Influence of residual stress on the fracture toughness of semi-elliptical cracks in aluminum: a numerical and experimental investigation

چکیده مقاله

This research employs finite element analysis to explore the fracture behavior of a semi-elliptical crack under cyclic loading conditions, with a specific focus on the influence of residual stress. The study of this particular crack geometry is relevant as fatigue failures commonly propagate as semicircular or semi-elliptical cracks. Furthermore, the maximum surface crack size was determined using the J-integral method. To validate the finite element analysis results, experimental tests were performed on the aluminum alloy, producing a force versus crack opening diagram. Additionally, scanning electron microscope (SEM) imaging was used to analyze the fracture surfaces of samples both with and without residual stress. The experimental results aligned closely with the simulation data. The fracture surface of the sample containing residual stress revealed a mixed-mode failure, featuring both dimples (indicating ductile fracture) and cleavage facets (indicating brittle fracture). Furthermore, micro-cracks initiated by the residual stress caused earlier fracture and reduced plastic deformation. The results also showed that tensile residual stress at the tip of a semi-elliptical crack reduces fracture toughness. Consequently, the maximum allowable surface crack size is smaller in components with residual stress than in those without it.