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Lecture : The formulation of gradient theories for singlecrystal plasticity at small length scales: size effects

Pubblicato da federica venerdì, 28 maggio 2010 | Rubriche: Home, IN-Agenda

Facoltà di Ingegneria Leggi tutto

31 maggio 2010
15:30a18:30

Lunedì 31 maggio dalle 15.30

Aula di Consiglio

Lecture : The formulation of gradient theories for singlecrystal plasticity at small length scales: size effects

 

 

This talk discusses a finite-deformation, gradient theory of single crystal  plasticity – concentrating on the steps involved in its formulation. The theory  is based on a system of microscopic force balances, one balance for each  slip system, derived from the principle of virtual power, and a mechanical  version of the second law that includes, via the microscopic forces, work  performed during plastic flow. When combined with thermodynamically  consistent constitutive relations the microscopic force balances become flow  rules for the individual slip systems. Because these flow rules are in the form  of partial differential equations requiring boundary conditions, they are nonlocal.  The chief new ingredient in the theory is a free energy dependent on  densities of geometrically necessary dislocations. Predictions of the theory  obtained via computations are shown to agree well with discrete dislocation  simulations. Further – using published experimental data for several polycrystalline  materials – it is shown that the theory explains the D –1 dependence of the initial yield stress on the grain size D in the submicron to several micron range.

Per maggiori informazioni:  Paolo Podio Guidugli ppg@uniroma2.it