Thursday, 24 September 2020

Speaker: Prof. Rafael Estevez

Laboratoire SIMaP, Science et Ingéniérie des Matériaux et Procédés, Université de Grenoble Alpes

Crossed looks at (brittle) fracture descriptions :
gaining insight from models confrontations and comparisons with experiments on PMMA

Abstract

The presentation starts with a brief presentation of D. Leguillon’s double criterion (DC) for the description of abrupt crack initiation from notches of different geometry. The related predictions are compared to new set of experimental observations on PMMA and discussed. In a second part, the DC approach is used as numerical experiments and its predictions is shown to provide insight and guidelines for the calibration of cohesive parameters. This provides an alternative or complementary information to other identification protocol based on DIC measurements. In a last part, DC predictions are confronted to a phase field model of fracture and the interpretation of the underlying length scale in phase fields models is discussed. What is learned from such “dialectic confrontations” between different descriptions of fracture mechanics is then highlighted.


Biography

Rafael Estevez’s research concerns the micromechanics of materials. He did his PhD on the topic of homogenization of elasto-plastic media. Then, during a post-doc in E. Van der Giessen’s group, he changed topic and started focusing on fracture mechanics, initially on impact fracture of polymers but later on all classes of materials as small crack growth in ceramic polycrystals and metal fracture during his stay at INSA Lyon as assistant professor. Since 2010, this is extended to incluse interface mechanics and integrity of heterogeneous structures at SIMaP (Univ. Grenoble Alpes) as full professor. The methodology combines modelling, predictions and experimental fracture mechanics for the identification of cohesive models and provide reliable predictions. This can then be integrated in a multi-scale approach of fracture, for instance providing a physically based criterion at the micro-scale to be used at a macro-scale for predictions ta the scale of a structure. During the last five years, a new work related the influence of interface on design on structures within a topology optimization framework has been initiated, in collaboration with CMAP’s group (G. Allaire) and collaborators in Grenoble (LJK) to combine micromechanics of materials and maths (Math-erials exchanges).

References