• 대한조선학회논문집
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• 제45권3호
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• pp.309-314
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• 2008

An experimental method to estimate the added mass of a marine propeller has been developed for the axial rigid body motion in still water, and the experiments have been carried out. The experimental result has been compared to the theoretical result by PRODAS based on the unsteady lifting surface theory. The experimental method developed in this research and the theoretical method by PRODAS have been validated by confirming good agreements between the experimental results and the theoretical ones. Also the comparison to the results by empirical formula has been made and discussed.

• 한국생산제조학회지
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• 제21권1호
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• pp.182-189
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• 2012

This study suggests a dynamic design process for deciding properly design parameters of a mass-spring type Wave Energy Converter (WEC) to achieve sufficient energy conversion from wave to power generator. The WEC mechanism, in this research, consists of a rigid sprung body, a platform, suspension springs and dampers. The rigid sprung body is supported on the platform via springs and dampers and vibrates translationally in the heave direction under wave excitation. At last the resulting heave motion of the sprung body is transmitted to rotating motion of the electric generator by rack and pinion, and transmission gears. For the purpose of vibration analysis, the WEC mechanism has been simply modelled as a mass-spring-damper system under harmonic base excitation. Its maximum displacement transmissibility and steady state response can be determined by using elementary vibration theory if the harmonic ocean wave data were provided. With the vibration analysis results, the suggested dynamic design process of WEC can determine all the design parameters of the WEC mechanism, such as sprung body mass, suspension spring constant, and damping coefficient that can give sufficient relative displacement transmissibility and the associated inertia moment to drive the electric generator and transmission gears.

• 품질경영학회지
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• 제49권3호
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• pp.255-268
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• 2021

Purpose: We sought to understand why a high-speed rotating projectile featuring a fuze-and-body assembly sometimes exhibited airburst, and we intended to improve the flight stability by eliminating airburst. Methods: We performed characteristic factor analysis, structural mechanics modeling, and dynamic modeling and simulation; and we scheduled firing tests to discover the cause of airburst. We used a step-by-step procedure to analyze the reliability function for selecting the bonding force standard that prevents airburst. Results: The 00MM high-speed rotating projectile features a fuze bonded to a body assembly; the bonding sometimes can break on firing. The resulting contact force, vibration and roll damping during flight generated yaw. Flight became unstable; fuze operation triggered an airburst. Our reliability test improved the bonding force standard (the force was increased). When the bonding force was at least the minimum required, a firing test revealed that airburst/flight instability disappeared. Conclusion: Analysis and identification of the causes of flight instability and airburst render military training safer and enhance combat power. Ammunition must perform as designed. Our method can be used to set standards that improve the performances of similar types of ammunition.

• 한국소음진동공학회논문집
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• 제22권11호
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• pp.1057-1063
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• 2012

A cycloid speed reducer is a type of the speed reducers. The cycloid speed reducer has a eccentric rotating motion and offset to avoid some problem of assembly, so it has a disadvantage for vibration. In this paper, a multi-body dynamic model is developed for a cycloid speed reducer and the dynamic behaviors of the reducer are investigated. The cycloid speed reducer consists of cycloidal plate gears, housing gear, input shaft, output pin and shaft, and eccentric bearings. Using a CAD program, each component of cycloid reducer is modeled based on the offset and multi-body simulations are performed using Recurdyn. As a result, the pin reaction force and the amplitude of bearing displacement are increased by the offset.

• 드라이브 ㆍ 컨트롤
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• 제11권4호
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• pp.46-52
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• 2014

This study suggests a small-sized screw decanter specialized for dredging sites. Generally, conventional screw decanters are composed of a cylinder and a cone. However, the suggested screw decanter simply has a cone based on a cone-type bowl structure. In this research, a commercial analysis tool is used to establish an optimal design for the bowl and the screw conveyor. Moreover, the base frame, where the main bearings that support the spindle of the bowl and the screw conveyor are installed, is optimally designed considering the weight of the rotating body and the deflection caused by the high centrifugal force. Furthermore, the natural frequency range of the spinning body, the bowl and the screw conveyor, is applied to this base frame; it is designed not to correspond to the resonance frequency range and achieves stability as a result. This study suggests an optimal design for the rotating body and the base frame of a screw decanter considering its vibration characteristics. Such a design will prevent overuse of materials and help to reduce the weight and volume-and the price-of a screw decanter.

