A numerical investigation of 3-D small-scale yielding fatigue crack growth

Implementation of a plastically dissipated energy criterion for three dimensional modeling of fatigue crack growth

“…Numerous earlier investigations of fatigue crack growth have revealed a strong 3-D effect along the crack front (through the thickness) on important features such as crack closure levels [41,42]. The crack front is subjected to a multi-axial state of stress that varies along the crack front, influencing the size and shape of the plastic zone.…”

Numerical simulation of plasticity induced crack closure: Identification and discussion of parameters

“…Since the reversed zone is smaller than the forward zone, its size is critical for the definition of L 1 . According to Solancki et al [28], there must be 3-4 linear elements within the reversed plastic zone, while Roychowdhury and Dodds [21] suggested 2-3 linear elements. Solanki et al [28] indicated that a crack growing under cyclic loading with R = 0 had a reversed plastic zone about 1/10 the size of the forward plastic zone (while for a stationary crack this is about 1/4 the size).…”

3D modelling of plasticity induced fatigue crack closure-effect of material constitutive relations

“…Both of these models ignore the Bauschinger effect in cyclic plasticity and thus, they over predict the crack opening level. This is because the Bauschinger effect tends to increase the plastic deformation in the reversed loading at the crack tip resulting in a reduction in the crack opening level [3,4]. Although the kinematic hardening model considers the Bauschinger effect, there is a need to consider alternate material models that can more adequately capture the hardening or softening process associated with cyclic plasticity.…”

“…The region away from the crack tip consists of single layered brick elements as shown in Figure 1(a-i) with a transition to five layers through the half-thickness of the plate in the vicinity of the crack tip (see Figures 1(a-ii) and 1(a-iii)). These five layer thicknesses are chosen to match the works of Roychowdhury and Dodds Jr. [3,9] which have layer thicknesses of 0.25t, 0.15t, 0.05t, 0.03t and 0.02t where the smallest layer was located on the exterior surface of the model (z = 0.5t). These thicknesses allow for adequate capture of the state of stress through the half-thickness of the plate which rapidly changes from near plane strain conditions at the interior of the geometry to near plane stress conditions at the exterior surface [10][11][12].…”

“…These 3-D crack closure studies are characterized by models that mostly employ either an elastic-perfectly-plastic, an isotropic strain hardening or a linear kinematic hardening material models for the solution of the elastic-plastic deformation. Of these, only the kinematic hardening model captures the Bauschinger effect in cyclic plasticity, which has been shown to have an important effect on the crack closure process [3,4]. Consequently, the solutions to the nonlinear crack tip fields employing the above material models vary.…”