Deformation mechanics and ductile damage in burnishing process of AA6061-T6 aluminum alloy

Plastic strain and ductile damage are two factors affecting the mechanical properties of parts processed by burnishing process. It is well known that excessive processing in burnishing leads to surface damage and defects. In this study, a numerical model has been developed to determine the loading mechanism and damage distribution in the burnishing. Ductile damage was investigated by the MMC criterion by the appropriate subroutine in the commercial code Abaqus. Fracture tests were performed including compression, uniaxial tension, notched tension and in-plane shear. In order to calibrate the MMC criterion, an inverse and combined experimental-numerical method has been used. The stress and strain state in single-stage and multi-stage burnishing has been comprehensively investigated. According to the results, the deformation is applied locally and the loading path in burnishing is highly nonlinear and non-proportional. The results indicate changes in plastic strain and stress state along the thickness of the part. The greatest amount of damage occurred at the surface of the part, while the greatest plastic strain occurred below the surface. Comparing simulation results with experimental tests indicate the accuracy of predicting surface damage and failure by the numerical model. As the penetration depth increases, larger tensile stresses are applied to the material, thus increasing the damage growth rate. According to the experimental results, surface failure (flaking) and defects were formed at a penetration depth of 0.11 mm, while the results from FE simulations predicted a critical penetration depth of 0.13 mm, with a prediction error of 18.2%.