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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Contribution de la rhéologie et de la tribologie à l'usure de produits cellulosiques alvéolaires

Mezence, Kény 10 November 2011 (has links)
Les applications tribologiques des matériaux cellulaires en présence de liquide nécessitent une connaissance de leurs modes d’endommagement, mais elles restent peu connues à l’heure actuelle. L’étude, la compréhension et la modélisation du comportement d’un matériau composite cellulaire nécessitent une approche pluridisciplinaire due au caractère hétérogène du matériau qui reste difficilement caractérisable. Ce matériau peut être analysé suivant 3 axes bien distincts : les propriétés rhéologiques (analyses sous état de déformation complexe en compression et en cisaillement avec des rhéomètres adaptés), la morphologie des alvéoles (analyses 3D optiques et tomographiques), les propriétés tribologiques (analyse en frottement de l'interface et des particules d'usure). L’intérêt majeur de notre approche est d'aborder simultanément ces 3 axes et de comprendre leurs interactions respectives. La tomographie aux rayons X, suivie d’un traitement mathématique assisté par ordinateur, complété par l'analyse des particules d'usure a permis d'identifier les morphologies responsables des fonctions spécifiques du matériau cellulaire. Un tribo-abrasimètre innovant avec des surfaces abrasives modèles a mis en évidence l’importance des cinématiques dans l’endommagement du matériau. Des méthodes de caractérisation ont été mises au point afin de quantifier la dégradation tribologique du matériau permettant également de mesurer l’impact du vieillissement (chimique, thermique et mécanique). / Tribological applications of cellular materials in the presence of liquid require acknowledge of their modes of damage, but they remain little known at present. The study, understanding and modeling the behavior of a composite cell requires a multidisciplinary approach due to the heterogeneity of the material that is difficult to characterize. This material can be analyzed along three distinct axes: the rheological properties (analysis in complex state of deformation in compression and shear with adapted rheometer), the morphology of the cells (3D optical tomographic analysis), the tribological properties (analysis in interface friction and wear particles). The major advantage of our approach is to simultaneously address these three areas and to understand their interactions. The X-ray tomography, followed by computer-assisted mathematical treatment, supplemented by the analysis of wear particles identified morphologies responsible for specific functions of cellular material. A tribo-abrasimeter with innovative models abrasive surfaces highlighted the importance of kinematics in the damage of the material. Characterization methods have been developed to quantify the tribological degradation of the material can also measure the impact of aging(chemical, thermal and mechanical).
2

Racionalizace výroby součásti / Rationalization of a part production

Bartl, Lukáš January 2017 (has links)
The assigned thesis is focused on the proposal of rationalization solutions to the component Bonnet, which is a standard representative of the most important sections of broader spectrum of customer´s components. The introduction part describes the component basis, according to which the standard representative was chosen, later on characterised from the point of view of seriality. The following large part of classfying the time comsumption in machinery is essential for the calculations as such, which are the essential part of this dissertation. The proposal of production rationalization is concerned with the exclusion of unnecessary losses and using existing ressources with the help of a higher level of machinery, technology, work organisation, production and management, which lead to a higher labour productivity. The technological production preparation ensures the documentation processing, the proposal of semi-finished product, machines, fastening, measuring and calculation of necessary technological specifications for ensuring the production. In the final part, there is to be found the technical and economical evaluation of rationalization proposals, which numerically evaluates the analysed outputs of this thesis.
3

Trochoidal Milling of AlSiCp with CVD Diamond Coated End Mills

Nguyen, Tony 01 January 2018 (has links)
Metal matrix composites have seen a rise in demand within the last decade. Aluminum alloy reinforced with silicon carbide particles is a type of particle metal matrix composite that has seen applications in the aerospace, ground transportation, and electronics industry. However, the abrasive SiC particles have made this material difficult to machine through conventional machining strategies. This research will focus on using computer aided manufacturing with trochoidal tool paths to maximize machining productivity and extend the tool life of CVD diamond coated end mills. The focus of this research will be on AlSiCp with a high volume fraction of reinforcement (30%) to expand the potential applications of this pMMC. The cutting experiments are divided into three parts: cutting test, confirmation test, and endurance test. Taguchi method will be used to perform an analysis of variance and signal-to-noise ratio to optimize a combination of material removal rate, average cutting forces, and surface roughness. The optimal cutting conditions were found to be 254 mm/min, 30°, and 9500 r/min for MRR+AvgFxy+Ra, 1524 mm/min, 30°, and 9500 r/min for MRR+AvgFxy, and 1524 mm/min, 90°, and 9500 r/min. The cutting conditions for MRR+AvgFx+Ra was not considered for the endurance tests as the machining productivity was too low to be considered a feasible option in the industry. It was concluded that trochoidal milling under wet cutting conditions produced nearly half the tool wear as previous research with conventional milling strategies. However, the longer the CVD diamond coated end mills were engaged in the AlSiCp workpiece, the more dominant the abrasive wear mechanisms appear and cause tool damage. It was concluded that square end mills may not be suitable for machining AlSiCp and that future research should focus on varying the tool geometry or utilizing ball end mills.
4

Optimalizace obráběcího procesu s průmyslovou aplikací na obráběcím centru / Optimisation of machining process for an industrial application and a CNC machining centre

Soukupová, Veronika January 2020 (has links)
Tato diplomová práce byla vypracována v průmyslovém kontextu, během stáže ve firmě Metso. Zlepšení obráběcího procesu zajišťovacích šroubů bylo cílem této práce, aby byla umožněna budoucí automatizace zakládání obrobku do stroje. Zlepšení bylo zhodnoceno na základě úrovně autonomie během obrábění, eliminace neprogramovaných zastavení stroje operátorem a dostačujícího odvodu třísek. Implementace automatických systému do číslicově řízeného obráběcího centra umožňuje zvýšení produktivity. Před automatizováním obráběcího procesu však musí být proces optimalizován. Zejména dostatečná fragmentace třísek a jejich evakuace jsou klíčové. Dlouhé nedělené třísky můžou poškodit systémy jako například automatický měnič nástrojů, dopravník třísek nebo průmyslového robota. Dostatečná lámavost třísek může být zaručena správným výběrem technologie a strategie obrábění, výběrem řezného nástroje a řezných podmínek pro daný materiál obrobku.

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