An Analytic Hierarchy Process for a General Ranking of Friction Stir Welding Parameters Optimized Through the Design of Experimental Arrays

Abstract

Objective: This study aims to rank friction stir welding parameters using the analytic hierarchy process (AHP). Methods:The proposed approach includes two phases to achieve a general ranking of the parameters through the separate estimation of their weights on each metal type and aggregation. The criteria used in the AHP for ranking are the contribution percentages and the degrees of the parameters obtained from the analysis of variance of experimental studies. The data were obtained from literature that used the design of experimental arrays to optimize these parameters on multiple properties and many similar and dissimilar metals. Fourteen parameters were assigned in the present analysis, namely rotational speed (RS), traverse speed (TS), axial force (AF), pin profile (PP), tilt angle (TA), the ratio between shoulder diameter and pin diameter (D/d ratio), shoulder diameter (SD), pin diameter (Pd), plunge depth (PD), pin length (PL), tool offset (TO), shoulder concavity (SC), number of passes (NOP) and base metal side (BMS). Results:The parameters were classified into highly significant, moderately significant, and insignificant based on their rankings. The RS, TS, TA, and PP were the highest-ranking parameters with a total contribution of 83.4% to outputs. The insignificant parameters included the D/d ratio, BMS, SC, AF, and Pd, with a low total contribution of 14%. The moderately significant parameters were the TO, NOP, SD, PD, and PL. Conclusion:The above-mentioned significant parameters could be controlled to maximize the response. The failure to achieve the target specified in the standard by controlling only highly significant parameters signifies a need for further modification of the FSW process. Therefore, parameters of moderate significance are potential parameters that need to be controlled to achieve the target. To limit the selection between these parameters, reference should be made to the type of metal used and then the parameters with the greatest impact on the metal are selected, i.e. controlling PL for aluminum, NOP, and SD for magnesium, and TO for aluminum-to-steel and aluminum-to-copper.