• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.131-133
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• 2014

Vibration exposure of the KTX and ITX-saemaeulho on the Gyung-Bu line was evaluated and compared in terms of human health based on ISO 2631. RMS value of KTX was calculated as much lower than ITX-saemaeulho in all travel sections. When VDV result of the two trains drived return travel from Seoul to Busan in single day is compared on the health guidance caution zone of ISO 2631, vibration exposure of KTX is safer than ITX-saemaeulho which is marginally under the caution line.

• Journal of Mechanical Science and Technology
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• v.19 no.7
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• pp.1405-1413
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• 2005

Malfunctions or critical fatigue problems often occur in mistuned periodic structural systems since their vibration responses may become much larger than those of perfectly tuned periodic systems. These are called vibration localization phenomena and it is of great importance to accurately predict the localization phenomena for safe and reliable designs of the periodic structural systems. In this study, a simple discrete system which represents periodic structural systems is employed to analyze the vibration localization phenomena. The statistical effects of mistuning, stiffness coupling, and damping on the vibration localization phenomena are investigated through Monte Carlo simulation. It is found that the probability of vibration localization was significantly influenced by the statistical properties except the standard deviation of coupling stiffness.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.6
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• pp.44-50
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• 2021

This study analyzed the stability of antenna equipped on vehicles by the link of modal analysis and random vibration analysis with the vibration data of MIL-STD-810H, METHOD 514.8. As a result of the random vibration analysis of antenna, the maximum equivalent stress 41.9MPa and minimum margin of safety 8.37 was generated in the bracket of antenna by the vertical direction vibration. Thus, it was found that antenna has enough stability during the operation.

• Journal of Magnetics
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• v.22 no.1
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• pp.109-121
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• 2017

Ferrofluids are a special category of smart nanomaterials which shows normal liquid behavior coupled with superparamagnetic properties. One of the earliest and most prospective applications of ferrofluids is in damping, which has prominent advantages compared with conventional damping devices: simplicity, flexibility and reliability. This paper presents the basic principles that play a major role in the design of ferrofluid damping devices. The characteristics of typical ferrofluid damping devices including dampers, vibration isolators, and dynamic vibration absorbers are compared and summarized, and then recent progress of vibration energy harvesters based on ferrofluid is briefly described. Additionally, we proposed a novel ferrofluid dynamic vibration absorber in this paper, and its damping efficiency was verified with experiments. In the end, the critical problems and research directions of the ferrofluid damping technology in the future are raised.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.9
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• pp.71-77
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• 2022

In times of war or emergencies, weapon systems, such as radars, must receive stable power. This can be achieved using improved onboard portable power systems made of steel containers. However, a breakdown can occur in the event of random vibration during transportation via a vehicle or train. Electrical-power shortages or restrictions pose a significant threat to security. In this study, Composite Wheeled Vehicle(CWV) data and rail cargo data with Acceleration Spectral Density(ASD), specified in MIL-STD-810H METHOD 514.8, were interpreted as input data of the three-axis random vibration method using ANSYS 19.2. Modal analysis was performed up to 500 Hz, and deformations in modes 1 to 117 were calculated to utilize all ASD data. The maximum equivalent stress in the three-axis direction was obtained using a random vibration analysis. Similarly, the margin of safety was calculated using the derived equivalent stress and material properties. Overall, the analysis verified that the portable container designed for the power supply system satisfied the required vibration demands.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.550-555
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• 2007

This paper introduces the mechanical vibration-measurements of vibration on ships(ISO 20283). Regulations and guidelines for vibration of hull structures, propulsion machinery and onboard equipments on ship were established mainly by classification societies or International Association of Classification Societies(IACS). The initial draft of ISO 20283 was proposed by USA and based on US military standards. Though these are not suitable to passenger and merchant ships, many experts have felt the need of the ISO regulation for the vibration measurement on ship. Hence, these standards are re-drafted and reviewed by particulate ISO members. In this paper, authors introduce the important agendas and the controversial items during setup of ISO 20283.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.466-469
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• 2002

The vibration measurement of the AC motor, the most typically used vibration source, is essential to evaluate the causes of unexpected excessive vibration in many mechanical systems. The motor contributes to excite the resonance of the mechanical systems, and in turn tilt amplified vibration of the mechanical parts cause the motor to vibrate severely. Without the vibration evaluation on the motor itself, it is time consuming to solve the vibration problems. This paper deals the vibration measurement method for the AC motor itself.

• Journal of Magnetics
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• v.19 no.3
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• pp.300-308
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• 2014

This paper develops a moving-magnet electromagnetic actuator for fast steering mirror (FSM). The actuator achieves a reasonable compromise between voice coil actuator and piezoelectric actuator. The stroke of the actuator is between the strokes of a piezoelectric actuator and a voice coil actuator, and its force output is a linear function of air gap and excitation current within our FSM travel range. Additionally, the actuator is more reliable than voice coil actuator as the electrical connection in the actuator is static. Analytically modeling the actuator is difficult and time-consuming. Alternatively, numerous finite element simulations are carried out for the actuator analysis and design. According to the design results, a real prototype of the actuator is fabricated. An experimental test system is then built. Using the test system, the force output of the fabricated actuator is evaluated. The test results validate the actuator analysis and design.

• Journal of Magnetics
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• v.19 no.2
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• pp.130-139
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• 2014

This paper focuses on the modeling and analysis a novel two-axis rotary normal-stress electromagnetic actuator with compact structure for fast steering mirror (FSM). The actuator has high force density similar to a solenoid, but its torque output is nearly a linear function of both its driving current and rotation angle, showing that the actuator is ideal for FSM. In addition, the actuator is designed with a new cross topology armature and no additional axial force is generated when the actuator works. With flux leakage being involved in the actuator modeling properly, an accurate analytical model of the actuator, which shows the actuator's linear characteristics, is obtained via the commonly used equivalent magnetic circuit method. Finally, numerical simulation is presented to validate the analytical actuator model. It is shown that the analytical results are in a good agreement with the simulation results.

• Journal of Magnetics
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• v.20 no.1
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• pp.69-78
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• 2015

This paper focuses on the design of a flux-biased rotary electromagnetic actuator with compact structure for fast steering mirror (FSM). The actuator has high force density and its torque output shows linear dependence on both excitation current and rotation angle. Benefiting from a new electromagnetic topology, no additional axial force is generated and an armature with small moment of inertia is achieved. To improve modeling accuracy, the actuator is modeled with flux leakage taken into account. In order to achieve an FSM with good performance, a design methodology is presented. The methodology aims to achieve a balance between torque output, torque density and required coil magnetomotive force. By using the design methodology, the actuator which will be used to drive our FSM is achieved. The finite element simulation results validate the design results, along with the concept design, magnetic analysis and torque output model.