Crack Path Selection in Dynamic Fracture

Series/Event Type: 
Description: 

Our fundamental understanding of dynamic ‘simple’ cracks in brittle solids is excellent, yet the criteria for path selection of moving cracks remain unknown. We evaluate the criteria for path selection in dynamic fracture in two ways: first, we deflect dynamic cracks using sparsely implanted defects, and second, we drive them to undergo an intrinsic oscillatory instability in defect-free media. Our experiments cover a wide range of crack velocities, from 10-95% of their limiting velocity within the brittle material. We obtain dense measurements of the strain fields surrounding the crack tip via high-speed imaging - and these measurements reveal that path selection for such rapid and strongly perturbed cracks is determined by the direction of maximal strain energy density rather than by a local symmetry criterion. These results suggest a mechanism for material toughening in brittle solids, whereby a crack is steered, deflected and even stopped by embedded inclusions.

Speaker: 
John Kolinski, EPFL
Location: 
Bowen Hall
Room number or other detail: 
Bowen Hall Room 222
Date/Time: 
Friday, February 28, 2020 - 12:30pm

Speaker Bio

After spending three years as a Fulbright-Israel post-doc at the Hebrew University of Jerusalem, Israel, where he worked on water bells and brittle fracture mechanics with Jay Fineberg and Eran Sharon, Kolinski moved to Lausanne, Switzerland where he is currently a tenure-track assistant professor in the Mechanical Engineering Department at the EPFL. Kolinski submitted his PhD thesis in Applied Physics at Harvard University in 2014. There, he focused on the dynamics of liquid droplet impact on a smooth, solid surface. With his group in Lausanne, he continues to study interfacial mechanics in two main areas: crack stability in brittle fracture, and stability of the three-phase contact line.
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