OPTIMIZATION OF WELD BEAD UNDERCUTS IN TUNGSTEN INERT GAS MILD STEEL WELD USING RESPONSE SURFACE METHODOLOGY

Authors: *Ozigagun A, Achebo J.I

DOI Info: N/A

ABSTRACT

Weld quality is adversely affected by the presence of undercuts, and this defect can reduce the strength and load bearing capability of welded joints. The aim of this study was to develop a model to optimize the undercut using response surface methodology. The experimental design yielded expert 30 run using central composite design (CCD). The tungsten inert gas welding equipment was used to produce 150 weld specimens from mild steel plates measuring 10 mm x 60 mm x 40 mm for this study and the undercut was measured using the nondestructive wiki scanner. The second order polynomial model was adopted, taking current, voltage, gas flow rate and welding speed as input and undercut as response. To test for the model significance, adequacy and validity, the goodness of fit was determined via analysis of variance (ANOVA). The p values of the undercut models was 0.019 which is lower than 0.05, indicating the model was significant. The R² value of 0.76 and a signal to noise ratio of 7.491 indicate that the undercut model is potent. The numerical optimal solution shows that a combination of current of 180.04 A, voltage of 18 V, welding speed of 3.01 mm/min and gas flow rate of 21.94 L/min will produce the least undercut of 0.0299 mm with a desirability value of 1.00. In this study an approach using the response surface method for optimizing weld undercut has been successfully introduced and its effectiveness and efficiency well demonstrated.

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