German Aerospace Center DLR, Institute of Materials Research, Cologne,
University of Parma, Parma,
(Received 20 March 2000; accepted 5 December 2000)
Standard test methods of mixed-mode fracture toughness still do not exist, even though a decrease of fracture toughness with increasing Mode II (shear components) has been observed for a number of steels. A J-estimation scheme for mixed-mode loaded single-edge notched specimens is therefore developed in this paper. In accordance with the ASTM Standard E 1820-99, the evaluation of the plastic part of J is based on the measurement of the dissipated plastic energy weighted by a ηpl-factor. Two different approaches for the ηpl-factor are derived. Factors from both showed good correlation with finite element calculations for the specific case of a compact-tension-shear specimen (C(TS)), Finally, a simple clip gage setup for the measurement of the crack-opening displacements needed for the evaluation of the dissipated plastic energy is presented. The problem of the qualification of the mixed-mode crack initiation data is not specifically addressed, but some general comments on this topic are given at the end of the paper.
Paper ID: JTE12251J