A Combined MCDM Approach for Parametric Hierarchy in Friction Stir Lap Welding of Dissimilar Polycarbonate to Nylon‐6

ABSTRACT The present work addresses the feasibility of friction stir lap welding (FSLW) for the joining of polycarbonate to nylon‐6 sheets in overlapped configuration. The effects of tool rotational speed, traverse speed, plunge depth using different tool pin profiles (swept ratios) were studied on quality characteristics of dissimilar welds using response surface methodology (RSM). The second‐order regression models were significant for joint efficiency and weld hardness. The lowest traverse speed (15 mm/min) resulted in the highest weld strength and elongation whereas square pin indicated the weakest welds with undercut flaws. The strongest weld (31.3 MPa) without much ductility was noticed using hexagonal pin at 1600 rpm, 15 mm/min and 0.1 mm, while cylindrical pin at 2400 rpm made stronger (31.0 MPa) weld with higher ductility. The strength and ductility were balanced using AHP‐entropy weights (0.349, 0.582, 0.069 for strength, elongation and hardness, respectively). The welding experiments were ranked using CoCoSo, MABAC and grey relational analysis. All three approaches selected the same best condition (1600 rpm, 15 mm/min, 0.3 mm) using hexagonal pin (28.9 MPa, 17.1 mm elongation) that showed the highest weld ductility with adequate strength. Moreover, the rankings methods agreed high closeness (Spearman correlations of 0.951–0.991) that can precisely rank the parametric levels.