Structural analysis of aircraft fuselage section and determination of boundary conditions and fatigue spectrum loading of its curved stiffened panels

• Κύριος συγγραφέας: Κορδάς, Παναγιώτης
• Άλλοι συγγραφείς: Kordas, Panagiotis
• Γλώσσα: English
• Έκδοση: 2022
• Θέματα: Stiffened panel; Test-rigs; Virtual modeling; Fatigue spectrum; Ενισχυμένο κέλυφος; Δοκιμαστική διάταξη; Εικονικό μοντέλο; Φάσμα κόπωσης

The primary objective of this thesis is the determination of the optimum experimental configurations for the experimental investigation of curved stiffened panels behavior. A test rig of this type should be capable of simulating the structural response of aircraft fuselage sections under static and fatigue loading. A virtual representation of a fuselage barrel is constructed, and its validity checked for simple load cases after comparing stress results with those from analytical and semi-empirical formulations. The finite element model of the fuselage is characterized by geometrical dimensions and material content typical for passenger airplanes. The literature research conducted, aims to propose potential experimental assemblies that impose a specific set of boundary and loading conditions unto the panel. The sources reviewed, were focused on setting up test-rigs that accommodated panels (at test article or component level) for buckling testing with the presence of internal pressure. At the same time, after recreating a fuselage in FE format for post processing data comparison with potential panel models, it is attempted to code a fatigue spectrum as a load sequence. The methodology for producing alternating fatigue stress cycles, that share similar attributes with those attained from real in-flight measurements, is presented in all its phases. The method to end up with a random load sequence, which simulates real life flight conditions, is based upon the exceedance diagram of the normalized stresses, the definition of different flight types and the ordering of the load factors in dimensional form. The present paper juxtaposes the fatigue spectrum obtained through the application of the original methodology with that from, a modified, adapted for fuselage damage inspection and repairs, approach put forward by the FAA. Additionally, as a final step, a third possible load sequence is seeked out, unique to this thesis that utilizes vertical acceleration data, that correlates to normalized bending stress amplitudes, for the definition of a novel flight block, meaning a fatigue spectrum that corresponds to a given number of flights.