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Theses

Vibrations non-linéaires des structures fissurées :
Application aux rotors de turbines

Abstract : The aim of this work is to study the dynamic response of a cracked rotor to establish some possibilities for early on line crack detection. First, a review on experimental, numerical and analytical works on the dynamics of cracked rotors is given. Then, an original method of calculating the behavior of a cracked beam section in bending with shearing effects is presented. The nonlinear behavior relations are derived from a three-dimensional model taking into account the unilateral contact conditions on the crack's lips. Based on an energy formulation, this method could be applied to any geometry of crack. The exploration by different numerical integration methods of the vibratory response of some models of cracked rotors is presented in the third chapter of this thesis. The uncracked parts of the rotor are represented by elements of bar or beam type, and the cracked section by a nonlinear spring taking into account the breathing mechanism of the cracks. At the end of this part, an original method of construction of a finite element of a cracked beam is presented. The final chapter is devoted to the analytical study of the system with two dof. The breathing mechanism of the crack is taken into account by considering specific periodic variation of the global stiffness of the system. The differential equations system is solved using the harmonic balance method. The linear stability of the periodic solutions is studied by the Floquet theory. Some vibratory parameters are proposed as crack indicators.
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https://pastel.archives-ouvertes.fr/tel-00325964
Contributor : Saber El Arem <>
Submitted on : Tuesday, September 30, 2008 - 7:27:35 PM
Last modification on : Wednesday, October 14, 2020 - 3:52:12 AM
Long-term archiving on: : Thursday, June 3, 2010 - 10:10:55 PM

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  • HAL Id : tel-00325964, version 1

Citation

Saber El Arem. Vibrations non-linéaires des structures fissurées :
Application aux rotors de turbines. Matériaux. Ecole des Ponts ParisTech, 2006. Français. ⟨tel-00325964⟩

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