H Zarrinzadeh - PhD student, Department of Civil and Environmental Engineering, AmirKabir University of Technology, Tehran, Iran
M.Z Kabir - Professor, Department of Civil and Environmental Engineering, AmirKabir University of Technology, Tehran, Iran
A Deylami - Assistant Professor, Department of Civil and Environmental Engineering, AmirKabir University of Technology, Tehran, Iran

An extended finite element method (XFEM) is developed to investigate fatigue crack growth of repaired shell structure. Studies on crack growth rates with respect to fatigue cycles of loading are performed for a cracked cylindrical panel with different lay-up patch configurations under mixed-mode condition, and also for a repaired pipe with a through-the-thickness longitudinal crack. The geometry of the proposed model is selected such that one can compare the results with conventional finite element method. By this method, any crack geometry can be embedded in the FEM mesh configuration with no need to coincide the crack geometry with element nodes and so re-meshing with fine mesh generation is not needed in the current method which can lead to less time-consuming iterations. A MATLAB® stand-alone code was prepared for structure modelling with eight-nod doubly curved shell elements in the X-FEM framework.

XFEM, Fatigue crack growth, Stress intensity factor, degenerated shell element, composite patch