• Title/Summary/Keyword: Defect Phenomena

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A Study of the Acclerated Degradation Phenomena on th Amorphous Silicon Thin Film Transistors with Multiple Stress (복합 스트레스에 의한 비정질 실리콘 박막 트랜지스터에서의 가속열화 현상 연구)

  • 이성규;오창호;김용상;박진석;한민구
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.43 no.7
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    • pp.1121-1127
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    • 1994
  • The accelerated degradation phenomena in amorphous silicon thin film transistors due to both electrical stress and visible light illumination under the elevated temperature have been investigated systematically as a function of gate bias, light intensity, and stress time. It has been found that, in case of electrical stress, the thrshold voltage shifts of a-Si:H TFT's may be attributed to the defect creation process at the early stage, while the charge trapping phenomena may be dominant when the stressing periods exceed about 2 hours. It has been also observed that the degradation in the device characteristics of a-Si:H TFT's is accelerated due to multiple stress effects, where the defect creation mechanism may be more responsible for the degradation rather than the charge trapping mechanism.

A Study on Effect of Shot Peening on Fracture Toughness of Spring Steel (스프링강의 파괴인성에 미치는 쇼트피닝 효과에 관한 연구)

  • Ha, K.J.;Park, K.D.
    • Journal of Power System Engineering
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    • v.7 no.2
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    • pp.66-72
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    • 2003
  • Recently, the steel parts used at the aerospace and automobile industries are required to be used light weight parts. Therefore, used material, steel have to be a high stress, which is an indispensable condition in this field. At the consideration of parts design, high hardness of the lightweight parts have an benefit of saving fuel and material. A high stress of metal has a point of difference according to the shape of design, external cyclic load and condition of vibration. A crack generates on the surface of metal or under yield stress by defect of inner metal defect or surface defect and slowly, this crack grow stable growth. Finally, rapidity failure phenomena is happen. Fatigue failure_phenomena, which happen in metal, bring on danger in human life and property therefor, anti-fatigue failure technology take an important part of current industries Currently, the shot peening is used for removing the defect from the surface of steel and improving the fatigue strength on surface. Therefore, this paper investigated the effect on frcature toughness using shot peening which is improve the resistance of crack growth and crack expansion rate by fatigue that make a compressive residual stress on surface.

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Phenomena of Hyperbolic Heat Conduction in the Hot Mold with an Inner Defect (내부결함이 있는 고온 금형에서의 쌍곡선형 열전도 현상)

  • Lee, Gwan-Su;Im, Gwang-Ok;Jo, Hyeong-Cheol;Kim, U-Seung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.7
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    • pp.952-957
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    • 2001
  • In the glass forming process, the phenomena of hyperbolic heat conduction in the hot mold with an inner defect are studied analytically. It is shown that the temperature predicted by the parabolic model is underestimated compared to the one by the hyperbolic model. As the rmal wave is reflected from the area with defects and then arrives at the surface supplied by the heat flux, it is expected that there exists thermal shock in the materials. The area with defects is assumed to be adiabatic since its thermal conductivity is much lower compared to the one of the material. The results also indicate that the sudden temperature -jump in the mold surface can cause diverse problems such as glass defect (embryo mark, etc), oxidation of mold and coating, and change of material properties.

Prediction of Defect Formation in Ring Rolling by the Three-Dimensional Rigid-Plastic Finite Element Method (3차원 강소성 유한요소법을 이용한 환상압연공정중 형상결함의 예측)

  • Moon Ho Keun;Chung Jae Hun;Park Chang Nam;Joun Man Soo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.10
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    • pp.1492-1499
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    • 2004
  • In this paper, defect formation in ring rolling is revealed by computer simulation of ring rolling processes. The rigid-plastic finite element method is employed for this study. An analysis model having relatively fine mesh system near the roll gap is used for reducing the computational time and a scheme of minimizing the volume change is applied. The formation of the central cavity formation defect in ring rolling of a taper roller bearing outer race and the polygonal shape defect in ring rolling of a ball bearing outer race has been simulated. It has been seen that the results are qualitatively good with actual phenomena.

Weld Defect Formation Phenomena during High Frequency Electric Resistance Welding

  • Choi, Jae-Ho;Chang, Young-Seup;Kim, Yong-Seog
    • Journal of Welding and Joining
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    • v.19 no.3
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    • pp.267-273
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    • 2001
  • In this study, welding phenomena involved in formation of penetrators during high frequency electric resistance welding were investigated. High speed cinematography of the process revealer that a molten bridge between neighboring skelp edges forms at apex point and travels along narrow gap toward to welding point at a speed ranging from 100 to 400 m/min. The bridge while moving along the narrow gap swept away oxide containing molten metal from the gap, providing oxide-free surface for a forge-welding at upsetting stand frequency of the budge formation, travel distance and speed of the bridge were affected by the heat input rate into strip. The travel distance and its standard deviation were found to have a strong relationship with the weld defect density. Based on the observation, a new mechanism of the penetrator formation during HF ERW process is proposed.

