to be done in this area. Face recognition is a problem that scarcely clamoured for attention before the computer age but, having surfaced, has involved a wide range of techniques and has attracted the attention of some fine minds (David Mumford was a Fields Medallist in 1974). This singular application of mathematical modelling to a messy applied problem of obvious utility and importance but with no unique solution is a pretty one to share with students: perhaps, returning to the source of our opening quotation, we may invert Duncan's earlier observation, 'There is an art to find the mind's construction in the face!'.

Linear and nonlinear waves, by G. B. Whitham. Pp.636. £50. 1999. ISBN 0 471 35942 4 (Wiley).

https://www.tcd.ie/Physics/people/Graham.Cross/SF%20Poster%202011/Schuh-ActaMater07-Mechanical%20behaviour%20of%20amorphous%20alloys.pdf

Mechanical behavior of amorphous alloys

We present in this work a visco-plastic self-consistent (VPSC) anisotropic approach for modeling the plastic deformation of polycrystals, together with a thorough discussion of the assumptions involved and the range of application of such approach. We use the VPSC model for predicting texture development during rolling and axisymmetric deformation of Zirconium alloys, and to calculate the yield locus and the Lankford coefficient of rolled Zircaloy sheet. We compare our results with experimental data and find that they are in good agreement with the available experimental evidence. We also compare the VPSC predictions with the ones of a Full Constraints approach and observe that they differ both quantitatively and qualitatively: according with the predictions of the VPSC scheme, deformation is accommodated mostly by the soft systems, the twinning activity is much lower, and fewer systems are active, in average, per grain. These results are a consequence of having accounted for the grain interaction with its surroundings, which is a crucial aspect when modeling plastically anisotropic materials.

A self-consistent anisotropic approach for the simulation of plastic deformation and texture development of polycrystals : application to zirconium alloys

Dynamic and post-dynamic recrystallization under hot, cold and severe plastic deformation conditions

Strain gradient plasticity

A self consistent approach of the large deformation polycrystal viscoplasticity

A dislocation-based model for all hardening stages in large strain deformation

: Critical conditions for shear localization in thermoviscoplastic materials are obtained in closed form for idealized models of simple shearing deformations. The idealizations, which include the neglect of heat conduction, inertia, and elasticity, are viewed as quite acceptable for many applications in which shear bands occur. Explicit results obtained for the idealized, but fully nonlinear problem show the roles of strain rate sensitivity, strain hardening, and initial imperfection on the localization behavior. Numerical solutions for two steels are shown to exhibit the principal features reported for torsional Kolsky bar experiments on these steels. Mathematically exact critical conditions obtained for the fully nonlinear problem are compared with critical conditions obtained by means of linear perturbation analysis gives better agreement with the predictions fo the fully nonlinear analysis.

Analytical Characterization of Shear Localization in Thermoviscoplastic Materials

A micromechanical analysis of the behavior of saturated elastic porous media is presented. Pores are connected and saturated with a fluid at uniform pressure. The non-linear macroscopic response of the porous medium is assumed to be related to the existence of a network of microcracks in the solid phase. The progressive closure of cracks during loading is viewed to control the material non-linearity. Using averaging schemes based on both the classical and modified secant methods, the non-linearity of the overall response is shown to be sometimes controlled by an effective stress. The modified secant method accounts in a certain way for the non-uniform distribution of strains within the solid phase. Different definitions of the effective stress are found, each of them being a combination of the overall stress with the fluid pressure. The hypothesis of connexion between pores and microcracks is discussed in details. The consequences of this hypothesis on the non-linear overall response are illustrated and comparisons are made with experimental data.

Micromechanical approach to the behavior of poroelastic materials

In this paper the process of orthogonal cutting is studied by analytical means. A thermomechanical model of the primary shear zone is combined with a modelling of the contact problem at the tool-chip interface. A friction law is introduced that accounts for temperature effects. The effects of cutting conditions and material behaviour on the temperature distribution along the contact zone, on the mean friction and on the global cutting forces are evaluated. The experimental trends are shown to be well described by the proposed model. © 1998 Elsevier Science Ltd. All rights reserved.Keywords : A. cutting and forming, thermomechanical processes, B. viscoplastic material, friction.

Alain Molinari

Papers

A self consistent approach of the large deformation polycrystal viscoplasticity

A dislocation-based model for all hardening stages in large strain deformation

Analytical Characterization of Shear Localization in Thermoviscoplastic Materials

Micromechanical approach to the behavior of poroelastic materials

Modelling of orthogonal cutting with a temperature dependent friction law