2015-Sustainable Industrial Processing Summit
SIPS 2015 Volume 1: Aifantis Intl. Symp. / Multiscale Material Mechanics
| Editors: | Kongoli F, Bordas S, Estrin Y |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2015 |
| Pages: | 300 pages |
| ISBN: | 978-1-987820-24-9 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
< CD shopping page
Gradiend Plasticity Application for Modeling Size Effects at Various Scales
Avraam Konstantinidis1;1ARISTOTLE UNIVERSITY OF THESSALONIKI, Thessaloniki, Greece;
Type of Paper: Regular
Id Paper: 521
Topic: 1
Abstract:
The gradient theory of plasticity proposed by Aifantis in the 1980's was motivated by the Van der Waals thermodynamic theory of liquid-vapor transitions and its mechanical counterpart was advanced by Aifantis and Serrin. By allowing the flow stress to depend on the gradients (up to the second degree and order) of accumulated plastic strain, gradient plasticity was able to describe deformation patterning and the occurrence of shear bands in plastic solids. There were also other models of strain gradient plasticity proposed to consider size effect problems at the micron scale. The simple gradient plasticity model proposed by Aifantis was able to dispense with the mesh-size dependence of finite element calculations in the material softening regime, predict the thickness and spacing of shear bands, as well as account for size effects.
This work presents some modifications performed by the author and Aifantis through the use of wavelet analysis, neural networks and stochasticity. More precisely, the gradient plasticity model has been revised through the use of wavelet analysis in order to produce scale-dependent constitutive equations that have been used for modeling size effects in on tensile strength and fracture energy of brittle, heterogeneous and disordered materials, in good comparison with Carpinteri¢s Multi Fractal Scaling Law (MFSL), as well as the size effect on the yield stress and the ultimate strength of solid bars subjected to torsion and bending. In addition, the inverse Hall-Petch phenomenon has been modeled with the use of the aforementioned scale-dependent constitutive equations, as well as a gradient plasticity model enhanced with an interface energy term, the use of which is dictated by the fact that at the nanoscale interfaces play a dominant role in the mechanical behavior of nanocrystalline materials. Stochasticity-enhanced gradient plasticity models in 1D and 2D have also been implemented in cellular automata simulations for modeling size effects in metallic foams as well as mico/nanopillar compression experiments.