On the fracture toughness of irradiated F82H: Effects of loss of constraint and strain hardening capacity

Constraint loss adjustments, based on finite element (FE) stress analysis and local critical stress, sigma', critical stressed volume, V', cleavage criteria were applied to fracture toughness data from small pre-cracked bend bars of the IEA heat of F82H irradiated to 6.6 dpa at 300 degrees C in the High Flux Isotope Reactor. The 100 MPa root m master curve method reference temperature shifts were evaluated based on both the measured toughness (Delta T-m) and after size-adjusting the toughness to small-scale yielding conditions at reference specimen size (Delta T-o) with values of approximate to 142 and 205 degrees C, respectively. The model based prediction Delta T-o = C-o Delta(sigma(fl)), where C-o approximate to 0.68 and Delta(sigma(fl)) is the change in the average flow stress over 0-10% strain is in excellent agreement with Delta T-o. The FE analyses also demonstrates an upper-bound K-Jc that can be measured with these small bend bars for irradiated alloys that suffer severe loss of strain hardening. (C) 2011 Published by Elsevier B.V.