L51622 The Chevron Notched Drop-Weight-Tear-Test Specimen

This research is aimed at finding a new type of notch that would produce propagation data similar to that produced by the PC DWTT. High-toughness materials and materials that had previously been studied were used assuming that if the new notch worked on these materials it would be satisfactory for lower toughness materials. Several notch modifications were tried and most were no better than the standard pressed notch used in the API specimen.

A search for a new type of notch for the standard drop-weight-tear-test (DWTT) specimen has been completed. This new notch specimen is to replace the precracked DWTT specimen which has been shown to predict full-scale behavior but has received-little support from pipe manufacturers. The new notch is a chevron notch causing fracture initiation to occur at a machined point located at mid-wall thicknessand about 0.2 inch below the specimen edge (i.e., at the same depth as the pressed-in notch of the standard DWTT). No precracking or other severe prestraining, which may create strain aging problems, is required to produce the specimen. A good correlation was obtained between the chevron-notched DWTT and the Charpy V-notch specimens for conventionally rolled steels; this correlation effectively ties the chevron notched data to past fracture research data and to published correlations thatdescribe fracture in terms of Charpy upper-shelf energy. A procedure is included for preparing and conducting the Chevron notched DWTT.