Issue 41

L. Patriarca et alii, Frattura ed Integrità Strutturale, 41 (2017) 277-284; DOI: 10.3221/IGF-ESIS.41.37 277 Focused on Crack Tip Fields Study of strain localizations in a polycrystalline medium in presence of a quasi-static crack L. Patriarca, P.G. Luccarelli, S. Foletti Politecnico di Milano, Department of Mechanical Engineering, via La Masa 1, 20156, Milano, Italy luca.patriarca@polimi.it, pietrogiovanni.luccarelli@polimi.it, stefano.foletti@polimi.it A BSTRACT . 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. K EYWORDS . Crystal Plasticity; Digital image correlation; Polycrystalline aggregate. Citation: Patriarca, L., Luccarelli, P.G., Foletti, S., Study of strain localizations in a polycrystalline medium in presence of a quasi- static crack, Frattura ed Integrità Strutturale, 41 (2017) 277-284. Received: 28.02.2017 Accepted: 03.05.2017 Published: 01.07.2017 Copyright: © 2017 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION 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. CPFE are currently used to model several micro-mechanisms of deformation (slip, twinning, grain boundaries interaction, etc.) which cover a wide range of applications. CPFE are currently also adopted to fractured polycrystalline, especially when the cracks are small compared to the grain size, by Rice [1-3]. Recently, other studies focused on simulated crack propagation in single crystals [4-5] provided estimations of crack opening levels in comparison with experimental results. On the other I