• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.132-137
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• 1997

In this study, the effect of load torque on the synchronous whirling of a rotor system has been studied analytically. Results show that the critical value of load torque to damping exists above which synchronous response decreases with increasing load torque. It has been also shown that the synchronous whirling amplitudes are more sensitive to the value of eccentricity and the ratio of disk radius to shaft length of the rotor system than other design parameters for a fixed value of load torque.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.4 s.97
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• pp.429-436
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• 2005

In turbomachinery rotor, there are small differences in the structural and/or geometrical properties of individual blades, which are referred to as blade mistuning. Mistuning effect of the forced response of bladed disks can be extremely large as often reported in many studies. In this paper, the pattern optimization of intentional mistuning for bladed disks considering with damping and coupling effect is the focus of the present investigation. More specifically, the class of intentionally mistuned disks considered here is limited, for cost reasons, to arrangements of two types of blades (A and B, say) and Genetic Algorithm and steepest descent method are used to optimize the arrangement of these blades around the disk to reduce the forced response of blade with different damping and coupling stiffness. Examples of application involving both simple bladed disk models and a 17-blade industrial rotor clearly demonstrate the significant benefits of using this class of intentionally mistuned disks.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.211-217
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• 1998

A disk rotor dynamic analysis program called by DR. DAP is developed for disk drive spindle systems to analyze dynamic characteristics in operation and to estimate the effects of excitation sources. It is applicable to design for stabilization and to select parts of disk drive spindle systems. The disk drive spindle system in this program is modeled as a flexible shaft with multiple flexible disks, which is supported by bearings and driven by electric motor, and its complicated coupled vibration characteristics are analyzed by using a substructure synthesis technique with the assumed-modes method. All the coupled modes of interest can be well predicted by the example of a three disk hard disk drive with the three tuning parameters. It is also shown that, with the introduction of the excitation sources associated with the defects of ball bearing systems, the magnetic unbalance of spindle motor, the program can well predict the stability of the system, i.e., the possibility of resonance.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.620-622
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• 1992

Magnetic characteristics of a brushless disk type motor has been analyzed taking into account the magnetization distribution in the rotor magnet. This paper describes a method for calculating the 3D flux density in the air gap and calculates the induced voltage of the windings and the torque betweens the permanent magnet and the amateur current.

• Tribology and Lubricants
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• v.11 no.5
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• pp.150-155
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• 1995

In order to analyze the thermal effects of the rotor models, the finite element technique was used in this study. The length of the hat was investigated as a design parameter. At the start of each brake application the disk surface temperature rapidly increases to a maximum value and then decays due to external cooling and thermal conduction to the hat. The calculated results indicate that the long length of the hat shows the minimum deformation in axial direction, which is related to the thermal problems, coned wear, vibration and noise.

• Journal of Power System Engineering
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• v.10 no.3
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• pp.67-72
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• 2006

The effect of manufacturing parameters on wear and improve cooling of motorcycle break system was studied using a disk-on-pad type friction tester. Such parameters conditions have an effect on the wear and improve cooling factor such as applied load, sliding speed, frictional time and number of ventilated disk hole. However, it is difficult to know the mutual relation of these factor. In this study, the wear and cooling characteristics using design of experiment containing 4 elements were investigated for an optimal condition for the best motorcycle disk break system employing Taguchi robust experimental design. From this study, the result was shown that vents have an effect on convection area improving more cooling ability and reduced wear of the disk.

• Journal of KSNVE
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• v.8 no.3
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• pp.477-484
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• 1998

An analytical procedure on the base of the substructure synthesis and assumed modes method is developed to investigate the flexibility effect of bladed disk assembly on vibrational modes of flexible rotor system. In modeling the system, Coriolis forces, gyroscopic moments, and centrifugal stiffening effects are taken into account. The coupled vibrations between the shaft and bladed disk are then extensively investigated through the numerical simulation of simplified models, with varying the shaft rotational speed and the prewist and stagger angles of the blade. It is found that the Coriolis and inertia forces and the inertia torque, which are induced by the one nodal diameter modes of the bladed disk and vary depending upon the stagger and prewist angles, lead to the coupled motions of the shaft and the bladed disk.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.43-49
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• 1997

A rotating rigid disk, attached on a flexible shaft or supported by a torsional spring, experiences precessional whirling due to gyroscopic moment loading. It is well known in rotor dynamics area that, as the rotational speed increases, the precessional mode of the rotating rigid disk starts splitting into two: forward and backward precessional modes. On the other hand, it is also well known in disk vibration area that a rotating flexible disk also shows another kind of mode splitting phenomenon due to the rotation, resulting in forward and backward traveling waves. When rotating multiple flexible disks are coupled in vibration with the supporting Flexible shaft, the associated mode splitting should be compatible with the two seemingly different vibration analysis methods. This paper investigates the possibility of fusing the precessional and traveling wave mode splittings so that the bending coupled disk vibrations in HDD spindle systems can be better understood.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.101-109
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• 1997

An analytical procedure on the base of the substructure synthesis and assumed modes method is developed to investigate the flexibility effect of bladed disk assembly on vibrational modes of flexible rotor system. In modeling the system, Coriolis forces, gyroscopic moments, and centrifugal stiffening effects are taken into account. The coupled vibrations between the shaft and bladed disk are then extensively investigated through the numerical simulation of simplified models, with varying the shaft rotational speed and the pretwist and stagger angles of the blade. It is found that the Coriolis and inertia forces and the inertia torque, which are induced by the one nodal diameter modes of the bladed disk and vary depending upon the stagger and pretwist angles, lead to the coupled motions of the shaft and the bladed disk.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.4 s.247
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• pp.442-450
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• 2006

This paper describes the new modal analysis method to detect the presence of the breathing crack in a general rotor system with disk asymmetry and stator anisotropy. It is proposed that the modal analysis using directional frequency response functions (dFRFs), which, accounting for the directivity in modes, clears the heavily over-lapping of other harmonics occurring from non-isotropic properties in addition to those due to crack, can provide an effective method to detect the modes by a crack. The simulations from the simple general rotor model show that the r-dFRFs (reverse dFRFs) for asymmetry confirms a good indicator of the presence of the breathing crack and the instability is primarily influenced by the shaft asymmetry than the breathing crack.