Two types of specimen for crack tip opening angle (CTOA)measurement have been investigated for pipeline applications,i.e., the modified double cantilever beam (MDCB) (at NIST)and the drop-weight tear test (DWTT) specimen (at CANMET). Results of effects of specimen types, thicknesses and loading rates on CTOA are summarized and discussed. The main observations include: (i) For both MDCB and DWTT specimens tested at quasi-static loading rate, crack front tunnelling(i.e., with a deep triangular crack-tip shape) was present in high-strength steels; (ii) For DWTT specimens, CTOA values measured optically at the surface were signifi cantly higher than those from the simplifi ed single-specimen method (S-SSM)and measured at mid-thickness [on sections cut using electric discharge machining (EDM)]; and (iii) CTOA values from surface measurement of MDCB specimens were comparable to those derived from S-SSM of DWTT specimens, but the surface values of DWTT were higher than those of MDCB specimens.
Proceedings Title: Proceedings of the 8th International Pipeline Conference IPC2010 September 27-October 1, 2010, Calgary, Alberta, Canada
Conference Dates: September 27-October 1, 2010
Conference Location: Calgary, -1
Pub Type: Conferences
CTOA, MDCB, DWTT, ductile fracture, fracture toughness, pipe steel, test method