Damage Mechanics and Micromechanics of Localized Fracture Phenomena in Inelastic Solids
July 7, 2008 — July 11, 2008
Coordinator:
- George Z. Voyiadjis (Louisiana State University, Baton Rouge, LA, USA)
The proposed course is divided into two major parts: Damage Mechanics and Localization in Inelastic Deformation. The proposed course is intended to provide researchers and graduate students with a clear and thorough presentation of the recent advances in continuum damage mechanics for both metals and metal matrix composites as well as the micromechanics of localization in inelastic solids.
The major goal of the first part is to present many of the different constitutive damage models that have recently appeared in the literature. Another goal is to present the different approaches to this topic in a single complete course that will be easily accessible to researchers and graduate students in civil engineering, mechanical engineering, engineering mechanics, aerospace engineering, and material science. The following features of this part of the course are emphasized: a complete formulation of Damage Mechanics, new approaches in composite materials, recent experimental results performed on MMCs, computational approaches etc.
The main objective of the second part is to discuss efficient procedures of the numerical investigation of localized fracture in inelastic solids generated by impact-loaded adiabatic processes. Particular attention is focused on the proper description of a ductile mode of fracture propagating along the shear band for high impact velocities.
This procedure of investigation is based on utilization of the finite element or finite difference methods for regularized thermo-elasto-viscoplastic constitutive model of damage material.
In the first part a general constitutive model of thermo-elasto-viscoplastic damaged polycrystalline solids with a finite set of internal state variables is discussed. Physical foundations and experimental motivations are presented. Kinematics of finite deformation and fundamental definitions are given. The set of internal state variables consists of two scalars and one tensor, namely equivalent inelastic deformation, volume fraction porosity and the residual stress (back stress). The equivalent inelastic deformation can describe the dissipation effects generated by viscoplastic flow phenomena, the volume fraction porosity takes into account the microdamage evolution effects and the residual stress aims at the description of the kinematic hardening effects. The relaxation time is used as a regularization parameter. Fracture criterion based on the evolution of microdamage is assumed.
Some generalizations of the constitutive theory for accounting for microshear banding effects and for the fracture induced anisotropy generated by the evolution of the microdamage mechanisms are presented. By assuming that the relaxation time is equal to zero, the thermo-elasto-plastic (rate independent) response of the damaged material can be accomplished.
The next part is devoted to the identification procedure for the constitutive model. The material functions are assumed and the identification of the material constants for various materials is based on the results of available experimental observations.
In the numerical investigations we present all the above features.
It is noteworthy to stress that all considered numerical examples are motivated by recent experimental observations. Qualitative comparison of numerical results with experimental observed data has been presented. The numerical results obtained have proven the usefulness of the thermo-elasto-viscoplastic theory in the numerical investigation of dynamic shear band propagation and localized fracture.
The course is addressed to PhD students, researchers and industrial engineers who are involved in the fields of structural engineering and technology and are interested in recent developments in computational solid mechanics.