Usure des roues de TGV : une approche de type allliage forcé

Abstract : Circularity defects (AEL) appear in railway wheels during running. These circularity defects require periodic controls and machinings to eliminate them. The aim of the study is to determine the origin of the circularity defects and to developpe an accelerated test to compare different steels. For this study, we have used the concept of driven alloys which as show, for materials submitted to repeated stresses, that phase transformation occurring, depend on the value of an intensity of forcing. First of all, we have defined and calculated an intensity of forcing for the wheel. Next, we have performed a metallurgical study of several railway wheels, and we have shown a metallurgical transformation at the surface of the wheels, characterized by a transformed layer with metallurgical properties very different from those of the bulk steel. The wear of the wheel is due to a cyclic mechanism including metallurgical transformation, cracking and tearing off of the transformed material, and the increase of the AEL is due to a locally faster wear rate, caused by a shape defect or a microstructural heterogeneity. An accelerated test, based on high energy ball milling, has been developed to compare different steels. We success to determine and compare the cementite dissolution rate and we show that the cementite dissolution control the material wear rate. In the same way, attempts were used to simulate the wheel-rail contact. A metallurgical transformation, similar to this observed at the surface of the wheel, was obtained, and shows that shearing is necessary to obtain the metallurgical transformation of the material
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Theses
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http://docnum.univ-lorraine.fr/prive/INPL_T_2004_SAINT_AYES_G.pdf
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https://hal.univ-lorraine.fr/tel-01752318
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Submitted on : Thursday, March 29, 2018 - 1:40:54 PM
Last modification on : Monday, April 16, 2018 - 10:41:09 AM

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Grégory Saint-Ayes. Usure des roues de TGV : une approche de type allliage forcé. Autre. Institut National Polytechnique de Lorraine, 2004. Français. ⟨NNT : 2004INPL012N⟩. ⟨tel-01752318⟩

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