Issue 53

A. Chatzigeorgiou et alii, Frattura ed Integrità Strutturale, 53 (2020) 306-324; DOI: 10.3221/IGF-ESIS.53.24 306 Code development for the computational analysis of crack propagation in structures Antonios Chatzigeorgiou, Efstathios E. Theotokoglou, George I. Tsamasphyros School of Applied Mathematical and Physical Sciences, Dept. of Mechanics-Lab. of Testing and Materials, National Technical University of Athens, 5, Heroes of Polytechnion Avenue, Theocaris Bld., Zografou Campus, GR-157 73, Athens, Greece. anthatzigeorgiou@yahoo.gr, stathis@central.ntua.gr , tsamasph@gmail.com A BSTRACT . In this study, the main objective was the creation of a code, which gives the capability to a Finite Element Analysis Program with no built- in crack study tools, to study the propagation of a crack, in a cracked surface. For this purpose, the Finite Element Program FEMAP 11.3.2 with solver the NX NASTRAN has been used, and the proposed code was created, using the Application Program Interface (API) of the program. The Linear Elastic Fracture Mechanics (LEFM) theory has been applied to the code, and can predict, if the crack will propagate, the trajectory of the crack, as well as the number of cycle loads required for the propagation of the crack, for given boundary conditions and loads. Finally, the Stress Intensity Factors (SIF) produced by the program, were compared with results from an analytical method. Also, experimental results have been used, for the verification of the results of the trajectory of the propagation, and the cycle loads. K EYWORDS . Finite element analysis; Stress intensity factor; Crack tip opening displacement; Fatigue crack growth. Citation: Chatzigeorgiou, A., Theotokoglou, E. E., Tsamasphyros, G.I., Code development for the computational analysis of crack propagation in structures, Frattura ed Integrità Strutturale, 53 (2020) 306-324. Received: 20.03.2020 Accepted: 18.05.2020 Published: 01.07.2020 Copyright: © 2020 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 t is well known that numerous thin-wall metal structures, for instance in ships and airplanes, during their lifetime, show cracks in various places. If they are not detected and treated on time, they can be fatal to the structure, with devastating consequences for the crew and passengers, and of course to the environment. Therefore, predicting, locating, and generally studying cracks is of primary importance. For these reasons, methodologies, regulations, and computational tools have been developed, that can predict the creation of a crack, as well as the period that a structural detail can withstand fatigue cycle loads. In this paper, it is assumed that the crack already exists. Therefore, this study will focus on the study of the propagation of the crack. In the numerical analysis of cracked problems, a lot of methods and procedures have already been proposed [1–5]. The origin of the Fracture Mechanics seems to be located in 15th-16th century. According to some authors [6,7], Leonardo Da Vinci studied the fracture strength of iron wires of different lengths, using a device described on the Codice Atlantico [8]. Nowadays, researchers use various finite element analysis (FEA) software to study fracture mechanics problems [9,10]. I