Matériaux & Techniques 99, 751–759 (2011) c  EDP Sciences, 2012 DOI: 10.1051/mattech/2011135 www.mattech-journal.org Matériaux & Techniques Modélisation et simulation: procédés d’élaboration et de traitement/Modelling and simulation: materials processing Fracture mechanics of spot-welded steel sheets of equal thickness in Coach-peel specimens F. Bouafia LMPM, Mechanical Engineering Department, University of Sidi Bel Abbes, BP 89, Cite Arbi Ben M’Hidi, Sidi Bel Abbes 22000, Algeria e-mail: fbouafia2011@yahoo.fr Key words: Finite element method; spot weld; Fracture mechanics; stresses intensity factor; mixed mode Abstract – In the current paper, a numerical investigation based on the finite element method was constructed to analyse fracture mechanics of two L-shaped sheets welded with resistance welding. The fracture behaviour of the welded structure is considered with the assumption of a crack at the interface of the welded sheets. The study was treated as a linear elastic fracture mechanics problem in mixed mode, under plane stress conditions. Computations were performed using the commercial FE software package ABAQUS. The modelling results highlight the dependence of the stress intensity factors on key design pa- rameters of spot welds such as nugget diameter, bent curvatures, sheet thickness, material properties and the applied load. Mots-clés : Méthode des éléments-finis ; soudage par point ; mécanique de la rupture ; facteur d’intensité de contrainte ; mode mixte Received 12 January 2011 accepted 25 October 2011 Résumé – Mécanique de la Rupture du soudage par point des tôles d’acier d’épais- seur égale dans les plaques Coach-peel. Dans la présente étude, une étude numérique basée sur la méthode des éléments-finis a été construit pour analyser la mécanique de la rupture de deux plaques en forme de L soudé par soudage par résistance. Le comportement à la rupture de la structure soudée est considéré avec l’hypothèse d’une fissure à l’interface de plaques soudées. L’étude a été traitée comme un problème de la mécanique de la rup- ture linéaire élastique en mode mixte, sous les conditions des contraintes planes. Les calculs ont été effectués, en utilisant le logiciel commercial des éléments-finis ABAQUS. Les ré- sultats de la modélisation mettent en évidence la dépendance des facteurs d’intensité des contraintes sur les paramètres de la conception de points de soudure tels que le diamètre de la pépite, rayon des courbures, épaisseur de la tôle, les propriétés des matériaux, et la charge appliquée. S tructural joints between thin metal sheets are a crucial component of many engineering designs. Resistance spot-welding, which makes use of the con- tact resistance between metal parts to induce localised melting when an electric current is applied, is one of the frequently applied methods to join thin sheets. It is widely used in the automotive industry and occasionally by other industries such as refrigerator and washing machine manufacturers. A modern vehicle typically contains 2000 to 5000 spot welds [1]. Although resistance spot-welding has advantages in welding efficiency and au- tomation, fatigue and fracture, on the other hand, are the most critical failure modes of resistance-welded joints [2]. Thus, a com- plete understanding of how to analyse frac- ture mechanics of spot-welded joints, and how to use this analysis to make predictions about their performance, would greatly en- hance the efficient design of safe structures. The main task in the fracture mechan- ics analysis is to determine the fracture parameters such as notch stress, stress intensity factors and the J-integral. Over the past few years, researchers have stud- ied fatigue and fracture properties of welded structures by determining stress intensity Article published by EDP Sciences