Regression Modeling and Process Analysis of Plug and Spot Welds Used in Automotive Body Panel Assembly

Resistance spot welding is the primary welding process used in automotive body panel assembly. However, plug welding is widely used in automotive body repair due to its technical simplicity and cost benefits. In this paper, spot welding and plug welding using Tungsten Inert Gas (TIG) welding of an automotive body panel are compared. TIG welding is selected for plug welding because it offers the greatest flexibility to weld the widest range of materials, thicknesses, and types. The base material used in this study is JIS G3141 SPCC. Full factorial experimental design coupled with statistical and graphical analysis of the results using analysis of variance was applied to determine the significance of process parameters. Parameter interactions were investigated using regression analysis, model adequacy checks, and determination of optimum conditions. A genetic algorithm is used to predict the optimum combination of the process parameters to realize the highest strength level. For tensile-shear strength, the experimental results demonstrate that plug welding has a higher maximum load than spot welding. The optimum plug welding joints were obtained at a hole diameter of 9 mm and a welding current of 136 kA, with a maximum load of 8.2 kN. The maximum load of the spot weld joint, 7.4 kN, was found at a welding current of 70 kA, an electrode force of 0.25 MPa, and 10 cycles of welding time.