Structural Behavior of AA2024-T3 Weld Produced by Friction Spot Welding for Aircraft Application during Loading

Friction Spot Welding (FSpW) or also known as refill friction stir spot welding has been considered as a potential alternative to substitute riveted connections in aircraft structures enabling weight savings and production gains. Based on that fact, this work aims to study the structural behavior of the welds in lap joint configuration produced by FSpW in aluminum alloy 2024-T3 2 mm thickness during loading. This study was done by using Finite Element Method (FEM) based on experimental data from lap shear tests of the welds with single spot weld and multi spots of 2 and 3 spot welds in a row, and cross tensile test of single spot weld. The high and low load transfer in lap shear tests have also been investigated to determine optimum distance of the spot from the sample edge and distance between the spots or pitch in multi spot welds. In order to perform a fully analysis, the numerical model was calibrated and used to optimize the edge distance and the pitch. Then the results were validated using experimental tests for specific geometries. In addition a Digital Image Correlation system has been used to identify the strain field in the spot weld region. An analysis of the fracture using FEM was performed applying the optimum pitch and edges distance to understand the structural behavior during loading. Johnson-Cook (JC) model which expresses the equivalent stress as a function of the plastic deformation, strain rate and temperature, was used for numerical analysis. The results showed a good agreement between the numerical analysis and experimental test. The average lap shear strength of the welds with a single spot, 2 and 3 spot welds in a row are 10.4kN, 20.7kN, and 27.4kN, respectively. The maximum cross tensile strength of single spot weld is 4.5kN.