• Title/Summary/Keyword: Defect

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Robust Defect Size Measuring Method for an Automated Vision Inspection System (영상기반 자동결함 검사시스템에서 재현성 향상을 위한 결함 모델링 및 측정 기법)

  • Joo, Young-Bok;Huh, Kyung-Moo
    • Journal of Institute of Control, Robotics and Systems
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    • v.19 no.11
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    • pp.974-978
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    • 2013
  • AVI (Automatic Vision Inspection) systems automatically detect defect features and measure their sizes via camera vision. AVI systems usually report different measurements on the same defect with some variations on position or rotation mainly because different images are provided. This is caused by possible variations from the image acquisition process including optical factors, nonuniform illumination, random noises, and so on. For this reason, conventional area based defect measuring methods have problems of robustness and consistency. In this paper, we propose a new defect size measuring method to overcome this problem, utilizing volume information that is completely ignored in the area based defect measuring method. The results show that our proposed method dramatically improves the robustness and consistency of defect size measurement.

Effects of Defect Size on Crush Test Load of Butt Fusion Welded MDPE Pipes

  • Tun, Nwe Ni;Lai, Huan Sheng;Jeon, Gyu Min;Yoon, Kee Bong;Kil, Seong Hee
    • Journal of Energy Engineering
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    • v.24 no.4
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    • pp.55-62
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    • 2015
  • It is expected that the size of welding defect affects the mechanical performance of welded medium density polyethylene (MDPE) pipe joints. In this study, butt fusion welded MDPE pipe joints with a single spherical or planar defect of various sizes were studied using experimental crush testing and also by finite element method. The crush test showed that the mechanical performance of crush was not affected by the size and geometry of a single welding defect when the defect size was increased to 45% of the pipe's wall thickness. The simulation results indicated that the effect of the single welding defect on the Von Mises stress distribution near the defect explained the reason of the test results.

Nature of Surface and Bulk Defects Induced by Epitaxial Growth in Epitaxial Layer Transfer Wafers

  • Kim, Suk-Goo;Park, Jea-Gun;Paik, Un-Gyu
    • Transactions on Electrical and Electronic Materials
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    • v.5 no.4
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    • pp.143-147
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    • 2004
  • Surface defects and bulk defects on SOI wafers are studied. Two new metrologies have been proposed to characterize surface and bulk defects in epitaxial layer transfer (ELTRAN) wafers. They included the following: i) laser scattering particle counter and coordinated atomic force microscopy (AFM) and Cu-decoration for defect isolation and ii) cross-sectional transmission electron microscope (TEM) foil preparation using focused ion beam (FIB) and TEM investigation for defect morphology observation. The size of defect is 7.29 urn by AFM analysis, the density of defect is 0.36 /cm$^2$ at as-direct surface oxide defect (DSOD), 2.52 /cm$^2$ at ox-DSOD. A hole was formed locally without either the silicon or the buried oxide layer (Square Defect) in surface defect. Most of surface defects in ELTRAN wafers originate from particle on the porous silicon.

Non-Destructive Evaluation of Separation and Void Defect of a Pneumatic Tire by Speckle Shearing Interferometry

  • Kim, Koung-Suk;Kang, Ki-Soo;Jung, Hyun-Chul;Ko, Na-Kyong
    • Journal of Mechanical Science and Technology
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    • v.18 no.9
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    • pp.1493-1499
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    • 2004
  • This paper describes the speckle shearing interferometry, a non-destructive optical method, for quantitative estimation of void defect and monitoring separation defect inside of a pneumatic tire. Previous shearing interferometry has not supplied quantitative result of inside defect, due to effective factors. In the study, factors related to the details of an inside defect are classified and optimized with pipeline simulator. The size and the shape of defect can be estimated accurately to find a critical point and also is closely related with shearing direction. The technique is applied for quantitative estimation of defects inside of a pneumatic tire. The actual traveling tire is monitored to reveal the cause of separation and the starting points. And also unknown void defects on tread are inspected and the size and shape of defects are estimated which has good agreement with the result of visual inspection.

Growth and Dissolve of Defects in Boron Nitride Nanotube

  • Jun Ha, Lee;Won Ha, Mun
    • Proceedings of the Korean Society Of Semiconductor Equipment Technology
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    • pp.59-62
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    • 2004
  • The defect formation energy of boron nitride (BN) nanotubes is investigated using molecular-dynamics simulation. Although the defect with tetragon-octagon pairs (4-88-4) is favored in the flat cap of BN nanotubes, BN clusters, and the growth of BN nanotubes, the formation energy of the 4-88-4 defect is significantly higher than that of the pentagon-heptagon pairs (5-77-5) defect in BN nanotubes. The 5-77-5 defect reduces the effect of the structural distortion caused by the 4-88-4 defect, in spite of homoelemental bonds. The instability of the 4-88-4 defect generates the structural transformation into BNNTs with no defect at about 1500 K.

