University of Minnesota
Aerospace Engineering and Mechanics
Winter 1998 Seminar Series

Constitutive Equations and Length Scales in Solids

Regents' Professor David McDowell
G.W. Woodruff School of Mechanical Engineering
Georgia Institute of Technology


The application of micromechanics principles has led to valuable new understanding of the relation of the configuration of material microstructure or mesostructure to effective properties such as stiffness and thermal conductivity. Contributions have been most well-developed in the area of effective properties of damaged or reinforced materials, including effects of voids, microcracks and multiple phases with different elastic properties. In contrast, our understanding of the evolution of internal structure of the material and its influence on change of properties is in more nascent state. Specifically, principles for homogenization of evolving structure and its effect on properties must be developed that respect the role of extremal characteristics and their influence on driving forces for dissipative rearrangement of internal structure. Tacit application of volume averaging principles for a dissipation potential, for example, has perhaps subtle but very demanding limitations. This lecture deals with some of these issues of evolving structure, using the context of internal state variable (ISV) formalism as a means to convey some hierarchical principles of material evolution at multiple length and time scales. Applications include thermally activated flow and hardening of metals, textural anisotropy and intergranular interactions, and evolution of distributed damage in brittle microcracked solids.

Friday, February 20, 1998
209 Akerman Hall
2:30-3:30 p.m.

Refreshments served after the seminar in 227 Akerman Hall.
Disability accomodations provided upon request.
Contact Audrey Stark-Evers, Senior Secretary, 625-8000.