• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.10a
• /
• pp.888-891
• /
• 2005

Compared to the simple-beam springs, double-folded springs have advantages of the linearity even at the long stroke, so that they have been widely used for optical components such as optical switches and optical attenuators. Until now only the stiffness of the double-folded springs dn the perpendicular direction of the shuttle movement has been considered for the stable operation, however, the rotational stiffness of the splings has not been researched as much. Therefore, this paper suggests the double-folded springs of the maximum rotational stiffness with the constant stiffness in the stroke direction using the reliability based topology optimization (RBTO), whose operation properties were experimentally characterized.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 1986.11a
• /
• pp.42-46
• /
• 1986

회전축계가 위험한 공진 또는 불안한 상태를 나타내지 않고 조용하고 안정된 운전상태를 유지하려는 목적은 축의 휨강성, 몸체형상, 베어링의 크기 및 형상과 같은 설계변수를 최적화하는 것으로 이루어질 수 없는 경우가 빈번하다. 이런 경우에는 베어링 외부에 작용하는 "외부댐핑"을 이용하여 진동문제를 근본적으로 개선할 수 있다. 이를 위하여 베어링 외부에 별도로 설계한 스프링과 댐퍼를 설치한다. 본 연구에서는 윤활이론에 따라 명확히 계산되고 그 신빙성이 실험적으로 검증된 "동압유막 댐퍼"의 감쇄계수를 이용하여 외부댐핑을 갖는 회전축-구름베어링\ulcorner와 회전축-저어널 베어링계의 진동특성을 해석하고 회전축-구름베어링계의 실험적 모델을 제시하고자한다. 또한 해석결과와 실험을 토대로 회전축계의 진동특성에 미치는 특성수 및 설계변수를 명확히 도출하여 동특성을 고려한 회전축계의 최적 설계에 기여하고자 한다.축계의 최적 설계에 기여하고자 한다.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.12 no.4
• /
• pp.71-78
• /
• 2008

In the case of the railway bridges, uplift forces were occurred at the edge of the segments when vehicular loads were applied. These forces caused the compressive and tensile forces in the fastening system. In the past, a structural analysis has been performed to investigate the safety of fastening system which was modeled with one directional spring elements based on the compressive test of fastening system. In this case, the stiffness of the spring element was obtained from experimental study which was conducted by compressive load. Therefore, to perform rational and exact structural analysis, the translational stiffness of the fastening system obtained from the experimental study applied the tensile load and the rotational stiffness should be considered because it was occurred the tensile force as well as the compressive force in fastening system. In this study, an elastic and inelastic experimental study was performed for six specimens. The translational stiffness along the vertical axis of rail and the rotational stiffness along the strong axis of rail were investigated, also structural behavior of the fastening system was analyzed.

• Journal of the Society of Naval Architects of Korea
• /
• v.30 no.1
• /
• pp.125-133
• /
• 1993

Most studies on the vibration analysis of a beam-column with ends elastically restrained and various intermediate constraints have been based on the Euler beam theory, which is inadequate for beam-columns of low slenderness ratios. In this paper, analytical methods for vibration and dynamic sensitivity of a Timoshenko beam-column with ends elastically restrained and various intermediate constraints are presented. Firstly, an exact solution method is shown. Since the exact method requires considerable computational effort, a Rayleigh-Ritz analysis is also investigated. In the latter two kinds of trial functions are examined for comparisions : eigenfunctions of the base system(the system without intermediate constraints) and polynomials having properties corresponding to the eigenfunctions of the base system. The results of some numerical Investigations show that the Rayleigh-Ritz analysis using the characteristic polynomials is competitive with the exact solutions in accuracy, and that it is much more efficient in computations than using the eigenfunctions of the base system, especially in the dynamic sensitivity analysis. In addition, the prediction of the changes of natural frequencies due to the changes of design variables based on the first order sensitivity is in good agreements with that by the ordinary reanalysis as long as the changes of design variables are moderate.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.2D
• /
• pp.299-309
• /
• 2006

Railway noise and vibration has been recognized as major problems with the speed-up of rolling stock. As a kind of solution to these problems, the decrease of stiffness of track pad have been tried. However, in this case, overturning of rail due to lateral force should be considered because it can have effect on the safety of running train. Therefore, above two things - decrease of stiffness of track pad and overturning of rail due to lateral force - should be considered simultaneously for the appropriate determination of spring coefficient of track pad. With this viewpoint, minimum spring coefficient of track pad is estimated through the comparison between the theoretical relationship about the overturning of rail and 3-dimensional FE analysis result. Two kinds of Lateral force and wheel load are used as input loads. Extracted values from the conventional estimation formula and the Shinkansen design loads are used. It is found that the overturning of rail changes corresponding to the change of the stiffness of track pad and the ratio of lateral force to wheel load. Moreover, it is found that the analysis model can have influence on the results. Through these procedure, minimum spring coefficient of track pad is estimated.

