• Title/Summary/Keyword: weld defects

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A Study on the Size Evaluation of Disc and Band Type Flaw by Ultrasonic Tandem Testing (초음파(超音波)TANDEM사각법(斜角法)에 의한 원형(圓形) 및 띠형결함(形缺陷)의 크기 평가(評價)에 관한 연구(硏究))

  • Han, E.K.;Eom, H.S.;Kim, J.J.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.5 no.2
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    • pp.12-21
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    • 1986
  • Generally, butt welds with plate thickness $30{\sim}40mm$ are welded with groove angle $40^{\circ},\;60^{\circ},\;70^{\circ}$, etc. In the detection of internal weld defects, oblique testing with single probe has been mainly used. But, recently, in acccordance with enlargement of welded structure, thick plate with 100-200mm are frequently required. Thus I-groove welding method was lately developed and often used. In this case, most frequently generated defects are the lack of weld penetration and incomplete fusion between base metal and welding material. If we would detect by oblique testing with single probe, detecting flaw is occassionally impossible or very underestimated. In this study, the limit for applying tandem method was studied in dise and band type flaws. The estimation of flaw size could be within 10% error compared to real flaws.

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A Study on the Improvement of Double Injection-molding Keypad Process (이중 사출 키패드 성형 공정 개선에 관한 연구)

  • Hong, Min-Sung;Lee, Ji-Hoon;Shin, Soo-Hyun
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.20 no.5
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    • pp.659-665
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    • 2011
  • Recently, the plastic resin such as PC, ABS are widely used in IT market. Especially, in most cases the keypads mounted on the mobile phone are the dual-injection-plated type. Environmental regulation is based on the quality of injection-molded products and the minimum process steps are required to avoid the plating defects. Various parameters to produce the injection-molded plastic products make it difficult to obtain the desired stability. However, the past experience and the use of CAE analysis make it possible to predict the problems occurred in injection molding process. Especially, the problems of the weld lines such as runner balancing, bending, deformation and forming defects can be solved systematically and minimized by CAE analysis. Through this study, the non-uniform volumetric shrinkage and the difference in temperature distribution induce the deformation and the high value of stress causes the problems such as crack.

FSW Process Optimization for Al 2519 Alloys and Its Joint Characteristics(II) (후육 고강도 Al 2519합금의 FSW 접합기술 및 접합부 특성(II))

  • Kim, Heung-Ju;Jang, Ung-Seong;Yang, Gwang-Ha;Bang, Han-Seo
    • Proceedings of the KWS Conference
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    • 2005.06a
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    • pp.174-176
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    • 2005
  • On the basis of successful experiences and data from author's past experimental results of friction stir welding on thin aluminum plates, thick aluminum plate of high strength 2000 series has been carried out in this study. For various combination of rotating speed, welding speed and tool (RIWRC38-C) shape, the butt welded specimens has been prepared to check the metallurgical characteristics, hardness distributions and defects. From the results, feasible welding conditions have been obtained as 450 rpm rotating speed and 5 mm/min welding speed. Using these optimum welding parameters, 38.1mm-thickness A2519-T87 plates have been FSWelded in single pass. A good weld surface appearance and defects free weld zone has been observed in X-ray inspection. Softened region has been generated by dissolution of precipitates and coarsened microstructure in the stir zone after FSWeld.

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A Study on Paintless Molded Parts in TV Mask Front Using Gas-Assisted Injection Molding (가스사출성형을 이용한 TV MASK FRONT의 무도장 제품에 관한 연구)

  • 조재성
    • Transactions of Materials Processing
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    • v.11 no.8
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    • pp.691-700
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    • 2002
  • Injection molded plastic parts have many surface detects: weld line, sink mark, flow mark, gloss, shading, scratching, and so on. Because these surface faults have not been accepted esthetically, plastic parts are Produced through painting or texturing. The purpose of this paper is to develop a paintless molded part of TV Mask Front by flow control method and gas-assisted injection molding. In order to minimize defects from injection molding, this study was carried out using computer aided injection mold filling simulations using MF/FLOW and MF/GAS. Based on these numerical results, we developed FR(Flame Retardant) HIPS and established guidelines of part design, mold design, and Processing conditions. We have achieved of cost sayings, improvement of productivity, and utilization of recycling by eliminating surface defects and painting process.

Comparison of the weld quality of friction welding and laser welding for IN713LC and SCM440 steel (초내열합금 IN713LC와 SCM440의 마찰용접 및 레이저용접에 대한 특성 비교)

  • 황형철;염종택;박노광;이종욱;박진형
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2003.10a
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    • pp.207-210
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    • 2003
  • The purpose of this work is to find an appropriate welding approach for rotor assembly of a marine turbocharger. The friction welding and laser welding of dissimilar materials, IN713LC and SCM440 were investigated. The quality of the welded joints obtained from two welding processes was evaluated by microstructure observation, micro-hardness and tensile tests. The friction welded joint indicated a good bonding structure in the weld interface. On the other hand, the laser welded joint showed the weld defects and non-welded area in the weld interface.

