• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1996.10a
• /
• pp.324-329
• /
• 1996

Vibration characteristics of the feeding system in a CD-ROM drive are identified by a theoretical modeling as well as vibration experiments. For this purpose, we establish a vibration model due to the rigid-body motion and perform the modal testings using the impact hammer and shaker. The analysis and experiments show that the feeding system has three rigid-body vibration modes in the low-frequency region and two of them come from the tilting modes. In order to remove the harmful tilting modes for the tracking servo control, a methodology to find the optimal positions of the dampers is also proposed in this study.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.17 no.6 s.123
• /
• pp.524-530
• /
• 2007

This paper presents a friction model to realize self-excited vibration of multi-body systems. The friction coefficient is modeled with a spline function in most commercial codes. Even if such a function resolves the problem of discontinuity in friction force, it cannot realize self-excited vibration phenomena. Furthermore, as the relative velocity approaches zero, the friction coefficient approaches zero with the conventional model. So, slip occurs when small force is applied to the system. To avoid these problems a new friction model is proposed in this study. With the new friction model, the self-excited vibration can be realized since the friction coefficient changes with the relative velocity. Furthermore, the slip phenomena could be reduced significantly with the proposed model.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.12
• /
• pp.5689-5695
• /
• 2012

In this study, vibration properties of seat and human body are analyzed through test and numerical analysis methods by taking into account the viscoelastic characteristics of polyurethane foam as seat material which is applied for vehicle. These viscoelastic characteristics which show nonlinear and quasi-static behavior are obtained by compression test. In addition, the viscous elastic property of polyurethane foam is modelled mathematically by using convolution integral and nonlinear stiffness model. In order to analyze the performance on ride comfort of seat, vertical vibration model is established by using dynamic model of seat and vertical vibration model of human body at ISO5982, and so the related motion equations are derived. A numerical analysis simulation is applied by using the nonlinear motion equation with Runge-Kutta integral method. The dynamic responses of seat and human body on the input of vibration acceleration measured at the floor of the railway vehicle are examined. The variation of the index value at ride comfort on seat design parameters is analyzed and the methodology on seat design is suggested.

• Journal of the Korea Convergence Society
• /
• v.9 no.10
• /
• pp.371-376
• /
• 2018

The purpose of this study is to clarify the effects of whole-body vibration and to provide scientific basis for effective exercise by analyzing the differences in lower extremity muscle activation according to squat position during whole body vibration. In this study, muscle activation during whole-body vibration was measured in 10 healthy males in their 20s with no orthopedic conditions during standing posture, deep squat, half squat, and heel raise squat. Muscle activation was compared by measuring the root mean square (RMS) with electromyography electrodes attached to lateral gastrocnemius, tibialis anterior, vastus lateralis, and biceps femoris. The vibration intensity was applied in combinations of the volumes of 50 and 80 and the frequencies of 10, 25, and 40 Hz in each posture. The results showed that there were differences in muscle activations of external gastrocnemius, tibialis anterior, and vastus lateralis among the position(p<.05). The heal raise squat was found to have a high muscle activation effect.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1996.04a
• /
• pp.25-28
• /
• 1996

This paper addresses the issues and difficulties encountered in developing a 12-axis measurement system for the assessment of whole-body vibration exposed from the body contact area. The contents of related survey work and the ideas from Professor Griffin in ISVR, that have led to its successful development, are introduced here. The developed 12-axis measurement system is shown to satisfy the international standards of ISO 2631 and BS 6841 in EC. This system is expected to play a key role in assessing the ride quality of passenger cars that is rapidly becomes much interest in Korean car-makers and tyre-makers.

• Journal of Advanced Marine Engineering and Technology
• /
• v.33 no.4
• /
• pp.476-483
• /
• 2009

A linear compressor used in a refrigerator has higher energy efficiency than a reciprocating compressor, but its vibration level is still severe than others. The vibration level of linear compressor at the frequency of 60Hz is dominant since it is the exciting frequency of a motor. In this paper, a simulation tool to predict the shell vibration of the linear compressor was developed. The shell and body parts in a compressor were assumed to be 3-dimensional rigid body having both translational and rotational motion, while the reciprocating piston part has only 1-dimensional translational motion. The flexible loop-pipe was modeled by in-house code of finite element method. To verify the developed tool, five cases of different loop-pipe shapes were examined experimentally. The results by the developed tool showed good agreements with those by experiments.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.06a
• /
• pp.900-910
• /
• 2000

This study have been performed to investigate the dynamic behavior of the Korean High Speed Train(KHST) during the conceptual design process. This study gets a focus on the analysis of the rigid model, for which the yaw damper layout is modified in a nonlinear limit cycle analysis. In this study, influences of the system parameters such as stiffness of suspension and connection elements as well as damping coefficients were studied and an optimized parameter set is achieved. Throughout the dynamic calculation of KHST on the straight and the curved track, vibration accelerations in car body, ride comforts and wheel rail forces are investigated. Finally the vibration characteristics from rigid car body are compared with those due to the influence of elastic car body.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2012.10a
• /
• pp.613-616
• /
• 2012

A multi body simulation (MBS) model is developed for predicting the impact harshness of the vehicle. Impact harshness is the vehicle performance to evaluate the impulsive vibration behavior during driving over an obstacle of the road. Thus, the approach is simulated on the time domain for considering the transient behavior of the vehicle. The validity of vehicle component modeling of bushes, dampers and structure flexibilities is verified. The simulations are compared with the test results in both of vertical and longitudinal directions. In particular, the vertical vibration of the vehicle is significantly affected by the body flexibility. Through the sensitivity analysis, main factors for the impact harshness performance are investigated.

• Proceedings of the Korean Institute of Industrial Safety Conference
• /
• 1998.11a
• /
• pp.353-358
• /
• 1998

Vibrations exposured to human whole-body are transmitted through the contact area of a human body, such as feet, hip and back directly in contact with vibrating surface. they apparently leads to the decrease of human comfort, the reduction of working efficiency or normal activities, and, furthermore, causes the loss of health and safety. In this study, UH-1 vibration has been measured to produce the flight-time limitation at each mission Results of this study show that the most significant peaks appear at a main rotor blade-passage frequency and that the vibration level in ground is higher than that in airborne In addition, it is shown that the most affective aspect for the flight-time limitation is ground vibration level

• Proceedings of the KSR Conference
• /
• 2003.05a
• /
• pp.700-705
• /
• 2003

The object of this study is to ensure the stability of flat freight cars using vibration performance test and static load test of body structures. We examined the flat car though static load test and dynamic characteristics analysis related traveling stability and vibration performance. In the results of static load test of body structures for flat car, all structures satisfied allowable stress of materials. The vibration performance test was satisfied with allowable standards. Although flat car exceed speed a little at some speed interval, it was estimated that the cause was not cars but rail.