Optimization of Resistance Spot Weld Parameters using Grey Relational Analysis

Resistance spot welding approach in joining process which is widely accepted in the automotive industry to join steel parts of various thicknesses and types. The current practice in the automotive industry in determining the welding characteristics, which will be used in the welding process. This study concerns the employment of Taguchi Based grey relational analysis to determine the optimized joint characteristics in stainless steel & Mild steel joining of dissimilar materials. The joint characteristics, namely Electrode Force (KN), Weld Current (KA), Hold Time (Cycle) function of Average Tensile Shear Strength (kN), Average Weld Nugget Diameter (mm), Average Weld Indentation (mm). The experimentation in this work used a L9 orthogonal array with three factors with each factor having three levels. Taguchi Based grey relational analysis is employed to characterize the multiple quality characteristics of welded joint in terms of a relational grade. Analysis of variance (ANOVA) is then carried out to ascertain the relative influence of process parameters on the joint characteristics. The three factors used are welding current, weld time and electrode force. The three weld characteristics that were optimized are Average Tensile Shear Strength (kN), Average Weld Nugget Diameter (mm), Average Weld Indentation (mm). The analysis of variance (ANOVA) that was carried out showed that welding current gave the most significant contribution in the optimum welding schedule. The comparison test that was carried out to compare the current welding schedule and the optimum welding schedule showed distinct improvement in the increase of weld diameter and weld strength has well as decrease in electrode indentation.