Investigation fatigue crack initiation and propagation cruciform welded joints by extended finite element method (XFEM) and implementation SED approach

This study has used the strain energy density (SED) approach to evaluate the stress intensity factor (SIF) of cracked cruciform welded joints in Hardox 450 steel. A microstructural analysis was made of Hardox 450 steel which is composed of refined and tempered low carbon martensite. The obtained results of simulation will be compared with those provided by J-integral methode for different enriched zones and contours based on the extended finite element method (XFEM) coupled with the level set technique (LST).  Crack initiation and propagation under cyclic loading have been adopted for the modeling of cruciform welded joints

Modal spectral analysis of planar cracked structures subjected to seismic excitations by the eXtended Finite Element Method

The aim of this paper is to model planar structures containing stationary cracks and submitted to dynamic loads of seismic nature. This modeling aims to evaluate the dynamic stress intensity factor (DSIF), characterizing the resistance to brutal fracture of cracked structures, using two analysis strategies; the first is a modal (costs less and as precise as a method of direct resolution) and the other one is modal spectral (much less costly but not as much precise as the latter). The evaluation of the dynamic modal stress intensity factor DMSIF is performed using the extended finite element method (X-FEM) coupled with the modal and spectral modal analysis. The main advantage of the latter is its ability to model cracks independently of the mesh at a reduced computational time compared to the conventional finite element method. The proposed procedure is applied to a reference problem (Sailing cracked). Comparisons between DSIF Spectral and maximum of modal DSIF are discussed. In addition, the effects of orientation, length and location of crack on the variation of these DSIF are tested

Dynamic and fatigue modeling of cracked structures containing voids by XFEM

In this paper, we present quasi-static and dynamic modeling of linear elastic 2D structures containing simultaneously two types of material discontinuities, a void and a crack. The purpose of this modeling consists to evaluate the stress intensity factor (SIF) in dynamic and to predict the crack propagation in fatigue using the extended finite element method (X-FEM) [1] due to its high ability to treat material discontinuities without changing the regular meshing of the structure. This method is coupled with the interaction integral method [2] in the aim to quantify the SIF through the concept of the J integral. Some examples of validation of the computer code developed in this work were tested. The good correlation of the obtained results with the literature in dynamic (Song et al. [3]) and in fatigue (Giner et al. [4]) proves the effectiveness of the method as well as the developed computer code. As applications in the dynamic case, a parametric study on the presence, position and size of the void with respect to the crack and also on the crack type (crack edge and central crack) was conducted for some practical problems. References: [1] Belytschko T, Black T. ;Elastic crack growth in finite elements with minimal remishing. (1999), Int J numer Meth Engng, pp. 601-620. [2] Soheil Mohammadi: Extended Finite Element Method for Fracture Analysis of Structures, edité par Blackwell Publishing Ltd Singapore, (2008). [3] S.H. Song, G.H. Paulino, Dynamic stress intensity factors for homogeneous and smoothly heterogeneous materials using the interaction integral method, Int. J. Solids Struct. 43 (2006) 4830–4866 [4] E. Giner, N. Sukumar , J. E. Tarancon, F. J. Fuenmayor, An Abaqus implementation of the extended finite element method, Departamento de Ingenierıa Mecanica y de Materiales