The effect of strain biaxiality on the fracture of zirconium alloy fuel cladding

• Published in: Journal of nuclear materials 2021-10, Vol.554, p.153070, Article 153070
• Main Authors: Zouari, Ahmed, Bono, Matthew, Boulch, David Le, Jolu, Thomas Le, Crépin, Jérôme, Besson, Jacques
• Format: Article
• Language: English
• Subjects: Biaxial tests; Biaxiality effects; Critical loading; Damage accumulation; Digital imaging; Ductile fracture mechanism; Engineering Sciences; Failure; Forming limit diagram; Hoops; Mechanical tests; Mechanics; Mechanics of materials; Nuclear accidents & safety; Nuclear fuel elements; Pellet-cladding mechanical interaction (PCMI); Plane strain; Plastic deformation; Strain; Strain rate; Tensors; Zircaloy-4 cladding; Zircaloys (trademark); Zirconium; Zirconium alloys; Zirconium base alloys
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2021.153070

•Experimental device for tubular specimen under biaxial load.•Biaxiality effect on the fracture behavior of zirconium alloy cladding.•Fracture mechnisims of zirconium alloy cladding. During a Reactivity Initiated Accident (RIA), nuclear fuel cladding experiences a multiaxial loading state in which the Pellet-Cladding Mechanical Interaction (PCMI) produces a strain biaxiality ratio (εzz/εθθ) of between 0 and 1. This study examines the effect of the strain biaxiality ratio on the fracture of Zircaloy-4 fuel cladding. A new mechanical test has been developed in order to apply several levels of strain biaxiality. Digital Image Correlation (DIC) is used to measure the strain field, to identify the onset of cladding failure, and to obtain the corresponding critical loading state. Results show that the strain biaxiality has a significant effect on the hoop strain at failure, and the smallest fracture strain is obtained for nearly plane strain conditions. A model is proposed for the accumulation of damage due to plastic deformation, based on the Lode parameter of the plastic strain rate tensor. The model is used to predict the failure hoop strain as a function of the strain biaxiality ratio (εzz/εθθ), and good agreement is found between the experimentally measured and predicted failure strains.