organized by the Institute of Thermomechanics of the CAS, v. v. i.,
every first Wednesday of the month at 10:00
in the Conference Room B or A in the main building of the Institute of Thermomechanics of the CAS, v. v. i. (see directions)
 

Contact persons: Dr. Radek Kolman, Dr. Hanuš Seiner

 

Wednesday, November 9, 2016, 10:00, Conference Room A
 

 

Lecture outline:
For many materials, the deformation process at some stage leads to propagation and coalescence of existing defects and to initiation of new ones. If the defects grow sufficiently fast, the material can exhibit, on the macroscopic scale, a decrease of the averaged stress even at increasing strain. This phenomenon, referred to as softening, is one of the destabilizing factors that can, under certain conditions, lead to localization of inelastic deformation processes into narrow bands. An objective description of localized strain patterns in the framework of continuum mechanics requires special adjustments of material models, because for traditional models the width of the localized band can become arbitrarily small and, consequently, the numerical solution exhibits a pathological sensitivity to the discretization (e.g., to the size of finite elements).

This lecture provides an overview of various regularization techniques that can serve as localization limiters. In view of their diversity, localized solutions will be analyzed for a one-dimensional model problem only. We will identify which specific regularization techniques are suitable for elastoplastic models with softening and for damage models, and we will compare the corresponding localization conditions and localized profiles of plastic strain or damage, including their subsequent evolution. Such analysis will reveal why certain specific formulations based on nonlocal averaging or on gradient enhancements serve as reliable localization limiters while other formulations fail or suffer by various deficiencies.