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Robust knockdown factors for the design of spherical shells under external pressure: Development and validation

Wagner, Ronald and Hühne, Christian and Niemann, Steffen (2018) Robust knockdown factors for the design of spherical shells under external pressure: Development and validation. International Journal of Mechanical Sciences (141), pp. 58-77. doi: 10.1016/j.ijmecsci.2018.03.029. ISSN 0020-7403.

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In this paper a physically based and deterministic design procedure for spherical shells under external pressure is introduced. Within the new design concept the membrane energy of a sphere is incrementally reduced by means of perturbation cutouts, until a bending energy dominate state is identified. The threshold between membrane energy state and bending energy state represents a robust plateau for the buckling pressure. A comprehensive numerical investigation was performed in order to study the influence of radius-to-thickness ratio (R/t) as well as the dome height-to-base radius ratio (H/r). The results verify that both geometric properties ratios significantly influence the lower-bound buckling pressure, especially if plastic buckling occurs. Improved shell buckling design factors are given in the form of an simple analytic equation. The corresponding threshold KDFs were validated with a large number of buckling experiments and deliver much higher KDFs than currently used empirical guidelines. Based on the new design criterion lower-bound estimation for the buckling pressure of a tori-spherical bulkhead and the inner dome of the cryogenic upper stage ESC-A from the European space launch-vehicle Ariane 5 are determined.

Item URL in elib:https://elib.dlr.de/125094/
Document Type:Article
Title:Robust knockdown factors for the design of spherical shells under external pressure: Development and validation
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Wagner, RonaldRonald.Wagner (at) dlr.deUNSPECIFIED
Hühne, ChristianChristian.Huehne (at) dlr.dehttps://orcid.org/0000-0002-2218-1223
Niemann, SteffenSteffen.Niemann (at) dlr.dehttps://orcid.org/0000-0001-9272-0635
Date:June 2018
Journal or Publication Title:International Journal of Mechanical Sciences
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:Yes
DOI :10.1016/j.ijmecsci.2018.03.029
Page Range:pp. 58-77
Keywords:Buckling; Robust design; Knockdown factor; Imperfection sensitivity; Spherical shell; Tori spherical bulkhead; Plastic buckling; ESC-A; Orthogrid stiffened sphere
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:fixed-wing aircraft
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):L - Structures and Materials (old)
Location: Braunschweig
Institutes and Institutions:Institute of Composite Structures and Adaptive Systems > Functional Lightweight Structures
Deposited By: Niemann, Herr Steffen
Deposited On:14 Dec 2018 11:56
Last Modified:14 Dec 2018 11:56

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