• The Journal of the Korea Contents Association
• /
• v.10 no.11
• /
• pp.446-451
• /
• 2010

To investigate the vortex induced vibrations the 2-d.o.f. spring mounted circular cylinder was tested in the wind tunnel. The circular cylinder was designed to have the translational and the rotational mode uncoupled to each other. During the wind tunnel tests the resonance behaviors of the translational and the rotational modes by the locking-on phenomena were observed. From the locking-on phenomena observed it is shown that the vortex shedding is correlated with the responses of the structures. And the forces generated by the vortex shedding are influenced by the amplitudes and the frequencies of the cylinders.

• Korean Journal of Applied Biomechanics
• /
• v.19 no.3
• /
• pp.581-592
• /
• 2009

The purpose of this study is to examine the effect of the functional shoes through the kinetic comparison of normal-design running shoes and spring-loaded running shoes. For this, 12 healthy females from the age from 30 to 40 years participated in the EMG and ground reaction force experiment with testing kinetic variables. 12 subjects walked at the velocity of 1.7m/s. After analyzing variables in the spring-loaded running shoes and normal-design running shoes, the following conclusions were obtained; For the ground reaction force, spring-loaded running shoes have larger antero-posterior GRF than normal-design running shoes in the first and second apexes of antero-posterior ground reaction force. For the analysis of EMG, spring-loaded running shoes showed the higher muscle activation of rectus femoris muscle than norma-design running shoes. So the spring-loaded running shoes help improvement muscle strength of knee extensor.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.47 no.10
• /
• pp.712-719
• /
• 2019

This paper explores an implementation of finite element analysis and experiment in the design process of a tape spring hinge used for various CubeSat missions. Tape spring hinges consist of short-length hardened-steel strips with one-sided curvature, and thus the behavior is subject to large deformation with unpredicted non-linearity. Precise dimensions of a commercial tape spring are traced by the use of high-resolution digital camera, and thin-shell FEM analysis is conducted using ABAQUS program. Based on the rotation-moment analysis suggested in previous studies, parametric analysis is conducted by adjusting the contributing factors such as strip thickness and the subtended angle of the cross section. Finally the behaviors are investigated by both analytical and non-linear finite element methods, and the results are compared with the simple measurements. Further studies suggest a possible application in dynamic characteristics of hinges during CubeSat operations.

• Composites Research
• /
• v.34 no.4
• /
• pp.226-232
• /
• 2021

In this paper, development of tape-springs made of composite materials was conducted for the deployment structures along with design, analysis, fabrication, and numerical and experimental investigation of mechanical behavior of the tape-springs. To this end, the tape-springs were manufactured according to three stacking patterns, and numerical and experimental investigation were conducted to determine whether or not they were damaged during bending with various selected composite materials. Finally, optimal stacking patterns that do not cause damage were selected during bending. With this information, the four-point bending test was conducted to obtain the moment-rotation curves. From results, it was confirmed that the nonlinear hysteresis phenomenon of the tape-springs was properly realized according to folding and unfolding. Therefore, it was confirmed that the composite material tape spring was properly developed.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.2 no.1
• /
• pp.63-69
• /
• 1998

A rotating shaft system subjected to seismic motions has been investigated for the various operating modes at start-up. During an earthquake excitation, the rotor may hit the stator of machines due to the excessive deformation of shaft, and thus the response of rotating shaft system of which foundation is supported by the vibration isolation devices has been simulated. In order to examine the transient response of the rotating shaft system at the start-up to both the various operating conditions and the seismic excitation simultaneously, nonlinear equations of motion are derived and solved numerically using Runge-Kutta method. The response of the rotating shaft system is calculated according to the operating modes as recommended by the machine and the system parameters such as the spring stiffness of isolation devices.