• 한국공작기계학회논문집
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• 제14권5호
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• pp.41-48
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• 2005

The Rotating transmission is made up of belts, mass disks and gears. This transmission is controlled electro-mechanically by the motor and operation program. The control strategy of the system can be to change belts' stiffness and the masses of mass disk and gear. This system can be modeled as a rigid body, and also finds broad application in such diverse fields as machine tools, the cruise control system In automobiles, and control in the attitude and gimbals of spacecraft. This Transmission proves the necessity and effect of a closed loop control. The study of the Rotating Transmission excited by its base motion is able not only to predict the rotational performance, but to obtain the fundamental data for vibration isolation. In this research, we compared the response characteristics of the two controllers by means of the experiments on PD controller and PID controller added on integral action. Furthermore, we studied the response abilities such as steady state error, overshoot, and ect. and the response velocities such as rising time, settling time, and ect. in the rotating transmission.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.561-564
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• 2005

The quality of a rotating body such as a washing machine depends on the vibration characteristics. So, the researches to reduce the vibration of a washing machine are actively performing, but it is very difficult to conduct these experiments because there are many design parameters affecting the vibration behavior. Accordingly, in this study it was complete to build a modeling of a drum washing mashing to analyze and predict vibration behaviors. The design parameters which affect the vibration were found, and the method for the systematic analysis of the design parameters was suggested using axiomatic design. In the previous study, the effect of the gasket has not considered on vibration behaviors, but in this study it was considered. The simulation results showed good agreements with the experimental results in the vibration displacement and the vibration tendency of a drum washing machine.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.715-720
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• 2005

The rotating transmission is made up of belts, mass disks and gears. This precise piece of equipment is controlled electro-mechanically by the mote. and operation program. The control strategy and the transmission can be changed by belts' stiffness and change of the mass and gear. This transmission can be modeled as a rigid body, and also finds broad application in such diverse fields as machine tools, the cruise control system in automobiles, and control in the attitude and gimbals of spacecraft. The study of the rotating transmission excited by its base motion is not only able to predict the rotational performance, but obtain the fundamental data for vibration isolation. In this thesis, we studied the response abilities such as steady overshoot, undershoot and ect. and the response velocities such as rising time, settling time, and ect. in the rotating transmission through PD control experiment.

• 센서학회지
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• 제29권3호
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• pp.205-210
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• 2020

The aim of this study is to develop a vertical vibration compensator that attenuates the vertical vibration of ships. The vibration compensator was designed according to the principle of generating vertical excitation forces by rotating two eccentric bodies of the same mass in opposite directions at the same rotational speed. In addition, the structural stability was analyzed using the finite element method. The maximum stress in the drive shaft was 95.6 MPa, which was approximately 35% of the allowable stress of the shaft material (SM45C, 270 MPa). The acceleration signals of the vibrator compensator body and the testbed were determined to evaluate the efficiency of the vibration compensator and the designed excitation forces. Subsequently, the excitation forces were estimated based on the relationship between force and acceleration. The estimated results were very close to the theoretical values with an error of less than 3%.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.360-368
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• 2010

Noise and vibration triggered by pile driving in a construction site not only give hard time to the surrounding areas but could also cause residents nearby to file civil complaints to the extent of bringing construction to a halt. To deal with this issue, construction engineers have worked strenuously to develop low noise & low vibration pile methods. A noise & vibration-free screw concrete pile method proposed in this study is one of the successful outputs. It penetrates pile underground by rotating and pressing in body of the pile to avert noise and vibration while maximizing bearing capacity. A prototype of noise and vibration-free precast screw pile method was manufactured, which is not seen anywhere in Korea and elsewhere, and have undergone pilot tests twice to determine construction method.