COMPARATIVE MULTI-CRITERIA OPTIMIZATION OF TUNGSTEN INERT GAS (TIG) WELDING PARAMETERS USING TOPSIS AND COPRAS TECHNIQUES

Abstract

This study presents a comparative multi-criteria optimization of Tungsten Inert Gas (TIG) welding parameters using the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) and Complex Proportional Assessment (COPRAS) methods. The study aimed to identify the most suitable combination of welding voltage, current, and shielding-gas flow rate based on the combined mechanical performance of welded joints. Twenty experimental runs formulated using design exert 7.01 were evaluated using tensile strength, elongation, and hardness as equally weighted beneficial criteria. The experimental parameters included welding voltages of 16 25 V, currents of 96–213 A, and shielding-gas flow rates of 11–19 L/min. The measured mechanical properties varied across the experimental conditions, demonstrating the difficulty of selecting an optimal welding condition using a single response. TOPSIS ranked Run 6 as the best-performing alternative, with a voltage of 20.5 V, current of 154.5 A, and shielding-gas flow rate of 11 L/min. This condition achieved a tensile strength of 483.4 MPa, elongation of 16.3%, and hardness of 189.5 BHN. COPRAS also identified Run 6 as the highest-ranked alternative, indicating agreement between the two decision-making techniques regarding the preferred experimental condition. The results demonstrate the potential of integrating multi-criteria decision-making methods to balance competing mechanical responses and support systematic selection of TIG welding parameters. However, the selected condition represents the best-ranked alternative among the twenty experimental runs rather than a confirmed global optimum. Further investigations involving replicate experiments, weld microstructural characterization, and defect assessment are recommended to validate the robustness and practical applicability of the identified condition. This comparative framework provides a useful basis for evidence-based welding parameter selection and improved assessment of welded-joint performance.