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Optimization of Machining Technologies for Special Applications
Ohnišťová, Petra ; Maňková, Ildikó (referee) ; Neslušan, Miroslav (referee) ; Píška, Miroslav (advisor)
This thesis is focused on the optimization of the milling technologies for special applications with respect to the required fatigue properties of aircraft components. The theoretical part of the thesis describes in detail the key features of the high-speed and high-feed milling, surface integrity after milling and fatigue characteristics of the studied component. The key aim of the work is devoted to the analysis of the influence of the cutting conditions of the high-speed peripheral and high-feed face milling of the bottom wing panel from aluminium alloy 7475-T7351 on the surface integrity in relation to the final fatigue properties. Therefore, the part of the work is a study of metallographic structure of the material, measurement of the accompanying machining phenomenon and quantities, advanced analysis of the surface integrity (amplitude characteristics, S-N parameters), manufacturing of the highly accurate fatigue samples and fatigue testing. Furthermore, the development of sample damage during in situ tensile loading and the development of sample damage during cyclic in situ fatigue tensile loading is also studied. The achieved results and fractography of fracture surfaces show that the studied cutting conditions have a significant effect on the quality of machining and resistance to mechanical stress, but they are not a decisive factor in terms of the fatigue crack nucleation. The effect of the achieved topography for the studied cutting conditions is suppressed by the presence of large intermetallic inclusions (Al7Cu2Fe; Al-Cr-Fe-Cu-Si) with a size from 2 µm to 20 µm, being the origin on the fatigue crack nucleation.
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