• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.215-218
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• 2007

In this paper a dynamic behavior(natural frequency) of a cracked cantilever beam subjected to follower force is presented. In addition, an analysis of the flutter and buckling instability of a cracked cantilever beam subjected to a follower compressive load is presented. Based on the Euler-Bernouli beam theory, the equation of motion can be constructed by using the Lagrange's equation. The vibration analysis on such cracked beam is conducted to identify the critical follower force for flutter insstability based on the variation of the first two resonant frequencies of the beam. Besides, the effect of the crack's intensity and location on the flutter follower force is studied. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.99-104
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• 2007

In this paper a dynamic behavior(natural frequency) of a cracked cantilever beam with tip mass and follower force is presented. In addition. an analysis of the flutter and buckling instability of a cracked cantilever beam subjected to a follower compressive load is presented. Based on the Euler-Bernouli beam theory, the equation of motion can be constructed by using the Lagrange's equation. The vibration analysis on such cracked beam is conducted to identify the critical follower force for flutter ins stability based on the variation of the first two resonant frequencies of the beam. Besides. the effect of the crack's intensity and location on the flutter follower force is studied. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations.

• Steel and Composite Structures
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• v.23 no.1
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• pp.1-16
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• 2017

This paper is presented to solve the buckling problem of functionally graded truncated conical shells subjected to displacement-dependent pressure which remains normal to the shell middle surface throughout the deformation process by the semi-analytical finite strip method. Material properties are assumed to be temperature dependent, and varied continuously in the thickness direction according to a simple power law distribution in terms of the volume fraction of a ceramic and metal. The governing equations are derived based on first-order shear deformation theory which accounts for through thickness shear flexibility with Sanders-type of kinematic nonlinearity. The element linear and geometric stiffness matrices are obtained using virtual work expression for functionally graded materials. The load stiffness also called pressure stiffness matrix which accounts for variation of load direction is derived for each strip and after assembling, global load stiffness matrix of the shell which may be un-symmetric is formed. The un-symmetric parts which are due to load non-uniformity and unconstrained boundaries have been separated. A detailed parametric study is carried out to quantify the effects of power-law index of functional graded material and shell geometry variations on the difference between follower and non-follower lateral buckling pressures. The results indicate that considering pressure stiffness which arises from follower action of pressure causes considerable reduction in estimating buckling pressure.

• Korean Journal of Materials Research
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• v.9 no.2
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• pp.199-204
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• 1999

As the engine design change to get high efficiency and performance of commercial diesel engine, surface wear of the cam follower becomes an important issues as applied load increasing at the contact face between cam follower and cam. Purpose of this study is the developing of the ceramic cam follower made of silicon nitride ceramic which is more wear resistant than the cast iron and sintered cam follower. Ceramic cam follower was made by direct brazing of thin ceramic disk to steel can follower body using active bracing alloy. Effect of joining condition on the interfacial phases and joining strength wer examined at bvarious joining temperatures, times, and cooling rates. Crowning resulted from the difference of thermal expansion coefficient after direct brazing without using any stress-relieving inter layer was measured. Interfacial phases are mainly titanium silicide and titanium nitride which are the products between active metal(Ti) in brazing alloy and silicon nitiride. Maximum joining strength of the ceramic metal joint, measured by DBS method, was 334MPa. Crowning(R) of the prototype ceramic cam follower was 1595mm. As machining for crowning is not necessary, production cost can be reduced.

• Journal of Mechanical Science and Technology
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• v.20 no.9
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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.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.82-85
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• 2002

A compact rail to rail CMOS voltage follower is presented. The circuit is based on the symmetrical class AB voltage follower and can operate under supply voltages of ${\pm}$ 1.5 V. The proposed circuit has power dissipation of 5.2㎽ under quiescent condition and can drive ${\pm}$1.25 V to 250$\Omega$ load with a total harmonic distortion of less than 0.5 percent and cut off frequency of 237 ㎒. Although simple, the proposed circuit enables the output transistors to drive load efficiently.

