Issue 41

V. Shlyannikov et alii, Frattura ed Integrità Strutturale, 41 (2017) 31-39; DOI: 10.3221/IGF-ESIS.41.05 31 Focused on Multiaxial Fatigue Effect of different environmental conditions on surface crack growth in aluminum alloys V. Shlyannikov, R. Yarullin, I. Ishtyryakov Kazan Scientific Center of the Russian Academy of Sciences, Russia shlyannikov@mail.ru, yarullin_r@mail.ru , ivan_200999@mail.ru A BSTRACT . Fatigue surface crack growth is studied through experiments and computations for aluminum alloys D16T and B95AT (analogue of 2024 and 7075 aluminum). Subjects for studies are cylindrical hollow specimens with external semi-elliptical surface crack. The variation of fatigue crack growth rate and surface crack paths behavior was studied under cyclic loading for different environmental conditions. Uniaxial tension tests were carried out at low (-60°C), room (+23°C) and high (+250°C) temperature. For the same specimen configuration and the different crack front position as a function of cyclic loading and temperatures conditions the distributions of governing parameter of the elastic-plastic stress fields in the form of I n -factor along various crack fronts was determined from numerical calculations. This governing parameter was used as the foundation of the elastic-plastic stress intensity factor (SIF). Both elastic and plastic SIF approach was applied to the fatigue crack growth rate interpretation. It is found that there is a steady relationship between the crack growth rate and the plastic SIF in the form of general curve within a relatively narrow scatter band for all tested specimens at different temperatures. K EYWORDS . Surface crack; Aluminum alloys; Crack growth; Environmental conditions; Fatigue fracture diagram; Plastic SIF. Citation: Shlyannikov, V., Yarullin, R., Ishtyryakov., I., Effect of different environmental conditions on surface crack growth in aluminum alloys, 41 (2017) 31-39. Received: 28.02.2017 Accepted: 15.04.2017 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 he circular cylindrical metallic components of aircraft structure, power engineering elements, pressure vessel and piping are subjected to temperature variations from -60°C (213K) to more than 250°C (523K). In most cases, part-through flaws appear on the free surface of the cylinder and defects are approximately considered as semi- elliptical cracks. The fatigue growth analysis of surface cracks under different environmental conditions is very important for many engineering applications in order to quantify the structural safety according to the so-called damage tolerant design. Furthermore, other environmental effects should be taken into account to assess the structural component safety: for example, the humidity and salt air content play an important role especially under fatigue loading. T