The critical length of the hydride cluster in delayed hydride cracking of Zr-2.5wt% Nb

In delayed hydride cracking (DHC) of Zr-2.5wt% Nb alloy, the hydride cluster at the crack tip has a critical length, which is a function of the stress intensity factor KI and other parameters. When KI > KIH, the threshold stress intensity factor, the hydride cluster must grow to this critical length before it will fracture. On the other hand, when KI KIH near KIH. A modified experimental method was used, that permitted the hydride clusters to be formed and fractured individually. The hydride clusters were observed to be wedge-shaped, in agreement with the predictions by Metzger and Sauve (PVP, vol. 326, ASME, 1996). The lengths of hydride cluster measured in this work are compared with existing theoretical predictions. A good general agreement was obtained, but some differences are discussed.