María Bertinetti

An iterative approach to mechanical properties of MMCs at the onset of plastic deformation

Abstract The current work presents a generalized Eshelby model allowing interaction among reinforcing particles under a Mori-Tanaka like scheme. Different aspect ratios and geometries are studied in the elastic and incipient elasto-plastic regime for a model SiC Al composite. The fibers are taken as purely elastic and the matrix is regarded elastic perfectly plastic responding to a Von Mises yield criterion. The phenomenon of plastic localization in the vicinities of the inclusions is carefully described for different reinforcement volume fractions and thermo-mechanical loading. Equivalent stress, hydrostatic pressure and elastic and plastic strains are depicted as contour levels around a representative inclusion. Effective coefficients of thermal expansion of composites are calculated both under purely elastic composite response and at the onset of plastic localized deformation. The influence of plastic strain over those effective coefficients is shown to be detectable. The simulated stress-strain curves show the influence of interaction stresses over macroscopic yield stress by isolating this phenomenon from matrix hardening. Accumulated elastic energies and plastic work are calculated to show the different nature of purely thermal and mechanical loads.

Self-Consistent Homogenization Methods for Predicting Forming Limits of Sheet Metal

© 2012 Signorelli and Bertinetti, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Self-Consistent Homogenization Methods for Predicting Forming Limits of Sheet Metal

A Theoretical Study on Forming Limit Diagram Predictions Using Viscoplastic Polycrystalline Plasticity Models

The Forming Limit Diagrams (FLDs) of textured polycrystalline sheet metals were investigated using micro-macro averaging and two types of grain-interaction models: Full-Constraint (FC) and Self-consistent (SC) schemes, in conjunction with the Marciniak–Kuczynski (MK) approach. By referring to previous FLD studies based on the FC-Taylor model ─ Wu and coworkers [Effect of an initial cube texture on sheet metal formability, Materials Science and Engineering A, 364:182–7, 2004] and Inal and coworkers [Forming Limit comparison for FCC and BCC sheets, International Journal of Plasticity, 21:1255-1266, 2005] ─ we found that the MK-FC strategy leads to unrealistic results. In the former case, the researchers found that an increasing spread about the cube texture produces unexpectedly high limit strains. In the latter work, Inal et al. predicted a remarkably low forming-limit curve for a FCC material and an extremely high forming-limit curve for a BCC material, in the biaxial-stretching range. Our investigations show that simulations performed with the MK-VPSC approach successfully predict more reliable results. For the BCC structure, the MK-VPSC predictions do not give the extreme values predicted when calculations are carried out with the MK-FC approach. In the FCC case, with decreasing textural intensity ─ from the ideal cube texture, through dispersions around the cube texture with increasing cut-off angles, to a random texture ─ a smooth transition in increasing limit strains was obtained. Furthermore, these results suggest that the selected constitutive model is critical for predicting the behavior of materials that exhibit a qualitative change in crystallographic texture, and hence, evolve anisotropically during mechanical deformation.