• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.419-420
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• 2006

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.498-502
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• 2004

In a link-motion mechanism, numerous links are interconnected and each link executes a constrained motion at a high speed. Due to the complicated constrained motions of the constituent links, dynamic unbalance forces and moments are generated and transmitted to the main frame. Therefore unwanted vibration is produced. This degrades productivity and precise work. Based on constrained multi-body dynamics, the kinematic analysis is carried out to enable design changes to be made. This will provide the fundamental information for significantly reducing dynamic unbalance forces and moments which are transmitted to the main frame. In this work, a link-motion punch press is selected as an example of a link-motion mechanism. To calculate the mass and inertia properties of every link comprising a link-motion punch press, 3-dimensional CAD software is utilized. The main issue in this work is to eliminate the first-order unbalance force and moment in a link-motion punch press. The mass, moment of inertia link length, location of the mass center in each link have a great impact on the degree of dynamic balancing which can be achieved maximally. Achieving good dynamic balancing in a link motion punch press is quite essential fur reliable operation at high speed.

• The Journal of the Acoustical Society of Korea
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• v.16 no.1
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• pp.54-59
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• 1997

The vehicle vibrations result from the exciting forces which are caused by air resistance, engine firing, tire mass unbalance and tire uniformity. Especially, the shake and shimmy phenomena in the steering system are closely related to the vehicle vibration, the tire unbalance, and the tire uniformity. This study presents the shimmy phenomena due to the tire mass unbalance and the tire uniformity in order to investigate their effects.

• Tribology and Lubricants
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• v.17 no.1
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• pp.56-63
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• 2001

The dynamic behavior of rotor-bearing system used in swash plate compressor has been investigated using the combined methodologies of finite elements and transfer matrices. The finite element is formulated including the field element for a shaft section and the point element for swash plate, disk pulley and bearings. The Houbolt method is used to consider the time march for the integration of the system equations. The transient whirl response of rotating shaft supported on roller bearings is obtained, considering compression forces and unbalance forces at swash plate and driving pulley. And, the steady state displacements of the rotor are compared with a variation in unbalance mass. Results show that the loci of rotating shaft considering unbalance forces and external compression forces are more severe in flutter motion than with only unbalance forces.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.11
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• pp.1387-1395
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• 2013

When the center of mass of a railway wheel is not aligned with the geometrical center of the wheel axis, wheel unbalance occurs. If a railway vehicle runs without removing the wheel unbalance, vibrations will be produced. This will also cause wear and damage of the axle bearing. In this study, dynamic analysis of a railway vehicle with wheel unbalance was conducted to examine the reduction in critical speed and the resonance of the car-body and the effect on the magnitude of wheel unbalance was examined. In addition, the calculation of the car-body vibration owing to static and dynamic unbalance in the railway wheel shows that two-plane balancing is necessary.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.9
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• pp.107-115
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• 2020

The rotation accuracy of the main spindle that determines the accuracy of CNC machine tools is closely related to the quality of production because it directly affects the shape error and surface roughness of the workpiece. Therefore, the main spindle requires high rotation accuracy, rigidity, and rotation technology. This rotation accuracy is greatly affected by the bearing, center alignment between rotating parts, assembly tolerance, and unbalance of the rotation mass. In this study, the effects of the unbalance of the rotation mass of the main spindle on the rotation accuracy were investigated experimentally. In particular, we tried to study the technical reasons for improving the unbalance of the main spindle and maintaining the rotation accuracy as we verified the correlation between the vibration characteristics of CNC machine tools due to the specifically set unbalance amount and the surface roughness of the workpiece.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.602-607
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• 1997

Ball balance belong to a kind of automatic balancers opten referred to as direct balancer or passive mass systems. In such systems the balancing is achieved with free masses. One of the most prevalent problems encountered in washing is the vibration during spin cycle. The primary cause of this vibration is mass unbalance associated with non unform distribution of clothes. Front loading type machine of European style, especially, has inherent unbalance mass due to its shape and this then makes the vibration worse than top loading type machine, which is more popular in Korea. Since the mass distribution of cloths is random and can not be predicted in advance, direct automatic balances appear to be the only feasible alternative. The results form computer simulation and experimental testing will be presented together with stability implications.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.801-806
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• 2008

Large quantity of bending deformation as well as rotating torque fluctuation at the balance shaft are main struggles during the operation in a high speed rotation and thereby, two issues should be cleared at the design process of balance shaft module. Since two issues are highly related with balance shaft itself and particularly much sensitive to the location of both supporting bearing and unbalance mass, the design strategy on balance shaft should be investigated at the aspect of controlling two critical issues at the early stage of balance shaft design. To tackle two main problems, the formulation of objective function that minimizes critical issues, both bending deformation as well as torque fluctuation, is suggested to derive the optimal information on balance shaft. Then, optimal informations are reviewed at the practical logics and the guideline at the selection of locations, both supporting bearing and unbalance mass, is addressed at the final chapter.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.4
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• pp.104-110
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• 2012

The spindle with a built-in motor can be used to simplify the structure of machine tool system, while the rotor has unbalance mass inevitably. A high-speed spindle can be very sensitive to rotating mass unbalance which has harmful effect on many machine tools. Therefore, the balancing procedure to reduce vibration in rotating system is certainly needed for all high-speed spindles. So, it was performed with a spindle-bearing system for CNC automatic lathe by using numerical procedure. The spindle is supported by the angular contact ball bearings and the motor rotor is fixed at the middle of spindle. The spindle-bearing system has been investigated using combined methodologies of finite elements and transfer matrices. The balancing was performed through influence coefficient method and the comparison was made by whirl responses between before balancing and after balancing. As a result, balancing of simple spindle model reduced whirl orbit magnitude in case of a completely assembled spindle model.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.4
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• pp.1-7
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• 2010

Large quantity of bending deformation as well as irregular rotating torque fluctuation are the main struggles of the balance shaft module during a high speed rotation. Since two issues are much sensitive to the location of both supporting bearing and unbalance mass at a balance shaft, it is recommended to construct a design strategy on balance shaft at the early stage so as to save developing time and effort before approaches to the detailed design process. In this paper, an optimal design formulation is proposed to minimize the elastic strain energy due to bending as well as the kinematic energy of polar moment of inertia in rotation. Case studies of optimal design are conducted for different mass ratio as well as linear combination of objective function and its consequence reveals that global optimum of balance shaft model is existed over possible design conditions. Simulation shows that best locations of both supporting bearing and unbalance are globally 20% and 80%, respectively, over total length of a balance shaft.