University of Minnesota
Aerospace Engineering and Mechanics
Spring 1999 Seminar Series



Entropic Elasticity of Martensites


Professor Lev Truskinovsky

Department of Aerospace Engineering and Mechanics, University of Minnesota


Abstract


In a typical strain test, shape memory wires exhibit a characteristic hardening on the stage of microstructure development. In experiments, the degree of hardening is often related to the defectiveness or the inhomogeneity of the sample. We suggest a new interpretation of the hardening in martensites as the effect of entropic, rubber-like elasticity. We assume that the sample can be represented as an ensemble of ideal sub-samples and adopt a canonical distribution which introduces a new parameter with the dimension of temperature. This parameter characterizes the degree of defectiveness of the sample. At zero effective temperature we recover the results of the classical energy minimization. At finite temperatures the usual statistical averaging produces the desired hardening as a result of strain dependence of the configurational entropy. This effect is intimately related to the non-convexity of the energy and is absent if the energy is quadratic.

Friday, May 7, 1999
209 Akerman Hall
2:30-3:30 p.m.


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