La fiabilité des arbres entaillés dans les machines agricoles : Applications sur les arbres clavetés

Abstract : The fatigue resistance in service of shaft with key seat is an important parameter in the reliability of strongly sought structures such as the agricultural pieces. Evolution, in design, towards lighter structures and in use towards more and more austere requests in service, give the necessity of a better knowledge of the monotonous and cyclic behavior of shaft with key-seat. This thesis is devoted to study, at the same time, the effect of the geometry of key-seats and the influence of the cyclic loading mode (rotating bending and torsion). New database for fatigue behavior of specimens with key-seats of different geometry sizes under different loading modes (rotating bending and torsion) has receiving. Here also should be noted that the new grips system for biaxial machine test has improved tests performance near endurance limit conditions. Using the Finite Element method, the influence of the geometrical parameters and the type of key-seats on the stress concentration factor was determined. Analytical equations, for every type of key-seats ans loading mode, were proposed. The new ?volumetric approach? gives a good description of the fatigue failure, where the traditional approaches (hot spot) simplified are not appropriate to characterized especially in the case of shafts with key-seats. This new approach gives an effective stress in the volume of fatigue process zone, taking into account the relative stress gradient in this volume. This effective stress gives the estimation of life duration by returning this stress on Wöhler's curve of smooth specimens for the same of loading mode
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Nawar Kadi. La fiabilité des arbres entaillés dans les machines agricoles : Applications sur les arbres clavetés. Mécanique [physics.med-ph]. Université Paul Verlaine - Metz, 2001. Français. ⟨NNT : 2001METZ013S⟩. ⟨tel-01775502⟩

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