Lab Home | Phone | Search
Center for Nonlinear Studies  Center for Nonlinear Studies
 Home 
 People 
 Current 
 Affiliates 
 Visitors 
 Students 
 Research 
 ICAM-LANL 
 Publications 
 Conferences 
 Workshops 
 Sponsorship 
 Talks 
 Colloquia 
 Colloquia Archive 
 Seminars 
 Postdoc Seminars Archive 
 Quantum Lunch 
 Quantum Lunch Archive 
 CMS Colloquia 
 Q-Mat Seminars 
 Q-Mat Seminars Archive 
 P/T Colloquia 
 Archive 
 Kac Lectures 
 Kac Fellows 
 Dist. Quant. Lecture 
 Ulam Scholar 
 Colloquia 
 
 Jobs 
 Postdocs 
 CNLS Fellowship Application 
 Students 
 Student Program 
 Visitors 
 Description 
 Past Visitors 
 Services 
 General 
 
 History of CNLS 
 
 Maps, Directions 
 CNLS Office 
 T-Division 
 LANL 
 
Tuesday, March 08, 2016
3:30 PM - 4:30 PM
CNLS Conference Room (TA-3, Bldg 1690)

Q-Mat Seminar

MODELING THE CONSTITUTIVE RESPONSE OF AGGREGATES: THE IMPORTANCE OF INTRODUCING PROBABILISTIC DISTRIBUTIONS

Carlos Tomé
MST-8

The macroscopic mechanical response of polycrystals is the average manifestation of local behavior and states inside the grains. Such local behavior and states (i.e. stress distributions, dislocations, grain size, twin structures, etc) is usually very inhomogeneous. As a consequence, macroscopic models that rely on describing the mechanical response in terms of effective average magnitudes (i.e. average dislocation density) may be insufficient when the aforementioned inhomogeneity affects the macroscopic response, such as when strain-path-changes are involved.

In our DOE-BES Program on Materials of Hexagonal Structure we are developing a paradigm for linking length scales, consisting in introducing statistical characterization of micro-structure and stress distributions into grain-scale models. The latter are, in turn, implemented probabilistically into the polycrystal plasticity frameworks VPSC and E-VPSC.

We present three applications of such approach. In Example 1 twin nucleation in HCP is treated as a stochastic event driven by local stresses and atomistic states at grain boundaries. Such approach explains the proportion of active twin variants and texture evolution associated with mechanical deformation of Mg and Zr. In Example 2 we show how twin growth is affected by back stresses induced by the twin shear transformation and the reaction to it exerted by neighboring grains. Grain size and neighbor misorientation are treated stochastically in the model. In Example 3 we show that a model of intra-granular stress distributions inside grains explains the relaxation of internal stress associated with strain holds and Bauschinger effects associated with strain reversals. BIOGRAPHY: Tome earned a doctorate in physics from the National University of La Plata, Argentina, and joined the Laboratory in 1996. He pioneered the theoretical and numerical development of physically based modeling of the mechanical behavior of polycrystals. Tome has published more than 170 papers in international journals, with more than 12,000 citations. The Structural Materials Division of The Minerals, Metals & Materials Society (TMS) presented him the 2013 Distinguished Scientist/Engineer Award. In 2015 he received the Khan International Medal and he was just named a Laboratory Fellow.

Host: Amanda Neukirch