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MODELISATION DU CHAMP MAGNETIQUE INDUIT PAR DES TOLES IDENTIFICATION DE L'AIMANTATION Application à l'immunisation en boucle fermée d'une coque ferromagnétique

Abstract : A ship with a ferromagnetic hull, placed in the earth's magnetic field and under mechanical constraints, gets a magnetisation which creates a local anomaly ofthe field. The closed loop degaussing is a system that allows the ship to evaluate this magnetic anomaly at each moment and to compensate it. To perfect this technique, ifs necessary to develop a tool which' can predict the magnetisation of the hull. This magnetisation can be divided into two parts: the first is the induced magnetisation and the second the permanent one. Firstly, this work proposes a study of the different numerical methods to calculate the induced magnetisation (Le. the reaction of the material in an external field). We were especially interested in boundary element methods which leads to distributions of charges or tangential dipoles on the hull. The second part deals with a method to evaluate the permanent magnetisation. This magnetisation depends on the magnetic history of the ship (hysteresis, magnetostriction... ), so a deterministic calculus is not possible. Then, magnetic sensors are placed onboard the ship and allow to build a mathematical model for magnetization. We propose an original approach to solve this ill-posed inverse problem based upon a good knowledge of the magnetic behavior of the material. Once the model has been obtained, ifs possible to calculate the field outboard. Our approachhas been validated by measurements taken onboard a mock-up ofa ship.
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Submitted on : Wednesday, December 22, 2010 - 2:23:42 PM
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Olivier Chadebec. MODELISATION DU CHAMP MAGNETIQUE INDUIT PAR DES TOLES IDENTIFICATION DE L'AIMANTATION Application à l'immunisation en boucle fermée d'une coque ferromagnétique. Sciences de l'ingénieur [physics]. Institut National Polytechnique de Grenoble - INPG, 2001. Français. ⟨tel-00549747⟩

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