Seminars

Over the past two decades, classical variational phase-field models have seen broad adoption in various attempts by many different researchers seeking 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 experimental observations. The conclusion is that they cannot possibly describe fracture nucleation in general, simply 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 disruptive model which generalizes the phase-field regularization of the variational theory of brittle fracture of Francfort and Marigo, by including arbitrary material strength.  As an interesting application, 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.