On the estimation of the elastoplastic work needed to initiate crack tearing

A three-dimensional elastoplastic analysis of mixed-modeKI/KIIaround the crack front

“…The 3D LE model is validated for pure mode-I loading conditions (i.e., for cracks with 0°) in [6]. The validation of this new study (for cracks with  0°) is performed considering similar numerical results presented by Wilson [7] and by Merah and Albinmousa [8].…”

“…The Ansys Parametric Design Language (APDL) is used to solve these problems. Further details about the pure mode I numerical problem can be found in [6].…”

“…Quadratic elements (3D SOLID186) are used in these FE simulations, and only the fractions of the volumes corresponding to their plastified Gauss integration points are counted as part of the 3D pz around the crack fronts (ε eq ≥ ε Y ). Hence, the smallest unit of volume considered in the pz models and in the calculation of the plastic work U PL performed inside them became 1/8 of the total volume of the element [6]. When this modified SE(T) specimen with an inclined crack (which provides mixed mode I-II conditions simply by varying its crack inclination angle ) is large and its residual ligament is much larger than its crack size, there are well-known, easy to deduce analytical expressions for its SIFs K I and K II .…”

“…To show how inappropriate this practice can be, a recent work [6] used extensive 3D incremental EP numerical simulations to calculate the plastic work U PL dissipated inside the pzs under a same K I value but different  n /S Y and a/W conditions. That work quantitatively evaluates the use of U PL to estimate the onset of crack tearing in practical EP fracture applications, and presents some experimental evidence that supports such simple and physically appealing idea.…”

“…To do so, this work describes and uses an improved methodology for evaluating 3D pz volumes around crack fronts based on 3D EP submodeling finite element (FE) techniques proposed and detailed studied elsewhere [6]. This methodology can be used to eval-uate cracked components under different transversal constraint levels.…”