Nonlinear Identification of Weld Penetration Control System in Pulsed Gas Metal Arc Welding

Arc welding is generally used to join thick metals in many engineering applications. However, poor penetration often occurs due to arc heat diffusion into the base metal. Hence, arc welding of thick metals normally requires grooving and/or preheating of the base metal and sometimes requires multiple passes for very thick metals or metals with high conductivity, such as aluminum alloys. In gas metal arc welding of thick metals with grooves and preheating, complicated melt flow and heat transfer are caused by the combined effect of droplet impingement, gravity, electromagnetic force, surface tension, and plasma arc pressure. Understanding these complicated transport phenomena involved in the welding process is critical in improving the penetration depth and weld quality. In this study, mathematical models and associated numerical techniques have been developed to study the effects of grooves and preheating on melt flow, diffusion of species, and weld penetration in gas metal arc welding of thick metals. Complex melt flow, transient weld pool shape and distributions of temperature and species in the weld pool are calculated. The continuum formation is adopted to handle liquid region, mushy zone and solid region. VOF technique is used to handle transient deformed shape of weld pool surface. The preliminary results show both grooves and preheating have important effects on the melt flow in weld pool and the weld penetration. Computer animations showing the evolutions of temperature; melt flow; and the interaction between droplets and weld pool will be presented.

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Sensing of the weld penetration at the beginning of pulsed gas metal arc welding

Journal of Manufacturing Processes ◽

10.1016/j.jmapro.2017.07.002 ◽

2017 ◽

Vol 28 ◽

pp. 343-350 ◽

Cited By ~ 4

Author(s):

Pengfei Bai ◽

Zhijiang Wang ◽

Shengsun Hu ◽

Shangwen Ma ◽

Ying Liang

Keyword(s):

Arc Welding ◽

Gas Metal Arc Welding ◽

Weld Penetration ◽

Metal Arc Welding

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Dynamic Modeling and Adaptive Control of the Gas Metal Arc Welding Process

Journal of Dynamic Systems Measurement and Control ◽

10.1115/1.2899235 ◽

1994 ◽

Vol 116 (3) ◽

pp. 405-413 ◽

Cited By ~ 28

Author(s):

Jae-Bok Song ◽

David E. Hardt

Keyword(s):

Adaptive Control ◽

Control System ◽

Arc Welding ◽

Gas Metal Arc Welding ◽

Welding Process ◽

Weld Bead ◽

Adaptive Control System ◽

Bead Width ◽

Metal Arc Welding ◽

Arc Welding Process

Control of the welding process is a very important step in welding automation. Since the welding process is complex and highly nonlinear, it is very difficult to accurately model the process for real-time control. In this research, a discrete-time transfer function matrix model for gas metal arc welding process is proposed. This empirical model takes the common dynamics for each output and inherent process and measurement delays into account. Although this linearized model is valid only around the operating point of interest, the adaptation mechanism employed in the control system render this model useful over a wide operating range. Since welding is inherently a nonlinear and multi-input, multi-output process, a multivariable adaptive control system is used for high performance. The process outputs considered are weld bead width and depth, and the process inputs are chosen as the travel speed of the torch and the heat input. A one-step-ahead (or deadbeat) adaptive control algorithm combined with a recursive least-squares methods for on-line parameter estimation is implemented in order to achieve the desired weld bead geometries. Control weighting factors are used to maintain the stability and reduce excessive control effort. Some guidelines for the control design are also suggested. Command following and disturbance rejection properties of the adaptive control system for both SISO and MIMO cases are investigated by simulation and experiment. Although a truly independent control of the outputs is difficult to implement because of a strong output coupling inherent in the process, a control system for simultaneous control of bead width and depth was successfully implemented.

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Characterization of GMAW (Gas Metal Arc Welding) Penetration Using Ultrasonics

Materials ◽

10.3390/ma13102307 ◽

2020 ◽

Vol 13 (10) ◽

pp. 2307

Author(s):

Lu Zhang ◽

Gorkem Okudan ◽

Alexandra-Del-Carmen Basantes-Defaz ◽

Ryan M. Gneiting ◽

Sankaran Subramaniam ◽

...

Keyword(s):

Arc Welding ◽

Numerical Models ◽

Gas Metal Arc Welding ◽

Plate Thickness ◽

Ultrasonic Signal ◽

Weld Penetration ◽

Ultrasonic Methods ◽

Quantitative Correlation ◽

Metal Arc Welding ◽

Welding Defects

Welding defects such as lack of penetration, undercutting, crater crack, burn-through and porosity can occur during manufacturing. Assessing weld quality using nondestructive evaluation methods is important for the quality assurance of welded parts. In this paper, the measurement of weld penetration, which is directly related to weld integrity, is investigated by means of ultrasonics. Both linear and nonlinear ultrasonic methods are studied to assess their sensitivities to weld penetration. Welded plates with different penetration depths controlled by changing weld heat input are manufactured using gas metal arc welding (GMAW). Microscopic properties are assessed after the ultrasonic measurements are completed. Numerical models are built using the weld profile obtained from macrographs to explain the relationship between linear ultrasonic and weld penetration. A quantitative correlation between weld morphology (shape, width and depth) and the energy of linear ultrasonic signal is determined, where the increase of weld bead penetration exceeding the plate thickness results in decrease of the energy of the ultrasonic signal. Minimum detectable weld morphology using linear ultrasonics is defined depending on the selected frequency. Microhardness measurement is conducted to explain the sensitivity of nonlinear ultrasonics to both weld penetration and heterogeneity in weld. The numerical and experimental results show that the weld geometry influences the ultrasonic measurement other than the materials’ properties.

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