The determination of mode-I fracture toughness (by means of the Brazilian disc configuration) in the light of data provided by the 3D digital image correlation technique
International Journal of Building Pathology and Adaptation
ISSN: 2398-4708
Article publication date: 3 May 2022
Issue publication date: 14 March 2024
Abstract
Purpose
The determination of mode-I fracture toughness of brittle structural materials by means of the notched Brazilian disc configuration is studied. Advantage is taken of a recently introduced analytical solution and, also, of data provided by an experimental protocol with notched marble specimens under diametral compression using the loading device suggested by International Society for Rock Mechanics (ISRM) and also the three-dimensional digital image correlation (3D-DIC) technique.
Design/methodology/approach
The analytical solution highlighted the role of geometrical factors, like, for example, the width of the notch, which are usually disregarded. The data of the experimental protocol were comparatively considered with those concerning the response of the specific material under uniaxial tensile load.
Findings
This combined study provided interesting data concerning some open issues, as it is the exact crack initiation point and the level of the critical load causing crack initiation. It was definitely indicated that the crack initiation point is not a priori known (even for notched specimens) and, also, that the maximum recorded load does not correspond by default to the critical load responsible for the onset of catastrophic macroscopic fracture.
Originality/value
It was suggested that the load considered critical one for the determination of mode-I fracture toughness KIC is erroneous. At a load equal to about 70% of the maximum one, a process zone is formed (zone of non-reversible phenomena) around the notch's crown, designating termination of the validity of any linear elastic solution used to determine the normalized stress intensity factors (SIFs). Moreover, at a load level equal to about 95% of the macroscopically observed fracture load, crack propagation has already begun. Therefore, the experimental procedure must be monitored with additional equipment, providing an overview of the displacement field developed during loading.
Keywords
Acknowledgements
This research was partly co-financed by Greece and the European Union (European Social Fund – ESF) through the operational programme “Human Resources Development, Education and Lifelong Learning 2014–2020” in the context of the project “Critical assessment and revision of the standard regarding the determination of the Mode I fracture toughness, KIC, of brittle building materials using a combination of innovative experimental techniques, numerical simulations and analytical methods” (MIS 5049181).
Citation
Kourkoulis, S.K., Pasiou, E.D., Markides, C.F., Loukidis, A., Stavrakas, I. and Triantis, D. (2024), "The determination of mode-I fracture toughness (by means of the Brazilian disc configuration) in the light of data provided by the 3D digital image correlation technique", International Journal of Building Pathology and Adaptation, Vol. 42 No. 1, pp. 175-192. https://doi.org/10.1108/IJBPA-02-2022-0032
Publisher
:Emerald Publishing Limited
Copyright © 2022, Emerald Publishing Limited