• Journal of the Korean Society for Nondestructive Testing
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• v.14 no.1
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• pp.16-22
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• 1994

In contrast to the machineries using rolling element bearings, systems with journal bearings generally operate in large scale and under severe loading condition such as steam generator turbines and internal combustion engines. Failure of the bearings in these machineries can result in the system breakdown. To avoid the time consuming repair and considerable economic loss, the detection of incipient failure in journal bearings becomes very important. In this experimental approach, acoustic emission monitoring is applied to the detection of incipient failure caused by several types of abnormal operating condition most probable in the journal bearing systems. It has been known that the intervention of foreign materials, insufficient lubrication and misassembly etc. are principal factors to cause bearing failure and distress. The experiment was conducted under such designed conditions as hard particles in the lubrication layer, insufficient lubrication, and metallic contact in the simulated journal bearing system. The results showed that acoustic emission could be an effective tool to detect the incipient failure in journal bearings.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.9
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• pp.1078-1085
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• 2011

Prediction of a minimum crack size for growth, which is defined as a crack size that grows fast enough to keep ahead of its removal by contact wear and periodic grinding, is the most demanding work to prevent rail from fatigue failure and develop cost effective railway maintenance strategy In this study, we investigated the wheel load increment due to a rail defect during a train ran over it, and its effect on the minimum crack size for growth. For this purpose, we developed simulation software based on the Fletcher and Kapoor's "2.5D" model and measured wheel load increment during a train passed over a defect. A maximum contact pressure and contact patch size were calculated by 3D FEM and crack growth analyses were performed by varying two of dominant contact contributors; surface friction coefficient(0.1, 0.2, 0.3 and 0.4) and crack aspect ratio. The minimum crack sizes for growth were calculated from 0.29 to 1.44mm depending on the contact conditions. They were decreasing with increasing surface friction coefficient and decreasing with crack aspect ratio(a/b).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3168-3175
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• 2010

Lumber support as the part of automotive seat supports the pressure applied on waist by clearing the tiredness of passenger at long driving. In this study, lumbar support of automotive seat is modelled. Various bids are built up at its bed. The main purpose is to look for adequate model on comfortableness by calculating displacement according to applied force when some passenger sit at automotive seat. Full build -up type of 5 rows can be seen most suitable for passenger's comfortableness and its durability as the inner displacement of 5mm and contact force of 500 N.

• Journal of the Korean Society for Railway
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• v.16 no.1
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• pp.26-31
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• 2013

The reduction unit is one of the most important components for railway vehicles because the torque of the motor must be transmitted to the wheels of the vehicle by the reduction unit. The faults in the reduction units of high-speed trains are caused by damage such as gear, fatigue. These have serious impacts on safety of the train during operation. To address this development of a system for monitoring, fault diagnosis of the reduction unit is needed to keep the vehicle running safely. Before that can be accomplished, it is most important to understand the vibration characteristics of the reduction unit in a normal state. Vibration diagnosis technology using characteristic-analysis of vibration waveform and frequency is known to be the most effective method for fault diagnosis. In this paper, we analyzed the vibration characteristics of the reduction units two Korean high-speed trains (KTX and KTX II), under normal conditions, by two test methods (driving gear test, full-vehicle test).

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.5
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• pp.142-151
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• 2005

To predict the fatigue life of the Hub Bearing Unit(HBU), preload effect and initial axial clearance have to be considered. Various theory and equations for the HBU design used in the passenger car are well developed in many literatures. But most design hand book for bearings or bearing catalogues do not consider the initial axial clearance and preload effect. So there are limits and difficulties to use those data in actual bearing design. To consider the preload effect and initial axial clearance, complex elliptic integrals and nonlinear equations are involved. These equations are difficult to solve during the design process. In order to solve these problems effectively, a program is developed to solve these equations reliably and to help the designer in obtaining the performance data of the HBU such as load distribution, maximum contact stress and fatigue life. The preprocessor of the program helps users to prepare the input data through a dialog box and the post processor makes graphical presentation of the result. In this paper, theoretical and numerical background for the prediction of the fatigue life of the HBU is explained. A simple example is presented to show the usefulness of developed program.

• Journal of the Korean Society for Heat Treatment
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• v.21 no.1
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• pp.10-19
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• 2008

To investigate the effect of ultrasonic nano-crystalline surface modification (UNSM) treatment on rolling contact fatigue and residual stress properties of bearing steels, this paper carried out a rolling contact fatigue test, measured residual stress and retained austenite, performed a wear test, observed microstructure, measured micro hardness, and analyzed surface topology. After the UNSM treatment, it was found that the surface became minute by over $100{\mu}m$. The micro surface hardness was changed from Hv730~740 of base material to Hv850~880 with about 20% improvement, and hardening depth was about 1.3 mm. The compressive residual stress was measured as high as -700~-900 MPa, and the quantity of retained austenite was reduced to 27% from 34%. The polymet RCF-6 ball type rolling contact fatigue test showed over 4 times longer fatigue lifetime after the UNSM treatment under 551 kgf load and 8,000 rpm. In addition, this paper observed the samples, which went through the rolling contact fatigue test, with OM and SEM, and it was found that the samples had a spalling phenomenon (the race way is decentralized) after the UNSM treatment. However, before the treatment, the samples had excessive spalling and complete exploration. Comparison of the test samples before and after the UNSM treatment showed a big difference in the fatigue lifetime, which seems to result from the complicated effects of micro particles, compressive residual stress, retained austenite, and surface topology.

