03. Bachelor's Thesis

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Browsing 03. Bachelor's Thesis by Subject "aerospace"

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    Design of load-and-misalignment-insensitive gearing for aerospace, automotive and naval applications.
    (Nazarbayev University School of Engineering and Digital Sciences, 2017-04) Akiltayev, Ali; Beysekenov, Ilyas
    The operation of gears is usually accompanied with noise and vibrations that are caused by various sources. Two of the major ones are load and misalignment, which induce high magnitudes of stress on gear teeth. Hence, the main aim of this project is to mitigate their effects by proposing new design topology, which will address both issues without compromising performance of power transmission. The approach to be used in reaching load-insensitivity is to apply tooth profile modifications along with preloading and torque splitting topology, while, possible solution to the misalignment issue is implementation of gear web modification. In both cases, parametric study is used to check behavior of different systems: in part of load analysis, mesh stiffness variation is analyzed using Kisssoft software and dynamics of entire system is analyzed in Matheamatica, while misalignment effects are studied using ANSYS static structural studies. The above studies led to several important findings. Firstly, during the studies of mesh stiffness we found that loaded transverse contact ratio is more important than theoretical one for obtaining mesh curve with minimal fluctuations. Namely when loaded TCR is slightly less than integer it is possible to achieve desirable constant mesh stiffness, while being exactly integer causes spikes in the curve. Secondly, applying tip relief to spur gears changes the relationship between theoretical and loaded TCR: in case of gears with tip relief, loaded TCR is less than theoretical one, while for ordinary gears loaded TCR is always higher than theoretical. Thirdly, when helical gears have high (over than 2) integer overlap contact ratio (OCR) the effect of TCR is almost negligible. Finally, real-time self-preloading was proved to enable achieving constant mesh stiffness for wide range of loads. Also, split-torque topology helps to reduce overall level of vibrations. To find a solution for gear misalignment, 4 different gear web designs were studied: ordinary, spoked, split-pinion (modification of spoked pinion) and multicomponent topologies. Several observations were made during the study. As it was expected, stress in ordinary gears gets more concentrated with increase of misalignment. Spoked pinion topology showed complicated behavior, but still was effective in terms of stress redistribution. Fragmented pinion and multicomponent topologies helped to achieve the best stress distribution, but have some limitations, such as high structural complexity of multicomponent pinion and high stress in the spokes of fragmented pinion. More studies should be conducted to find their optimal configurations.