• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.07a
• /
• pp.193-194
• /
• 2005

By the high-temperature pad conditioning process: The slurry residues in pores and grooves of the polishing pad were clearly removed. These clear pores and enlarged grooves made the slurry attack the oxide surface. The changed slurry properties by high-temperature pad conditioning process made the oxide surface hydro-carbonate to be removed easily.

• Proceedings of the KSR Conference
• /
• 2011.10a
• /
• pp.800-806
• /
• 2011

Thermal expansion which occurs at the high speed rail joint is proportional to the free length from the point of fixity. This thermal expansion behaves similar to free expansion because the girder longitudinal stiffness is much larger than longitudinal resistance of rail pads. But the longitudinal displacement in the long rail is nominal because the longitudinal support condition of the girder is normally MFM(movable-fix-movable) system. Due to these girder expansion characteristics, there is longitudinal relative displacement at the rail pad and rail fastener spring which connects rail and girder. If the relative displacement between rail and girder is beyond the elastic limit for the rail pad, rail fastener system shall be applied using sliding fastener to prevent rail pad damage and fastener separation resulting from slip. On the other hand, train vertical vibration and tilting can occur due to the lack of fastener vertical force if the sliding fastener is applied at the girder joint. In the high speed rail bridge, vibration can occur due to the spring stiffness of the elastomeric bearing, also both vertical downward and upward displacement can occur. The elastomeric bearing vertical movement can cause rail displacement and finally the stability of the ballast is reduced because the gravel movement is induced.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.33 no.4
• /
• pp.337-345
• /
• 2009

This paper investigates the reliability of district heating pipes at thermo-elastic fatigue loading. District heating pipes, subjected to $120^{\circ}C$ and $16kg_f/cm^2$ due to water distributing service through inside the pipes, should endure long term cyclic thermal-mechanical loadings. The heating pipes are the co-centric tubes of steel pipe, poly urethane(PUR) insulator, and high density poly ethylene(HDPE) case. On installation, foam pad is externally wrapped for accommodating stress reduction near the bend sections of pipes. However, there have been frequent reports on the failures of bend sections in the middle of long term service. This study scrutinizes the observed failures near the bend sections through applying the finite element methods. Specially in this study, heating pipes are studied on the influence of foam padding on failures and proposed new designs for reinforced bend without foam pad.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.16 no.11
• /
• pp.2487-2494
• /
• 2012

In this paper, a thermal energy harvesting circuit with MPPT control is designed. MPPT(Maximum Power Point Tracking) control function is implemented using the linear relationship between the open-circuit voltage of a thermoelectric generator(TEG) and its MPP voltage. The designed MPPT control circuit traces the maximum power point by periodically sampling the open circuit voltage of a TEG, makes the reference voltages using sampled voltage and delivers the maximum available power to load. Simulation results show that the maximum power efficiency of the designed circuit is 94%. The proposed thermal energy harvesting circuit is designed with $0.35{\mu}m$ CMOS process, and the chip area except PAD is $1168.7{\mu}m{\times}541.3{\mu}m$.

• Elastomers and Composites
• /
• v.53 no.4
• /
• pp.220-225
• /
• 2018

Resilient pads play a major role in reducing the impact of loads on a rail in a rail-fastening system, which is essentially used for a concrete track. Although a compression set test is commonly used to measure the durability of a resilient pad, the static spring constant is often observed to be different from the fatigue test. In this study, a modified compression set test method was proposed to monitor the variations in the compression set and static spring constant of a resilient pad with respect to temperature and time. In addition, the life of the resilient pad was predicted by performing an acceleration test based on the Arrhenius equation.

• Tribology and Lubricants
• /
• v.36 no.1
• /
• pp.27-33
• /
• 2020

Self-equalizing tilting pad thrust bearings are usually employed in turbomachines to achieve high stability and reliability. A tilting pad bearing can incorporate self-equalizing links to handle the misalignment between the bearing and the thrust collar. In this popular design method, the pads sit on the upper-level plates and the lower-level plates stay on the retainer base. With misalignment, the pads that are heavily loaded are pushed down. Consequently, the link pushes up the pads on the opposite side, keeping the bearing surface parallel to the thrust collar surface. The self-equalizing link is used to handle the misalignment from the thermal and mechanical effects. In this study, the experimental investigation deals with the performance of self-equalizing tilting pad thrust bearings. The test rig for evaluating the performance of bearing is developed which can control the misalignment angle. Simultaneous measurements are taken for the force acting on each pad. Pad metal temperature and oil film thickness are functions of the shaft speed, bearing load, misalignment angle, and design of leveling plates. The effect of misalignment on bearing performance is discussed. The results demonstrate that the load on each pad depends on the test conditions(especially misalignment angle), and the load influences the performance of bearings.

