CEEM Seminar Series | John Dolbow | Duke University | Classical variational phase-field models cannot predict fracture nucleation
Classical variational phase-field models cannot predict fracture nucleation
Notwithstanding the evidence against them, classical variational phase-field models continue to be used and pursued in an attempt to describe fracture nucleation in elastic brittle materials. In this context, the main objective of the first part of this talk is to provide a comprehensive review of the existing evidence against such a class of models as descriptors of fracture nucleation. To that end, a review is first given of the plethora of experimental observations of fracture nucleation in nominally elastic brittle materials under quasi-static loading conditions, as well as of classical variational phase-field models, with and without energy splits. These models are then confronted with the experimental observations. The conclusion is that they cannot possibly describe fracture nucleation in general. This is because classical variational phase-field models cannot account for material strength as an independent macroscopic material property. The second part of the talk will introduce an emergent class of phase-field models that can predict fracture nucleation. Emphasis will be placed on a recent model by Lopez-Pamies and collaborators (2020), which is a natural generalization of the phase-field regularization of the variational theory of brittle fracture of Francfort and Marigo (1998). In particular, I will highlight our recent work that includes a complete quantitative analysis of where and when fractures nucleate and propagate in Brazilian tests (static and dynamic) and how to interpret their results appropriately. Finally, I will share a recent result that illustrates how this emergent class of phase-field models can be recast in a variational setting. This talk is a result of joint efforts with Yangyuanchen Liu, Oscar Lopez-Pamies, Gilles Francfort, and Christopher Larsen.
Professor John Dolbow
John Dolbow is a Professor of Mechanical Engineering and Materials Science at Duke University, where he directs the Duke Computational Mechanics Laboratory. He is an Assistant Vice President for Research at Duke. Professor Dolbow received his BS in Mechanical Engineering from the University of New Hampshire, and his Ph.D. in Theoretical and Applied Mechanics from Northwestern. As a faculty member at Duke University, he holds appointments in Mechanical Engineering and Materials Science, Civil and Environmental Engineering, and Mathematics. His research concerns the development of computational methodologies and models for problems in fracture mechanics. He has received various accolades for his research, including Young Investigator awards from both the USACM and the IACM. He has held visiting appointments at Harvard University, the Okinawa Institute of Science and Technology, and Sandia National Laboratories. He is the Editor-In-Chief of the journal Finite Elements in Analysis and Design. He currently serves as the Secretary-General of the International Association for Computational Mechanics.