Squishy Physics

Next seminar: Wednesday December 12th in Pierce Hall 209 at 6 PM:

 

Plastic dynamics and failure precursors in soft matter

 

 

Stefano Aime

SEAS Harvard University

Department of Physics, Montpellier

 

Abstract:

The failure of materials under constant or periodic load is widespread, occurring from geological scales, as in earthquakes, to biological and soft-matter systems, with huge implications to everyday life and material science. Despite consistent efforts in this field, failure is very often undesired, uncontrolled and unpredicted: surprisingly, or maybe unsurprisingly, it turns out that what is so common in our daily experience is based on profound science that is not yet fully understood.

We investigate the microscopic signature of failure in model colloidal systems under shear stress by simultaneously measuring their mechanical response and microscopic dynamics. On the one hand, the study of the oscillatory yielding of colloidal glasses exhibits a dynamic transition reminiscent of melting: we show that its main features are captured by an Ising-like model, and we discuss intriguing analogies with thermodynamic phase transitions. On the other hand, colloidal gels under a constant, subcritical load fail suddenly after a long induction time, with little if any macroscopic signs of weakening, with strong analogies with catastrophic geological events such as earthquakes, landslides or snow avalanches. Here, we show that the microscopic dynamics of the colloidal gels exhibit dramatic changes, from reversible particle displacements to bursts of irreversible plastic rearrangements that precede its macroscopic failure by several hours.

 

 

Squishy Physics & Pizza Seminar Series

When: Wednesday Evenings - Pizza served at 5:55 PM, talks start at 6 pm till...

Where: Room 209, Pierce Hall, 29 Oxford St, on the Harvard Campus. Directions and parking instructions are here.

What: These talks are informal, with emphasis on new results and ideas, rather than polished presentations. The Squishy audience members typically include soft matter scientists, physicists, engineers, chemists, and biologists.  The goal is to stimulate discussion with the audience.  Talks are typically about 45 minutes long, with lots of questions along the way.

Pizza: Only the finest! 

How to join the weekly Squishy Physics mailing list: please visit the Signup Page.

Directions: Where: Squishy Physics talks are held in Pierce Hall room 301, 29 Oxford Street, Cambridge, MA. See Harvard Campus map here.

Parking: Metered parking is available on Oxford Street.  Speakers, please contact Matthew Zahnzinger to obtain a parking permit.  

Squishy Physics is sponsored by the Cabot Corporation, Dean Cherry Murray and the Weitz Research Group.

If you have comments or suggestions or would like to give a talk, please contact Joerg Werner, Stefano Aime, or Perry Ellis.

Here is the upcoming schedule