Simulation of the surface defects influence on the aluminum alloy behaviour under the cyclic load conditions

Aluminum and its alloys, such as the Al–Si–Mg alloy, are widely used in various industrial and engineering fields due to their mechanical properties. In this case, the defects occurring during the casting process adversely affect the behavior of this alloy under cyclic load conditions. Therefore, the study aimed to investigate the surface defect influence on the material's fatigue strength is currently of great importance. The paper presents a numerical investigation based on the finite element method intended to evaluate the effect of the interaction of the complex-shaped defects on the stress of the Al–Si–Mg aluminum alloy. The developed complex-defect model consists of a hemispherical main (base) defect and a secondary defect at the bottom of the main one. The authors use the Chaboche model to describe the material’s behavior under the cyclic load conditions. The paper contains the computational solution constructed with the ANSYS Workbench platform. The authors supposed that it is possible to approximate the considered complex defect form by an equivalent simplified defect. The study shows that the maximum von Mises stress values for the complex-shaped defects are achieved at the joint of the secondary defect with the main one. In the case of an equivalent defect, the maximum values are observed at the defect's bottom and on the periphery. The authors comparatively estimated the uncertainty obtained using an equivalent defect and the cases of three complex-shaped defects and three hemispherical defects without additional (secondary) damage. This estimation shows that in the case of a complex-shaped defect, the equivalent defect model has an error of 14.5 %, which is 6.5 % greater than in the case of the hemispherical defects without secondary damages at the bottom.