Physics Colloquium - The Mysterious Disconnect between Nonequilibrium Physics and Materials Research

Event Date: 

Tuesday, March 29, 2016 - 4:00pm

Event Date Details: 

 

Broida 1640

In principle, nonequilibrium physics lies at the heart of applied materials research.  The most important phenomena, such as deformation and failure, involve flows of energy and entropy through systems that are driven away from thermal and mechanical equilibrium. However, the basic principles that govern these flows have been elusive, and theories of these phenomena have been largely phenomenological and non-predictive.  In my opinion, physicists and materials scientists are equally to blame for this situation.  The physicists have not taken seriously enough the second law of thermodynamics, and prominent materials scientists have declared it to be irrelevant.

I will focus on dislocation theory as an area where this disconnect has been especially clear, but where I think that progress is now being made.  I will argue that a basic interpretation of the second law requires that the dislocations in a deforming crystalline solid be characterized by a thermodynamically defined effective temperature that differs from the ambient temperature.

Using this idea, plus energy conservation, dimensional analysis, and only a small number of physics-based material parameters, my colleagues and I have been able to understand some of the most puzzling results of strain-hardening and shock-loading experiments.  If time permits, I will show results of a similar analysis of plasticity and fracture in bulk metallic glasses.

Prof. James Langer