Prediction of Tensile Shear Strength of Resistance Spot Welded AA 5052 Using Regression Analysis Model

Abstract

Resistant spot welding (RSW) of aluminium alloys including AA 5052 is increasingly being applied in aerospace, automotive and marine industries because of the rapidity of the process and unique properties of AA 5052 including high strength-to-weight ratio, excellent corrosion resistance and lower cost. Common issue of concern with the RSW of aluminium alloys is the inconsistency in the weld quality. In this work, the tensile shear strength (TSS) and nugget size of the resistant spot welded 1.2 mm AA 5052 were investigated. The nugget size was optimised to meet AWS-D17.2 (aerospace) standard. The welding process parameters involved are weld current (ranging between 16.3 and 20.0 kA), weld time (0.2025–0.2475 ms) and weld pressure (0.936–1.144 bar). A combination of statistical analytical techniques including full factorial design of experiment, ANOVA, hierarchy rule and regression analysis was used to optimise and develop a mathematical model predicting the TSS of the weldment. The nugget sizes and the microstructure of the welded joints were examined using optical microscopy. The significance of the single effects and interaction effects of the parameters on the TSS was determined and reported. A maximum TSS of about 63.61 MPa was found, in this work, at 20.0 kA weld current, 0.2475 ms weld time and 1.144 bar weld pressure. This is an improvement over the highest obtainable (~41 MPa) in a typical local sheet metal company (Coraza System Malaysia Sdn. Bhd) in Malaysia. A numerical regression model with R2 of 91.13% was developed for the TSS indicating high compatibility of the model to the experimental results.