• Structural Engineering and Mechanics
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• v.58 no.1
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• pp.59-91
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• 2016

Laminated composite shells are commonly used in various engineering applications including aerospace and marine structures. In this paper, using semi-analytical finite strip method, the buckling behavior of laminated composite deep as well as thick shells of revolution under follower forces which remain normal to the shell is investigated. The stiffness caused by pressure is calculated for the follower forces subjected to external fibers in thick shells. The shell is divided into several closed strips with alignment of their nodal lines in the circumferential direction. The governing equations are derived based on first-order shear deformation theory which accounts for through thickness-shear flexibility. Displacements and rotations in the middle surface of shell are approximated by combining polynomial functions in the meridional direction as well as truncated Fourier series with an appropriate number of harmonic terms in the circumferential direction. The load stiffness matrix which accounts for variation of loads direction will be derived for each strip of the shell. Assembling of these matrices results in global load stiffness matrix which may be un-symmetric. Upon forming linear elastic stiffness matrix called constitutive stiffness matrix, geometric stiffness matrix and load stiffness matrix, the required elements for the second step analysis which is an eigenvalue problem are provided. In this study, different parameter effects are investigated including shell geometry, material properties, and different boundary conditions. Afterwards, the outcomes are compared with other researches. By considering the results of this article, it can be concluded that the deformation-dependent pressure assumption can entail to decrease the calculated buckling load in shells. This characteristic is studied for different examples.

• Journal of Korean Neurosurgical Society
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• v.46 no.2
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• pp.144-151
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• 2009

Objective: To compare two testing protocols for evaluating range of motion (ROM) changes in the preloaded cadaveric spines implanted with a mobile core type Charite$^{TM}$ lumbar artificial disc. Methods: Using five human cadaveric lumbosacral spines (L2-S2), baseline ROMs were measured with a bending moment of 8 Nm for all motion modes (flexion/extension, lateral bending, and axial rotation) in intact spine. The ROM was tracked using a video-based motion-capturing system. After the Charite$^{TM}$ disc was implanted at the L4-L5 level, the measurement was repeated using two different methods: 1) loading up to 8 Nm with the compressive follower preload as in testing the intact spine (Load control protocol), 2) loading in displacement control until the total ROM of L2-S2 matches that when the intact spine was loaded under load control (Hybrid protocol). The comparison between the data of each protocol was performed. Results: The ROMs of the L4-L5 arthroplasty level were increased in all test modalities (p < 0.05 in bending and rotation) under both load and hybrid protocols. At the adjacent segments, the ROMs were increased in all modes except flexion under load control protocol. Under hybrid protocol, the adjacent segments demonstrated decreased ROMs in all modalities except extension at the inferior segment. Statistical significance between load and hybrid protocols was observed during bending and rotation at the operative and adjacent levels (p< 0.05). Conclusion: In hybrid protocol, the Charite$^{TM}$ disc provided a relatively better restoration of ROM, than in the load control protocol, reproducing clinical observations in terms of motion following surgery.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.7 s.124
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• pp.605-610
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• 2007

In this paper a dynamic behavior(natural frequency) of a cracked cantilever beam subjected to follower force is presented. In addition, an analysis of the flutter and buckling instability of a cracked cantilever beam subjected to a follower compressive load is presented. Based on the Euler-Bernoulli beam theory, the equation of motion can be constructed by using the Lagrange's equation. The vibration analysis on such cracked beam is conducted to identify the critical follower force for flutter instability based on the variation of the first two resonant frequencies of the beam. Besides, the effect of the crack's intensity and location on the flutter follower force is studied. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations.

• Journal of Korean Society of Steel Construction
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• v.17 no.6 s.79
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• pp.699-705
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• 2005

This paper investigates critical loads of tapered cantilever columns with a tip mass, subjected to a follower force. The linearly tapered solid rectangular cross-sections are adopted as the column taper. The differential equation governing free vibrations of such columns, also called Beck's columns, is derived using the Bernoulli-Euler beam theory. Both divergence and flutter critical loads are calculated from the load-frequency curves that are obtained by solving the differential equation. The critical loads are presented as functions of various non-dimensional system parameters, namely, the taper type, the subtangential parameter, and the mass ratio.