University of Minnesota
Aerospace Engineering and Mechanics
Fall 1996 Seminar Series


Damage. Gradient of Damage: A Macro-Micro Effect


Dr. Michel Frémond

Laboratoire des Matériaux et des Structures du Génie Civil

Champs sur Marne, France



Abstract

Damage, for instance damage of concrete, results from microscopic motions. Our basic idea is that the power of those microscopic motions must be accounted for in a predictive theory. Thus, we decide to modify the expression of the power of the internal forces and assume that this power depends on the damage rate and its gradient which are related to the microscopic motions. The models issued from this formulation are free of spurious mesh sensitivity and are able, when compared to experimental results, to predict correctly the behavior of some concrete structures. It results also in a good prediction of the structural size effect which is particularly important in civil engineering.

Because the theory is based on the idea that damage is produced by microscopic motions, one can ask: What occurs when macroscopic motions become microscopic and vanish? It is shown in an example, that the source of damage due to macroscopic deformations vanishes and is replaced by a microscopic source of damage. Both of them are established by the same amount of external work. Thus there is continuity when going from macroscopic motions to microscopic ones.


Friday, October 18, 1996
209 Akerman Hall, 2:30 - 3:30 p.m.


Refreshments served after each seminar in 227 AKERMAN HALL .
Disability accommodations provided upon request.
Contact Leslie Petrus : Secretarial Assistant.

petrus@aem.umn.edu (612) 625-8000.