• Title, Summary, Keyword: Weld pool

Search Result 116, Processing Time 0.048 seconds

A STUDY ON WELD POOL MONITORING IN PULSED LASER EDGE WELDING

  • Lee, Seung-Key;Na, Suck-Joo
    • Proceedings of the KWS Conference
    • /
    • /
    • pp.595-599
    • /
    • 2002
  • Edge welding of thin sheets is very difficult because of the fit-up problem and small weld area In laser welding, joint fit-up and penetration are critical for sound weld quality, which can be monitored by appropriate methods. Among the various monitoring systems, visual monitoring method is attractive because various kinds of weld pool information can be extracted directly. In this study, a vision sensor was adopted for the weld pool monitoring in pulsed Nd:YAG laser edge welding to monitor whether the penetration is enough and the joint fit-up is within the requirement. Pulsed Nd:YAG laser provides a series of periodic laser pulses, while the shape and brightness of the weld pool change temporally even in one pulse duration. The shutter-triggered and non-interlaced CCD camera was used to acquire a temporally changed weld pool image at the moment representing the weld status well. The information for quality monitoring can be extracted from the monitored weld pool image by an image processing algorithm. Weld pool image contains not only the information about the joint fit-up, but the penetration. The information about the joint fit-up can be extracted from the weld pool shape, and that about a penetration from the brightness. Weld pool parameters that represent the characteristics of the weld pool were selected based on the geometrical appearance and brightness profile. In order to achieve accurate prediction of the weld penetration, which is nonlinear model, neural network with the selected weld pool parameters was applied.

  • PDF

A Study of tow-Power Density Laser Welding Process with Evolution of me Surface (자유표면변형을 고려한 저에너지밀도 레이저 용접공정 해석)

  • Ha Eung-Ji;Kim Woo-Seung
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.28 no.10
    • /
    • pp.1202-1209
    • /
    • 2004
  • In this study, numerical investigation has been performed on the evolution of weld pool geometry with moving free surface during low-energy density laser welding process. The free surface elevates near the weld pool edge and descends at the center of the weld pool if d$\sigma$/dT is dominantly negative. It is shown that the predicted weld pool width and depth with moving free surface are a little greater than those with flat weld pool surface. It is also believed that the weld pool surface oscillation during the melting process augments convective heat transfer rate in the weld pool. The present analysis with moving free surface should be considered when We number is very small compared to 1.0 since the deformation of the weld pool surface is noticeable as We number decreases.

A Study of Weld Quality Control in Arc Welding Using the Digital Image Processing (화상처리에 의한 아크용접에서의 용접품질제어에 관한 연구)

  • 김동철;이세현;엄기원
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • /
    • pp.499-503
    • /
    • 1994
  • The feedback control systems of welding process using visual information can improve weld qualities. However, it is very difficult to get the visual information of weld pool since welding are is much stronger than light from weld pool. To explore the possibility of extending the capability of automatic welding machines a study of a closed loop controlled welding system consisted of a GTA welding machine, a vision system, a stepping motor system and a digital computer was undertaken. Particularly, in this system, a CCD camera with 850nm long pass filter was focused on the weld pool to give a weld pool image. Subsequently, image analysis technique has been developed to measure a weld pool width. Using this weld pool width measurement, a colsed loop control system adjusted welding speed to maintain constant weld pool width.

  • PDF

Behavior of Weld Pool Shape and Weld Surface Deformation as a Function of Spot-GTA Welding Position for 304 Stainless Steel (Spot-GTA 용접자세에 따른 304 스테인리스강 용융지 표면 및 용접부 형상 거동)

  • Kang, Nam-Hyun;Park, Yeong-Do;Cho, Kyung-Mox;Singh, Jogender;Kulkarni, Anil
    • Journal of Welding and Joining
    • /
    • v.26 no.2
    • /
    • pp.62-68
    • /
    • 2008
  • Effects of gravitational orientation on gas tungsten arc welding (GTAW) for 304 stainless steel were studied to determine the critical factors for weld pool formation, such as weld surface deformation and weld pool shape. This study was accomplished through an analytical study of weld pool stability as a function of primary welding parameters (arc current and arc holding time), material properties (surface tension and density), and melting efficiency (cross-sectional area). The stability of weld pool shape and weld surface deformation was confirmed experimentally by changing the welding position. The arc current and translational velocity were the major factors in determining the weld pool stability as a function of the gravitational orientation. A 200A spot GTAW showed a significant variation of the weld pool formation as the arc held longer than 3 seconds, however the weld pool shape and surface morphology for a 165A spot GTAW were 'stable', i.e., constant regardless of the gravitational orientation. The cross-sectional area of the weld (CSA) was one of the critical factors in determining the weld pool stability. The measured CSA ($13.5mm^2$) for the 200A spot GTAW showed a good agreement with the calculated CSA ($14.9mm^2$).

Weld pool size estimation of GMAW using IR temperature sensor (GMA 용접공정에서 적외선 온도 센서를 이용한 용융지 크기 예측)

  • 김병만;김영선;조형석
    • 제어로봇시스템학회:학술대회논문집
    • /
    • /
    • pp.1404-1407
    • /
    • 1996
  • A quality monitoring system in butt welding process is proposed to estimate weld pool sizes. The geometrical parameters of the weld pool such as the top bead width and the penetration depth plus half back width are utilized to prove the integrity of the weld quality. The monitoring variables used are the surface temperatures measured at three points on the top surface of the weldment. The temperature profile is assumed that it has a gaussian distribution in vertical direction of torch movement and verify this assumption through temperature analysis. A neural network estimator is designed to estimate weld pool size from temperature informations. The experimental results show that the proposed neural network estimator which used gaussian distribution as temperature information can estimate the weld pool sizes accurately than used three point temperatures as temperature information. Considering the change of gap size in butt welding, the experiment were performed on various gap size.

