The Influence of Sample Geometry on the Mechanical Properties and Failure Mechanisms of 6111 Aluminum Alloy Tensile Specimens

This research focuses on the commercial 6111 aluminum alloy as the subject of investigation. By designing tensile specimens with the same characteristic dimensions but varying fillet radii, the effects of fillet radius on the tensile properties and stress concentration effects of the aluminum alloy were studied through tensile testing and digital image correlation techniques. The results demonstrate that with an increase in fillet radius, the failure strength and stress distribution of the aluminum alloy specimens have both undergone alterations. This phenomenon can be attributed to the reduction of stress concentration at the fillet due to the larger fillet radius. Further verification through digital image correlation reaffirms that samples with a fillet radius of 10mm exhibit notable stress concentration effects at the fillet, while specimens with a fillet radius increased to 40mm display uniform plastic deformation across the parallel section. The study also reveals that during the tensile process, dislocations migrate along slip planes inclined at a 45-degree angle to the stretching direction. The enlargement of fillet radius leads to a deceleration in dislocation movement rate and a decrease in dislocation density. As a result, material local strain hardening rate is reduced, and crack formation is suppressed. The established relationship between fillet radius and stress concentration location factor indicates that a smaller fillet radius corresponds to a weaker stress concentration location effect. This research sheds light on the significant influence of geometric shapes of aluminum alloy tensile specimens on their mechanical properties and deformation mechanisms. Moreover, it provides a theoretical basis for optimizing specimen design.