• Proceedings of the KSME Conference
• /
• 2000.04a
• /
• pp.760-765
• /
• 2000

The study deals with the development of a computational procedure for evaluating the temperature rise in dry and lubricated multi-layered contacts of head/disk interface. A transient computational model with a transformed rectangular computational domain is utilized. A model and a computational method for micro-contact with sub-lubricated zone, including friction heat generation, have been presented. The model was applied, taking full account of the changes in contact area and contact load due to frictional heating. The computational distribution of temperature is obtained with the analytical findings for various composition and contact conditions. Especially, a rapid rise ($220^{\circ}C$ or above) in read head temperature lese to a saturation in the influence of a thermal spike on signal performance. This general class of problems can be treated provided that heat generation distribution and layer properties are known.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.8 no.3
• /
• pp.217-223
• /
• 1984

An attempt is made to predict the wear behavior of ion-nitrided metal, when wear arises from asperity interactions. The analysis demonstrates that wear mechanisms are not inconsistent with observed behavior, indicates and approaches to a better appreciation of the effects of such factors as nitrided layer formation and surface topographical features. It was found on ion-nitriding that penetration rate and case development are faster and wear properties of the final product are more improved than conventional gas and salt-bath methods of nitriding.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.29 no.7 s.238
• /
• pp.795-804
• /
• 2005

As the flying height of a slider in a hard disk drive decreases, the slider and disk are more likely to come in contact and generate contamination particles. Since particle contamination can cause serious problems including thermal asperity, it must be prevented to increase storage capacity. When particles are generated in a HDD, particles can be charged and have a few number of elementary charges. In this paper, the size distribution of particles and electrical current due to particle according to the disk rotational speed were measured. Also, the average number of elementary charges was calculated from experimental data. SEM images of particles were obtained by using a particle sampler designed in our laboratory.

• Tribology and Lubricants
• /
• v.11 no.5
• /
• pp.172-176
• /
• 1995

This study deals with thermomechanical cracking between the friction surface and the interior of the brake disc. Analytical model considered in this study was a semi-infinite solid subjected to the thermal loading of an asperity moving with a high speed. The temperature field and the thermal stress state were obtained and discussed on the basis of Von Mises and Tresca Yielding Criterion. Analytical results showed that the dominant stress in cracking of friction brake is thermal stress and cracking location is dependent on the friction coefficient of contact and Peclet number. On the basis of analytical results thermomechanical cracking model is proposed.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2001.11a
• /
• pp.331-340
• /
• 2001

Elastic-Plasitc Finite element analysis is peformed about the TiN coated medium. The normal contact is simulated by a rigid asperity pressing the surface of an elastic-plastic half-surface. The case of a surface film stiffer than the substrate is considered, and general solutions for the subsurface stress and deformation fields are presented for several coating thickness. Additionally, the critical normal loads for deformation in the substrate and coating fracture are calculated when the yield of TiN film follows the Maximum Principal Stress Theory and Von Mises Theory. The results can be subsumed in failure maps for TiN thin film on steel.

• 정보저장시스템학회:학술대회논문집
• /
• 2005.10a
• /
• pp.179-183
• /
• 2005

Particles in the HDD can cause serious damages such as scratches and thermal asperity(TA) at the head/disk interface(HDI). Accordingly, particles cause data loss including physical and electrical damages. To improve the reliability of head-disk interface, understanding the damage characteristics at the HDI due to particle interactions is required. The materials such as $A1_2O_3$, TiC and aluminum were used in this experiment. The size and hardness of particles injected into the HDI are closely relevant to surface damage caused the data loss on the disk and head. In this paper, a variety of scratches were analyzed using scanning electron microscope(SEM) and atomic force microscope(AFM). In order to analyze defects of very small size on the disk, optical surface analyzer(OSA) was also used.

• Journal of the Korean Geotechnical Society
• /
• v.16 no.6
• /
• pp.161-172
• /
• 2000

자연암석절리 및 인공 절리에 대하여 일정수직응력제어, 일정 수직하중제어 그리고 무한 강성제어가 가능한 암석 절리면 전단기 시험기를 개발하였다. 이 시험기는 전단변위에 의한 첩촉면적의 변화량을 계산하여 하중변화량을 조절하여 일정수직응력상태를 유지한다. 수직하중에 따른 시험기 강성에 의한 변화향이 제어 프로그램 내에서 제어되어 순수한 시편의 변위량을 출력하도록 하였다. 전단하중에 따른 시험기 강성에 의한 변위량은 상, 하부 전단상자의 상대변위 측정으로 최소화하였다. 전단거동 중의 자유도는 전당방향에 대하여 수평이도, 연직이동, 피칭, 롤링이 가능하도록 하였다. 자연절리면을 모사한 석고시편에 대하여 일정 수직응력 제어, 일정수직하중제어 그리고 무한 강성제어 조건으로 시험하여 제어상태 검증 및 비교를 하였다. 또한 경사각이 16.7˚와 22.6˚인 톱니형 시편에 대하여 시험한 결과 경사각 16.7˚와 22.6˚는 JRC로 10과 15를 나타내었으며, 첨두팽창각이 첨두전단강도에서 발생되며, Barton의 모델과 잘 일치함을 보였다.

• Transactions of the Society of Information Storage Systems
• /
• v.7 no.2
• /
• pp.65-69
• /
• 2011

Head Disk Interface (HDI) in a Hard Disk Drive (HDD) has decreased to achieve high areal density. Thus, the contact between a slider and a disk becomes more important. The contact between the slider and the disk can cause severe wear and damage of both the slider and the disk. Especially, Touch Down (TD) that the contact occurs continuously and repeatedly is extremely dangerous. Therefore, it is necessary to analyze the unstable bouncing vibration of the slider in head-disk interface. In this paper, we investigate the characteristic and causes of the Touch Down.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.21 no.5
• /
• pp.237-244
• /
• 2017

This study proposes a numerical model to explain the closely placed double modes in the vibration of a layered stone pagoda system. The friction surface between the stones is modelled as the Timoshenko finite element while each stone layer is modelled as a rigid body. It is assumed that the irregular asperity on the friction surface enables the stone to be excited. This results in the closely placed modes that are composed of natural modes and self-excited modes. To examine the validity of the proposed model, a set of modal testing and analysis for a layered stone pagoda mock-up model has been conducted and a set of closely placed double modes are extracted. Applying the extended sensitivity-based system identification technique, the various system parameters are identified so that the modal parameters of the proposed numerical model are the same with those of the experimental mock-up. For a horizontal impulse excitation, the simulated acceleration responses are compared with measurements.

• Proceedings of the KIEE Conference
• /
• summer
• /
• pp.1109-1111
• /
• 2004

This paper deals with the calculation of contact resistance depending on the applied force by modeling surface roughness. The true contact surface area is made up of many asperities of varying heights which is close to Gaussian distribution. The mean square deviation and the mean value of the Gaussian distributed asperity heights were determined in this paper. The elastic deformation of the surface asperities according to the increasing of applied force were considered. The contact resistance was also calculated by using the Greenwood analysis.