• 한국구조물진단유지관리공학회 논문집
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• 제12권1호
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• pp.127-134
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• 2008

내진설계기준이 점차 강화되고 다경간 연속화에 대한 시도가 증가됨에 따라 기존의 내진설계로는 지진력의 처리가 곤란하여 다점고정장치와 감쇠를 통해 지진에너지를 소산시키는 장주기화, 분산, 감쇠를 통해 지진력을 효과적으로 감소시키는 면진장치의 사용이 날로 증가하고 있다. 그러나 내진장치 적용에 대한 다양성 부재와 장치를 적용한 설계경험의 부족 등의 이유로 특정교량에 적절한 내진장치를 선정하는데 상당한 어려움이 따르고 있다. 따라서 본 연구에서는 다양한 내진장치가 적용된 교량의 지진시 거동특성에 대한 연구를 수행하여 받침장치 선정시 활용할 수 있도록 하였다.

• 대한조선학회논문집
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• 제56권6호
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• pp.550-558
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• 2019

The roll motion of a general vessel, which is more influenced by resonance as compared to other motions, adversely affects the passenger and hull. Therefore, reducing the roll motion through an anti-rolling system is critical, and most ships use various devices such as anti-rolling tanks, bilge keels, and fin stabilizers to accomplish this. In this study, a simplified model is developed for the application of an anti-rolling device for unmanned semi-submersible vessels. The applied anti-rolling device is installed on the stern and stem of a ship using a pair of servo motors with added weight, and the motor is controlled through the Arduino. The moment of the motor is designed and implemented based on a mathematical model such that it is calculated through the restoring force according to the heel angle of the ship. The performance of the proposed system was verified by utilizing the roll damping coefficient calculated by the free-roll decay test and logarithmic decrement method and was validated by a towing tank test. The system is expected to be used for unmanned vessels to perform sustainable missions.

• 한국구조물진단유지관리공학회 논문집
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• 제26권4호
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• pp.1-10
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• 2022

이 연구에서는 강재 스프링을 감쇠 장치로써 사용 가능성을 평가하기 위해서, 강재 스프링의 인장 및 반복하중 실험을 수행하였다. 주요 실험변수는 강재의 종류(SAE9254 및 SS275), 스프링상수(700 N/mm, 1,000 N/mm 및 1,400 N/mm) 및 SAE9254의 열처리 유·무이다. 인장 실험 결과, SAE9254로 제작된 강재 스프링의 설계 스프링상수와 측정 스프링상수의 비는 1.08 ~ 1.13이며, SS275로 제작된 강재 스프링의 설계 스프링상수와 측정 스프링상수의 비는 0.86 ~ 0.97로 측정되었다. 항복 이후 열처리 유·무에 따른 SAE9254로 제작된 스프링의 하중-변위 관계 기울기는 약 240 ~ 251 kN/mm 및 92 N/mm 이었으며, SS275로 제작된 스프링의 하중-변위 관계 기울기는 거의 0이었다. 반복하중 실험 결과에서 모든 실험체는 KDS 41 17 00 (2019)에서 요구하는 변위 의존형 감쇠 장치의 적합 조건인 변위 원점에서의 하중 조건, 최대변위에서 하중 조건 그리고 에너지 소산 능력 조건을 모두 만족하였다. 그리고 열처리 안 된 SAE9254 및 SS275로 제작된 강재 스프링의 등가 감쇠비는 열처리 된 SAE9254로 제작된 스프링에 비해 각각 약 2.8배 및 1.9배 높은 수준이었다.

• 제어로봇시스템학회논문지
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• 제16권6호
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• pp.579-585
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• 2010

In this paper, an assistive device for a knee joint to help a disabled person to stand up by supporting power is presented. The device is designed and controlled by using damping characteristics of the MR (Magneto-Rheological) damper. The MR damper helps the person to sit slowly and safely. A DC motor supports muscle power in the case of standing motion. Thus the device helps the disabled person to sit down and stand up. Through the experiments, it is feasible that an assistive device can help the disabled person to standup according to the foot pressure change.

