Detecting stable crack onset at ductile-brittle transition in steels

Ductile crack initiation and growth promoted by hydrogen in steel

“…A peak appeared on the 67(J/cry) vs. J/cry curve for the non-charged specimen, and the J/cry value for the maximum of tT(J/cry) almost coincided with that obtained by the potential method in accord with the previous results reported for a high-strength, lowcarbon steel [23]. In the case of the hydrogen-charged specimen, no peak appeared.…”

“…An alternative method for determining the onset of ductile crack initiation on an Rcurve has been devised by Fujii et al [23]. Their method is based on the finite element analysis procedure of Needleman and Tvergaard [24] for examining the crack-tip stress and strain fields in a ductile porous material.…”

“…Assuming inclusion distributions of two types, i.e., small and large, Needleman and Tvergaard [24] predicted a small "jog" or uprise would appear in the COD vs. d-integral curves when larger voids coalesced with the crack tip. The method devised by Fujii et al [23] depended on the gradient of a line from the origin intersecting d vs. d/cry curve. The method devised by Fujii et al [23] depended on the gradient of a line from the origin intersecting d vs. d/cry curve.…”