Numerical modeling and comparison study of elliptical cracks effect on the pipes straight and with thickness transition exposed to internal pressure, using XFEM in elastic behavior.

The present work deals with the effect of an external circumferential elliptical crack located at thickness transition on a varied stepped diameter pipe . The purpose is the application of the extended finite element method (XFEM) for the calculation of SIF at the thickness transition region of pipe considering internal pressure and compare the effect of the crack between pipes straight and with thickness transition. To model a crack with precision , enrichment functions are used to enrich the displacement approximation, the level set functions are calculated from the crack mesh and definition of the strategy of integration has been performed. A comparative study is made on SIF of crack defect in straight pipe compared to one with thickness transition using XFEM for the crack and pipe geometrical parameters variations. The result shows that the XFEM is an effective and practical tool for elliptic crack modeling in a pipe with thickness transition because a crack is easily modeled through enrichment functions.The comparison of the SIF of a similar defect between pipes shows that a pressurized pipe with thickness transition is more sensitive to the used cracks.