• Title/Summary/Keyword: Laser Welding Monitoring

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Fast Fourier Transform Analysis of Welding Penetration Depth Using 2 kW CW Nd:YAG Laser Welding Machine

  • Kim, Do-Hyung;Chung, Chin-Man;Baik, Sung-Hoon;Kim, Koung-Suk;Kim, Jin-Tae
    • Journal of the Korean Society for Nondestructive Testing
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    • v.28 no.4
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    • pp.372-376
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    • 2008

  • We report experimental results on the correlations between welding penetration depth and the frequencies of the radiation from the welding pool. Various welding samples such as SUS304, brass, SUS316, etc. have been investigated with 2 kW CW Nd:YAG laser welding machine. The radiation signals from the plume generated by the interactions between the welding sample and laser with respect to the defocusing length was measured with fiber system collecting the plume signal. Analysis of the frequencies by using fast Fourier transform (FFT) shows that the penetration depth is deep as plume signal frequencies are low, shallow penetration depth for high frequencies. Frequencies up to 250 Hz for obtained signals can be analyzed with the discrete FFT. This is the useful method fur closed loop control of the laser power with respect to the welding penetration depth and is used for real time inspection of the welding quality.

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Production of Laser Welded Tube for Automobile Bumper Beam from 60kgf/$\textrm{mm}^2$Grade Steel Sheet (60kgf/$\textrm{mm}^2$급 자동차 범퍼빔용 레이저 용접 튜브 제조기술 및 장치연구)

  • Seo, Jung;Lee, Je-Hoon;Kim, Jong-Soo;Kim, Jung-O;Kang, Hee-Sin;Lee, Moon-Yong;Jung, Byung-Hoon
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.7
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    • pp.136-144
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    • 2004

  • Optimal process and system to produce the laser welded tube for one body formed bumper beam are studied. The calculated size of tube is a thickness of 1.4mm, diameter of 105.4mm and length of 2000mm. The tube is shaped from a cold rolled high strength steel sheet(tensile strength: 60kgf/$\textrm{mm}^2$ grade). Two roll bending method is the optimal tube shaping process compared to UO-bending, bending on press brake, multi-step continuous roll forming and 3 roll bending methods. Weld quality monitoring and seam tracking along the butt-joint lengthwise to the tube axis are also studied. The longitudinal butt-joint is welded by the $CO_2$ laser welding system equipped with a seam tracker and plasma sensor. The constructed $CO_2$laser tube welding system can be used for the precision seam tracking and the real-time monitoring of weld quality. Finally, the obtained laser welded tube can be used for one-body formed automobile bumper beam.

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The Relationship between In-process Signals and Weld Defect in $CO_2$ Laser Lap Welding of Zn-coated Steel for Shipbuilding (조선용 아연코팅강판의 $CO_2$ 레이저 겹치기 용접시 인프로세스 측정신호와 용접결함과의 관련성)

  • Kim, Jong-Do;Lee, Chang-Je;Lee, Jae-Bum;Suh, Jeong
    • Laser Solutions
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    • v.13 no.3
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    • pp.1-6
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    • 2010

  • The in-process monitoring of $CO_2$ welding of Zn-coated steel plates has been studied and compared with that of conventional thin plates. Relationships between weld defects and plasma emission signals were evaluated in laser lap joint of thick Zn-coated steel. According to the study, weld defects were found to increase with Zn content. As a result, measured plasma emission signals also decreased. In case of plate with $15{\mu}m$-thick Zn-coated layer, defects caused by evaporation of Zn could, therfore, controled by gap of 0.1mm, resulting in a stable emission signals. However, the amplitude of signals fluctuated very widely. Variation of amplitude sould be limited in 3-8V by FFT smoothing.

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A study on manufacturing of laser welded tube from 60kgf/$mm^2$Grade Steel Sheet for one-body forming (60kgf/$mm^2$급 일체화 성형용 레이저 용접 튜브 제조에 관한 연구)

  • Seo, Jung;Lee, Je-Hoon;Kim, Jung-Oh;Kang, Hee-Sin;Lee, Mun-Yong;Jung, Byung-Hoon
    • Proceedings of the KWS Conference
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    • 2003.11a
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    • pp.18-20
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    • 2003

  • Optimal processing and system to produce the laser welded tube for one body formed bumper beam are studied. The calculated size of tube is a thickness of 1.4mm, diameter of 105.4mm and length of 2000mm. The tube is shaped from cool rolled high strength steel sheet(tensile strength: 60kgf/$\textrm{mm}^2$ grade). Two roll bending method is the optimal tube shaping process compared to UO-bending, bending on press brake, multi-step continuous roll forming and 3 roll bending methods. Weld quality monitoring and seam tracking along the butt-joint lengthwise to the tube axis are also studied. The longitudinal butt-joint is welded by the $CO_2$ laser welding system equipped with a seam tracker and plasma sensor. The constructed $CO_2$ laser tube welding system can be used for the precision seam tracking and the real-time monitoring of weld quality. Finally, the obtained laser welded tube can be used for one-body formed automobile bumper beam.

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