• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.248-251
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• 2004

The vibrational behavior of a front load washing machine is heavily influenced by the floor stiffness on which the washing machine is installed. In case the floor stiffness is extremely low like a wooden floor (we call it a 'soft floor, S/F'), it is quite probable that a washer's rigid body mode exists in the operating frequency range. In this case, the outer frame vibration level would be very high, but the mitigation scheme is quite limited except the excitation force abatement by acquisition of the optimal inertia in the internal vibratory system and the diaphragm's stiffness with the minimum force transfer.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.38-45
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• 2020

A magnetically levitating capsule train, which runs inside the sub-vacuum tube, can reach ultra-fast speeds by dramatically reducing the aerodynamic drag and friction. The capsule train uses the superconductor electrodynamic suspension (SC-EDS) method for levitation. The SC-EDS method has advantages, such as a large levitation gap and free of gap control, which could reduce the infra-construction cost. On the other hand, disadvantages, such as the large variation of the levitation-guidance gap and small damping characteristics in levitation-guidance force, could degrade the running stability and ride comfort of the capsule train. In this study, a dynamic analytical model of a capsule train based on the SC-EDS was developed to analyze the running dynamic characteristics. First, as important factors in the capsule train dynamics, the levitation and guidance stiffness in the SC-EDS system were derived, which depend non-linearly on the velocity and gap variation. A 3D dynamic analysis model for capsule trains was developed based on the derived stiffness. Through the developed model, the effects of the different running speeds on the ride comfort were analyzed. The effects of a disturbance from infrastructure, such as the curve radius, tube sag, and connection joint difference, on the running stability of the capsule train, were also analyzed.

• Journal of Aerospace System Engineering
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• v.16 no.3
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• pp.63-72
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• 2022

The purpose of this paper was to understand the dynamics of deployment of large mesh antennas, and to provide a numerical method for determining the dynamic stiffness and the driving forces for the design. The deployment structure was numerically modeled using the frame elements. The eigenvalue analysis was demonstrated, with respect to the folded and unfolded configurations of the antenna. A multibody dynamic model was formulated with Kane's equation, and simulated using the pseudo upper triangular decomposition (PUTD) method for resolving the constrained problem. Based on the multibody model, the kinetics of the deployment, the motor driving forces, and the feasibility of the designed deployment structure were investigated.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.4
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• pp.243-250
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• 2024

Recently, accidents involving structural elements, formwork, and shore have occurred continuously during concrete pouring, especially in multistory-shored RC structure systems with non-typical stories with increased slab thicknesses. In previous studies, an analysis was conducted on the stiffness of concrete and distribution of slab construction loads when some slab thicknesses were increased under the same conditions. This study analyzed the construction load, construction damage parameter, and shoring force by varying the construction conditions, such as the construction period and number of shores, as well as the design conditions, such as the thickness increment and number of thickness increment slabs, in a multistory-shored RC structure system with non-typical stories with increased slab thickness.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.4 s.247
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• pp.387-392
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• 2006

This paper predicts the modified mass and stiffness of structure using the sensitivity coefficients with the iterative method. The sensitivity coefficients are obtained by the change of the eigenvectors according to structural modification. The method is applied to an examples of a 3 degree of freedom system by modifying mass and stiffness. The predicted mass and stiffness are in good agreement with these from the structural reanalysis using the modified mass and stiffness.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.04b
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• pp.131-136
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• 1993

일반적으로 공작기계 주축계에 대해서 요구되는 기본적인 항목들로는 고강성, 고감쇠, 고회전정밀도, 저발열, 장수명 등이 있다. 최근에는 이러한 기능들과 함께 가공능률과 가공정밀도의 향상을 도모하기 위해서 고속절삭을 실현햐ㄹ 수 있는 공작기계 주축계의 고속화, 즉 고속 주축계에 대한 연구가 활발히 진행되고 있다. 본 연구에서는 고속주축계의 동특성을 체계적으로해석하기 위해서 주축회전수의 영향을 고려한 유한요소모델(finite element model)을 도입하였다. 특히 주축은 세장비가 비교적 자기 때문에 Timoshenko보 이론으로, 베어링은 유한한 폭을 가지고 있기 때문에 반경방향 외에도 모멘트방향의 강성 및 감쇠특성을 가지고 있는 것으로 모델화 하였다. 그리고 고속주축계의 설계조건들을 도출하기 위해서 동특성 해석결과들로 부터 고속주축계의 모드매개변수들인 고유진동수와 감쇠비에 대한 주축 회전수, 베어링의 지지특성, 베어 링의 간격, 주축재료의 내부감쇠율 등의 영향을 고찰하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.5
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• pp.756-768
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• 1997

In order to control a dynamic gait of quadrupedal walking robot, the equations of motion of the whole mechanism are required. In this research, the equations of motion are formulated analytically using Kane's dynamic approach. As a dynamic gait model, a trot gait has been adopted. The degree of freedom of whole mechanism could be reduced to 7 by idealizing the kinematic feature of the trot gait. Using the equations of motion formulated, the results of the redundant-joint torque analysis and the simulation of dynamic walking motion are presented.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.11
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• pp.731-738
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• 2015

This study proposed the method of the multi-crack detection using the sensitivity coefficient matrix which is calculated from the change of eigenvalues and eigenvectors before and after the crack. Each crack is modeled by a rotational springs. The method is applied to the cantilever beam with miulti-crack. The eigenvalues and eigenvectors are determined for different crack locations and depths. The prediction of multi-crack detection are in good agreement with the results of structural reanalysis.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1995.06a
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• pp.37-47
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• 1995

본 논문은 마찰력을 측정하는 시스템에 동특성 변화를 주어서, 이에 의해 발생하는 마찰현상의 변화와 수직하중의 변동특성에 관하여 측정을 하였으며, 미끄럼속도 및 하중조건 변화와 미끄럼운동을 하는 두물체 재료조합 변화에 따른 상기의 마찰특성변화에 관하여 실험적 및 이론적 고찰을 행하였다. 시스템의 동특성 변화를 주기 위하여 시스템의 강성(Stiffness)의 변화를 주었고, 또한 수직 하중 부과 방법을 Dead weight를 이용한 방법과 공압(Pneumatic)에 의한 방법을 비교함으로써 관성력 및 감쇠(Damping) 특성에 변화를 주었다. 시험 대상의 물체들은 강(Steel) 및 폴리머류의 Rosin과 PTFE를 선정하여, 재료변화에 따른 마찰특성 변화를 유도하였다.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.2
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• pp.93-98
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• 2006

This study provides a comprehensive experimental study on the dynamic characteristics of a flexible matrix composite(FMC) driveshaft. A primary objective is to verify the analytic results of the FMC drivetrain based on the equivalent complex modulus approach and the classical lamination theory. A test rig has been constructed, which consists of a FMC shaft, a foundation beam, bearings, external dampers and a driving motor. The frequency response functions and transient responses are obtained from the external excitation and the spin-up testings. It turns out that the analytic results are in good agreement with the experimental ones.