• Title/Summary/Keyword: weld time

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Time-dependent Crack Growth in X20CrMoV 12 1 Steel Weld joint (X20CrMoV 12 1 강의 용접부에서의 균열진전 특성연구)

  • Lee, N.W.;Kim, K.S.;Chung, Y.K.;Park, J.J.
    • Proceedings of the KSME Conference
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    • 2000.11a
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    • pp.322-327
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    • 2000
  • This paper investigates the time-dependent crack growth in X20CrMoV 12 1 steel weld joints. Crack growth test are carried out $545^{\circ}C$ on side-grooved 1/2T CT specimens under static loads. A simulated material is produced for the intercritical HAZ, where fracture normally occurs. Constitutive properties are obtained for the simulated HAZ material as well as for the base metal and weld metal. Finite element analyses of crack growth are performed on the models with and without a HAZ layer, using the experimental crack length-time history. The inclusion of HAZ layer increase the load line velocities significantly. The crack growth rates are correlated reasonably well with $C^*$. The smallest crack size for the validity of $C^*$ is found much smaller than the ASTM crack initiation size for 1T CT specimen of creep ductile materials.

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Prediction of Welding Imperfection with Idealization of Welding and Their Accuracy (용접이상화에 의한 용접부정의 예측과 정도)

  • Lee, Jae-Yik;Chang, Kyong-Ho;Kim, You-Chul
    • Journal of Welding and Joining
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    • v.31 no.5
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    • pp.15-19
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    • 2013
  • In order to reduce a grand compute time in prediction of welding distortion and residual stress by 3D thermal elastic plastic analysis, idealization of welding that is methods to heat input simultaneously in all weld metal on the same welding direction is carried out on two weld joints(butt welding and fillet welding). Then, the accuracy of acquired results is investigated through the comparison of the high accuracy prediction results. The thermal conduction analysis results by idealization of welding, the temperature is raised accompany with beginning of heat input because all of weld metal is heated input at the same time. On the other side, the temperature witch predicted with high accuracy is raised at the moment heating source passes the measuring points. So, there is difference of time between idealization of welding and considering of moving heat source faithfully. However, temperature history by idealization of welding is well simulated a high accuracy prediction results.

Weld Quality Monitoring System Development Applying A design Optimization Approach Collaborating QFD and Risk Management Methods (품질 기능 전개법과 위험 부담 관리법을 조합한 설계 최적화 기법의 용접 품질 감시 시스템 개발 응용)

  • Son, Joong-Soo;Park, Young-Won
    • Journal of Institute of Control, Robotics and Systems
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    • v.6 no.2
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    • pp.207-216
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    • 2000
  • This paper introduces an effective system design method to develop a customer oriented product using a design optimization process and to select a set of critical design paramenters,. The process results in the development of a successful product satisfying customer needs and reducing development risk. The proposed scheme adopted a five step QFD(Quality Function Deployment) in order to extract design parameters from customer needs and evaluated their priority using risk factors for extracted design parameters. In this process we determine critical design parameters and allocate them to subsystem designers. Subsequently design engineers develop and test the product based on these parameters. These design parameters capture the characteristics of customer needs in terms of performance cost and schedule in the process of QFD, The subsequent risk management task ensures the minimum risk approach in the presence of design parameter uncertainty. An application of this approach was demonstrated in the development of weld quality monitoring system. Dominant design parameters affect linearity characteristics of weld defect feature vectors. Therefore it simplifies the algorithm for adopting pattern classification of feature vectors and improves the accuracy of recognition rate of weld defect and the real time response of the defect detection in the performance. Additionally the development cost decreases by using DSP board for low speed because of reducing CPU's load adopting algorithm in classifying weld defects. It also reduces the cost by using the single sensor to measure weld defects. Furthermore the synergy effect derived from the critical design parameters improves the detection rate of weld defects by 15% when compared with the implementation using the non-critical design parameters. It also result in 30% saving in development cost./ The overall results are close to 95% customer level showing the effectiveness of the proposed development approach.

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Implementation of Automatic Teaching System for Subassembly Process in Shipbuilding (선박 소조립 공정용 로봇 자동교시 시스템의 구현)

  • 김정호;유중돈;김진오;신정식;김성권
    • Journal of Welding and Joining
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    • v.14 no.2
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    • pp.96-105
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    • 1996
  • Robot systems are widely utilized in the shipbuilding industry to enhance the productivity by automating the welding process. In order to increase productivity, it is necessary to reduce the time used for robot teaching. In this work, the automatic teaching system is developed for the subassembly process in the shipbuilding industry. A alser/vision sensor is designed to detect the weld seam and the image of the fillet joint is processed using the arm method. Positions of weld seams defined in the CAD database are transformed into the robot coordinate, and the dynamic programming technique is applied to find the sub-optimum weld path. Experiments are carried out to verify the system performance. The results show that the proposed automatic teaching system performs successfully and can be applied to the robot system in the subassembly process.

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Monotoring Secheme of Laser Welding Interior Defects Using Neural Network (신경회로망을 이용한 레이저 용접 내부결함 모니터링 방법)

  • 손중수;이경돈;박상봉
    • Laser Solutions
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    • v.2 no.3
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    • pp.19-31
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    • 1999
  • This paper introduces the monitoring scheme of laser welding quality using neural network. The developed monitoring scheme detects light signal emitting from plasma formed above the weld pool with optic sensor and DSP-based signal processor, and analyzes to give a guidance about the weld quality. It can automatically detect defects of laser weld and further give an information about what kind of defects it is, specially partial penetration and porosity among the interior defects. Those could be detected only by naked eyes or X-ray after welding, which needs more processes and costs in mass production. The monitoring scheme extracts four feature vectors from signal processing results of optical measuring data. In order to classify pattern for extracted feature vectors and to decide defects, it uses single-layer neural network with perceptron learning. The monitoring result using only the first feature vector shows confidence rate in recognition of 90%($\pm$5) and decides whether normal status or defects status in real time.

