Microscopic Origins of Fracture Toughness

ERC Consolidator Grant microKIc

This ERC-funded project aims at developing an experimentally validated multiscale modelling framework for the prediction of fracture toughness of metals.

The resistance to crack propagation is undoubtedly one of the most important properties of structural materials. However, our current mechanistic understanding of the fracture processes in typical semi-brittle materials like steels, refractory metals, or semiconductors is not sufficiently advanced to predict the fracture toughness K_Ic and its dependence on the microstructure, temperature, and strain rate. Therefore, K_Ic is commonly regarded as a phenomenological material parameter for fracture mechanics models that require experimental calibration. A quantitative understanding of the relation between physical, crystallographic and in particular microstructural properties and the failure resistance of a material is, however, crucial for improving the performance of materials and material models. Understanding crack-microstructure interactions is, furthermore, of fundamental importance for fatigue fracture, stress corrosion cracking and hydrogen embrittlement.

The aim of the ERC-funded project microK_Ic is to study fracture in model materials in order to gain a detailed understanding of the microscopic crack-tip processes during fracture initiation, propagation and arrest, and to systematically study the interactions of cracks with constituents of the microstructure. To this end, we perform fully 3D, large-scale atomistic simulations on cracks in bcc-based materials. Insights and parameters from these simulations are used to develop in collaboration with M. Fivel a coupled finite element - discrete dislocation dynamics code. In addition to the simulations, micromechanical fracture tests on notched cantilever beams with well-defined microstructures are carried out in the group of J. Best as well as at the Friedrich-Alexander-Universität Erlangen-Nürnberg.

The ultimate goal of microKIc is to use this experimentally validated multiscale modelling framework to develop a microstructure-sensitive, physics-based micromechanical model of the fracture toughness.