[Seminar] John Dolbow ‘The Brazilian Test: An Illustration of the Interplay Between Strength and Energetics in the Fracture of Solids’

Résumé :

In this talk, I will present problems from both quasi-static and dynamic fracture that illustrate the interplay between strength and energetics. As a prototypical example, the Brazilian test will be examined. The Brazilian test has become a standard approach to indirectly measure the tensile strength of brittle materials with relatively large compressive strengths. The test is simple to set up and execute, and it readily lends itself to theoretical analysis. It consists of a circular disk of the material loaded in compression until it fails, typically via a sudden fracture that splits the specimen in two. While relatively simple to understand, the test has proven elusive to various models for fracture. This is likely because it represents a problem of crack nucleation, particularly under a significant degree of compression. What is perhaps under-appreciated is the extent to which this oversight has permitted for the development and acceptance of standardized expressions for tensile strength that can be widely inaccurate. In this talk, 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. I will also illustrate how representations of material strength in various phase-field models can lead to dramatically different predictions in simulations of quasi-static and dynamic fracture.