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Welding stability assessment in the GMAW-S process based on fuzzy logic by acoustic sensing from arc emissions

Cayo E. H., Alfaro S. C. A.

Journal of Achievements in Materials and Manufacturing Engineering

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2012

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Vol. 55, nr 1

18--25

EN

Purpose: The present research work has as purpose detecting perturbations, measuring and assessing the welding stability in GMAW process in short circuit mode named hereafter as GMAW-S process. Design/methodology/approach: Welding trials were performed with a set of optimal input welding parameters. During experiments were induced some perturbations on the welding trajectory. It causes alteration on the stability of welding resulting as consequence geometrical shape deformations. During each experiments, acoustic emission signal coming from electric arc as well as arc voltage and welding current were acquired aided by a card acquisition and virtual instrumentation software. A heuristic model was performed as knowledge base rules of a fuzzy logic system. This system has two inputs and one output. Some additional welding trials were performed for assessing its performance. Findings: It was performed a welding stability assessment system based on fuzzy logic. As well as, this system is based on non-contact sensing what reduces the loading effects on the welding process. Research limitations/implications: In the present work was monitored just the acoustic emissions coming from arc. Although that, the results were satisfactory, an approach on data fusion of sensors including electromagnetic emission sensors could improve the quality assessments system. Originality/value: The non-contact welding stability assessment methods have reduces loading effects and a heuristic approach on the relations between arc emissions and welding stability allows quantifying nonlinear variables such as knowledge and experience of skilled welders, such that, it is possible to represent linguistic terms numerically what could be used as an on-line monitoring system of welding processes.

2

Relationship between geometrie welding parameters and optical-acoustic emissions from eleetrie are in GMAW-S proeess

Cayo E. H., Alfaro S. C. A.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 46, nr 1

79--87

EN

Purpose: Show the relationship between geometrie characteristics of the weld bead and the optical-acoustic emissions from electric arc during welding in the GMAW-S process. Design/methodology/approach: Bead on plate welding experiments was carried out setting different process parameters. Every welding parameter group was set aiming to reach a high stability level what guarantee a geometrical uniformity in the weld beads. In each experiment was simultaneously acquired arc voltage, welding current, infrared and acoustic emissions; from them were computed parameters as arc power, acoustic peaks rate and infrared radiation rate. It was used a tri-dimensional LASER scanner for to acquire geometrical information from the weld beads surface as width and height of the bead. Depth penetration was measured from sectional cross cutting of weld beads. Findings: Previous analysis showed that the arc emission parameters reach a stationary state with different characteristic for each experiment group which means that there is some correlation level between them. Posterior analysis showed that from infrared parameter is possible to monitoring external weld bead geometry and principally its penetration depth. From acoustic parameter is possible to monitoring principally the external weld bead geometry. Therefore is concluded that there is a close relation between the arc emissions and the weld bead geometry and that them could be used to measuring the welding geometrical parameters. Research limitations/implications: After analysis it was noticed that the infrared sensing has a better performance than acoustic sensing in the depth penetration monitoring. Infrared sensing also sources some information about external geometric parameters that in conjunction with the acoustic sensing is possible to have reliable information about weld bead geometry. This method of sensing geometric parameters could be applied in other welding processes, but is necessary to have visibility of the arc, it means that for example this method cannot be used in the submerged arc welding - SAW process. Originality/value: The using two or more sensors for monitoring welding parameters increases the performance and reliability of the measurements. In this case, the monitoring of the weld bead geometric parameters could be possible from sensing arc emission and potentially it could be used as an on-line monitor, avoiding any complex electric connections of sensors into the welding process.

3

Comparison between AC and MF-DC resistance spot welding by using high speed filming

Alfaro S. C. A., Vargas J. E., Wolff M. A., Vilarinho L. O.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 24, nr 1

333-339

EN

Purpose: In this work it will be carried through the filming of the formation and growth of the nugget in resistance spot welding executed in AC and MF. A comparison for same times in both the processes will be carried through to verify which of the used processes offers better conditions, control and results as well as will help for one better understanding of the process aiming at the optimization. Design/methodology/approach: Two different spot welding machine (AC and MF-DC) had been used, and a digital high-speed camera. The weld points had been carried through in 3 galvanized steel different plate configurations. The electrodes had been truncated to obtain one better visualization for the weld nugget formation. The comparison of the formation and development between the weld point of each process (AC and MF) is shown in 7 pictures in the same values of time. Findings: For currents below 2 kA, no nugget was observed, and the formation of same after 10 degrees cycle for bigger current of 3 kA. The MF-DC welding offers the possibility of obtaining nuggets more uniforms within shorter times (depending on the plate configuration). Research limitations/implications: In this work the AC machine is limited by the values of current of welding and pressure of the electrodes: (2 - 6) kA e (87 - 261) kgf respectively. Other materials: aluminum, stainless steel or material exactly dissimilar could be used following the line of this research. Bigger currents levels can also be used. Originality/value: The idea to compare resulted for the same process of welding under different conditions (equipment, materials and or parameters) makes possible the choice of these better conditions used to the optimization of the process.