Issue 47

S. K. Kourkoulis et alii, Frattura ed Integrità Strutturale, 47 (2019) 247-265; DOI: 10.3221/IGF-ESIS.47.19 247 Fracture and Structural Integrity: ten years of ‘Frattura ed Integrità Strutturale’ Analytical and numerical study of the stress field in a circular semi- ring under combined diametral compression and bending Stavros K. Kourkoulis, Ermioni D. Pasiou, Christos F. Markides National Technical University of Athens, School of Applied Mathematical and Physical Sciences, Department of Mechanics, Laboratory for Testing and Materials, 5, Heroes of Polytechnion Avenue, Zografou Campus, Theocaris Building, 157 73, Greece stakkour@central.ntua.gr, epasiou@teemail.gr, markidih@mail.ntua.gr A BSTRACT . The stress field developed in a circular semi-ring under the com- bined action of diametral compression and bending is explored both analytically and numerically. The analytic solution is implemented by means of the complex potentials technique as it was formulated by Muskhelishvili, while for the nu- merical study a finite element model, properly validated based on experi- mental data, is used. The analytic solution provided closed formulae for the stress field along strategic loci of the specimen, while the numerical model permitted thorough parametric investigation of the dependence of critical quantities on geometrical and loading factors. The idea behind the study is to assess the potentialities of the circular semi-ring as a possible substitute of the familiar Brazilian disc, in the direction of curing drawbacks of the latter. It was concluded that a circular semi-ring subjected to eccentric diametral com- pression provides reliable data for the tensile strength of very brittle materials, relieved from ambiguities characterizing the standardized Brazilian-disc test. K EYWORDS . Circular semi-ring; Brazilian-disc test; Tensile strength; Complex potentials; Finite element method; Stress field. Citation: Kourkoulis S.K., Pasiou E.D, Mar- kides Ch.F., Analytical and numerical study of the stress field in a circular semi-ring under combined diametral compression and bending, Frattura ed Integrità Strutturale, 47 (2019) 247-265. Received: 21.08.2018 Accepted: 28.10.2018 Published: 01.01.2019 Copyright: © 2019 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 he implementation of standardized uniaxial tensile tests, with specimens made of brittle materials (as for example various hard rocks and rock-like geomaterials), encounters insuperable difficulties, related mainly to local fragmen- tation of the specimens during gripping and, also, fracture of the specimens in the immediate vicinity of the gripping area (rendering the data of the tests unreliable, given that the stress field in these regions is not purely uniaxial). In an attempt to overcome the problem, the engineering community is long ago seeking for alternative configurations that could provide at least an estimation of the uniaxial tensile strength of very brittle structural materials. Among the alternative configurations proposed, the one most widely accepted worldwide, is that of a circular disc compressed by diametral forces, T