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Wednesday, May 08

Predicting the Deformability and Strength of Noncrystalline Materials

James Langer, University of California, Santa Barbara, Santa Barbara
Joint Institute for Neutron Sciences Seminar
11:00 AM — 12:00 PM, JINS, Building 8630, Room A-202
Contact: Hope Moore-Webb (, 865.576.8630


Predictive theories of noncrystalline plasticity must contain two basic ingredients: (1) A dynamic model of flow defects, i.e. the analogs of dislocations in crystals; and (2) A thermodynamic measure of the structural disorder that determines the populations and behaviors of these defects. It is becoming increasingly clear, in a widening variety of physical circumstances, that the relevant flow defects are two-state shear transformation zones (STZ's), and that the relevant measure of disorder is the effective temperature, i.e. the thermodynamic temperature of just the structural degrees of freedom. In this presentation, I will illustrate recent progress, with applications primarily to bulk metallic glasses, by showing results for stress-strain-strain rate relations, frequency-dependent viscoelastic responses, and fracture toughness. If time permits, I will say more about the theoretical principles.