Three-dimensional interpretation of cleavage fracture tests of cladded specimens with local approach to cleavage fracture

Electricite de France has conducted during these last years an experimental and numerical research programme in order to evaluate fracture mechanics a nalyses used in nuclear reactor pressure vessels integrity assessment, rega rding the risk of brittle fracture. Two cladded specimens made of ferritic steel A508 C13 with stainless steel cladding, and containing shallow subcla d flaws, have been tested in four point bending at very low temperature to obtain cleavage failure. The crack instability was obtained in base metal b y cleavage fracture, without crack arrest. The tests have been interpreted by local approach to cleavage fracture (Beremin model) using three-dimensio nal finite element computations. After the elastic-plastic computation of s tress intensity factor K-J along the crack front, the probability of cleava ge failure of each specimen is evaluated using m, sigma(u) Beremin model pa rameters identified on the same material. The failure of two specimens is c onservatively predicted by both analyses. The elastic-plastic stress intens ity factor K-J in base metal is always greater than base metal fracture tou ghness K-1c. The calculated probabilities of cleavage failure are in agreem ent with experimental results, The sensitivity of Beremin model to numerica l aspects is finally exposed. (C) 2000 Published by Elsevier Science S.A. A ll rights reserved.