Issue 42

J. Klon et alii, Frattura ed Integrità Strutturale, 42 (2017) 161-169; DOI: 10.3221/IGF-ESIS.42.17 161 Focused on Mechanical Fatigue of Metals Pilot evaluation of a fracture process zone in a modified compact tension specimen by X-ray tomography Jiří Klon, Stanislav Seitl, Hana Šimonová, Zbyněk Keršner Brno University of Technology, Faculty of Civil Engineering, Veveří 331/95, 602 00 Brno, Czech Republic klon.j@fce.vutbr.cz, http://orcid.org/0000-0002-9551-2185 seitl.s@fce.vutbr.cz , http://orcid.org/0000-0002-4953-4324 simonova.h@vutbr.cz, http://orcid.org/0000-0003-1537-6388 kersner.z@fce.vutbr.cz , http://orcid.org/0000-0003-4724-6166 Ivana Kumpová, Daniel Vavřík Institute of Theoretical and Applied Mechanics AS CR, v. v. i., Prosecká 809/76, 190 00 Praha 9, Czech Republic kumpova@itam.cas.cz, http://orcid.org/0000-0001-8556-4996 vavrik@itam.cas.cz , http://orcid.org/0000-0002-8599-9903 A BSTRACT . In the case of quasi-brittle material, there is a zone of non-linear behaving material, near the crack tip. A major part of this zone forms a so- called fracture process zone (FPZ), where mechanisms of material toughening take place. The main idea is to estimate the size of the fracture process zone under various types of load by using X-ray tomography. The estimation of the zone is supported by the theory of linear elastic fracture mechanics (LEFM) that could be a limit case of quasi-brittle mechanics. The size of the zone envelop is provided in X-ray snaps and compared with the theoretical size from LEFM. K EYWORDS . Fracture process zone; X-ray; Concrete; Composites; Stress intensity factor; Compact tension specimen. Citation: Klon, J., Seitl, S., Šimonová, H., Keršner, Z., Kumpová, I., Vavřík, D., Pilot evaluation of a fracture process zone in a modified compact tension specimen by X-ray tomography, Frattura ed Integrità Strutturale, 42 (2017) 161-169. Received: 16.06.2017 Accepted: 21.07.2017 Published: 01.10.2017 Copyright: © 2017 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION n the case of quasi-brittle materials, there is a zone of non-linear behaving material, near the crack tip. A major part of this zone forms a so-called fracture process zone (FPZ), where mechanisms of material toughening take place [1, 2]. Tensile softening is caused by these mechanisms. This softening is caused for example by crack deflection, crack bridging by the aggregate grain, friction of crack faces, blinding of cracks in the pores, crack branching, etc. The FPZ has recently begun to be considered in the models for description of quasi-brittle fracture. Mechanisms that take place in the FPZ and cause tensile softening in fact change mechanical parameters of the material [3]. The authors assume that one of the changed parameters is also material density, which is different for the main material, and the material that is in the FPZ. I