• 한국정밀공학회지
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• 제21권8호
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• pp.129-135
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• 2004

This paper discussed on the effect of an intermediate support on the stability of elastic material subjected to dry friction force. It is assumed in this paper that the dry frictional force between a tool stand and an elastic material can be modeled as a distributed follower force. The elastic material on the friction material is modeled for simplicity into an elastic beam on Winkler-type elastic foundation. The stability of beams on the elastic foundation subjected to distributed follower force is formulated by using finite element method to have a standard eigenvalue problem. The first two eigen-frequencies are obtained to investigate the dynamics of the beam. The eigen-frequencies yield the stability bound and the corresponding unstable mode. The considered beams lose its stability by flutter or divergence, depending on the location of intermediate support.

• 대한기계학회논문집A
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• 제28권2호
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• pp.143-148
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• 2004

This paper discussed on the stability of elastic material subjected to dry friction force for low boundary conditions: clamped free, clamped-simply supported, simply supported-simply supported, clamped-clamped. It is assumed in this paper that the dry frictional force between a tool stand and an elastic material can be modeled as a distributed follower force. The friction material is modeled for simplicity into a Winkler-type elastic foundation. The stability of beams on the elastic foundation subjected to distribute follower force is formulated by using finite element method to have a standard eigenvalue problem. It is found that the clamped-free beam loses its stability in the flutter type instability, the simply supported-simply supported beam loses its stability in the divergence type instability and the other two boundary conditions the beams lose their stability in the divergence-flutter type instability.

• PNF and Movement
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• 제22권1호
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• pp.23-30
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• 2024

Purpose: Ankle instability is a common issue in both daily activities and sports, often leading to recurrent injuries. Elastic taping is a non-pharmacological intervention used to improve ankle stability. This study aimed to investigate the immediate effects of elastic taping on ankle stability, center of pressure (COP) movement, and foot pressure distribution. Methods: A single-group pre-posttest design was employed, with 30 participants included in the study. Plantar pressure and COP parameters were measured before and after the application of elastic taping. Taping was administered in three distinct patterns to enhance ankle stability. Results: Immediate effects of elastic taping were evident in COP parameters. Following taping application, there was a significant decrease in COP total displacement, COP area, and COP velocity. However, no significant changes were observed in plantar pressure parameters. Conclusion: The application of elastic taping in this study demonstrated immediate effects on ankle stability and COP parameters, indicating its potential as a viable intervention for improving balance. Further research with larger sample sizes and long-term follow-up is needed to elucidate the sustained effects of elastic taping on ankle stability.

• Structural Engineering and Mechanics
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• 제8권2호
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• pp.193-205
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• 1999

A formulation for the dynamic stability analysis of cylindrical shells resting on elastic foundations is presented. In this previously not studied problem, a normal-mode expansion of the partial differential equations of motion, which includes the effects of the foundation as well as a harmonic axial loading, yields a system of Mathieu-Hill equations the stability of which is analyzed using Bolotin's method. The present study examines the effects of the elastic foundation on the instability regions of the cylindrical shell for the transverse, longitudinal and circumferential modes.

• Advances in nano research
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• 제17권1호
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• pp.1-8
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• 2024

In this paper, stability analysis of sandwich toroidal shell segments (TSSs) with carbon nanotube (CNT)-reinforced face sheets featuring various types of auxetic cores, surrounded by elastic foundations under radial pressure is presented. Two distinct types of auxetic structures are considered for the core, including re-entrant auxetic structure and graphene origami (GOri)-enabled auxetic structure. The nonlinear stability equilibrium equations of the longitudinally shallow shells are formulated using the von Karman shell theory, in conjunction with Stein and McElman approximation while considering Winkler-Pasternak's elastic foundation to simulate the interaction between the shell and elastic foundation. The Galerkin method is employed to derive the nonlinear stability responses of the shells. The numerical investigations show the influences of various types of auxetic-core layers, CNT-reinforced face sheets, as well as elastic foundation on the stability of sandwich shells.

