Two-parameter J-A concept in connection with crack-tip constraint

The paper presents theoretical and numerical aspects of the two-parameter J-A approach in elastic-plastic fracture mechanics in connection with crack-tip constraint. This approach is based on the three-term asymptotic expansion for the stress field near the tip of mode I crack in an elastic-plastic solid. It is shown that the parameter A can be introduced in fracture criterion as a constraint parameter. The constraint parameter A and the J-integral for various configurations of standard specimens and the hardening exponent is computed by means of three-dimensional elastic-plastic stress analyses employing finite element method. The magnitude of the constraint parameter A decreases (higher constraint) with the increase of relative specimen thickness. The unified JC-A master curve is constructed for different geometry and thickness of specimens. The two-parameter J-A fracture criterion allows estimating whether elastic approach is conservative or non-conservative. Relationship between the crack-tip constraint parameters A, A2, Q and S¯p of elastic-plastic fracture mechanics is investigated.