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$CO_2$ Weldability of Zn Coated Steel Sheet(1) - Weld Defects and Its Characteristics in Welds - (아연도금강판의 $CO_2$ 용접특성(1) - 용접부 결함의 종류와 특성 -)

  • 이종봉;안영호;박화순
    • Journal of Welding and Joining
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    • v.18 no.1
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    • pp.91-96
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    • 2000
  • Characteristics of the weld defect, such as a blowhole and a pit in lap-jointed fillet Co₂ welds of Zn-coated steel sheet were studied in order to make clear the sequence of the blowhole formation during welding. Main conclusions obtained are as follows: 1) Blowhole, wormhole and pit were found in fillet welds, although the optimum welding condition of 200A-23V-100cm/min was applied. 2) Zn was only detected at the solidification boundary at the early stage of the blowhole formation. 3) Most of the blowholes was started to form at lap-joint by the Zn vapor. With increasing of the Zn vapor and its pressure, the blowhole was develope to th bed surface until the completion of weld solidification. 4) The behavior of the blowhole in growth was similar to that of the columnar dendrite during welding.

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Development of Intelligent Filler Wire Feeding Device for Improvement of Weld quality (용접부 품질향상을 위한 지능형 용접 와이어 공급 장치 개발)

  • Lee J.S.;Sohn Y.I.;Park K.Y.;Lee K.D.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.06a
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    • pp.950-955
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    • 2005
  • This paper describes an intelligent filler wire feeding device which can control 3- dimensional seam tracking and the filler wire speed by measuring the gap position and the joint gap width in laser welding. By means of visual sensor controlled filling the missing material into the joint gap and 3 dimensional seam tracking, lineup errors from manufacturing tolerances and the repeatability of lineup jigs and weld robot can be balanced and at an even seam quality which avoids weld defects. In this paper, we assessed weld quality in 2mm sheets of A16061 which had various gap width by using the intelligent filler wire feeding device.

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Stress Concentration of Longitudinal Rib to Deckplate Welded Joint in Orthotropic Steel Bridge Decks (강상판 종리브.바닥강판 응접연결부의 응력집중)

  • 장동일;최동호;최준혁;김도환
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1999.04a
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    • pp.343-350
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    • 1999
  • Orthotropic steel bridge decks are potentially liable to cause fatigue cracks due to weld defects, residual stresses, and in-plane or out-of-plane stresses. In particular, the cracks propagated through deckplate in longitudinal rib to deckplate joints occur at weld toe and weld root due to stress concentrations. Numerical parametric studies are performed to show the Influence of the parameters on the stress concentration at the connection between the longitudinal rib and the deckplate. The parameters include root gap, toe angle $\theta$, toe radius $\rho$, and weld penetration. This study provides a fundamental point for the improvement of fatigue resistance and the estimation of the fatigue crack propagation in wekded joint details.

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The Weldability of Aluminum Ball in Electrolyte Injection Hole by Nd:YAG Laser (리튬이온전지의 전해액 주입구 볼에 대한 Nd:YAG 레이저 용접성)

  • Kim, Jong-Do;Yoo, Seung-Jo;Kim, Jang-Soo
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2005.11a
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    • pp.25-26
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    • 2005
  • This study suggested the occurrence source of weld-defects and its solution methods in a welding of Electrolyte injection hole by pulsed Nd:YAG laser. In experiment, the ramp down was used in order that solidification crack was removed. Furthermore, shrinkage stress and heat input were reduced by changing of weld trajectory and defocused distance. As a results of a experiment, a sound weld bead shape and crack-free weld bead can be obtained.

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The Weldability of Aluminum Ball in Electrolyte Injection Hole by Nd:YAG Laser (리튬이온전지의 전해액 주입구 볼에 대한 Nd:YAG 레이저 용접성)

  • Kim, Jong-Do;Yoo, Seung-Jo;Kim, Jang-Soo
    • Journal of Advanced Marine Engineering and Technology
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    • v.30 no.6
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    • pp.740-745
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    • 2006
  • This study suggested the occurrence source of weld-defects and its solution methods in a welding of Electrolyte injection hole by pulsed Nd:YAG laser. In experiment, the ramp down was used in order that solidification crack was removed. Furthermore. shrinkage stress and heat input were reduced by changing of weld trajectory and defocused distance. As a results of a experiment, a sound weld bead shape and crack-free weld bead can be obtained. In conclusion this show that the welding stability is greatly affected by modulation of laser pulse shape for the same laser energy and welding parameters.