• Smart Structures and Systems
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• 제23권3호
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• pp.215-225
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• 2019

In the present paper, the nonlocal strain gradient refined model is used to study the thermal stability of sandwich nanoplates integrated with piezoelectric layers for the first time. The influence of Kerr elastic foundation is also studied. The present model incorporates two small-scale coefficients to examine the size-dependent thermal stability response. Elastic properties of nanoplate made of functionally graded materials (FGMs) are supposed to vary through the thickness direction and are estimated employing a modified power-law rule in which the porosity with even type of distribution is approximated. The governing differential equations of embedded sandwich piezoelectric porous nanoplates under hygrothermal loading are derived through Hamilton's principle where the Galerkin method is applied to solve the stability problem of the nanoplates with simply-supported edges. It is indicated that the thermal stability characteristics of the porous nanoplates are obviously influenced by the porosity volume fraction and material variation, nonlocal parameter, strain gradient parameter, geometry of the nanoplate, external voltage, temperature and humidity variations, and elastic foundation parameters.

• 한국소음진동공학회논문집
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• 제11권6호
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• pp.216-222
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• 2001

The paper presents the dynamic stability of a flexible shoe in drum brake systems subjected to a frictional force. The frictional force between the drum and the shoe is assumed as a distributed frictional force, while the shute is modeled as an elastic beam supported by two translational springs at both ends and elastic foundations. Governing equations of motion are derived by energy expressions, and their numerical results are obtained by employing the finite element method. The critical distributed frictional force and the instability regions are demonstrated by changing the stiffness of two translational springs and elastic foundation parameters. It is also shown that the beam loses its stability by flutter and divergence depending on the stiffness of elastic supports and elastic foundation parameters. Time responses of beams corresponding to their instability types are also demonstrated.

• 한국시뮬레이션학회논문지
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• 제8권2호
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• pp.111-122
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• 1999

The paper presents a stability analysis of uniform Timoshenko beams resting on two-parameter elastic foundations. The two-parameter elastic foundations were considered as a shearing layer and Winkler springs in soil models. Governing equations of motion were derived using the Hamilton's principle and finite element analysis was performed and the eigenvalues were obtained for the stability analysis. The numerical results for the buckling stability of beams under axial forces are demonstrated and compared with the exact or available confirmed solutions. Finally, several examples were given for Euler-Bernoulli and Timoshenko beams with various boundary conditions.

• Journal of Mechanical Science and Technology
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• 제20권9호
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• pp.1355-1360
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• 2006

This paper presents the dynamic stability of a cantilevered Timoshenko beam with a concentrated mass, partially attached to elastic foundations, and subjected to a follower force. Governing equations are derived from the extended Hamilton's principle, and FEM is applied to solve the discretized equation. The influence of some parameters such as the elastic foundation parameter, the positions of partial elastic foundations, shear deformations, the rotary inertia of the beam, and the mass and the rotary inertia of the concentrated mass on the critical flutter load is investigated. Finally, the optimal attachment ratio of partial elastic foundation that maximizes the critical flutter load is presented.

• 한국전산구조공학회논문집
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• 제20권6호
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• pp.709-717
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• 2007

본 연구는 종동력을 받는 탄성기초위에 놓여 있는 보에 있어서 중간 지지가 보의 안정성에 미치는 영향에 대하여 논하고 있다. 해석에 있어서, 종등력을 받는 탄성기초위에 놓여 있는 보의 안정성과 동적응답은 유한요소법을 이용하였다. 또, 동적 응답에 대한 진동의 감쇠를 관찰하기 위하여 모드 중첩법이 사용되었다. 해석 결과, 종동력을 받는 탄성기초위에 놓여 있는 보는 중간 지지의 위치에 따라 플러터 타입과 다이버젼스 타입에 의해 안정성을 잃게 된다.