Evaluation of two-parameter approaches to describe crack-tip fields in engineering structures

The application of two-parameter approaches to describe crack-tip stress fields has generally focused on Ramberg-Osgood (RO) power law material behavior, which limits the range of applicability of such approaches. In this work we consider the applicability of a J-Q or J-A₂ approach (the latter is designated here as the J-A approach) to describe the stress fields for RO power law materials and for a material whose tensile behavior is not described by a RO model. The predictions of the two-parameter approaches are compared with full field finite-element predictions. Results are presented for shallow and deep-cracked tension and bend geometries, as these are expected to provide the expected range of constraint conditions in practice. A new approach for evaluating Q is proposed for a RO material, which, for a given geometry, makes Q dependent only on the strain hardening exponent.