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Expansion of Thin-Film Transistors' Threshold Voltage Shift Model using Fractional Calculus (분수계 수학을 사용한 박막트랜지스터의 문턱전압 이동 모델 확장)

  • Taeho Jung
    • Journal of the Semiconductor & Display Technology
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    • v.23 no.2
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    • pp.60-64
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    • 2024
  • The threshold voltage shift in thin-film transistors (TFTs) is modeled using stretched-exponential (SE) and stretched-hyperbola (SH) functions. These models are derived by introducing empirical parameters into reaction rate equations that describe defect generation or charge trapping caused by hydrogen diffusion in the dielectric or interface. Separately, the dielectric relaxation phenomena are also described by the same reaction rate equations based on defect diffusion. Dielectric relaxation was initially modeled using the SE model, and various models have been proposed using fractional calculus. In this study, the characteristics of the threshold voltage shift and the dielectric relaxation phenomena are compared and analyzed to explore the applicability of analytical models used in the field of dielectric relaxation, in addition to the conventional SE and SH models.

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Mobile Device NDF(No Defect Found) Cost Estimation (모바일 디바이스의 원인불명고장에 관한 비용 추정)

  • Lee, Jewang;Lee, Jungwoo;Han, Chang Hee
    • Journal of Korean Society of Industrial and Systems Engineering
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    • v.44 no.2
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    • pp.102-114
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    • 2021
  • NDF (No Defect Found) is a phenomenon in which defects have been found in the manufacturing, operation and use of a product or facility, but phenomenon of defects is not reproduced in the subsequent investigation system or the cause of the defects cannot be identified. Recently, with the development of the fourth industrial revolution, convergence of hardware and software technologies in various fields is spreading to products such as aircraft, home appliances, and mobile devices, and the number of parts is increasing due to functional convergence. The application of such convergence technologies and the increase in the number of parts are major factors that lead to an increase in NDF phenomena. NDF phenomena have a significant negative impact on cost, reliability, and reliability for both manufacturers, service providers and operators. On the other hand, due to the nature of NDF phenomena such as difficult and intermittent cause identification and ambiguity in judgment, it is common to underestimate the cost of NDF or fail to take appropriate countermeasures in corporate management. Therefore, in this paper, we propose a methodology for estimating NDF costs by the PAF model which is a quality cost analysis model and ABC (Activity Based Costing) technique. The methodology of this study suggests a detailed procedure and the concept to accurately estimate the NDF costs, using ABC analysis, accounting system information, and IT system data. In addition case studies have validated the methodology. We think this could be a valid methodology to refer to when estimating the cost of other parts. And, it is meaningful to provide important judgment information in the decision-making process based on quality management and ultimately reduce NDF costs by visualizing them separately by major variable factors.

Relations between Resonance Structures in Photoionization Spectra in Three-Channel-Systems Studied by Multichannel Quantum Defect Theory

  • Lee, Chun-Woo
    • Bulletin of the Korean Chemical Society
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    • v.33 no.7
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    • pp.2168-2176
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    • 2012
  • Relations between fitted parameters for photoionization spectra both below and above the thresholds in the systems involving 3 channels are obtained using phase-shifted version of the multichannel quantum-defect theory. Analytical continuation of the photoionization cross sections in the form of ${\langle}{\sigma}_{below}{\rangle}_{v_{below}}={\sigma}_{above}$ examined using several representations.

A Defect Detection of Thin Welded Plate using an Ultrasonic Infrared Imaging (초음파 열화상 검사를 이용한 박판 용접시편의 결함 검출)

  • Cho, Jai-Wan;Chung, Chin-Man;Choi, Young-Soo;Jung, Seung-Ho;Jung, Hyun-Kyu
    • Journal of Institute of Control, Robotics and Systems
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    • v.13 no.11
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    • pp.1060-1066
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    • 2007
  • When a high-energy ultrasound propagates through a solid body that contains a crack or a delamination, the two faces of the defect do not ordinarily vibrate in unison, and dissipative phenomena such as friction, rubbing and clapping between the faces will convert some of the vibrational energy to heat. By combining this heating effect with infrared imaging, one can detect a subsurface defect in material efficiently. In this paper a detection of the welding defect of thin SUS 304 plates using the UIR (ultrasonic infrared imaging) technology is described. A low frequency (20kHz) ultrasonic transducer was used to infuse the welded thin SUS 304 plates with a short pulse of sound for 280ms. The ultrasonic source has a maximum power of 2kW. The surface temperature of the area under inspection is imaged by a thermal infrared camera that is coupled to a fast frame grabber in a computer. The hot spots, which are a small area around the defect tip and heated up highly, are observed. From the sequence of the thermosonic images, the location of defective or inhomogeneous regions in the welded thin SUS 304 plates can be detected easily.

A Study on the Quality Improvement of Electrical Master Box in Aircraft Vibration Environment (항공기 진동 환경에서의 전원분배장치 품질개선 연구)

  • Seo, Youngjin;Lee, Yoonwoo;Jang, Minwook;Jo, Jihyung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.8
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    • pp.181-189
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    • 2019
  • An aircraft power distribution device distributes and controls the power generated by the generator and provides overcurrent protection. There are many defect phenomena that make AC power distribution impossible during flight, which poses a problem in because some electronic equipment cannot be operated. We describe a process of deriving the root cause of defects by using vibration testing equipment to simulate the vibration conditions during aircraft flight, which result in defects. The results show that the cause of the defect is internal wiring damage caused by the vibration of the contactor of the AC power distribution device. Therefore, the shape of the contactor was improved to solve this problem. We also improved the test procedure by performing defect detection tests using vibration testing equipment to detect a faulty contactor. As a result of the improvements, a component certification test and flight test proved that the defect phenomena of the AC electrical master box were improved.