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Visualization of weld plume using high-speed holography (고속 홀로그래피에 의한 용접 플룸 거동의 가시화)

  • 백성훈;박승규;김민석;정진만;김철중
    • Journal of Welding and Joining
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    • v.17 no.1
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    • pp.71-76
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    • 1999
  • The real-time holographic interferometer with digital high-speed camera is applied to the experimental study of laser induced plasma/plume in pulsed Nd:YAG laser welding. A pulsed Nd:YAG laser with 1.2 kW average power is applied to generate laser induced plume. The recording speed of the high-speed camera is 3,000 f/s. The high speed photographs of weld plume without another visualization method, are compared with the visualization photographs with holographic interferometer. The radiation intensity from the laser induced plume is recorded by the high speed photographs, which fluctuated during laser radiation and disappeared after laser end. The density distribution of the plume is recorded by the holographic visualization method. The experimental results show the process of generation of the laser induced plasma/plume, and give the feasibility of quantitative measurement of laser induced plume in laser welding.

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Welding Quality Evaluation on the LASER Welding Parts of the Spacer Grid Assembly for PWR fuel Assembly (경수로 원전연료용 지지격자의 LASER 용접품질 평가)

  • Song, Gi-Nam;Yun, Jeong-Ho;Gang, Hong-Seok;Lee, Gang-Hui;Kim, U-Gon;Kim, Su-Seong
    • Proceedings of the KWS Conference
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    • 2005.06a
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    • pp.109-111
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    • 2005
  • Nuclear fuel assemblies for pressurized water reactors(PWR) are loaded in the reactor core throughout the residence time of three to five years. A spacer grid assembly, which is an interconnected array of slotted grid straps and is welded at the intersections to form an egg crate structure, is one of the main structural components of the nuclear fuel assembly. The spacer grid assembly is structurally required to have enough buckling strength under various kinds of lateral loads acting on the nuclear fuel assembly so as to keep the nuclear fuel assembly straight. To meet this requirement, it is necessary to weld the welding parts carefully and precisely. In this study, laser welding qualities of the spacer grid assembly welded by several welding companies, such as weld strength, weld penetration depth, and weld bead size, are examined and compared.

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Fatigue Assessment of Butt Joint with Weld Defect in Steel Bridge (강교 용접 결함부의 피로평가)

  • Juhn, Gui Hyun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.2 no.1
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    • pp.98-107
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    • 1998
  • There are many weld defects such as surface crack, lack of fusion, and imcomplete penetration in the butt joint of the existing steel bridges. The crack-like defects may significantly reduce the fatigue life of the structure. This paper presents the procedure and the results of the fatigue assessment of the butt joints with weld defect in the existing steel girder bridge. The butt joints with imcomple penetration were instrumented with strain gages to determine the stress histogram under normal traffic. Based on the measured stress histogram the crack propagation analyses were performed for the fatigue assesment. By using the suggested procedure and methodology, one can decide the time of periodic inspection and the necessity of repair of the butt joints with serious weld defects in the existing steel bridge.

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Fatigue Crack Propagation Behavior for Electron Beam Welded Joint of SUS 321 (SUS 321 전자비임 용접부의 피로균열진전거동)

  • 김재훈
    • Journal of the Korean Society of Safety
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    • v.12 no.2
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    • pp.57-64
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    • 1997
  • Fatigue crack propagation behaviors and life prediction for SUS 321 plate and its electron beam weld metal were investigated using compact tension specimens. The larger the stress ratio is, the faster the crack propagates, but the variation of crack propagation rate decreases. The effect of stress ratio is greater in the slow crack propagation area than in the faster one. The crack propagation rate of electron beam weld metal is faster than that of base metal because of hardening, weld defect and residual stress in welding area. The crack propagation rate of transverse weld metal has a lower than that of base metal due to the effect of residual stress, but in the time of passing through welding area, has a higher rate. The crack propagation rate using $\Delta$K$_{eff}$ can be well plotted regardless of stress ratio. The fatigue life prediction method of considering crack closure more exactly predicts fatigue life than conventional one. conventional one.e.

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Mixed Mode Control of Constant Power and Constant Current for Resistance Spot Welder using Dynamic Resistance Characteristics (동저항 특성을 이용한 저항 스폿 용접기의 정전력과 정전류의 혼합모드 제어)

  • Kang, Sung-Kwan;Jung, Jae-Hun;Nho, Eui-Cheol
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.64 no.11
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    • pp.1571-1577
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    • 2015
  • A new mixed mode control of constant power and constant current for resistance spot welding inverter is proposed to improve the weld quality. The conventional control scheme adopts constant current or constant power control mode, however, it is not easy to guarantee the high weld quality because of the nonlinear resistance characteristics of the welding point. The proposed method utilizes the nonlinear characteristics by measuring the dynamic resistance in real time. Therefore, it is possible for the welder to be controlled adaptively depending on the welding state. Experimental results show that the proposed control scheme improves the weld quality by 6.8 times compared with the conventional constant current mode control.