Issue 31

R. Citarella et alii, Frattura ed Integrità Strutturale, 31 (2015) 138-147; DOI: 10.3221/IGF-ESIS.31.11 138 FEM simulation of a crack propagation in a round bar under combined tension and torsion fatigue loading R.Citarella, M.Lepore Dept. of Industrial Engineering – University of Salerno - Fisciano (SA), Italy. rcitarella@unisa.it A. Maligno Institute for Innovation in Sustainable Engineering, University of Derby, Quaker Way, DE1 3HD Derby (UK). a.maligno@derby.ac.uk V. Shlyannikov Researches Center for Power Engineering Problems of Russian Academy of Sciences, Lobachevsky Street, 2/31, 420111, Kazan, Russia. shlyannikov@mail.ru A BSTRACT . An edge crack propagation in a steel bar of circular cross-section undergoing multiaxial fatigue loads is simulated by Finite Element Method (FEM). The variation of crack growth behaviour is studied under axial and combined in phase axial+torsional fatigue loading. Results show that the cyclic Mode III loading superimposed on the cyclic Mode I leads to a fatigue life reduction. Numerical calculations are performed using the FEM software ZENCRACK to determine the crack path and fatigue life. The FEM numerical predictions have been compared against corresponding experimental and numerical data, available from literature, getting satisfactory consistency. K EYWORDS . Surface flaw; Tension and torsion; Crack growth prediction; FEM; G-criterion. I NTRODUCTION umerical modelling of three-dimensional (3D) fatigue crack growth under mixed mode conditions represents a crucial factor in fracture mechanics in order to assess the residual life of components. The fatigue growth analysis of surface cracks is one of the most important elements for structural integrity prediction of the circular cylindrical metallic components (bars, wires, bolts, shafts, etc.), in the presence of initial and accumulated in service damages. In most cases, part-through flaws appear on the free surface of the cylinder and defects are approximately considered as semi-elliptical cracks. Multi-axial loading conditions including tension/compression, bending and torsion are typical for the circular cylindrical metallic components of engineering structures. The problem of residual fatigue life prediction of such type of structural elements is complex and the closed solution is often not available because surface flaws are three-dimensional in nature. N