• Journal of the Korea Society of Computer and Information
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• v.25 no.5
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• pp.209-216
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• 2020

As depository system for negotiation or reimbursement to the victim in criminal case is reflected to consideration for diminishing punishment and hence, it is very important in the process. According to the current law, one needs to fill out victim's personal information such as name, address, and ID number for processing depository. However, if the victim is sexual violence victim, all the personal information is covered up becoming anonymous. Therefore, it becomes difficult for the accused person to get necessary information. Such covering up action is to prevent further second damage that may be caused such as threatening for the negotiation whereas victim has no willingness to forgive the accused. However, even if the accused person regrets his/her crime and make reimbursement to the victim, as they have no personal information on the victim it becomes impossible for them to make the depository. If we apply ESCROW system here it will allow victims to avoid any direct contact with the accused person as well as preventing any privacy disclosure. Also, for the accuse person, they can show how much they regret by making depository within their capability.

• Journal of Korean Medical classics
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• v.13 no.1
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• pp.253-268
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• 2000

1613년허준소간적(年許浚所刊的)${\ll}$동의보감(東醫寶鑑)${\gg}$불지시의사학종사자적연구과제(不只是醫史學從事者的硏究課題). 인위(因爲)${\ll}$동의보감(東醫寶鑑)${\gg}$병불시단순적의서(?不是單純的醫書), 이차서구유료도가내단사상급역학사상등철학사고지고(而此書具有了道家內丹思想及易學思想等哲學思考之故). ${\ll}$동의보감(東醫寶鑑)${\gg}$소출간적나시대수연성리학점굴료수위(所出刊的那時代雖然性理學占掘了首位), 단시차서소구적도교색채비임하의서갱농후(但是此書所具的道敎色彩比任何醫書更濃厚). 내경편적체계시피(內景篇的體系是被)${\ll}$황정경(黃庭經)${\gg}$영향적(影響的). 작위수련서(作爲修鍊書), ${\ll}$황정경(黃庭經)${\gg}$시도교주요경전지일是道敎主要經典之一). 비서인위인체즉시신적세계(比書認爲人體卽是神的世界), 인체적각기관우시저사신소주적안댁(人體的各器官又是這些神所住的安宅). 내경편이차(內景篇以此)${\ll}$황정경(黃庭經)${\gg}$위자爲資), 구성료기본체계급기주요내용(構成了基本體系及其主要內容). 우기시(尤其是), 내경편접수도가역학사상이설명천인상응(內景篇接受道家易學思想而說明天人相應). 즉(卽), 내경편접수(內景篇接受)${\ll}$참동계(參同契)${\gg}$주급(注及)${\ll}$회남자(淮南子)${\gg}$등도교문헌리소재적(等道敎文獻裏所載的)'발생론(發生論)', 인이음양오행적정기래해설만물여인지상응관계(因而陰陽五行的精氣來解說萬物與人之相應關係). 차정기계승위내단사상적정기신론(此精氣繼承爲內丹思想的精氣神論). 정여기(精與氣), 기여신(氣與神), 신여정시재우불단지호상접촉호상융화적관계상(神與精是在于不斷地互相接觸互相融化的關係上). 필자인위내경편이정기신론위주(筆者認爲內景篇以精氣神論爲主), 장의서인진료도교수련적경계(將醫書引進了道敎修鍊的境界). 단시(但是), 본론문불지간분석연구내경편소인적(本論文不至干分析硏究內景篇所引的)${\ll}$황제내경(黃帝內經)${\gg}$등의서포함적도교관(等醫書包含的道敎觀). 요시리해(要是理解)${\ll}$동의보감(東醫寶鑑)${\gg}$소인의서적사상기원급기내용(所引醫書的思想起源及其內容), 대연구내경편급(對硏究內景篇及)${\ll}$동의보감(東醫寶鑑)${\gg}$전편적철학성취유흔대적방조(全篇的哲學性就有?大的幇助). 차시필자요계속요연구적과제파료(此是筆者要繼續要硏究的課題擺了).

• Korean Journal of Optics and Photonics
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• v.28 no.1
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• pp.1-8
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• 2017

A method for inspecting defects in display substrates utilizing Fourier optics is proposed in this paper. A cost-effective inspection system can be realized with the proposed method, because it does not require a high-magnification microscope. Also, the proposed method can avoid tight tolerance for variations in displacement between substrate and camera, which is stems from shallow depth of field of the high-magnification microscope. In addition, possible damage caused by collisions between substrate and the inspection equipment can be avoided. The decision algorithm can be simpler than for a conventional inspection system, because spatial shift of periodic substrate patterns does not affect the intensity distribution of the diffracted light, by the Fourier transform property. The proposed method is explained with numerical studies, and experiments are carried out to check its feasibility for color-filter substrates of a liquid-crystal display.

• Composites Research
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• v.24 no.6
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• pp.12-17
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• 2011

Interfacial durability and electrical properties of CNT or ITO coated PVDF nanocomposites were investigated for self-sensor and micro actuator applications. Electrical resistivity of nanocomposites for the durability on interfacial adhesion was measured using four points method via fatigue test under cyclic loading. CNT/PVDF nanocomposite exhibited lower electrical resistivity and good self-sensing performance due to inherent electrical property. Durability on the interfacial adhesion was good for both CNT and ITO/PVDF nanocomposites. With static contact angle measurement, surface energy, work of adhesion, and spreading coefficient between either CNT or ITO and PVDF were obtained to verify the correlation with interfacial adhesion durability. The optimum actuation performance of CNT or ITO coated PVDF specimen was measured by the displacement change using laser displacement sensor with changing frequency and voltage. The displacement of actuated nanocomposites decreased with increasing frequency, whereas the displacement increased with voltage increment. Due to nanostructure and inherent electrical properties, CNT/PVDF nanocomposite exhibited better performance as self-sensor and micro actuator than ITO/PVDF case.