Crack-tip-opening-displacement-based description of three-dimensional elastic-plastic crack border fields

Characterization of elastic-plastic crack-tip fields has been great developed in the framework of the classical dominating parameter J-integral, which has a limit of the basic assumptions of small deformation and simple proportional loading. A stable and effective parameter is still a challenge for three-dimensional (3D) elastic-plastic fracture problems. Based on the crack-tip-openingdisplacement (CTOD) conception and out-of-plane stress constraint factor T-z, a new elastic-plastic stress intensity factor K delta-Tz is proposed to dominate the 3D elastic-plastic crack border fields. Detailed 3D finite element simulations are performed for four typical testing specimens, which are the centre-cracked tension specimens, compact specimens, single-edge cracked tension specimens and single-edge-notched bending specimens under three-point bending. It is shown that for specimens with different geometries and thicknesses, K delta-Tz is proven to be more stable than the classical J-integral via the experiment data and simulation results, in which the maximum change in J-integral can be over 340% while the change in K delta-Tz is within 7.78%. Good agreements are obtained between the CTOD-based K delta-Tz description and simulation results for the 3D elastic-plastic crack border stress fields under all the simulated conditions.