Comments on CTOA transferability in “Crack tip opening angle during unstable ductile crack propagation of a high-pressure gas pipeline” [204 (2018) 434–453]

•This discussion shows that CTOA is closely similar in small-scale and large-scale tests, supporting the transferability of CTOA from DWTT-type specimens to pipe.•The results support the transferability of CTOA at crack velocity of 10 m/s to 200 m/s. When axial fast ductile fracture occurs in high-pressure gas pipes, the plane of the crack opening does not necessarily remain parallel to the pipe axis. There is in general a tilt angle between the opening flanks and the pipe axis. The present discussion shows that taking into account the presence of a tilt angle results in larger estimates of surface CTOA than those reported in a recent paper (Shibanuma et al., 2018). Considering the effect of tilt angle, the data reported in Shibanuma et al. (2018) support the transferability of CTOA from DWTT-type specimens to full-scale pipe.