Analyses of Stress-State-Dependent Ductile Damage and Fracture Behavior of Zirconium

In this study, the fracture behavior of zirconium was investigated by a hybrid experimental and numerical simulation method. Uniaxial tensile tests were conducted on samples of various geometries, thereby covering a wide range of stress states at fracture characterized by stress triaxiality between 0.05 and 0.96 and Lode angle parameter between 0.01 and 0.95. Stress state-related parameters of each geometry were collected and used to calibrate the parameters of the modified Bai-Wierzbicki (MBW) model. With the calibrated MBW model, the fracture of zirconium can be predicted. Additionally, the fracture surfaces of the pure shear and pure tension samples were analyzed using a scanning electron microscope (SEM), revealing that shear mode dominates the failure at a low stress triaxiality range from 0 to 1/3, while ductile fracture dominates the failure at a middle stress triaxiality range from 1/3 to 1. The deep understanding of the fracture behaviors and mechanisms of zirconium under various stress states in this study contributes to the safety assessment of cladding tubes used in nuclear power plants.