• 한국해양공학회지
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• 제25권1호
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• pp.8-13
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• 2011

A compact array system of small buoys is used for wave energy extraction. To evaluate the performance of this system, hydrodynamic analysis is carried out in regular waves using the higher order boundary element method. The motion response of each buoy is calculated considering hydrodynamic interactions caused by other buoys. The effect of energy extraction device is modeled as a linear damping load. The efficiencies of energy conversion are compared using the various sizes and arrangements of the array system and the damping coefficients for energy extraction. The increase in size or the packing ratio of the system gives better efficiency. However, the wave condition and the cost for the system should be considered to optimize performance from the perspective of engineering and economics. The proposed nondimensionalized damping coefficient for energy extraction is 0.1~0.5.

• 한국소음진동공학회논문집
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• 제13권10호
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• pp.760-766
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• 2003

This paper is concerned with the eddy current damper which can be used to enhance the damping of the host structure. The operating principle of the eddy current damper is first explained in detail. The dynamic interaction between the magnets and the copper plate produces eddy current thus resulting in the damping force. By attaching the eddy current damper to the host structure, the damping of the total structure can be increased so that vibrations can be suppressed. The advantage of the eddy current damper is that it doesn't require any electronic devices and power supply The effect of the eddy current damper on the global dynamic characteristics of the structure is investigated by considering the cantilever with the eddy current damper. Experimental results show that the eddy current damper is an effective device for vibration suppression.

• Coupled systems mechanics
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• 제9권1호
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• pp.47-62
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• 2020

In this paper we study the control for nonlinear geometric instability problem of a deep or a shallow truss or yet a frame structure. All the structural models are built with geometrically exact truss and beam finite elements.The proposed models can successfully handle large overall motion under static or dynamic conservative load.The control strategy considers adding a damping from either friction device or viscous damper.This kind of control belong to well-known concept of passivity. Different examples are presented in order to illustrate the proposed theoretical developments.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.136-141
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• 2003

This paper is concerned with the eddy current damper which can be used to enhance the damping of the host structure. The operating principle of the eddy current damper is first explained in detail. The dynamic interaction between the magnets and the copper plate produces eddy current thus resulting in the damping force. By attaching the eddy current damper to the host structure, the damping of the total structure can be increased so that vibrations can be suppressed. The advantage of the eddy current damper is that it doesn't require any electronic devices and power supply. The effect of the eddy current damper on the global dynamic characteristics of the structure is investigated by considering the cantilever with the eddy current damper. Experimental results show that the eddy current damper is an effective device for vibration suppression.

• 동력기계공학회지
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• 제22권6호
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• pp.80-86
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• 2018

A damper is a hydraulic device designed to absorb or eliminate shock impulses which is acting on the sprung mass of car body. It converts the kinetic energy of the shock into another form of energy, typically heat. The main mechanism for providing damping is by shearing the hydraulic fluid as it flows through restrictions. Since the damping mechanism depends on the flow restrictions, these restrictions are very important in damper design. Damper engineers often try several combinations of valve shims, piston orifices and bleed orifices before finding the best combination for a particular setup on a car. Therefore, the ability to tune a damper properly without testing is of great interest in damper design. For this reason, many previous researches have been done on modeling and simulation of the damper. This paper explains a genetic algorithm method to find the optimal parameters for the design objective and the simulation results agree well with the targeted damping characteristics.

• Smart Structures and Systems
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• 제7권5호
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• pp.379-392
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• 2011

This paper presents a multi-functional system, consisting of a magnetorheological (MR) damper and an electromagnetic induction (EMI) device, and its applications in stay cables. The proposed system is capable of offering multiple functions: (1) mitigating excessive vibrations of cables, (2) estimating cable tension, and (3) harvesting energy for wireless sensors used health monitoring of cable-stayed bridges. In the proposed system, the EMI device, consisting of permanent magnets and a solenoid coil, can converts vibration energy into electrical energy (i.e., induced emf); hence, it acts as an energy harvesting system. Moreover, the cable tension can be estimated by using the emf signals obtained from the EMI device. In addition, the MR damper, whose damping property is controlled by the harvested energy from the EMI device, can effectively reduce excessive cable vibrations. In this study, the multi-functionality of the proposed system is experimentally evaluated by conducting a shaking table test as well as a full-scale stay cable in a laboratory setting. In the shaking table experiment, the energy harvesting capability of the EMI device for wireless sensor nodes is investigated. The performance on the cable tension estimation and the vibration mitigation are evaluated using the full-scale cable test setup. The test results show that the proposed system can sufficiently generate and store the electricity for operating a wireless sensor node twice per day, significantly alleviate vibration of a stay cable (by providing about 20% larger damping compared to the passive optimal case), and estimate the cable tension accurately within a 2.5% error.