Damage mechanics analysis (Gurson model) and experimental verification of the behaviour of a crack in a weld-cladded component

Abstract

During emergency core cooling situations, the criticality of hypothetical cracks located in the ferritic base material beneath the austenitic cladding is strongly influenced by the integrity of the cladding: if the cladding is intact, the crack tip loading is significantly reduced compared with the case where the cladding is assumed to be broken. In order to assess this situation, a three-point-bend specimen consisting of a ferritic block with an austenitic cladding and a semi-elliptical crack in the ferritic base material beneath the cladding was tested and evaluated. The global (i.e., load versus displacement curve) and local (i.e., ductile crack extension in ferrite and austenite) behaviour of this specimen was predicted by means of two- and three-dimensional finite-element analyses based on the Gurson model. The material characterization was done in terms of Gurson material parameters utilizing sub-sized tension tests with improved evaluation and fracture mechanics tests with precracked Charpy-type specimens. A good agreement between analyses and experiment could be achieved.