• Title/Summary/Keyword: weld defect

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Construction of Chaoral Post-Process System for Integrity Evaluation of Weld Zone (용접부 건전성 평가를 위한 카오럴 후처리 시스템의 구축)

  • Lee, Won;Yoon, In-Sik
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.11
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    • pp.152-165
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    • 1998
  • This study proposes the analysis and evaluation method of time series ultrasonic signal using the chaoral post-process system for precision rate enhancement of ultrasonic pattern recognition. Chaos features extracted from time series data for analysis quantitatively weld defects For this purpose, feature extraction objectives in this study are fractal dimension, Lyapunov exponent, shape of strange attrator. Trajectory changes in the strange attractor indicated that even same type of defects carried substantial difference in chaoticity resulting from distance shifts such as nearby 0.5, 1.0 skip distance. Such difference in chaoticity enables the evaluation of unique features of defects in the weld zone. In quantitative chaos fenture extraction, feature values of 0.835 and 0.823 in the case of slag inclusion and 0.609 and 0.573 in the case of crack were suggested on the basis of fractal dimension and Lyapunov exponent. Proposed chaoral post-process system in this study can enhances precision rate of ultrasonic pattern recognition results from defect signals of weld zone, such as slag inclusion and crack.

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The Analysis of Circumference Through-Wall Cracked Pipe Considering Weld Characteristic (용접부 강도불균질을 고려한 원주방향관통균열 배관의 파괴역학 해석법)

  • Park, Bo-Gyu;Oh, Chang-Kyun;Kim, Yun-Jae;Kim, Young-Jin;Kim, Jong-Sung;Jin, Tae-Eun
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.31-36
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    • 2004
  • Defective components of interest include not only homogeneous components, but also components with weldments where tensile properties vary across the weldment. Noting that the region near the weldment is the most vulnerable place for crack initiation and subsequent growth, defect assessment methods for homogeneous structure. Moreover, weldment width and crack location also affects the deformation and fracture behavior of the welded joints. These weld characteristics can evaluate using plastic limit load. So in this paper, evaluate plastic limit load both full circumference part-throughwall cracked pipes and circumference through-wall cracked pipes considering weld characteristics. And using evaluate results, proposed J-integral and crack opening displacement(COD) estimate method based on reference stress method.

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A Study on the Characteristics of Zr-4 End Cap Welded Joints Using Resistance Upset Welding (저항업셋 용접법을 이용한 Zr-4 End Cap용접부의 특성에 관한 연구)

  • 박철주;김형수;이영호;강원석
    • Journal of Welding and Joining
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    • v.10 no.4
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    • pp.240-249
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    • 1992
  • The objective of this study is to investigate the characteristics of welded joints on the Zircaloy-4 resistance upset welding for HWR(Heavy Water reactor)fuel rods. To estimate the characteristics of welded joints, the various tests were performed on the test coupons systematically with a wide range of each welding parameters in terms of a tensile test, burst test, knoop hardness test and metallography. Major results obtained in this study are as follows: 1. The tube and machined with 120.deg. projection was the reliable weld joint design for the nuclear fuel rod end cap welding. 2. As the weld current and the amount of upset increased linearly with increasing welding main heat input, it could make an estimate of their variation in accordance with the phase shift control. 3. It was found that an increase in squeeze force has an effect on the upset contour of welded joint because the amount of upset were increased by the change of squeeze force.

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Design of Welded Joints Using Stress Intensity Factors (응력확대계수를 이용한 용접이음부 설계 연구)

  • Park, Ji-Woo;Gu, Man-Hoi;Choi, Chang;Sung, Wan
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1996.11a
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    • pp.1058-1062
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    • 1996
  • The assessments of weld defects by fracture mechanics are performed for design of welded Joints. In general, butt, T-type, and L-type welded joint are useful for welding structure. When linear weld defects are in welded joint, stress intensity factors for each joints are calculated by finite element method. Analysis results are shown for the fracture modes and characteristics of joint types. And they are founded for the weaken order of welded joints being T-type, butt, L-type.

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Weldability of Aluminized Sheet Steels for Automobile Application(II) (Effect of Coating Conditions on Laser Weld Quality) (자동차용 알루미늄도금 강판의 용접성(II) (도금조건이 레이저용접 품질에 미치는 영향))

  • 김기철;차준호;이조영
    • Proceedings of the KWS Conference
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    • 2003.05a
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    • pp.102-104
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    • 2003
  • Laser weldability of aluminized steels of 0.8mm thick has been investigated. Test materials were cut from the commercial steels that were produced at the Coating Mill of POCOS. Test coupons for welding were prepared by using a conventional shearing machine and no additional edge treatment was peformed. Nd:YAG laser welding system was mainly applied to make weld specimens. Test results revealed that almost no spattering was observed even though the welding was peformed with no overlap joint clearance. Bead quality of aluminized steel laser weld was smooth and stable. According to x-ray inspection results, it was proved that the laser welds of aluminized steels were metallurgically defect free.

