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 schem
e for mixed-mode loaded single-edge notched specimens is therefore develope
d in this paper. In accordance with the ASTM Standard E 1820-99, the evalua
tion of the plastic part of J is based on the measurement of the dissipated
plastic energy weighted by a eta (pl)-factor. Two different approaches for
the eta (pl)-factor are derived. Factors from both showed good correlation
with finite element calculations for the specific case of a compact-tensio
n-shear specimen (C(TS)). Finally, a simple clip gage setup for the measure
ment of the crack-opening displacements needed for the evaluation of the di
ssipated plastic energy is presented. The problem of the qualification of t
he mixed-mode crack initiation data is not specifically addressed, but some
general comments on this topic are given at the end of the paper.