Research Topics

Discontinuities modeling

We seek to model arbitrary strong and weak discontinuities propagation in solid mediums such as cracks and phase fronts. We focus on the development of the eXtended Finite Element Method combined with Level Sets to achieve this goal. We are mainly focused on the development of new techniques to solve non-linear three-dimensionnal quasi-static and dynamic crack propagation. We propose particular non-linear solvers and time integrators within the X-FEM to perform fast and efficient computations and also develop ad-hoc experiments to validate our numerical methods.

Forming processes

Higher order functions such as B-Spline and NURBS functions, massively used in Computer Aided Design and that are built into the Isogeometric Analysis are promissing new basis for powerful numerical methods. Within the isogeometric analysis, we develop particular numerical scheme to simulate elastic-plastic incompressible solids at large strains, higher order shells and geometrically exact contact algorithms. The final goal is to obtain a NURBS-based framework to accurately simulate metal forming with an accurate geometric description and precise non-linear stress states. This work is done in collaboration with Professor Thomas J.R. Hughes' group at the University of Texas at Austin and Dr Yuri Bazilevs at the University of California San Diego.

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Pictures and animations

2D and 3D dynamic crack growth

Work in collaboration with Anthony Gravouil and Hubert Maigre. Pictures and animations done using Paraview.

Simulation of Kalthoff's experiment
This example deals with the numerical simulation of Kalthoff's experiment of the failure mode transition under pure mode-2 loading. The experimental configuration is the following: a plate with two symmetrical edge cracks is impacted by a projectile at a given speed V0. By modifying the projectile's velocity, Kalthoff observed a transition in the type of failure. At low velocity, i.e. under low strain rate, brittle failure is observed with a simultaneous propagation of the two cracks with a global angle between 60° and 70°. If one increases the projectile's speed, a transition between brittle fracture and shear band propagation (with a propagation angle of approximatively -10°) occurs. We consider here only the brittle propagation with in impact velocity of 20m/s.
Compact Compression specimen
The Compact Compression Specimen experiment first introduced by Bui et al and further developed by Maigre and Rittel. The interest of the CCS experimentis that there is always a mixed-mode loading condition at the crack tip. The test rig is a Split Hopkinson Pressure Bar (Kolsky bar), the input bar is modelled by the experimental dynamic load.
Semi-infinite crack in an infinite medium
A semi-infinite mode I crack in an infinite medium submitted to a tensile stress wave is considered. The analytical solution for the mode I dynamic stress intensity factor was obtained by Freund. We consider a finite geometry, therefore we can only compare the results with the analytical solution until the tensile stress wave is reflected on the bottom side and reaches again the crack tip.

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Quasi-static crack growth with plasticity and contact

Work in collaboration with Anthony Gravouil and Alain Combescure. Pictures and animations done using Gmsh and mencoder.

Closing effects due to plasticity in a Compact Tension specimen

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Projection method for large strain incompressibility

Work in collaboration with Yuri Bazilevs, Victor M. Calo and Thomas J.R. Hughes. Pictures done using GMV.

Pinching of an incompressible toroidal solid
This example exploits the ability of NURBS to exactly represent conic sections. It consists of the pinching of a toroidal solid. A nearly incompressible Neo-Hookean material model is considered (equivalent Poisson ratio of 0.4998). Because of symmetry, one quarter of the structure is considered, with a mesh of 4x16x2 elements with quadratic and cubic NURBS.

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Publications

Refereed Article Journals

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Refereed Conferences Proceedings

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Selected Conferences

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Ph.D. Thesis

"Fatigue crack growth simulation using the extended finite element method with plasticity and contact-friction." (in French)
"Simulation numérique de la propagation de fissure en fatigue par la méthode des éléments finis étendus: prise en compte de la plasticité et du contact-frottement." (PDF )

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Laboratoire de Mécanique des Contacts et des Structures - Equipe Mécanique des Solides et des Endommagements
INSA de Lyon
20 avenue Albert Einstein
Bâtiment Joseph Jaquard
69621 Villeurbanne Cedex
France
office: +33 (0) 4 72 43 71 05
fax: +33 (0) 4 72 43 89 13
e-mail: thomasDOTelguedjATinsa-lyonDOTfr
(Spam protection: please change DOT by "." and AT by "@" to use this e-mail address)

Last updated on August 6th, 2008.