A novel hybrid multi-criteria decision methodology for assessing tool materials in friction stir welding process

Multi-criteria decision-making (MCDM) methods play a crucial role in assisting decision-makers when faced with conflicting alternatives and the need to select the most favourable choice. While various MCDM methods exist, hybrid MCDM methods aim to incorporate the advantageous attributes of multiple MCDM methods into a coherent framework, enhancing the efficiency and robustness of the decision-making process. In contrast to integration, where MCDM methods are used sequentially, hybridization enables the utilization of complementary aspects from different methods, capitalizing on the strengths of each. This research proposes a novel hybrid MCDM methodology called Criteria-wise Alternative Ranking and Correlation Analysis for Composite Scoring (CARCACS) to address the weight determination of criteria and ranking of alternative solutions in MCDM problems. CARCACS offers distinct advantages, avoiding variations caused by different normalization equations and weight determination techniques, thereby ensuring consistent and reliable results. The method ranks alternative solutions based on each criterion, correlates the criteria to determine appropriate weights, and calculates a composite score for each alternative. The final ranking of alternatives is established based on these composite scores. To validate the efficiency and reliability of CARCACS, comprehensive sensitivity analyses are conducted using existing case studies, as well as a new case study on tool material selection for friction stir welding (FSW) in joining steel to aluminium alloy. Comparison with existing MCDM methods demonstrates its effectiveness, and sensitivity analyses confirm the reliability of CARCACS under various conditions. The results affirm the validity of CARCACS, with H13 tool steel consistently identified as the best FSW tool material alternative, demonstrating its effectiveness and applicability in MCDM problems.