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Prise en compte de l'intégrité de surface pour la prévision de la tenue en fatigue de pièces usinées en fraisage

Abstract : This study is dedicated to the influence of ball-end tool finishing milling on surface integrity and fatigue life of components made of high-strength bainitic steels. Surface integrity, defined in terms of microgeometry, residual stresses and hardening, was experimentally characterized for different values of the machining parameters, including the tool inclination. Fluctuations of the residual stresses field – measured by X-ray diffraction – perpendicular to the grooves generated by the tool were exhibited at different depths beneath the surface. Fatigue bending tests performed on machined or polished flat specimens, submitted or not to a heat treatment to relax the residual stresses, exhibited the influence of the surface integrity on fatigue life. Fatigue tension tests and self-heating measurements exhibited a competition between micro-plasticity and micro-cracking mechanisms. A hybrid approach is proposed to predict the mechanical state induced by the milling process. This approach consists in simulating – without modelling the removal of the material- the effect of a thermo-mechanical loading equivalent to the cutting process. This thermo-mechanical loading should be derived from temperature and cutting forces measurements preformed during cutting tests. A probabilistic approach is proposed to predict the influence of surface integrity on fatigue life. This approach was validated for cases when micro-cracking mechanism is predominant. The approach is then based on fracture mechanics and takes account of the micro-geometry via the micro-cracks size population measured in the valleys of the grooves generated by the tool.
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Submitted on : Wednesday, August 31, 2011 - 3:39:37 PM
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  • HAL Id : tel-00610030, version 2

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Nicolas Guillemot. Prise en compte de l'intégrité de surface pour la prévision de la tenue en fatigue de pièces usinées en fraisage. Autre. École normale supérieure de Cachan - ENS Cachan, 2010. Français. ⟨NNT : 2010DENS0052⟩. ⟨tel-00610030v2⟩

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