된 증분량을 갖는 점을 개선하여, 수렴정도에 따라 증분량을 변화시킴으로써, 여러개의 임계점을 갖는 비선형 거동을 보다 효율적으로 추적하도록 하였다. 또한 하중 및 변위 증분법을 전환점을 첫 단계의 기울기에 비례한 값으로 대체함으로써 사용자의 편리를 도모하였다. 트러스, 공간 뼈대, 아치, 쉘 구조물 등의 기하학적 비선형 해석 예제를 통하여, 본 연구에서 제시한 개선된 하중 및 변위 증분의 조합법의 적용성을 입증하였다.

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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
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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.

Load Carrying Capacity of Geogrid-Encased Stone Columns in Soft Ground (연약지반에 시공되는 지오그리드 감쌈 스톤컬럼의 하중지지 특성)

  • Yoo, Chung-Sik;Kim, Sun-Bin
    • Journal of the Korean Geosynthetics Society
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    • v.7 no.4
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    • pp.25-36
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    • 2008
  • This paper presents the results of numerical investigation on support mechanism of geogrid-encased stone columns for use in soft ground. A number of cases were analyzed using a axial-and 3D stress-pore pressure coupled model that can effectively model construction sequence and drainage as well as reinforcing effects of geogrid-encased stone columns. The results indicated that the geogrid encasement tends to significantly improve the load carrying of a stone column. Also revealed was that such a confinement effect depends on encasement length and stiffness of geogrid. It is also shown that there exist critical encasement length and stiffness of geogrid for a given condition.

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