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1

An experimental study on optimizing for tandem gas metal arc welding process

Lee J. P., Park M. H., Kim D. H., Jin B. J., Shim J. Y., Kang B. Y., Kim I. S.

Journal of Achievements in Materials and Manufacturing Engineering

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2015

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Vol. 68, nr 2

72--79

EN

Purpose: To enhance productivity and provide high quality production material in a GMA welding process, weld quality, productivity and cost reduction affects the number of process variables. In addition, a reliable welding process and conditions must be implemented to reduce weld structure failure. Design/methodology/approach: The research investigates the interaction between the welding parameters (welding speed, distance between electrodes, and flow rate of shielding gas) and bead geometry for predicting the weld bead geometry (bead width, bead height). Taguchi techniques are applied to bead shape to develop curve equation for predicting the optimized process parameters and quality characteristics by analysing the S/N ratio. Findings: The experimental results and measured error is within the range of 10% presenting satisfactory accuracy. The curve equation was developed in such a way that you can predict the bead geometry of constructed machinery that can be used for making tandem welding process. Research limitations/implications: In various industries the welding process mathematical model is not fully formulated for the process parameter and on the welding conditions, therefore only partial variables can be predicted. Originality/value: This paper focused on the anode-cathode distance that can prevent arc blow in tandem GMA welding process. We also analysed the welding quality characteristics according to the bead geometry and welding parameters through S/N ratio dependent on the welding speed and flow rate variation of shielding gas. Finally, a mathematical model being able to predict the welding quality based on the given welding parameters using statistical method has been developed.

2

A study on on-line mathematical model to control of bead width for arc welding process

Son J. S., Lee J. P., Park M. H., Kim D. H., Jin B. J., Ki K. S., Kim C. G., Kim I. S.

Archives of Materials Science and Engineering

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2015

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Vol. 72, nr 2

78--85

EN

Purpose: Recently, not only robotic welders have replaced human welders in many welding applications, but also reasonable seam tracking systems are commercially available. However, fully adequate control systems have not been developed due to a lack of reliable sensors and mathematical models that correlate welding parameters to the bead geometry for the automated welding process. Design /meth o d o lo g y/ap p ro ach : In this paper, two on-line empirical models using multiple regression analysis are proposed in order to be applicable for the prediction of bead width. For development of the proposed models, an attempt has been made to apply for a several methods. For the more accurate prediction, the prediction variables are first used to the surface temperatures measured using infrared thermometers with the welding parameters (welding current, arc voltage) because the surface temperature are strongly related to the formation of the bead geometry. The developed models are applied to monitor and control the bead width as welding quality. Findings: The developed two on-line empirical models are able to predict the optimal welding parameters required to achieve desired bead width and weld criteria, help the development of automatic control system and expert system and establish guidelines and criteria for the most effective joint design. Research lim ita tio n s /im p lic a tio n s : This research was concentrated to develop on the on-line empirical models that can predict bead width in robotic GMA welding process. The developed empirical models can only be employed to control the bead width for butt welding. O rig in ality /va lu e : It has been realized that with the use of the developed algorithms, the prediction of bead width becomes much simpler to even a novice user who has no prior knowledge of the robotic GMA welding process and optimization techniques.

3

On the convergence of the method of lines for quasi-nonlinear functional evolutions in Banach spaces

Jin B. J., Kim J. K.

Journal of Applied Analysis

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2000

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Vol. 6, nr 1

105-127

EN

This paper is concerned with the existence of global limit solutions for the quasi-nonlinear functional evolution problem x`∈ A(t, xt) x+ G(t, xt, Ltx),t ∈ [0,T], (FDE, φ) x0=φ, where A(t, ψ 1) and G(t , ψ 1,Lt ψ 2) are defined, with respect to ψ 1, on a subspace of the space PC([-r, 0],X) of all piecewise continuous functions f : [--r, 0] → X. An appropriate subspace of PC([--r, t],X) is the domain of definition of the nonlinear operators Lt, t ∈ [0,T]. The operators A(t, ψ)x are w-dissipative and Lipschitz - like in (t, ψ ) which are more general conditions than those of Karsatos-Liu. The operators G and Lt are Lipschitzian mappings on their respective domains. Moreover, we investigate the uniqueness and strong solution for such problem.