• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 추계학술대회논문집
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• pp.28-31
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• 1997

Buckling analysis of thin compressed beam has been carried out. Pre-buckling and post-buckling are simulated by finite element method incorporating with the incremental nonlinear theory and the Newton-Raphson solution technique. In order to find the bifurcation point, the determinent of the stiffness matrix is calculated at every iteration procedure. For post-buckling analysis, a small perturbed initial guess is given along the eigenvector direction at the bifurcation point. Nonlinear elastic buckling and elastic-plastic buckling of cantilever beam are analyzed. The buckling load and buckled shape of the two models are compared.

• Steel and Composite Structures
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• 제22권1호
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• pp.91-112
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• 2016

In this paper, post-buckling behavior of sandwich plates with functionally graded (FG) face sheets under uniform temperature rise loading is examined based on both sinusoidal shear deformation theory and stress function. It is supposed that the sandwich plate is in contact with an elastic foundation during deformation, which acts in both compression and tension. Thermo-elastic non-homogeneous properties of FG layers change smoothly by the variation of power law within the thickness, and temperature dependency of material constituents is considered in the formulation. In the present development, Von Karman nonlinearity and initial geometrical imperfection of sandwich plate are also taken into account. By employing Galerkin method, analytical solutions of thermal buckling and post-buckling equilibrium paths for simply supported plates are determined. Numerical examples presented in the present study discuss the effects of gradient index, sandwich plate geometry, geometrical imperfection, temperature dependency, and the elastic foundation parameters.

• Journal of Advanced Marine Engineering and Technology
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• 제12권3호
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• pp.29-42
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• 1988

With the Hertzian contact theory, it is possible to determine the bearing load distributing pattern among the balls and rollers and also variations of the load-displacement relationships for rolling elements contacting raceways according to bearing clearance, load distribution, contact forces and dimensions of bearing components (i.e diameter of raceway and rolling elements), etc. In this paper the calculation theories of contact load and normal approach between two raceways under radial load are reviewed, and compared these calculation results with those of experimental results. A new calculation theory for elastic displacement of outer-race of ball bearing under radial load is developed by authors by application of energy method, which is independent on the effects of roughness, bending or eccentricity of bearing with driving shaft, and is effective in measuring the location of its defect.

• Steel and Composite Structures
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• 제18권2호
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• pp.443-465
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• 2015

In this paper, an efficient and simple trigonometric shear deformation theory is presented for thermal buckling analysis of functionally graded plates. It is assumed that the plate is in contact with elastic foundation during deformation. The theory accounts for sinusoidal distribution of transverse shear stress, and satisfies the free transverse shear stress conditions on the top and bottom surfaces of the plate without using shear correction factor. Unlike the conventional trigonometric shear deformation theory, the proposed sinusoidal shear deformation theory contains only four unknowns. It is assumed that the mechanical and thermal non-homogeneous properties of functionally graded plate vary smoothly by distribution of power law across the plate thickness. Using the non-linear strain-displacement relations, the equilibrium and stability equations of plates made of functionally graded materials are derived. The boundary conditions for the plate are assumed to be simply supported on all edges. The elastic foundation is modelled by two-parameters Pasternak model, which is obtained by adding a shear layer to the Winkler model. The effects of thermal loading types and variations of power of functionally graded material, aspect ratio, and thickness ratio on the critical buckling temperature of functionally graded plates are investigated and discussed.

• 한국정밀공학회지
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• 제17권11호
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• pp.69-74
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• 2000

Roughness of curved surfaces finished with flexible tools depends on the tool/work contact pressure and area. In this study, non-Hertzian closely conforming elastic contact theory is employed to analyze the tool/work contact and to generate a tool path producing a constant pressure at initial contact points. Finishing experiments on curved surfaced are conducted using the tool path. For comparison, curved surface finishing is also performed along the tool path producing a constant tool/work interference depth. It is demonstrated that the tool path of constant contact pressure improves the finished surface roughness.

