• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.2
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• pp.478-487
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• 1991

In this study, dynamic stability of discontinuous free Timoshenko beam, barring a concentrated mass, under constant follower force is considered. Governing differential equations are derived based on the extended Hamilton's principle and finite element method is applied for numerical analysis. Conclusions of the study are as follows : (1) Without force direction control, (i) the critical follower force at instability is increased with concentrated mass regardless of discontinuity. (ii) the minimum critical follower force is located in the vicinity of discontinuity position .xi.$_{d}$=0.75. (iii) at mass location .mu. .leq.0.5 the force at instability is decreased as magnitude of concentrated mass is increased but, at .mu. .geq. 0.5 the force is increased as the mass is increased. (2) With force direction control, (i) shear deformation parameter S contributes insignificantly to the force at instability when S>10$^{[-993]}$ (ii) maximum critical follower force can be obtained for the discontinuity location .xi.$_{d}$=0.25. (iii) the critical follower force is increased as magnitude of concentrated mass .alpha. is increased at mass location .mu. .geq.0.4, but is increased, .mu ..leq.0.4.4.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.1
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• pp.43-49
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• 1986

The stability behavior of the cantilever beam carrying several masses and subjected to a follower force at its free end is investigated. The effects of the location and the mass ratio of the concentrated masses on the stability of the system are discussed. An optimal location of the concentrated mass is determined to give maximum critical follower force. Discontinuities of the flutter load are observed for the system with more than two concentrated masses.

• The Journal of Korean Academy of Prosthodontics
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• v.31 no.4
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• pp.643-659
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• 1993

This study was performed for the purpose of evaluating the stress distributions around five different types of implants according to their structures. The stress distribution around the surrounding bone was analysed by two-dimensional photoelastic method. Five epoxy resin models were made, and vertical and lateral forces were applied to the models. A circular polariscope was used to record the isochromatic fringes. The results of this study were summerized as follows : 1. Threaded type implants showed more even stress distribution patterns than cylinderical type implants when vertical and lateral forces were applied. 2. The stress concentrated patterns were observed at the neck portion and middle portion of the cylindrical type implants comparing with threaded type implants when vertical force was applied. 3. Model 1 and model 4 which are tthreaded type implants showed similar stress distribution patterns at the middle and apical portions and more stress was concentrated at the neck porion of model 1 comparing with model 4 when vertical force was applied. The stresses around model 1 were more evenly distributed when lateral force was applied. 4. More stress was concentrated at the neck and middle portion of cylindrical type implants than threaded type implants when lateral force was applied. 5. Model 1 showed the most even stress distribution patterns when lateral force was applied and stress distribution did no occured at the apical portion of modedl 2 when lateral force was applied. 6. There were almost no differences in stress concentrated patterns with or without having hollow design. And the stress concentrated patterns were observed at the corner of apex in model 5 which has hollow design when vertical force was applied.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.4
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• pp.625-630
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• 2002

To determine the residual stress, concentrated forces instead of distributed stresses, are assumed to be released around the hole drilled through. Concentrated forces are consisted with pairs of concentrated farces which have opposite directions and small distances. Residual stress determination on assumption of concentrated forces is compared numerically with normal method based on Kirsch's solution and proved to be available when released strains are measured at a little distance.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.765-766
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• 2006

Interior Permanent Magnet Synchronous Motor(IPMSM) have many advantages such as high power density, wide speed range and so on. With the IPMSM, miniaturization and energy efficient design can be achieved in comparison with Surface Permanent Magnet Synchronous Motor(SPMSM). In order to secure miniaturization and manufacturing efficiency of the motor, it has concentrated winding, because concentrated winding can reduce the motor volume and make manufacturing to be simple compared with the distributed winding. However, according to the pole-slot combinations motor parameters can be changed and unexpected normal force can be generated. Especially, unbalanced normal force in airgap can cause serious vibration and acoustic problem. Accordingly, in this paper, normal force and parameters variation of concentrated winding IPMSM are investigated according to the pole-slot combinations.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.10
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• pp.1033-1041
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• 2008

The purpose of this paper is to investigate natural frequencies of tapered thick plate with concentrated masses subjected to in-plane force on pasternak foundation by means of finite element method and providing kinetic design data for mat of building structures. Finite element analysis of rectangular plate is done by using rectangular finite element with 8-nodes. For analysis, plates is supported on pasternak foundation. The Winkler parameter is varied with 10, 102, the shear foundation parameter is 5. The taper ratio is applied as 0.0, 0.25, 0.5 and the ratio of the concentrated mass to plate mass as 0.25, 0.5 respectively. As results, we can see that when stiffener's sizes or foundation parameter are larger, the natural frequency increases, and when the concentrated mass or taper ratio or in-plane stress is larger, the natural frequency decreases.

• Journal of the Korean Society for Precision Engineering
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• v.8 no.4
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• pp.107-117
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• 1991

The dynamic stability problem of nonconservative system is one of the important problems. In this study, flexible missile with mass variation is regarded as a free Timoshenko beam subjected to a controlled follower force. The stability was studied numerically through the finite element method. Through the study, the obtained results are as follows: [1] Without force direction control (1) In the case of no mass reduction, the existence of concentrated mass increases critical follower force. (2) Mass reduction rate of the beam slightly effects on the change of critical follower force. [2] With force direction control (1) Shear deformation parameter S contributes insignificantly to the force at instability when $S{\geq}10^4$. (2) With mass variation, increase of concentrated mass increases critical follower force at instbility. (3) The type of promary instability is determined by the sensor location.

• Structural Engineering and Mechanics
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• v.4 no.5
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• pp.469-484
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• 1996

Green's functions are obtained in exact closed-forms for the elastic fields in bi-material elastic solids with slipping interface and differing transversely isotropic properties induced by concentrated point and ring force vectors. For the concentrated point force vector, the Green functions are expressed in terms of elementary harmonic functions. For the concentrated ring force vector, the Green functions are expressed in terms of the complete elliptic integral. Numerical results are presented to illustrate the effect of anisotropic bi-material properties on the transmission of normal contact stress and the discontinuity of lateral displacements at the slipping interface. The closed-form Green's functions are systematically presented in matrix forms which can be easily implemented in numerical schemes such as boundary element methods to solve elastic problems in computational mechanics.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.04a
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• pp.161-168
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• 1999

The concept of seismic design was induced in our country which was poor in it for the scarcity of recognition and insufficiency of funds. Recently many specialists are enforcing the provisions of seismic design. But because seismic force of seismic design is very great and all the seismic force are concentrated on the fixed bearings and substructure the bearings are the seismic force are concentrated on the fixed bearings and substructure the bearings are destroyed so that seismic design lose its basic concept. In addition when the earthquake which exceeds seismic design force takes place the bridge is collapsed. For these reasons the developed seismic isolation design concept was appeared which diminishes seismic force itself by period shift and additional damping distributes it to each superstructures evenly. Therefore this study introduced the method which combines PC-LEADeR(design program for L.R.B) with SAP 2000(linear elastic analysis) and performs the seismic isolation design more elaborately and simply verified the propriety of that method and examined the force control of L. R. B.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.1
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• pp.124-131
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• 1987

The parameteric instability of the cantilever beam carrying two concentrated masses subjected to a periodic follower force is investigated theoretically and experimentally. The effects of the constant follower force and the periodic follower force the mass ratio and the location of the concentrated mass on the parametric instability of the system are discussed. In experiment, the nonconservative follower force is produced by the magnetic force of the electromagnet. The theoretical and the experimental results on the parameteric instability are in good agreement each other.