• Title/Summary/Keyword: Velocity Defect

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A Study about the Construction of Intelligence Data Base for Micro Defect Evaluation (미소 결함 평가를 위한 지능형 데이터베이스 구축에 관한 연구)

  • 김재열
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2000.04a
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    • pp.585-590
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    • 2000
  • Recently, It is gradually raised necessity that thickness of thin film is measured accuracy and managed in industrial circles and medical world. Ultrasonic Signal processing method is likely to become a very powerful method for NDE method of detection of microdefects and thickness measurement of thin film below the limit of Ultrasonic distance resolution in the opaque materials, provides useful information that cannot be obtained by a conventional measuring system. In the present research, considering a thin film below the limit of ultrasonic distance resolution sandwiched between three substances as acoustical analysis model, demonstrated the usefulness of ultrasonic Signal processing technique using information of ultrasonic frequency for NDE of measurements of thin film thickness, sound velocity, and step height, regardless of interference phenomenon. Numeral information was deduced and quantified effective information from the image. Also, pattern recognition of a defected input image was performed by neural network algorithm. Input pattern of various numeral was composed combinationally, and then, it was studied by neural network. Furthermore, possibility of pattern recognition was confirmed on artifical defected input data formed by simulation. Finally, application on unknown input pattern was also examined.

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Effects of the PIG Draft Velocity on the Defect Signals in MFL NDT System (자기 누설 비파괴 탐상 시스템에서 PIG의 주행속도가 검출신호에 미치는 영향)

  • 박상호;박관수
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.52 no.10
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    • pp.475-483
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    • 2003
  • In this paper, dynamic characteristics of the magnetic flux leakage(MFL) type non-destructive testing(NDT) are analyzed. Effects of a sensor speed in MFL PIG system and remanent magnetization of the gas pipeline are analyzed by using 3 dimensional nonlinear finite element analysis including eddy current and hysteresis characteristics. Results show that the speed of the sensor reduces the magnitude of the sensing signals where as the hysteresis of the pipeline distorts the sensing signals.

The Moving Photocarrier Grating (MPG) Technique for the Transport Properties of α-Se:As Films

  • Park, Chang-Hee;Lee, Kwang-Sei;Kim, Jeong-Bae;Kim, Jae-Hyung
    • Transactions on Electrical and Electronic Materials
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    • v.6 no.6
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    • pp.280-283
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    • 2005
  • The moving photocarrier grating (MPG) technique for the determination of the carrier mobilities and the recombination lifetime of $\alpha$-Se:As films has been studied. The electron and hole drift mobility and the recombination lifetime of $\alpha$-Se films with arsenic (As) additions have been obtained from measurement of the short circuit current density $j_{sc}$ as a function of grating velocity and spatial period. The hole mobility decreases due to defect density of hole traps when x exceeds 0.003, whereas the hole mobility increases for the case of low As addition (x$\le$0.003). We have found an increase in hole drift mobility and recombination lifetime, especially when As with (x = 0.003) is added into the $\alpha$-Se film.

Non-contact Ultrasonic Technique for the Thin Defect Evaluation by the Lamb-EMAT (비접촉 Lamb-EMAT를 이용한 두께감육 평가에 관한 연구)

  • Kim, Tae-Hyeong;Park, Ik-Geun;Lee, Cheol-Gu;Kim, Yong-Gwon;Kim, Hyeon-Muk;Jo, Yong-Sang
    • Proceedings of the KWS Conference
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    • 2005.06a
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    • pp.194-196
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    • 2005
  • Ultrasonic guided waves are gaining increasing attention for the inspection of platelike and rodlike structures. At the same time, inspection methods that do not require contact with the test piece are being developed for advanced applications. This paper capitalizes on recent advances in the areas of guided wave ultrasonics and noncontact ultrasonics to demonstrate a superior method for the nondestructive detection of thinning defects simulating hidden corrosion in thin aluminum plates. The proposed approach uses EMAT(electro-magnetic acoustic transducer) for the noncontact generation and detection of guided plate waves. Interesting features in the dispersive behavior of selected guided modes are used for the detection of plate thinning. It is shown that mode cutoff measurements provide a qualitative detection of thinning defects. Measurement of the mode group velocity can be also used to quantify of thinning depth.

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Cavitation Damage Behavior of Inconel 625 Coating Layer by Arc Thermal Spraying Method in Sea Water (아크 용사법을 이용한 Inconel 625 코팅 층의 해수 내 캐비테이션 손상 거동)

  • Park, Il-Cho;Kim, Seong-Jong
    • Journal of the Korean institute of surface engineering
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    • v.48 no.6
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    • pp.349-353
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    • 2015
  • In this paper, arc thermal spray coating was conducted onto the SS400 steel using Inconel 625 wires in order to improve the durability of marine steel structures, and then investigated cavitation damage behavior of Inconel 625 coating layer in sea water. For the Inconel 625 coating layer, surface hardness appeared similar to that of existing high velocity oxy-fuel coating technology with 380~480 HV, but the porosity of about 6 % was larger relatively. During the cavitation experiment, pit damages were originated and grown at the rough surface and pore defect area of Inconel 625 coating layer. And, after the 72 hours of experimental time, weight loss of Inconel 625 coating layer exhibited gradually increasing tendency due to surface damage effect of the undercut.

