Prediction of damage-growth based fatigue life of polycrystalline materials using a microstructural modeling approach

Fatigue crack initiation and crystallographic growth in 316L stainless steel

“…For this reason, the 2D representative volume element (RVE) is extruded to a thin 3D RVE. For this extrusion a statistical method consistent with the EBSD map is applied [9].…”

“…1 (a) is a rectangle of 139×146 μm containing 385 grains whereas the coarse-grain map, Fig.1 (b) is a rectangle of 260×260 μm containing 388 grains. This amount of grains is sufficient for a domain in order to be considered as a RVE of the fatigue macro response [9]. The thickness of the fine-and coarse-grain RVEs is set to 3 μm and 6 μm, respectively.…”

“…Anisotropic behavior of materials at the microscale has been proved to play a pivotal role for fatigue crack initiation [9,10]. The inherent anisotropic mechanical response of neighboring grains leads to permanent (inelastic) microstructural deformations even under stresses below the macroscopic yield stress of the materials.…”

“…3 Many studies have been conducted over the years to distinguish and characterize mechanisms of fatigue crack initiation and subsequent crystallographic growth (see the review by Castelluccio et al [12]). Quite recently, a microstructural-based model has been developed entitled Sistaninia-Niffenegger fatigue (SNF) model for predicting microstructurally short fatigue crack formation in polycrystalline materials on basis of a microstructure measured by electron backscatter diffraction (EBSD) [9]. This model is able to predict the overall response of the crystalline materials to cyclic loading by considering the strain localization at the level of the microstructure emanating from the anisotropy of the mechanical properties of the individual grains.…”

Integrated experiment and modelling of microstructurally-sensitive crack growth

“…Kupka et al [27] also adopted a cohesive zone approach to describe grain boundary separation based on a normal traction stress criterion coupled with fracture energy for crack initiation in their micro-cantilever crystal plasticity model. An alternative technique involves a non-local damage method [28][29][30] which calculates the degradation of the material stiffness to model damage and fracture where some author [29] have combined the method with local crystal plasticity to investigate microstructural-sensitive crack nucleation and propagation. One advantage with these methods is the flexibility to integrate user specified criteria illustrated by Vajragupta et al [31] for cleavage fracture in their dual-phase steel, where the martensitic 'phases' employed a maximum principal stress criterion, and ductile damage of the ferrite phase employed a criterion based on stress triaxiality and equivalent plastic strain.…”