Issue 41

S.M.J. Razavi et alii, Frattura ed Integrità Strutturale, 41 (2017) 424-431; DOI: 10.3221/IGF-ESIS.41.53 424 Notched graphite under multiaxial loading S.M.J. Razavi, M. Peron, J. Torgersen, F. Berto Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology (NTNU), Norway javad.razavi@ntnu.no , mirco.peron@ntnu.no , jan.torgersen@ntnu.no , filippo.berto@ntnu.no A BSTRACT . Cylindrical specimens made of polycrystalline graphite and weakened by circumferential V-notches under mixed mode I/III loading were studied in this research. Different geometries of V-notches varying the notch opening angle and the notch tip radius were tested. Appling various ratios of tensile and torsion loads, the multiaxial static tests have been conducted. Averaged Strain Energy Density (ASED) criterion previously presented by the same authors is employed here for the case of tension and torsion loadings applied in combination. The fracture behavior of the tested joints under multiaxial loading has been successfully predicted using the ASED criterion. K EYWORDS . Isostatic polycrystalline graphite; Mixed mode I/III; V-notch; Strain energy density. Citation: Razavi, S.M.J., Peron, M., Torgersen, J., Berto, F., Notched graphite under multiaxial loading, Frattura ed Integrità Strutturale, 41 (2017) 424-431. Received: 15.05.2017 Accepted: 23.05.2017 Published: 01.07.2017 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 ue to its good compromise between thermal and mechanical properties, isostatic graphite is widely used in various industrial applications. A bulk number of the components made of graphite is subjected to loads transferred by the other parts of the structure. According to this fact, numerous researches have been devoted to the fracture assessment of graphite. Considering the brittle behavior of this material, brittle fracture is a typical failure mechanism which usually happens after the initiation of micro-cracks in the most stressed parts of the structure, combined in some cases with a negligible amount of plasticity [1-4]. The majority of the studies focused on structural integrity of graphite components have been devoted to the investigation of cracked components by quantifying the fracture toughness under prevalent mode I loading [5-7]. Innovative techniques have been proposed in the literature for fracture assessment of isotropic graphite under mode I loading [8-10]. Although the brittle fracture of graphite components has been studied continuously for several years, only few predictive models are available for the fracture behavior of cracked components. Reviewing the published papers in the field of fracture behavior of graphite components reveals that only a limited number of researches are focused on the notch sensitivity of graphite components including the researches conducted by Bazaj and Cox [8] and Kawakami [9]. The fracture behavior of blunt notches has been studied in the past years by researchers, who have investigated the case of pure mode I loading and in-plane mixed mode loading [11-18]. Due to the lack of information about the multiaxial behavior of graphite components in the literature, the authors aimed to investigate the static behavior of isostatic graphite subjected to multiaxial loadings which can be applied as a D