A UNIFIED MODEL OF HYDRIDE CRACKING BASED ON ELASTOPLASTIC ENERGY-RELEASE RATE OVER A FINITE CRACK EXTENSION

A fracture criterion based on energy balance is proposed for elasto-pl astic cracking at hydrides in zirconium, assuming a finite length of c rack advance. The proposed elasto-plastic energy release rate is appli ed to the crack initiation at hydrides in smooth and notched surfaces, as well as the subsequent delayed hydride cracking (DHC) considering limited crack-tip plasticity. For a smooth or notched surface of an el astic body, the fracture parameter is related to the stress intensity factor for the initiated crack. For DHC, a unique curve relates the no n-dimensionalized elasto-plastic energy release rate with the length o f crack extension relative to the plastic zone size. This fracture cri terion explains experimental observations concerning DHC in a qualitat ive manner. Quantitative comparison with experiments is made for fract ure toughness and DHC tests on specimens containing certain hydride st ructures; very good agreement is obtained.