Sommaire:

The study of the yielding transition of amorphous materials is a complex phenomenon that can manifest with profoundly different macroscopic features in different circumstances.

While some materials yield abruptly, in a way often referred to as brittle, others exhibit an extended nonlinear deformation regime characterized by plasticity, a phenomenology typically called ductile failure. For one given material, yielding can be either ductile or brittle depending on the deformation rate and/or on the temperature. More recently, a series of computer simulation works suggested that, even under the same testing conditions (rate and temperature), ductile or brittle failure may be observed for the same material, depending on the previous mechanical or thermal history. Despite huge progress in this field, a comprehensive understanding of the transition between ductile and brittle yielding is still missing, mostly because stringent experimental validations of the ideas proposed in the literature are still scarce.

In this seminar I will present recent research project addressing two important questions related to the ductile to brittle transition:

1 - What is the interplay between the microscopic dynamic transition, the formation of shear bands and the macroscopic weakening of a Yield Stress Fluid?

2 - Can we use mechanical conditioning to effectively prepare the same YSF in different states with different yielding properties?

To address the first question, I will present results of simultaneous experimental study of the (a) rheological response of soft glasses, (b) mesoscopic deformation fields, and (c) microscopic plastic dynamics. Both homogeneous yielding and shear banding cases are studied [[1]].

For the second question, we combined experimental rheology and particle-dynamic simulations, with the aim to rationalize the role of internal stress distribution on material’s yielding properties, memory, ageing and annealing [[2]].


[1] Paolo Edera, Matteo Brizioli, Mahnoosh Madani, Elie N’Gouamba, Philippe Coussot, Veronique Trappe, George Petekidis, Fabio Giavazzi, Roberto Cerbino. Yielding under the microscope: a multi-scale perspective on brittle and ductile behaviors in oscillatory shear. https://arxiv.org/abs/2402.00221

[2] Paolo Edera, Minaspi Bantawa, Stefano Aime, Roger Bonneacaze, Michel Coitre. Tuning residual stress, directional memory and aging in soft glassy materials. https://arxiv.org/abs/2402.08293

Pour plus d'informations, merci de contacter Milani M.