Department of Aerospace Engineering

Midwest Mechanics Seminar Series: "Multiscale Modeling of Fracture in Metals"- Dr. William Curtin, Brown University

Dr. William Curtin

Dr. William Curtin

Brown University

Wednesday, October 14, 2009
1:10 PM
Alliant Energy-Lee Liu Auditorium
1140 Howe Hall

Multiscale Modeling of Fracture in Metals

Fracture in non-brittle crystalline materials involves material separation at the atomistic scale and dislocation plasticity, with its associated dissipation, occurring over much larger scales.  Thus, multiscale models are required to handle both the atomistic and mesoscale aspects of the deformation and fracture.  Here, we first present a methodology to connect continuum rate-dependent crystal plasticity to discrete dislocation plasticity, and validate the coupling method through analysis of crack growth.  The results show that continuum plasticity fails to describe the deformation at distances of less than a few microns from the crack tip.  Preliminary results on fatigue crack growth show the potential of the multiscale method to handle problems with both large spatial and temporal scales.  We then study fracture using the discrete dislocation model alone, with a cohesive-zone model for fracture, and examine how the cohesive zone parameters and internal material parameters, such as dislocation obstacle spacing, control the macroscopic fracture resistance.  We compare these results against the predictions of strain-gradient plasticity models and relate the gradient length scale to the internal material parameters.  Finally, we replace the cohesive zone model by an explicit atomistic region by using the multiscale Coupled Atomistic Discrete Dislocation model and examine crack tip processes controlling fracture in Al and Ni.  Near-term prospects for integration of all of these methods, plus quantum mechanical methods, into a full atom-to-continuum multiscale model are discussed.

Brief Bio: Dr. William Curtin received a combined 4 yr. ScB/ScM degree in Physics from Brown University in 1981 and a PhD in theoretical physics from Cornell University in 1986, working on the optical properties of metal nanoparticles and on statistical mechanics theories of freezing.  Dr. Curtin then joined the Applied Physics Group at the British Petroleum Research Laboratories (formerly SOHIO) in Cleveland, OH, where he worked on hydrogen storage in amorphous metal alloys, the statistical mechanics of crystal/melt interfaces, and the mechanics of ceramic and composites.  In 1993, he joined the faculty at Virginia Tech with a joint appointment in Materials Science & Engineering and Engineering Science & Mechanics.  In 1998, Professor Curtin returned to Brown University as a faculty member in the Solid Mechanics group of the Division of Engineering and was appointed the Elisha Benjamin Andrews Professor in 2006.

Professor Curtin is Director of the Center for Advanced Research Materials at Brown and Director of the NSF Materials Research Science and Engineering Center at Brown. He was appointed as a Guggenheim Fellow in 2005-06 to pursue research on Multiscale Modeling, has published over 130 peer-reviewed journal papers, been Principal Investigator overseeing more than $22M in research funding, and has presented many invited talks at national and international venues.