Abstract
Numerical techniques have been widely applied in many recent works to investigate micro-scale behavior of materials. This work focuses on the analysis of strain localizations in a Nickel-based alloy, Haynes 230. Numerical models and experiments concern the study of the strain field generated around the crack tip inside a polycrystalline medium when the crack is quasi-static (not propagating). Experimentally, the tests were conducted in load control; one face of the specimens was monitored by high-resolution Digital Image Correlation (DIC) technique to evaluate the strain field ahead of the crack tip. The simulations were conducted adopting an open source finite element code, Warp3D, which implements a state of art Crystal Plasticity (CP) model. The models of the polycrystalline matrix were created considering the data obtained inspecting the specimen surface by the Electron Back-Scatter Diffraction (EBSD) technique, which allowed defining grains size and orientations. Experimental and numerical results were then compared in terms of strain localizations to evaluate the prediction capabilities of the models. The comparison focused on strain field extension and active grains.
Highlights
I n the last two decades, crystal plasticity finite element (CPFE) methods have evolved creating a link between the theoretical studies on the micro-mechanics of materials and the continuum field of deformation theories
The tests were conducted in load control; one face of the specimens was monitored by high-resolution Digital Image Correlation (DIC) technique to evaluate the strain field ahead of the crack tip
Surface localizations can be nowadays performed at sub-grain scales by Digital Image correlation (DIC) and subsequently compared with the CPFE results to have a feedback on the predictive capabilities of the models
Summary
I n the last two decades, crystal plasticity finite element (CPFE) methods have evolved creating a link between the theoretical studies on the micro-mechanics of materials and the continuum field of deformation theories. The adoption of Voronoi structures was used to study the effect of a stationary crack in a C(T) polycrystalline specimen [8], the results pointed to analyze the heterogeneity of stress and strain fields acting at the crack tip. The CPFE simulations were conducted considering the real geometry of the specimen and adopting a CP algorithm implemented in Warp3D [10]: this code allows to represent the material behavior at the grain scale thanks to the adoption of physical and kinematics models, which for FCC materials, like Ni-based super-alloy, associate the plastic deformations mainly to dislocation motion according to the active slip systems. Are presented the adopted CP model, the CP parameters identification for the investigated alloy and the experimental procedure and the simulations involving the quasi-static crack
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