• Journal of KSNVE
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• v.9 no.6
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• pp.1234-1239
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• 1999

This research investigates the characteristicsw of NRRO in a 2.5" HDD by using FEM, modal testing and runout analysis, and reduces NRRO using visco-elastic damping material. Most frequency components of NRRO are generated by the defects of ball and rotating race, and they can be determined by the kinematic analysis of ball bearing. It also proposes the novel design of a spindle motor that can reduce NRRO effectively by inserting the visco-elastic damping material to one of the transmission path of NRRO, i.e., where the strain energy is highly concentrate. By this technique, NRRO is reduced by 27%. 27%.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.3
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• pp.41-47
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• 2005

This paper deals with a squeal noise in a brake system. It has been proved that the squeal noise is influenced by the angular misalignment of a disk, disk run-out, with the previously experimental study. In this study, a cause of the noise is examined by using FE analysis program(SAMCEF) and numerical analyses with a derived analytical equation of the disk based on the experimental results. The FE analyses and numerical results show that the squeal noise is due to the disk run-out as the experimental results and the frequency component of the noise equals to that of a disk's bending mode arising from the Hopf bifurcation.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.595-600
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• 2004

This paper deals with a cause analysis of a squeal noise in a brake system. It has been proved that the squeal noise is influenced by the angular misalignment of a disk, disk run-out, with the previously experimental study. In this study, a cause of the noise is examined by using FE analysis program(SAMCEF) and numerical analyses with a derived analytical equation of the disk based on the experimental results. The FE analyses and numerical results show that the squeal noise is due to the disk run-out as the experimental results and the frequency component of the noise equals to that of a disk's bending mode arising from the Hopf bifurcation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.223-228
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• 2006

Brake judder of an automotive vehicle is defined as an abnormal vibration of low frequency during braking. Under the assumption that judder occurs due to disc run-out and is a resonance phenomenon with a specific parts of the automobile, computational simulations using SAMCEF software were performed in this paper. The results show that the stabilizer of the car is a possible part which makes the judder vibration due to resonance. And initial braking velocity, the magnitude of run-out, and the friction coefficient between disk and pad are the influential factors to the brake judder.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.790-795
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• 2000

디스크마다 일정영역을 할당하여 위치정보를 기록하는 임베디드 서보방식 하드디스크는 데이터가 저장되는 데이터 영역사이에서 스핀들 런아웃, 공진과 디스크 플러터 등에 의하여 Gaussian 분포를 가지는 트랙에서 벗어나는 오차를 가지게 된다. 더높은 저장밀도와 빠른 기록속도를 요구함에 따라서 디스크의 회전속도가 올라감에 의한 디스크 면진동에 의한 헤드 위치오차가 중요하게 대두되고 있다. 본 연구에서는 헤드위치 오차량을 계산하기 위하여 고속탐색이 가능한 수정된 Barasch의 수치해석법, 유한요소법, 그리고 실험을 통하여 적용가능성을 확인하였으며 같은 드라이브내에서 디스크의 사이즈를 바꿈에 의한 디스크 동특성의 해석과 변환율을 이용하여 오류가 발생할 수 있는 트랙 벗어남과 저장밀도의 상관관계를 살펴보았다.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.5
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• pp.118-124
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• 2004

To investigate the mechanics of brake squeal noise, the sound and vibration of an actual brake system was measured using a brake dynamometer. The experimental results show that disk run-out due to the misalignment of brake disk varies with brake line pressure and becomes the important factor of brake squeal noise generation. Also, it was confirmed that the frequency of the squeal noise equals to the natural frequency of the disk bending mode.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.352-357
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• 2002

In recent years, the demand of mobile device, such as digital camera, camcoder and PDA, increases remarkably. So, requirements of the mobile information data storage used in the mobile devices increase noticeably also. 1' micro data storage is a kind of mobile storage ,which has a CF type II form factor, and the similar structure of the general 3.5' HDD. In this paper, we performed the vibration analysis of the 1' micro data storage, such as measurement of the NRRO of the disck, and modal analysis.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.11
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• pp.1176-1181
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• 2004

In high-capacity disk drives with ever-growing track density, the allowable level of position error signal(PES) is becoming smaller and smaller. In order to achieve the high TPI(track per inch) disk drive, it is necessary to improve the writing accuracy during the servo track writing(STW) Process through the reduction of track mis-registration sources. Among the main contributors of the non-repeatable runout(NRRO) PES, the disk vibration and the head-stack assembly vibration is considered to be one of the most significant factors. Also the most contributors of repeatable runout(RRO) come from the contributors of NRRO which is written-in at the time of STW process. In this paper, the effect of NRRO on servo written-in RRO is Investigated by experimentally, and the experimental result shows that the written-in RRO can be effectively reduced through a STW process under low dense medium condition such as semi-vacuum.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.5
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• pp.338-345
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• 2002

The study presents a new testing and analysis method for brake judder on vehicle. For the identification of the excitation mechanism of a brake judder, it is necessary to measure the dynamic brake disc geometry during braking on vehicle. The non-contact sensor system was used to monitor the brake disc geometry. Brake torque variation (BTV) caused by disc thickness variation (DTV) is the primary excitation for brake judder. The mechanical effects generating BTV are linked not only to initial manufacturing tolerances but also to uneven wear. Therefore, the brake disc geometry should be strictly managed to initial condition. The aim of this study has been to measure the dynamic DTV and runout on vehicle and analyze the influence of test parameters on brake judder and compare the disc component with vehicle matching about the DTV Profile. As a result of this study, The amplitude of brake judder is proportional to vehicle speed and fluid pressure fluctuation on braking. The major sources of brake judder are directly related to disc thickness variation and side runout variation of corner assembly (disc, hub. bearing).

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.238-241
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• 2008

A brake system in automobile is one of the important parts that directly affect the safety of passengers. Particularly, disk brake module is applied to almost all kinds of automobile brake system due to its remarkable braking power and braking distance. In the disk brake module of an automobile, the bolt for tire wheel is assembled to the disk brake hub by interference fit (bolt pressing process). The process induces small deformation whose range is within tens of ${\mu}m$ and this deformation may cause the runout badness of the whole disk brake module, and even braking problems such as judder or squeal phenomena which makes the loss of braking efficiency. In this study, bolt pressing fit into hub was simulated by $ANSYS^{TM}$, a commercial structure analysis program. Also, the aspect and the cause of hub displacement were analyzed and the solution for decreasing runout of hub was proposed.