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Process Design of Piston-Pin for Automobile by the Flow Control (유동제어를 통한 자동차용 피스톤-펀의 공정설계)

  • 김동진;김병민;이동주
    • Transactions of Materials Processing
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    • v.10 no.2
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    • pp.151-159
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    • 2001
  • Flow defect of a piston-pin for automobile parts is investigated in this study. In combined cold extrusion of piston-pin, lapping defect, which is a kind of flow defect, appears by the dead metal zone. This appearance evidently happens in products with a thin thickness to be pierced for the dimensional accuracy and the decrease of material loss. The flow defect that occurs in piston-pin has bad effects on the strength and the fatigue life of piston-pin. Therefore, it is important to predict and prevent defects in the early stage of process design. The best method that can prevent flow defect is removing or reducing dead metal zone through material flow control. The finite element simulations are applied to analyze the flow defect. This study proposes processes for preventing flow defect by removing dead metal zone. Then the results are compared with the experimental ones for verification. These FE simulation results are in good agreement with the experimental ones.

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Process Design to Prevent Flow Defect of Piston-Pin for Automobile (자동차용 피스톤-핀의 유동결함 방지를 위한 공정설계)

  • 김동진
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.155-158
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    • 2000
  • Flow defect of a piston-pin for automobile parts is investigated in this study. In cold forging of piston-pin Lapping defect a kind of flow defect appears by the dead metal zone. This appearance evidently happens in products with a thin piercing thickness for the dimension accuracy and the decrease of material loss. The best method that can prevent flow defect is removing dead metal zone. The finite element simulations are applied to analyze the flow defect. This study proposed processes for preventing flow defect by removing dead metal zone. Then the results are compared with the experiments for verification. These FE simulation results are in good agreement with the experimental ones.

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Propagation Characteristic of Ultrasonic on Slit Defect in Butt Joint (맞대기 용접부내의 인공 결함에서 초음파의 전파특성)

  • 남영현
    • Journal of Welding and Joining
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    • v.14 no.6
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    • pp.37-47
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    • 1996
  • An ultrasonic testing uses the directivity of the ultrasonic wave which propagates in one direction. The directivity is expressed as the relationship between the propagate direction and its sound pressure. The directivity of ultrasonic wave is related to determination of testing sensitivity, scanning pitch and defect location. This paper investigated the directivity of ultrasonic wave, which scattered from slit defect located in heat-affected zone (HAZ) in butt joint using visualization method. The directivity of shear waves scattered from slit defect were different according to probe direction (far defect, near defect) and probe position (forward movement, maximum echo position, backward movement). The difference of directivity of reflection wave was existed between 2 MHz and 4 MHz angle probes. In the case of 2 MHz angle probe, the directivity of reflection wave was appeared sharp form because of the relation wave length and defect size.

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A study on Improvement Method for Systematic Defect Management of Apartment Life-cycle (공동주택 생애주기의 체계적인 하자관리를 위한 개선 방안 연구)

  • Park, Chang-Wook;Yun, Seok-Heon
    • Proceedings of the Korean Institute Of Construction Engineering and Management
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    • pp.618-621
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    • 2007
  • The existing defect management is focused on step before closing work, a builder preliminary research and tenant preliminary research. Each step is not related. And the existing study on defect management mainly classify into work type and defect type according to work type. This study divide into defect part. Also this study propose PDA based web and 3DCAD for improving method of existing defect management.

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Performance evaluation of wavelet and curvelet transforms based-damage detection of defect types in plate structures

  • Hajizadeh, Ali R.;Salajegheh, Javad;Salajegheh, Eysa
    • Structural Engineering and Mechanics
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    • v.60 no.4
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    • pp.667-691
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    • 2016
  • This study focuses on the damage detection of defect types in plate structures based on wavelet transform (WT) and curvelet transform (CT). In particular, for damage detection of structures these transforms have been developed since the last few years. In recent years, the CT approach has been also introduced in an attempt to overcome inherent limitations of traditional multi-scale representations such as wavelets. In this study, the performance of CT is compared with WT in order to demonstrate the capability of WT and CT in detection of defect types in plate structures. To achieve this purpose, the damage detection of defect types through defect shape in rectangular plate is investigated. By using the first mode shape of plate structure and the distribution of the coefficients of the transforms, the damage existence, the defect location and the approximate shape of defect are detected. Moreover, the accuracy and performance generality of the transforms are verified through using experimental modal data of a plate.