The Effect of Inlet Distortion on a Centrifugal Compressor (입구 불균일 유동에 의한 원심압축기 스톨에 관한 실험적 연구)

  • Park, Jae-Hyoung;Kang, Shin-Hyoung
    • 유체기계공업학회:학술대회논문집
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    • 2003.12a
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    • pp.476-481
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    • 2003
  • In this paper, the effect of circumferential inlet distortion on performance and stall has been experimentally investigated in a high-speed centrifugal compressor, comparing distorted cases with undistorted one. The performance of compressor was slightly deteriorated by defect of inlet static pressure which is caused by the circumferential inlet distortion. As stall was fully developed the inlet distortion did not affect the number of stall cell and the propagation velocity. It also did not affect stall inception at 40,000 and 50,000 rpm. However stall occurred at the lower flow rate for distorted flow at 60,000 rpm. For 50,000 rpm a unexpected phenomenon occurred : stall occurred first and then it disappeared.

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Ultrasonic Inspection of Internal Defects of Potatoes (초음파를 이용한 감자의 내부결함검사)

  • Kim, In-Hoon;Jung, Kyu-Hong;Jang, Kyung-Young;Seo, Ryun;Kim, Man-Soo
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.3
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    • pp.82-88
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    • 2003
  • The nondestructive internal quality evaluation of agricultural products has been strongly required from the needs for individual inspection. Recently, the ultrasonic wave has been considered as a solution fur this problem, and an ultrasonic system was constructed for the ultrasonic NDE of fruits and vegetables in our previous work. In this paper, the practical applicability of our ultrasonic system is tested fur the inspection of internal defects (central cavity) in Atlantic potato. Sound speed and RMS of transmitted ultrasonic wave signal were measured and classification algorithm using 2 dimensional stochastic analysis. was presented. Experimental results showed greater value of sound speed and RMS (root mean square) of transmitted signal in normal samples than in abnormal samples with cavity. Also a stochastic method to distinguish normal and abnormal showed fault detection rate less than 5%.

Five layers in turbulent pipe flow (난류 파이프 유동 내 다섯 개의 영역)

  • Ahn, Junsun;Hwang, Jinyul
    • Journal of the Korean Society of Visualization
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    • v.18 no.3
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    • pp.109-115
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    • 2020
  • Five layers in mean flow are proposed by using the direct numerical simulation data of turbulent pipe flow up to Reτ = 3008. Viscous sublayer, buffer layer, mesolayer, log layer and core region are investigated. In the buffer layer, the viscous force is counterbalanced by the turbulent inertia from the streamwise mean momentum balance, and a log law occurs here. The overlap layer is composed of the mesolayer and the log layer. Above the buffer layer, the non-negligible viscous force causes the power law, and this region is the mesolayer, where it is the lower part of the overlap layer. At the upper part of the overlap layer, where the viscous force itself becomes naturally negligible, the log layer will appear due to that the acceleration force of the large-scale motions increases as the Reynolds number increases. In the core region, the velocity-defect form is satisfied with the power-law scaling.

A Methodology for Quality Control of Railroad Trackbed Fills Using Compressional Wave Velocities : I. Preliminary Investigation (압축파 속도를 이용한 철도 토공노반의 품질관리 방안 : I. 예비연구)

  • Park, Chul-Soo;Mok, Young-Jin;Choi, Chan-Yong;Lee, Tai-Hee
    • Journal of the Korean Geotechnical Society
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    • v.25 no.9
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    • pp.45-55
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    • 2009
  • The quality of railroad trackbed fills has been controlled by field measurements of density and bearing resistance of plate-load tests. The control measures are compatible with the design procedures whose design parameter is $k_{30}$ for both ordinary-speed railways and high-speed railways. However, one of fatal flaws of the design procedures is that there are no simple laboratory measurement procedures for the design parameters ($k_{30}$ or, $E_{v2}$ and $E_{v2}/E_{v1}$) in design stage. To overcome the defect, the compressional wave velocity was adopted as a control measure, in parallel with the advent of the new design procedure, and its measurement technique was proposed in the preliminary investigation. The key concept of the quality control procedure is that the target value for field compaction control is the compressional wave velocity determined at optimum moisture content using modified compaction test, and direct-arrival method is used for the field measurements during construction, which is simple and reliable enough for practice engineers to access. This direct-arrival method is well-suited for such a shallow and homogeneous fill lift in terms of applicability and cost effectiveness. The sensitivity of direct-arrival test results according to the compaction quality was demonstrated at a test site, and it was concluded that compressional wave velocity can be effectively used as quality control measure. The experimental background far the companion study (Park et al., 2009) was established through field and laboratory measurements of the compressional wave velocity.

The effect of 4-hexylresorcinol on xenograft degradation in a rat calvarial defect model

  • Kang, Yei-Jin;Noh, Ji-Eun;Lee, Myung-Jin;Chae, Weon-Sik;Lee, Si Young;Kim, Seong-Gon
    • Maxillofacial Plastic and Reconstructive Surgery
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    • v.38
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    • pp.29.1-29.9
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    • 2016
  • Background: The objective of this study was to evaluate xenograft degradation velocity when treated with 4-hexylresorcinol (4HR). Methods: The scapula of a cow was purchased from a local grocery, and discs (diameter 8 mm, thickness 1 mm) were prepared by trephine bur. Discs treated with 4HR were used as the experimental group. Untreated discs were used as the control. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), antibacterial test, endotoxin test, and scanning electron microscopy (SEM) were performed on the discs. In vivo degradation was evaluated by the rat calvarial defect model. Results: The XRD and FT-IR results demonstrated successful incorporation of 4HR into the bovine bone. The experimental disc showed antibacterial properties. The endotoxin test yielded results below the level of endotoxin contamination. In the SEM exam, the surface of the experimental group showed needle-shaped crystal and spreading of RAW264.7 cells. In the animal experiments, the amount of residual graft was significantly smaller in the experimental group compared to the control group (P = 0.003). Conclusions: In this study, 4HR was successfully incorporated into bovine bone, and 4HR-incorporated bovine bone had antibacterial properties. In vivo experiments demonstrated that 4HR-incorporated bovine bone showed more rapid degradation than untreated bovine bone.