Recently, with automobile body weight reduction trend, aluminium alloy sheets are introduced to automotive moving parts such as hood, trunk, and tailgate. Researches about joining technologies on aluminium alloy sheet are necessary. However aluminium alloy has many troubles with spot weldability. In this study, we evaluate effects of electrode face radius and electrode force on weldability of resistance spot welding of aluminium alloy 6061. The two electrode face radius conditions showed the same acceptable welding current rage to produce acceptable spot welding quality. However, high electrode force showed larger welding current process window than low electrode force in resistance spot welding of aluminium alloy 6061

Resistance spot welding is a crucial assembly process for vehicle body manufacturing. The quality of the weld joint significantly influences the rigidity and durability of the vehicle; therefore, it is necessary to inspect the weld quality. The indentation depth of the resistance spot welding joint is widely used as an indicator to evaluate the quality of welds. However, because indentation tests on resistance spot welds are typically performed by field workers, additional time and process are required for the tests. Moreover, several attempts to apply automatic methods have shown limitations in high efficiency and prediction accuracy. To address this problem, we measured electrode displacement using a linear variable differential transformer during resistance spot welding in this study. In addition, we established an estimated regression model using the measured electrode displacement data to predict the indentation depth. Multiple regression models were estimated through stepwise regression analysis, and the significance of the model was analyzed through analysis of variance and residual analysis. Indentation depth prediction was performed after the resistance spot welding process using the proposed regression model, and prediction accuracy higher than 93% was achieved. The coefficient of determination obtained for this model was 94.72%.

In this study, the welding quality prediction model with high reliability was developed for the 980 MPa grade TRIP steel with minimum conditions in resistance spot welding process using response surface methodology. The welding time and welding current were selected as the important parameters. The welding quality was predicted by deriving four parameters including tensile shear strength, nugget size, expulsion, and button fracture. The experiment was carried out by using the central composite design. Then, the regression equation derived using the result data was analyzed and the effect of the independent variable on the objective function was analyzed by ANOVA. The welding time had a very small effect on tensile shear strength and nugget, but welding current had a dominant effect on the two properties. Also, the reliability of the derived regression model equation is verified by R correlation coefficient and experiments.

Aluminium alloy sheets are being utilized in automotive parts such as hood, trunk, and tailgate. However, the spot welding of aluminium alloy has many problems, such as electrode sticking and expulsion, and therefore research on the resistance spot welding of aluminium alloy sheets is necessary. In this study, we evaluated the effects of electrode face thickness on the resistance spot weldability of aluminium alloy 6061. The two electrode face thickness conditions were compared, and the electrode face thickness was determined to be an important process variable that affected the spot weldability of aluminium alloy 6061.

In this study, resistance spot weldability of lightweight steel with high Al contents was evaluated using various electrode shapes. The six types of electrode shape were prepared with different electrode face diameter and radius. The tensile shear tests were carried out to investigate the failure behaviors. Also, the nugget size and hardness were measured and compared with various electrode shapes. The experimental results show that the acceptable weld current region for low density lightweight steel could be obtained with 10mm electrode face diameter and 76mm electrode face radius.