Effect of Stress Concentration on the Tensile Deformation of AZ31 Magnesium Sheets with Perforated Cylindrical Voids of Various Shapes and Sizes

The contribution of stress concentration factors to the tensile deformation of metallic sheets containing circular and elliptical holes of various sizes was quantitatively described by incorporating the effect of changes in the plastic zone due to stress concentration into the constitutive relationship. Perforated circular and elliptical holes were created through mechanical processing in AZ31 magnesium sheets manufactured by warm rolling, and the room temperature tensile properties were evaluated under a strain rate of 6.56 × 10^-4 s⁻¹. The tensile strength and yield strength of plates containing circular and elliptical holes both decrease with an overall linear slope as the void area fraction increases, and the elongation decreases significantly following an inverse parabolic relationship. While the shear lip size of an elliptical hole with a fixed radius of curvature remains constant, the shear lip size of a circular hole increases as the hole size increases. The plastic zone formed around the perforated hole can suppress crack growth through plastic deformation and stress relaxation in response to externally applied stress. As a result, the tensile strength and elongation of an elliptical hole with a fixed tip radius are relatively lower than those of a circular hole with a larger tip radius. In addition, by including the size of the plastic zone due to stress concentration in the plastic constraint factor, a modified configuration model could be presented, and the theoretical prediction results using the modified model were able to secure a prediction accuracy of at least 20% compared to the existing model.