• 한국정밀공학회지
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• 제20권4호
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• pp.49-58
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• 2003

In this study, the equation of motion of impacting elastic structures was derived through the theory, and the shape control of impact force using correlations of the dynamic characteristics and impact force history between two elastic structures was accomplished. Through numerical analysis and experiments, the classical contact mechanisms were verified, and the effects of the relative motion between impactor and elastic structure on the impact force shape were studied, and then the shape change of impact force depending on the impact position and mode shape of cantilever beam were analyzed. The 2-DOF impactor was designed and used. Reconstruction characteristics of impact force in cantilever beam were reviewed .

• Structural Engineering and Mechanics
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• 제61권6호
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• pp.721-736
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• 2017

In this paper, free vibration characteristics of functionally graded (FG) nanobeams embedded on elastic medium are investigated based on third order shear deformation (Reddy) beam theory by presenting a Navier type solution for the first time. The material properties of FG nanobeam are assumed to vary gradually along the thickness and are estimated through the power-law and Mori-Tanaka models. A two parameters elastic foundation including the linear Winkler springs along with the Pasternak shear layer is in contact with beam. The small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. The nonlocal equations of motion are derived based on third order shear deformation beam theory through Hamilton's principle and they are solved applying analytical solution. According to the numerical results, it is revealed that the proposed modeling can provide accurate frequency results of the FG nanobeams as compared to some cases in the literature. The obtained results are presented for the vibration analysis of the FG nanobeams such as the influences of foundation parameters, gradient index, nonlocal parameter and slenderness ratio in detail.

• 비파괴검사학회지
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• 제27권6호
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• pp.582-590
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• 2007

Imperfectly jointed interface serves as mechanical waveguide for elastic waves and gives rise to two distinct kinds of guided wave propagating along the interface. Contact acoustic nonlinearity (CAN) is known to plays major role in the generation of these interface waves called generalized Rayleigh waves in non-welded interface. Closed crack is modeled as non-welded interface that has nonlinear discontinuity condition in displacement across its boundary. Mathematical analysis of boundary conditions and wave equation is conducted to investigate the dispersive characteristics of the interface waves. Existence of the generalized Rayleigh wave(interface wave) in nonlinear contact interface is verified in theory where the dispersion equation for the interface wave is formulated and analyzed. It reveals that the interface waves have two distinct modes and that the phase velocity of anti-symmetric wave mode is highly dependent on contact conditions represented by linear and nonlinear dimensionless specific stiffness.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 I
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• pp.297-303
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• 2001

This research presents an analytical model to characterize the ball bearing vibration due to the waviness in a rigid rotor supported by multi-row ball bearings considering centrifugal force and gyroscopic moment of ball. The effects of centrifugal force and gyroscopic moment are introduced to the kinematic constraints and force equilibrium equations. The waviness of ball and races is modeled by the superposition of sinusoidal function and it is introduced to position vectors of race curvature center to use the Hertzian contact theory in order to calculate the elastic deflection and nonlinear contact force resulting from the waviness while the rotor has translational and angular motion. They can be determined by solving the nonlinear equations of motion with five degrees of freedom by using the Runge-Kutta-Fehlberg algorithm. The accuracy of this research is validated by comparing with the results of the prior researches. It characterizes the vibration frequencies resulting from the various kinds of waviness in rolling elements, the harmonic frequencies resulting from the nonlinear load-deflection characteristics of ball bearing resulting from the waviness interaction.

• 한국지반공학회논문집
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• 제23권3호
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• pp.89-100
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• 2007

본 논문과 함께 제출한 논문에서는 미시역학 기반의 새로운 탄소성 모델의 정식화에 대해 설명하였다. 본 논문에서는 사질토 변형의 탄성 및 탄소성 거동을 미시역학에 근거하여 자세히 분석하였다. 모델에 필요한 변수 평가를 위한 과정을 제시하였다. 등방 및 삼축 압축 시험에서 나타난 사질토의 탄성 거동을 분석한 결과, 직교 이방 탄성계수의 응력 종속성은 미시적 수직 강성에서 나타난 수직 접촉력의 거듭제곱 함수 형태가 반영되어 나타나며, 삼축 압축 응력 상태에서는 조직 이방성의 변화가 응력 종속성에 영향을 미침을 알 수 있었다. 미시역학적 해석을 통해 소성 변형이 매우 낮은 변형률 수준에서도 발현되며, 변형 중 사질토 강성의 비선형적 감소는 접촉점에서의 접선 방향 소성 변형에 의해 나타남을 밝혔다.