Issue 46

M. El Habiri et alii, Frattura ed Integrità Strutturale, 46 (2018) 34-44; DOI: 10.3221/IGF-ESIS.46.04 34 Developments in the fracture and fatigue assessment of materials and structures Effect of cold expansion on improving of fatigue initiation life in Aluminium alloy Mohamed El Habiri, Mustapha Benachour*, Nadjia Benachour University of Tlemcen, Ingeniery of Mechanical Systems and Materials Laboratory, Tlemcen, Algeria Faculty of Technology, Mechanical Engineering Department yacine2704@gmail.com, bmf_12002@yahoo.fr, nbenachour2005@yahoo.fr A BSTRACT . In this paper, numerical investigation was carried out to quantify the effect of the cold expansion on fatigue crack initiation in Aluminium alloy. The improvement in fatigue initiation life of specimen after the cold expansion process was investigated with the drilled hole of 2024 T351 Aluminium alloy plate. The applied degree of expansion (DCE%=100 (D- d)/d) is 4.6% where the effect of friction (µ=0.2) is considered. Residual stress field is determined using 3D Finite Element Analysis and shows the presence of compressive residual stress around the hole. The results showed a high compressive residual stress near the hole in exit face of the hole and at middle of the plate thickness around the hole. Local strain approach is applied in evaluation of fatigue initiation lives under Afgrow environment code. Fatigue initiation lives are improved by the presence of the compressive residual stresses comparatively to the drilled hole without of compressive residual stresses. Also, the fatigue initiation lives are increased with the increase in stress ratio for drilled hole and expanded hole K EYWORDS . Fatigue crack initiation; Cold expansion; Compressive residual stress; Stress ratio; Aluminium alloy. Citation: El Habiri, Med., Benachour, M., Benachour, N., Effect of cold expansion on improving of fatigue initiation life of Aluminium alloy, Frattura ed Integrità Strutturale, 46 (2018) 34-44. Received: 07.03.2018 Accepted: 09.04.2018 Published: 01.10.2018 Copyright: © 2018 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 reventing fatigue failures in aircraft structures is a principle aiming of aircraft designers and maintainers. The need to prevent fatigue failures and extended the fatigue life, improvement methodologies are necessaries. Fatigue phenomenon presents an essential failure mode in aircraft structures. The percentage of failure varies from 55 to 61% [1] in aeronautic components. In aircraft structures, the joints are carried out by mechanically fastened joints, adhesively and bonded joints. In fastened joints is necessary to improve the quality of holes by introducing compressive residuals stresses. The method to introduce the compressive residuals stress are such as shot peening [2, 3] laser shock [4, 5], and cold expansion [6-9]. P