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Weld Quality Quantification through Chaotic Analysis (카오스 분석을 통한 용접 품질 정량화)

  • Cho, Jung-Ho;Farson, Dave;Kim, Cheol-Hee
    • Journal of Welding and Joining
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    • v.28 no.1
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    • pp.72-76
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    • 2010
  • Irregular fluctuation of penetration depth in CW single mode fiber laser welding is analyzed statistically and chaotically. Among various chaos theories, one of the basic concept referred as Lyapunov exponent is applied to the analysis to quantify the irregularity of penetration. Especially, maximal Lyapunov exponent (MLE) is known as the representative value indicating chaotic degree of the system dynamics. MLE calculation method of experimental data is applied to longitudinal spiking defect in fiber laser weld. Laser power modulation is suggested as a remedy then the computed MLE value is compared to CW case. It is shown that the adoption of chaos theory, MLE computation, can be used as a measurement standard to prove the validity of the solutions to prevent the unexpected chaotic behavior of weld through this work.

Weldability of Al Alloys,Part I ;Cfacking and Porosity (알루미늄 합금의 용접특성 - part I : 균열 및 기공)

  • 이창희;장래웅
    • Journal of Welding and Joining
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    • v.10 no.3
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    • pp.1-12
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    • 1992
  • A literature review was conducted to survey informations available on the welding metallurgy of aluminum alloys and its effect on fusion weldability, especially on solidification cracking and pore formation. Solidification cracking behavior of Al weld is a complicate matter as compared to other high alloys, where a relatively simple Fe-X(most detrimental elements S, P, B, Si, etc) binary diagram can be successfully applicable. Both additive and synergistic effects of elements should be considered together. A same element play a different role from system to system. Porosity, caused by hydrogen contamination of the weld is one of the most troublesome welding problems. The primary sources of hydrogen are believed to be an absorbed moisture on the filler metal or base metal and in the shielding gas. It is extremely important that reliable quality-control procedures be employed to eliminate all possible sources of hydrogen contamination. Selection of proper process and parameters is sometimes more important than controlling of alloying elements in order to make a defect-free weld.

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A Study on Detecting and Monitoring of Weld Root Gap using Neural Networks (신경회로망을 이용한 용접 Root Gap 검출과 모니터링에 관한연구)

  • Kang Sung-In;Kim Gwan-Hyung
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.10 no.7
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    • pp.1326-1331
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    • 2006
  • Weld root gap is a important fact of a falling-off weld quality in various kind of weld defect. The welding quality can be controlled by monitoring important parameters, such as, the Arc voltage, welding current and welding speed during the welding process. Welding systems use either a vision sensor or an Arc sensor, both of which are unable to control these parameters directly. Therefore, it is difficult to obtain necessary bead geometry without automatically controlling the welding parameters through the sensors. In this paper we propose a novel approach using neural networks for detecting and monitoring of weld root gap and bead shape. Through experiments we demonstrate that the proposed system can be used for real welding processes. The results demonstrate that the system can efficiently estimate the weld bead shape and detect the welding defects.

The Defect Detection and Evaluation of Austenitic Stainless Steel 304 Weld Zone using Ultrasonic Wave and Neuro (초음파와 신경망을 이용한 오스테나이트계 스테인리스강 304 용접부의 결함 검출 및 평가)

  • Yi, Won;Yun, In-Sik
    • Journal of Welding and Joining
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    • v.16 no.3
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    • pp.64-73
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    • 1998
  • This paper is concerned with defects detection and evaluation of heat affected zone (HAZ) in austenitic stainless steel type 304 by ultrasonic wave and neural network. In experiment, the reflected ultrasonic defect signals from artificial defects (side hole, vertical hole, notch) of HAZ appears as beam distance of prove-defect, distance of probe-surface, depth of defect-surface on CRT. For defect classification simulation, neural network system was organized using total results of ultrasonic experiment. The organized neural network system was learned with the accuracy of 99%. Also it could be classified with the accuracy of 80% in side hole, and 100% in vertical hole, 90% in notch about ultrasonic pattern recognition. Simulation results of neural network agree fairly well with results of ultrasonic experiment. Thus were think that the constructed system (ultrasonic wave - neural network) in this work is useful for defects dection and classification such as holes and notches in HAZ of austenitic stainless steel 304.

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