Interaction effect of a main crack emanating from a semicircular notch and a microcrack D. Ouinas a, * , B.B. Bouiadjra b , N. Benderdouche c a Department of Mechanical Engineering, University of Mostaganem, Mostaganem 27000, Algeria b LECM, Faculty of Engineering, University of Sidi-BelAbbes, Sidi-BelAbbes 22000, Algeria c Faculty of Engineering, University of Mostaganem, Mostaganem 27000, Algeria article info Article history: Received 3 February 2008 Received in revised form 4 March 2008 Accepted 7 March 2008 Available online 9 May 2008 PACS: 62.20.Mk 47.11.Fq Keywords: Notch Interaction effect Damage Stress intensity factor (SIF) Finite element analysis abstract The study of morphology of fracture surfaces cannot only answer the whole of the problems arising from the damage of microcracking. This damage generates energy dissipation and a stress field redistribution which contributes to the dissipation of the energy stored in the structure, and favours the stable propa- gation of the main crack. In this work, the finite element method is used to analyze the interaction effect of a main crack emanating from semicircular notch and a microcrack in order to understand the different mechanisms induced by this interaction and in particular the effects of reduction and/or amplification of the stress field between the macro and the microcrack. Two cases were considered: transverse and lon- gitudinal displacement of the microcrack compared to the main crack. This kind of approach makes it possible to predict the predominating fracture mode, either by coalescence, or by deflection in the direc- tion of mode II. Ó 2008 Elsevier B.V. All rights reserved. 1. Introduction Understanding the fracture of materials phenomenon requires thorough investigation of the criteria of initiation and propagation of cracks, which in general, occur in the higher stress concentra- tions zones [1]. The analysis of the stress distribution in these de- fects and at their vicinity is important for the fracture behaviour of these materials. This analysis allows the prediction of the strength at fracture. The elastic behaviour of materials is affected by the presence of defects which can result in the weakening of the struc- ture and cause its destruction. Microcracks appear in the zones of high stress concentrations due to the geometrical or metallurgical effects [2,3]. Moreover, fracture is the consequence of various mechanisms related to the development of wide microcracked damaged zone. This damage of microcracked zone generates the development of the microcracks which coalesce until they form a macrocrack which propagates until failure of the structure occurs [4]. Indeed, the local deviations of the main crack of a material are influenced by the interactions between the microcracks and the main crack. An interesting study was carried out on the effect of presence of micro-crack near a main crack on the variation of the shape and the size of the plastic zone ahead of the main crack for small scale plasticity in aluminium alloy 2024 T3 [5]. Ductile fracture of materials takes place by decoherence of the matrix around inclusions, or by fragmentation of the latter. The inclusions are generally the origin of the stress concentrations in materials and can be a source of initiation and propagation of cracks [2]. Many authors [2,6–9] have studied the effect of the presence of inclusions; while numerous studies [10–13] have fo- cused on the influence of the notch effect on material behaviour. It is interesting to study the relations which may exist between the geometrical and the metallurgical defects as well as the mate- rials capacity to resist crack propagation. The present study con- sists in investigating the simulation of the main crack behaviour emanating from a semicircular notch and its interaction with a microcrack which may occur in various positions. 2. Finite element model Let us consider an elastic thin aluminium plate with a semicir- cular lateral notch having the following dimensions: length H = 204 mm; width w = 152 mm; thickness e = 1 mm and notch ra- dius q not ¼ 12:7 mm. The properties of the plate: Young’s modulus E and Poisson ratio m are given in Table 1. 0927-0256/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.commatsci.2008.03.014 * Corresponding author. E-mail address: douinas@netcourrier.com (D. Ouinas). Computational Materials Science 43 (2008) 1155–1159 Contents lists available at ScienceDirect Computational Materials Science journal homepage: www.elsevier.com/locate/commatsci