Continuum damage mechanics-coupled plasticity modeling of mechanical behavior in AA6061-T651 CMT-welded joints

This work focuses on understanding the mechanical behavior of CMT (cold metal transfer)-welded joints in AA6061-T651 aluminum alloy while establishing a correlation with the microstructural features observed in the weld zones. Furthermore, the mathematical framework of a coupled continuum damage mechanics and anisotropic plasticity model under finite strain formulation is presented. The aim is to accurately describe the mechanical behavior, fracture, and damage evolution of CMT-welded joints in AA 6XXX alloys. The calibration of the proposed model is performed using experimental data obtained from uniaxial tensile tests conducted on various weld zones, including the base material, heat-affected zone, and fusion zone. To capture the overall behavior of the welded joint, a composite framework is employed. This framework incorporates multiple in-series elasto-viscoplastic elements, each representing a specific welding zone. Demonstrating robust predictive capabilities, the model successfully predicts critical mechanical properties, including yield stress, ultimate tensile stress, and strain to fracture, for 6061-T651 aluminum alloy CMT welds and their respective weld zones. Notably, the model achieves a high degree of accuracy, with accuracy of approximately 0.8, 0.98, and 0.9, respectively, compared with experimental values. The experimental results and numerical simulations exhibit a close agreement, validating the accuracy and predictive capability of the proposed model. Additionally, the model demonstrates its ability to capture the evolution of damage throughout the loading process. The proposed modeling approach effectively captures the unique characteristics of each welding zone and provides valuable insights into the fracture and damage evolution of the welds.