• Journal of the Korean Society for Railway
• /
• v.14 no.2
• /
• pp.100-108
• /
• 2011

This paper investigates the structural stability and reliability on improving performance of flexible brake pad used in high speed train. To this end, an improved model of flexible pad was obtained through structural analysis. Brake pad specimens were subjected to modal, stroke and endurance tests to examine the dynamic characteristics and mechanical stability. The hot spot generation with increasing rotational speed was observed on chassis dynamometer equipment and then the structurally uniform contact between the disc and pad was achieved. The temperature distribution of flexible pad was measured using the infrared camcorder. Hence, the proposed flexible pad showed the better structural stability and thermal energy emission.

• Journal of the Semiconductor & Display Technology
• /
• v.6 no.2 s.19
• /
• pp.35-40
• /
• 2007

An integrated material removal model considering thermal, chemical and contact mechanical effects in CMP process is proposed. These effects are highly coupled together in the current modeling effort. The contact mechanics is employed in the model incorporated with the heat transfer and chemical reaction mechanisms. The mechanical abrasion actions happening due to the mechanical contacts between the wafer and abrasive particles in the slurry and between the wafer and pad asperities cause friction and consequently generate heats, which mainly acts as the heat source accelerating chemical reaction(s) between the wafer and slurry chemical(s). The proposed model may be a help in understanding multi-physical interactions in CMP process occurring among the wafer, pad and various consumables such as slurry.

• Journal of the Korean Society for Precision Engineering
• /
• v.19 no.10
• /
• pp.156-162
• /
• 2002

There are many factors affecting the results of CMP (Chemical Mechanical Polishing). Among them, the temperature is related to the removal rate and WIWNU (Within Wafer Non-Uniformity). In other words, the removal rate is proportional to the temperature and the variation of temperature distribution on a pad affects the non-uniformity within a wafer. In the former case, the active chemistry improves the rate of chemical reaction and the removal rate becomes better. But, there are not many advanced studies. In the latter case, a kinematical analysis between work-piece and pad can be obtained. And such result analysed from the mechanical aspect can be directly related to the temperature distribution on a pad affecting WIWNU. Meanwhile, the temperature change affects the quantities of both slurry and pad. The change of a pH value of the slurry chemistry due to a temperature variation affects the surface state of an abrasive particle and hence the agglomeration of abrasives happens above the certain temperature. And the pH alteration also affects the zeta potential of a pad surface and therefore the electrical force between pad and abrasive changes. Such results could affect the removal rate and etc. Moreover, the temperature changes the 1st and 2nd elastic moduli of a pad which are closely related to the removal rate and the WIWNU.

• Journal of the Korea Convergence Society
• /
• v.10 no.12
• /
• pp.287-292
• /
• 2019

This paper analyzes the thermal behaviors of genuine discs used in automobiles and discs coming out of tuning products through FEM analysis. Modeling with genuine disk modeling and tuning disks Model-1, Model-2, Model-3 and analyzing the disk rotation speed was set to 1000rpm. When the brake is operated, the thermal behavior of the disk surface, such as the operating temperature caused by the disk and pad contact, the friction surface temperature after the disk stop, and the thermal deformation, were analyzed. When the brake was activated (0-4.5 seconds), the tuning disk showed 34℃ higher than the original disk, and after the disk stopped (40.5 seconds), the tuning disk was analyzed 18℃ lowe, deformation due to the disk heat was deformed by 0.3mm for the tuning disk. Although there is an effect to reduce the fading phenomenon due to the thermal behavior of the pure disk and the tuning disk, it can be observed that there is no significant change in the thermal behavior due to the hole processing and the disk surface processing of the tuning disk.