"A phase-field approach to structured plastic deformations"

Dear All,

Mathematics, Mechanics, and Materials Unit (Fried Unit) would like to invite you to a Seminar by Prof. Gianni Royer-Carfagni, University of Parma, Italy.

Date: Wednesday, January 31, 2018
Time: 16:00-17:00
Venue: D015, Level D, Lab1

Speaker:
Professor Gianni Royer-Carfagni
Department of Engineering and Architecture, University of Parma, Italy

Title:
A phase-field approach to structured plastic deformations

Abstract:
A variational approach to determine the deformation of an ideally plastic substance is proposed by solving a sequence of energy minimization problems under proper conditions to account for the irreversible character of plasticity. The flow is driven by the local transformation of elastic strain energy into plastic work; remarkably the plastic part of the deformation localizes on slip surfaces, once that a certain energetic barrier for slip activation has been overcome. The resulting deformation is “structured” because it is associated with supplementary kinematical variables (the plastic slips), governed by an evolution law. This is a “phase field approach” because the matching condition at the slip interfaces are substituted by the evolution of an auxiliary phase field that, similarly to damage theory, is unitary on the elastic phase and null on the yielded phase.
The slip lines diffuse in bands, whose width depends upon a material length-scale parameter. The distinction of the elastic strain energy into spherical and deviatoric parts can also be used to incorporate in the model the idea of von Mises plasticity and isochoric plastic strain. Numerical experiments on representative problems in plane strain provide solutions with striking similarities with the results from classical Prandtl slip-line field theory of plasticity. However, whereas such a theory considers a rigid-plastic material, so that small boundary data provoke plastic glide in the whole body, the proposed model is much richer because, accounting for elastic deformations, it can describe the formation of slip bands at the local level, which can nucleate, propagate, widen and gradually diffuse by varying the boundary conditions.

Biography:
Civil Engineering degree. Ph.D. in Structural Engineering. Professor of Structural Mechanics, Department of Engineering and Architecture, University of Parma, Italy. Adjunct Professor, Department of Civil and Environmental Engineering, University of Houston, TX, USA. Research Associate of CNR (National Research Council of Italy). Italian representative in the CEN/TC 250/SC11 for the Eurocode on Structural Glass. Member of the steering committee for structural standards of CNR. Expert member in the Italian Ministry of Infrastructure and Transportation for non-traditional structural materials. Representative of the Italian Superior Council of Public Works in the Structural Engineering Committee (U73) of UNI (Italian Organization for Standardization). Vice-president of ATIV (Italian Association of glass technologists). Associate Editor of the Journal of Elasticity, ASCE Journal of Engineering Mechanics, Journal of the Mechanics of Materials and Structures. Coordinator of research projects supported by the European Community. Licensed professional engineer and designer of lightweight and special structures. Scientific publications and profile can be consulted in https://scholar.google.it/citations?user=ey8qQdMAAAAJ&hl=it.