  • PDF

Control of weld pool sizes in GMA welding processes using neural networks (신경회로를 이용한 GMA 용접 공정에서의 용융지의 크기 제어)

  • 임태근;조형석
    • 제어로봇시스템학회:학술대회논문집
    • /
    • /
    • pp.531-536
    • /
    • 1992
  • In GMA welding processes, monitoring and control of weld quality are extremely difficult problems. This paper describes a neural network-based method for monitoring and control of weld pool sizes. First, weld pool sizes are estimated via a neural estimator using multi-point surface temperatures, which are strongly related to the formation of weld pool, and then controlled using the estimated pool sizes. Two types of controllers using the pool size estimator are designed and tested. To evaluate the performance of the designed controllers, a series of simulation studies was performed.

  • PDF

Control of Weld Pool Size in GMA Welding Process Using Neural Networks (신경회로를 이용한 GMA 용접 공정에서의 용융지의 크기 제어)

  • 임태균;조형석;부광석
    • Journal of Welding and Joining
    • /
    • v.12 no.1
    • /
    • pp.59-72
    • /
    • 1994
  • This paper presents an on-line quality monitoring and control method to obtain a uniform weld quality in gas metal arc welding (GMAW) processes. The geometrical parameters of the weld pool such as the top bead width and the penetration depth plus half back width are utilized to assess the integrity of the weld quality. Since a good quality weld is characterized by a relatively high depth-to-width ratio in its dimensions, the second geometrical parameter is regulated to a desired one. The monitoring variables are the surface temperatures measured at various points on the top surface of the weldment which are strongly related to the formation of the weld pool The relationship between the measured temperatures and the weld pool size is implemented on the multilayer perceptrons which are powerful for realization of complex mapping characteristics through training by samples. For on-line quality monitoring and control, it is prerequisite to estimate the weld pool sizes in the region of transient states. For this purpose, the time history of the surface temperatures is used as the input to the neural estimator. The control purpose is to obtain a uniform weld quality. In this research, the weld pool size is directly regulated to a desired one. The proposed controller is composed of a neural pool size estimator, a neural feedforward controller and a conventional feedback controller. The pool size estimator predicts the weld pool size under growing. The feedforward controller compensates for the nonlinear characteristics of the welding process. A series of simulation studies shows that the proposed control method improves the overall system response in the presence of changes in torch travel speed during GMA welding and guarantees the uniform weld quality.

  • PDF

A study of low-power density laser welding process with evolution of free surface (자유표면변형을 고려한 저에너지밀도 레이저 용접공정 해석)

  • Ha, Eung-Ji;Kim, Woo-Seung
    • Proceedings of the KSME Conference
    • /
    • /
    • pp.133-138
    • /
    • 2003
  • In this study, numerical investigation has been performed on the evolution of weld pool geometry with moving free surface during low-energy density laser welding process. The free surface elevates near the weld pool edge if ${\partial}{\sigma}/dT$ is dominantly negative. On the contrary, the free surface rise at the center of weld pool in case of mainly positive ${\partial}{\sigma}/dT$. The predicted weld pool width and depth with moving free surface are 5∼15%$5{\sim}15%$ greater than those with flat weld pool surface. It is considered that weld pool surface oscillation during melting process augments convective heat transfer rate in the weld pool.

  • PDF

A Study on Weld Pool Oscillation for Pool Geometry Measurement (완전용입 풀의 진동을 이용한 형상측정에 관한 연구)

  • 유중돈
    • Journal of Welding and Joining
    • /
    • v.11 no.2
    • /
    • pp.62-73
    • /
    • 1993
  • Weld pool oscillation for the full-penetration GTA welding process was investigated for its possible application to weld penetration control through theoretical modeling and experiment. Energy method was used to estimate the natural frequency of the molten pool having the physically-acceptable weld geometry and oscillation modes. An unique experimental system was built which had the data acquisiton and video capabilities so that the pool oscillation signals and molten pool surfaces could be monitored continuously. Pool oscillation was detected through arc voltage and arc light emission simultaneously. The signal from arc light emission showed good coherence with that from arc voltage, and arc light generated the higher quality signal. The molten pool was found to oscillate in different oscillation modes based on the travel speed and weld geometry. The natural frequency estimated from the theoretical model agreed reasonably well with the experimental results.

  • PDF

A Study of Weld Pool width Control in Gas Tungsten Arc Welding Using the Digital Image Processing (화상처리에 의한 Gas Tungsten Arc 용접에서의 용융지폭제어에 관한 연구)

  • Kim, Dong-Cheol;Rhee, Sehun;Um, Ki-Woan
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.20 no.9
    • /
    • pp.2760-2769
    • /
    • 1996
  • The feedback control systems of welding process using visual information can improve weld qualities. However, it is very difficult to get the visual information of weld pool since the light intensity of welding arc is much stronger than that of the weld pool. To explore the possibility of extending the capability of automatic welding machines, a study of a closed loop controlled welding system consisted of a GTA welding machine, a vision system, a stepping motor system and a digital computer was undertaken. Particularly, in this system, a CCD camera with a long wavelength pass filter was used to get a better weld pool image. Subsequently, an image analysis technique has been developed to measure the weld pool width. Using this weld pool width measurement, a colsed loop control system adjusted welding speed to maintain a constant weld pool width.