Thesis /

ROMDOC-THESIS-2017-1235

Contribuţii la identificarea experimentală a sistemelor de aeronavă pe baza datelor măsurate şi a prelucrării avansate a semnalelor de răspuns

Flore, Lică
2016-09-28

Abstract: UNIVERSITY POLITEHNICA OF BUCHAREST FACULTY OF AEROSPACE ENGINEERING ABSTRACT OF PhD THESIS CONTRIBUTIONS TO EXPERIMENTAL AIRCRAFT SYSTEMS IDENTIFICATION BASED ON MEASURED DATA AND ADVANCED PROCESSING OF RESPONSE SIGNALS Thesis Tutor: Prof. PhD. Eng. Adrian Mihail STOICA PhD Student: Eng. Lica FLORE The thesis deals with experimental modal analysis used to identify the dynamic behaviour of mechanical systems for aircraft by measuring and determining eigen frequencies, modal shapes, modal damping and generalized parameters. These parameters are needed to understand and prevent mechanical damage to the system components and also to validate the finite element models. Modal analysis is a way of predicting the response of structures using mechanical superposition method. The main concerns of the conducted experimental investigation focused on: assessing the effectiveness and accuracy of different experimental methods, finding an optimal solution for the application of excitation, studying several methods of signal processing, achieving a combination of numerical and experimental methods in order to obtain a numerical model based on a small number of experimental data to provide acceptable accuracy. The results obtained are based on performing five case studies of representative aviation structures; such structures being designed and produced in certified organizations. Some conclusions are highlighted and presented derived from the investigation activities: the resonance phenomena is very difficult to control in terms of energy; significant time is required in tests conducted close to the resonance frequency of the structure with harmonic excitation because of the difficulties of phase matching and structure stabilization time; the response signal during pulse-excitation testing has a strong deterministic character which does not allow for a linear approximation for non-linear systems even when the coherence function is used; modal parameters are different in mechanically loaded and not loaded structures, the values of the modal parameters increase with loading; the nonlinear behaviour of the structure can be detected and evaluated through harmonic excitation techniques if the speed of frequency sweeping is low enough. Identification of the dynamic behaviour of aircraft structures shows a high degree of difficulty due to overlapping or neighbouring modes. Using additional instrumentation and an adequate analysis of the response time signal can lead to the isolation of such modes.

Keyword(s): Aeroelesticitate -- Teză de doctorat ; Identificarea sistemelor -- Aeronave -- Teză de doctorat ; Structuri mecanice -- Analiză dinamică -- Teză de doctorat ; Inginerie aerospaţială -- Teză de doctorat
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