• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.852-858
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• 2007

This paper investigates the dynamic characteristics of a tilted HDD spindle system with fluid dynamic bearings (FDBs). Tilting motion of a HDD spindle system may be caused by improper manufacturing tolerance, such as imperfect cylindricity between shaft and sleeve of FDBs, imperfect perpendicularity between shaft and thrust as well as the gyroscopic moment of the unbalanced mass of the rotating part. Tilting motion may result in the instability of the HDD spindle system and it may increase the disk run-out to limit memory capacity. This research proposes a modified Reynolds equation for the coupled journal and thrust FDBs to include the variable film thickness due to the cylindricity and the perpendicularity. Finite element method is used to solve the Reynolds equation for the pressure distribution. Reaction forces and friction torque are obtained by integrating the pressure and shear stress, respectively. The dynamic behavior is determined by solving the equations of a motion of a HDD spindle system in six degrees of freedom with the Runge-Kutta method to study whirling and tilting motions. This research shows that the cylindricity and the perpendicularity increase the tilting angle and whirl radius of the rotor.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.141-146
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• 2013

This research investigates the stability analysis for the rotating and the stationary grooved journal bearing. The dynamic coefficients of the journal bearing are calculated by using FEM and the perturbation method. When journal bearing is in whirling motion, the dynamic coefficients have time-varying components as a sine wave due to the reaction force of oil film toward the center of journal even in the steady state. The solutions for the equations of motion can be assumed as the Fourier series expansion. The equations of motion can be rewritten as the linear algebraic equations with respect to the Fourier coefficients. Then, stability of the grooved journal bearing can be calculated by Hill's infinite determinant. The periodic function of dynamic coefficients is derived using Fourier Fast Transform(FFT).The stability of journal bearing is determined as rotating speed increases and the stability of rotating grooved journal bearing is compared and discussed with the stability of stationary grooved journal bearing.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.986-992
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• 2014

This research investigates experimentally and numerically the tilting angle, eccentricity ratio, flying height of axial direction, friction torque, and critical mass of the HDD disk-spindle system due to HDD positioning angle. The tilting angle and the eccentricity ratio are the maximum when the HDD positioning angle is $90^{\circ}$ respect to horizontal position because the external force in radial direction and the torque applied to the rotating part are the maximum when the HDD positioning angle is $90^{\circ}$. The flying height increases with the increase of the HDD positioning angle because the direction of gravity applied to the rotating part changes. The friction torque increases with the increase of the HDD positioning angle until it becomes $60^{\circ}$, and decreases with the increase of the HDD positioning angle after it becomes $60^{\circ}$. The stability is the maximum when the HDD positioning angle is $90^{\circ}$.

• Journal of Advanced Marine Engineering and Technology
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• 제22권1호
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• pp.35-41
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• 1998

A Self-compensating liquid balancer is proposed, which consists of the vessel contains liquid available to compensate for rotor unbalance, and the vessel provides four sets of suction pipe and reservior. Under the centrifugal field the liquid moves through the pipe from the side of the unbalance mass to the reservior located on the symmetrically opposite side. The liquid balancer was confirmed experimentally to be useful for the balancing of rotor over the critical speed, and the whirling amplitude after balancing decreases to almost constant value in spite of the location and size of unbalance.

• 대한조선학회 특별논문집
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• 대한조선학회 2005년도 특별논문집
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• pp.134-137
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• 2005

Recently, in VLCC, shafting system is stiffer due to large engine power whereas hull structure is more flexible due to scantling optimization, which can be suffered from alignment damage by incompatibility between shafting and hull, In this study, shafting system without stern tube forward bush was adapted for less sensitive system against external factors. Also, shaft alignment analysis was considered with hull deflection at various ship loading conditions and stern tube after bush of long journal bearing was evaluated by static squeezing pressure and dynamic oil film pressure with sloping control. Whirling vibration was also reviewed to avoid resonance with propeller blade order. So, reliable shafting design for VLCC could be achieved through optimized alignment analysis for the system without stern tube forward bush.

• Composites Research
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• 제14권3호
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• pp.77-89
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• 2001

초고속 일체형 주축의 공진주파수가 일체형 주축 시스템의 모터 회전자의 질량과 주축의 굽힘 강성에 의존하기 때문에 초고속 주축 시스템의 동적 특성을 향상시키기 위해 주축과 회전자를 각각 고분자 기지 섬유강화 복합재료와 자성분말이 함침된 에폭시 수지를 이용하여 설계하였다. 설계된 복합재료 회전자의 자기 특성을 향상시키기 위해 내부에 강철 코어를 삽입하였으며, 강철 코어와 전도체 봉의 기하학적 형상의 변화가 전동기의 성능에 미치는 효과를 파악하기 위해 자기 해석을 수행하였다. 유한요소해석을 통해 복합재료 회전자의 최적의 기하학적 조건을 제안하였다. 또한 복합 재료 회전자 재료의 열특성을 파악하기 위해 TMA, DMA및 VSM을 이용한 기계적, 전자기적 물성측정을 수행하여 복합재료 회전자의 최적 설계에 적용하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1055-1056
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• 2007

Asymmetric electro-magnetic force caused by the frictional worn bearing, rotor misalignment and unbalanced rotor etc. generates an asymmetrical operation, vibration and electro-magnetic noise. The need for detection of these rotor eccentricities has pushed the development of monitoring methods with increasing sensitivity and noise immunity. This paper is proposed the analysis method of the squirrel-cage induction motor driven by IGBT inverter using finite element method (FEM) and subroutine. The effect of the unbalanced magnetic pull in the inverter-fed induction motor which is in asymmetrical whirling motion is presented. The analysis results of rotor eccentricity could compare with motors which have been made normal air-gap motor and irregular air-gap motor and verify reliability. The simulation and experiment results can be useful for on-line faults detection monitoring system of induction motors.

• Journal of Advanced Marine Engineering and Technology
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• 제33권8호
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• pp.1152-1161
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• 2009

신조선 선박에서 시운전 중 주 추진 시스템의 동력을 측정하는 방법은 스트레인 게이지를 이용하여 축의 변형률로부터 얻어지는 직접적인 방법과 기계적인 또는 전기적인 픽업을 이용하여 계측한 실린더연소압력으로부터 환산된 면적에 의한 간접적인 방법으로 구분할 수 있다. 이러한 동력은 장주기로 선박의 여러 가지 해상 운동에 의해서 그리고 단주기로는 축계의 비틀림, 축계 배치 및 횡진동의 영향에 의해서 변동한다. 본 논문에서는 축동력측정과 평가를 위하여 통계적인 해석법을 소개하고 있고, 저속2행정디젤엔진과 감속기를 포함 중속 4행정 디젤엔진 모델에 의해서 이들이 확인되고 있다.