Issue 46

A. Baltach et alii, Frattura ed Integrità Strutturale, 46 (2018) 252-265; DOI: 10.3221/IGF-ESIS.46.23 252 Numerical analysis and optimization of the residual stresses distribution induced by cold expansion technique Abdelghani Baltach University of Tiaret, Department of Mechanical Engineering, Tiaret, Algeria. baltachabdelghani@yahoo.fr Abdelkader Djebli, Mostefa Bendouba, El Hadj Besseghier, Abdelkrim Aid University Mostapha Stambouli-Mascara, Laboratory of Quantum Physics of Matter and Mathematical Modeling (LPQ3M), Mascara 29000, Algeria. djebliabdelkader@univ-mascara.dz , bendoubamos@yahoo.fr, besseghier.hadj@outlook.fr , aid_abdelkrim@yahoo.com A BSTRACT . This paper presents a numerical investigation about the influence of mandrel shape on residual stresses induced by the cold expansion procedure. Thus, ball and tapered pin are used for cold expanding the plate. As, the entrance face presents the lowest residual stresses throughout the hole thickness, we propose to solve this problem by varying the mandrel taper degree, instead of applying a double expansion. The obtained results show that the tapered pin is more suitable for the cold expansion. More, low taper increases the residual stresses at the entrance, reaching the values generated at the exit face. K EYWORDS . Cold expansion; Fastener hole; Residual stress; FEM method; Taper degree. Citation: Baltach, B., Djebli, A., Bendouba, M., Besseghier, El H., Aid, A., Numerical analysis and optimization of the residual stresses distribution induced by cold expansion technique, Frattura ed Integrità Strutturale, 46 (2018) 252-265. Received: 19.05.2018 Accepted: 24.07.2018 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 he technique of cold expansion of the fastener holes has been used over the last decades [1]. Essentially, as an efficient technique, it was introduced to the aircraft industry by Boeing Company about 50 years ago to enhance fatigue lives of fastener holes [2; 3]. Since then, considerable efforts have been done to improve the fatigue lifetimes of such structures. In fact, actually the cold expansion is used on almost all commercial and military aircraft in the world because of its proven performance to prevent the initiation and crack growth. Thus, it provides long-term benefits such as an important gain in structural fatigue life and then consequent economies in maintenance and essentially the structural safety level is significantly improved. However, the effectiveness of the cold expansion process depends on the magnitude T