Application of Central Composite Design, Response Surface Methodology in Predicting the Thermal Expansion of Mild Steel Weldment

Abstract

The compositional range of materials to be welded, the thickness of the base materials, and current type are the main determining variables in the choice of welding. However, thermal expansion in mild steel weldments occurs when the material expands or contracts when subjected to changes in temperature during welding or subsequent heating and cooling cycles. This expansion and contraction can lead to residual stresses, distortion, and even cracking in the weldment if not properly managed. Mild steel, like many other metals, expands when heated and contracts when cooled. One major challenge occurs when during welding, the high temperatures cause the metal to expand in the heat-affected zone (HAZ) and the weld zone itself, then as the weldment cools down, it contracts, but this contraction might not be uniform due to differences in cooling rates across the weldment. The present study aims to predict the thermal expansion of mild steel weldments in relation to the current, voltage and gas flow rate. The central composite design is used for the design of experiment of 20 experimental runs, while the Response Surface Methodology (RSM) was used for the analysis. The model used in the RSM is Quadratic, while the coefficient of determinant, R-Squared of 0.9642, Adj R-Squared, 0.9319, Pred R-Squared, 0.7133, Adeq Precision 22.307 were obtained. There was no outliner which showed that the model adequately predicted the response. The study establishes that thermal expansion of mild-steel weldment can be adequately predicted by applying expect system such as the Response Surface Methodology.