A Review of Chevron-Notched Fracture Specimens

This paper reviews the historical development of chevron-notched fracture specimens; it also compares stress-intensity factors and load line displacement solutions that have been proposed for some of these specimens. The review covers the original bend-bar configurations up to the present day short-rod and bar specimens. In particular, the results of a recent analytical round robin that was conducted by an ASTM Task Group on Chevron-Notched Specimens are presented. In the round robin, three institutions calculated stress-intensity factors for either the chevron-notched round-rod or square-bar specimens. These analytical solutions were compared among themselves, and then among the various experimental solutions that have been proposed for these specimens. The experimental and analytical stress-intensity factor solutions that were obtained from the compliance method agreed within 3% for both specimens. An assessment of the consensus stress-intensity factor (compliance) solution for these specimens is made. The stress-intensity factor solutions proposed for three- and four-point bend chevron-notched specimens are also reviewed. On the basis of this review, the bend-bar configurations need further experimental and analytical calibrations. The chevron-notched rod, bar, and bend-bar specimens were developed to determine fracture toughness of brittle materials, materials that exhibit flat or nearly flat crack-growth resistance curves. The problems associated with using such specimens for materials that have a rising crack-growth resistance curve are reviewed.