Small Scale Yielding Estimate of Second Elastic-Plastic Fracture Mechanics Parameter for 3D Crack Specimens

In elastic-plastic fracture mechanics (EPFM), for the conditions under low crack constraint, two-parameter approaches instead of single J-integral parameter approach are suggested to characterize structure fracture with acceptable accuracy. To enable extensive theoretical investigation and engineering application of J-A two-parameter approach, authors previously has suggested a small scale yielding estimate method for predicting the constraint (second) parameter values in J-A approach conveniently and effectively under small scale yielding conditions. The estimate method is developed based on two-dimensional (2D) plain strain condition. In current work, the previously developed small scale yielding estimate method is extended to three-dimensional (3D) crack structures to enable the estimate method appropriate for practical 3D engineering structures, e.g. the fracture analysis of sensor supporting structures. The extension and its validation process are carried out based on a 3D single edge cracked plate (SECP) specimen. Along the crack front of a thin 3D SECP specimen, the small scale yielding estimate method is applied and validated in three specific plains which perpendicular to the crack front. Material hardening exponent value 3, 5 and 10, and crack length ratio value 0.1, 0.3 and 0.7 are used in the estimate method extension and validation process, which cover the wide range of material and geometrical properties.