Fracture Mechanics
Salmi Houda; Hachim Abdeliah; Hanan El Bhilat; Khaled El Had
Abstract
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 ...
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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.
Damage Mechanics
E. Homaei; K. Farhangdoost; M. Akbari
Abstract
The aim of the study was to find the optimum combination of materials and thicknesses to provide a tough, damage resistant multi-layer system with numerical methods to restore the damaged teeth. Extended Finite Element Method (XFEM) was used to assess the critical loads for the onset of damage modes ...
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The aim of the study was to find the optimum combination of materials and thicknesses to provide a tough, damage resistant multi-layer system with numerical methods to restore the damaged teeth. Extended Finite Element Method (XFEM) was used to assess the critical loads for the onset of damage modes such as radial cracks and plastic deformation in dental prostheses, which consist of a brittle outerlayer (porcelain)/ metal (Au, Pd, Co)-core/ substrate (dentin) trilayer system. XFEM not only has the ability to model crack initiation process, but also could solve crack propagation problems. Generally speaking, porcelain layer shouldn't be thinner than 0.5 mm, as the stresses due to bending become tensile critically in porcelain undersurfaces and radial cracks would occur in low loads. Also, it could be concluded that XFEM in axisymmetric model could properly estimate crack initiation and propagation path. Yielding of metal core makes additional flexural stress at overlaying brittle surface and consequently, facilitates radial cracks. In dental applications, the optimum porcelain thickness would be between 0.75 and 1.25 mm. Furthermore, yield strength and stiffness of metal is better to be high sufficiently to prevent it from plastic deformation and ensuing radial cracks.
