Events Calendar

Astani CEE Department Seminar: The problem of dynamic fracture in brittle materials and its peridynamic solution

Speaker: Dr. Florin Bobaru, Mechanical and Materials Engineering, University of Nebraska-Lincoln

Abstract: Dynamic fracture in nominally brittle materials (in which plastic work is minimal) has significant technological relevance in, for example, designing material systems resistant to impact damage and penetration, cracking of pavement and infrastructure under shock loadings, hydraulic fracturing for enhanced extraction of oil and gas, mining operations, safety of long-term storage of spent nuclear fuel through vitrification, etc. Experiments on dynamic brittle fracture in amorphous materials exhibit a large variety of complex phenomena, including: crack branching, crack-path instabilities, successive branching events, secondary cracking. Modeling and simulation of dynamic fracture in brittle materials has been one of the most challenging problems in computational mechanics. In spite of significant efforts dedicated to this phenomenon over the past several decades (using cohesive-zone models, molecular dynamics methods, etc) fundamental issues and discrepancies between simulation results and experimental observations have remained unsolved.

In this talk I will present peridynamic (nonlocal) models for dynamic brittle fracture. I will show that peridynamics correctly reproduces many of important features of dynamic crack propagation. In particular, the crack propagation speed and the crack path obtained with peridynamics approach experimental values. We use the peridynamic model to also investigate the influence of the stress waves on the crack branching angle and the velocity profile of a propagating crack in a branching event. We observe that crack branching in peridynamics evolves as described by the phenomenology deduced from the experimental evidence: when a crack reaches a critical stage it splits into two or more branches, each propagating with the same speed as the parent crack, but with a much reduced process zone. The results confirm the recent belief that dynamic fracture in brittle materials happens through an evolution of micro-damage and micro-cracking, and is controlled by the “inner problem” taking place in the process zone rather than by the “outer problem” that classical fracture mechanics solves.


Biography: Education and employment history:

• B.S. (1995) Mathematics and Mechanics, University of Bucharest, Romania

• M.S. (1995) Mathematics and Mechanics of Solids, University of Bucharest, Romania

• Ph.D. (2001) Theoretical and Applied Mechanics, Cornell University, Ithaca, NY Associate Professor, Mechanical and Materials Engineering at University of Nebraska-Lincoln (since 2007). Assistant Professor of Engineering Mechanics, UNL (2001-2007). Visiting positions: Summer Research Fellow (2002 – 2004, 2005) at Sandia National Laboratories; Visiting Scholar (Sept.-Dec. 2008), The Fracture Group, Cavendish Lab, University of Cambridge, Cambridge, U.K.; Visiting Scholar (Jan.-Mar. 2009), Multiscale Dynamic Material Modeling Department, Sandia National Laboratories; Visiting Associate Professor (Apr.-Aug. 2011), Mechanical and Civil Engineering, California Institute of Technology, Pasadena, California.


Host: Dr. Jean-Pierre Bardet

Location: Kaprielian Hall (KAP) - 209 Conference Room

Audiences: Everyone Is Invited

Contact: Evangeline Reyes