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Theses

Usinage à grande vitesse efficace basé sur l'identification opérationnelle du comportement dynamique et l'optimisation du support de pièce

Abstract : High-speed machining plays a very important role in the engineering industry today. However, vibration phenomena during machining process can be detrimental to the quality of machined workpiece, the productivity and the durability of accessories, etc. Mastering the dynamic behavior of the coupled system (machine tool/spindle/tool/workpiece/workpiece holder) is the primordial key to successful high speed machining. The first objective of the thesis consisted in applying existing techniques of operational modal identification and proposing new identification techniques better adapted to take into account the specificities of machining: the presence of very predominant harmonics, the uncontrolled and unmeasured random excitation, and responses only recorded. Three new operational modal identification procedures have been proposed: the transmissibility method (PSDTM-SVD) (i) combined with kurtosis values and histograms, (ii) or hybridized with autocorrelation functions, (iii) and the new SCA-FDD method based on blind source separation. The effectiveness of the proposed methods has been validated by numerical examples and an experimental test. The second objective of the thesis was to propose a new design of the workpiece support using innovative materials, in order to make the dynamic behavior optimal with respect to machining stability. To increase the machining performance, the new composite workpiece holder must have a stiffness at least equal to that of the initial aluminum workpiece holder while having a higher damping ratio. A new hybrid composite laminate reinforced by carbon and flax fibers is then proposed. This combination enables to combine the advantages of two fiber types in a composite. Workpiece holders in carbon-flax hybrid composite laminates with different stacking sequences were fabricated for validation tests. In the case of machining with the composite workpiece holders, the machining stability is greatly increased compared to the initial aluminum workpiece holder. Among the different stacking sequences, the carbon-flax hybrid composite workpiece holder [C6/L8/C6] is the optimal solution in terms of machining performance and environmental impact. This solution increases machining stability by 283 % with a vegetable fiber volume ratio of 14 %.
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Submitted on : Tuesday, February 16, 2021 - 3:08:35 PM
Last modification on : Wednesday, February 24, 2021 - 4:16:03 PM

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  • HAL Id : tel-03143064, version 1

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van Dong Do. Usinage à grande vitesse efficace basé sur l'identification opérationnelle du comportement dynamique et l'optimisation du support de pièce. Génie mécanique [physics.class-ph]. Université Clermont Auvergne, 2020. Français. ⟨NNT : 2020CLFAC036⟩. ⟨tel-03143064⟩

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