h1

%0 Thesis
%A Lyssakow, Pawel
%T A coupled structural and economical design procedure for shell structures
%V 2021/01
%I RWTH Aachen University
%V Dissertation
%C Aachen
%M RWTH-2021-04918
%@ 978-3-8440-7989-0
%B Aachener Berichte aus dem Leichtbau
%P xx, 133 Seiten : Illustrationen, Diagramme
%D 2021
%Z Dissertation, RWTH Aachen University, 2021
%X Thin-walled shell structures such as those used for space launch vehicles have been the subject of research for many decades. Due to the currently increasing competition on the space launch vehicle market, decreasing the costs per launch is brought to the fore. To reduce launch costs, it is necessary to design structures that are optimized regarding their structural mass and manufacturing costs. Shell structures can be designed imperfection sensitive or imperfection tolerant. Designing imperfection sensitive shell structures is challenging as the imperfections that drastically reduce the load-carrying capacity of these structures are unknown at the beginning of the design procedure. However, if the manufacturing signature, which is the relation between the manufacturing process and the imperfection pattern, is known at the beginning of the design procedure, it will be possible to predict the load-carrying capacity of the investigated structures. The goal of this thesis is to develop and introduce a coupled structural and economical design procedure that can be used to design shell structures that are optimized regarding their structural mass and manufacturing costs. Therefore, a cost model for unstiffened isotropic shell structures based on the assembly out of multiple panels is derived. Cost and mass drivers are studied with the help of an example structure. The results show that it is beneficial to reduce the number of panels since in this case the load-carrying capacity increases, while simultaneously the manufacturing costs decrease. However, for a high manufacturing accuracy a high number of panels is beneficial and vice versa. It is shown that the chosen assembly method has a high impact on the manufacturing costs. Furthermore, the available sheet and the required panel sizes have a tremendous impact on the manufacturing costs and on the structural mass of the shell structure. Finally, a relation between the chosen panel combination and the buckling pattern is derived. The measurement system SIMS, which is capable of measuring geometric and thickness imperfections of cylindrical structures, is developed within this thesis. Afterwards, the SIMS is used to measure the geometric and thickness imperfections of six unstiffened isotropic flow-formed shell structures. A Fourier transformation of the measurement results is carried out. The Fourier coefficient driven imperfection patterns are used to derive the mean manufacturing signature of the investigated structures, leading to a KDF of 0.8. The manufacturing signature is validated with the help of the average KDF of 0.78, which was numerically calculated using the measurement results. Furthermore, it is shown that the impact of thickness imperfections on the load-carrying capacity is smaller than the impact of mid-surface imperfections, but not negligible.
%F PUB:(DE-HGF)11 ; PUB:(DE-HGF)3
%9 Dissertation / PhD ThesisBook
%U https://publications.rwth-aachen.de/record/819223